CN102797358B - Construction technique for ultralow-temperature high-property concrete for railway construction in frigid areas - Google Patents

Construction technique for ultralow-temperature high-property concrete for railway construction in frigid areas Download PDF

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CN102797358B
CN102797358B CN201210319814.2A CN201210319814A CN102797358B CN 102797358 B CN102797358 B CN 102797358B CN 201210319814 A CN201210319814 A CN 201210319814A CN 102797358 B CN102797358 B CN 102797358B
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concrete
ultralow
performance
temperature high
temperature
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CN102797358A (en
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廖太昌
帖锋斌
刘百成
魏杏色
谷炼平
张永鸿
薛琪
仲维玲
赵朝阳
马颖仙
曹万玲
张利民
冯艳娜
沈亚妮
冯英瑞
李坦
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China Railway 20th Bureau Group Corp
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China Railway 20th Bureau Group Corp
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Abstract

The invention discloses a construction technique for ultralow-temperature high-property concrete for railway construction in frigid areas. The construction technique comprises the steps as follows: A, mixing ultralow-temperature high-property concrete: gelled materials, sand, crushed stone, an efficient water reducing agent, compound antifreeze and water are evenly mixed to obtain the ultralow-temperature high-property concrete; the gelled materials are made by evenly mixing cement and mineral admixtures in the weight ratio of (88-78):(12-22); the weight ratio of the compound antifreeze to the mineral admixtures is (3-6):100; the compound antifreeze comprises 30 to 35 wt% of nitrate, 30 to 33 wt% of organic compound, 0.5 to 1wt% of calcium formate, and water as the rest; the nitrate is calcium nitrate or calcium nitrite; and the organic compound is methanol or alcohol; B, pouring the ultralow-temperature high-property concrete; and C, curing the ultralow-temperature high-property concrete. The construction technique has the advantages of reasonable design, simplicity in construction steps, convenience in operation, fast construction progress, low construction cost, and good structural quality of concrete used in construction.

Description

The concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area
Technical field
The invention belongs to concrete construction technology field, especially relate to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of a kind of severe cold area.
Background technology
Before Line for Passenger Transportation station, newly built railway Harbin to Qiqihar, civil works is positioned at the west and south, Heilongjiang Province, the main climatic characteristics in area along the line is: 39.8 ℃ of Extreme Maximum Temperatures, the extreme lowest temperature-42.6 ℃, the coldest monthly mean temperature is all lower than-15 ℃, total track length 280.893km, winter severe cold is dry very long, and the phase of stopping in winter reaches six months, and the soil maximum depth of frost penetration along the line is 1.89m～2.14m.According to the requirement of the special construction period arrangement of current visitor and the Ministry of Railways, winter construction is essential, and winter high performance concrete quality control on construction and the quality control on construction of ordinary concrete be different, ordinary concrete only need to be considered the heat of hydration problem of early strength and concrete in mass, high performance concrete not only will be considered first two, also to consider later strength and endurance quality, high performance concrete (High performance concrete, be called for short HPC) be a kind of novel High Technique Concrete, on the basis that increases substantially ordinary concrete performance, to adopt the concrete of modern concrete fabrication techniques.It usings durability as the leading indicator designing, and for different purposes requirements, following performance focus is guaranteed: durability, workability, applicability, intensity, volume stability and economy.For this reason, the feature of high performance concrete in configuration is to adopt low water binder ratio, selects high-quality raw material, and fine mineral admixture and the efficient additive of necessary admixture sufficient amount.At present, domesticly at aspects such as severe cold area concreting in cold weather experiences, without documents and materials, can use for reference.For high performance concrete early strength, whether affect later strength and endurance quality, just, how final setting time to control, critical intensity reaches how much to be unlikely to be subject to freeze injury etc. be all the problem of needs solution.Therefore, construction of railway project is significant from now on to instructing for research severe cold area construction of high-performance concrete.
Summary of the invention
Technical problem to be solved by this invention is for above-mentioned deficiency of the prior art, the concrete construction technology of ultralow-temperature high-performance for the construction of railways of a kind of severe cold area is provided, it is reasonable in design, construction sequence is simple, easy to operate and construction speed is fast, construction cost is low, and the concrete structure quality of having been constructed is good.
For solving the problems of the technologies described above, the technical solution used in the present invention is: the concrete construction technology of ultralow-temperature high-performance for the construction of railways of a kind of severe cold area, is characterized in that this technique comprises the following steps:
Step 1, ultralow-temperature high-performance concrete mixing: cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water are carried out after even mix, and acquisition unit weight is 2350kg/m 3～2450kg/m 3ultralow-temperature high-performance concrete; The concrete maximum water-cement ratio of described ultralow-temperature high-performance and sand coarse aggregate ratio, all according to the design drawing requirement that needs construction concrete structure, and design by mix proportion method for designing according to construction of railways; Described ultralow-temperature high-performance concrete refers to that being applicable to environment temperature is the high performance concrete of constructing under 0 ℃～-40 ℃ conditions;
The ratio that described cementitious material is 88～78 ︰ 12～22 by cement and mineral admixture according to weight ratio evenly mixes;
The water-reducing rate of described high efficiency water reducing agent is not less than 25%, and the weight ratio of described high efficiency water reducing agent and described cementitious material is 0.5 ︰ 100～1 ︰ 100;
The weight ratio of described compound antifreezer and described cementitious material is 3 ︰ 100～6 ︰ 100; The composition of described compound antifreezer is by weight: nitrate 30%～35%, and organic compound 30%～33%, calcium formate 0.5%～1%, surplus is water; Described nitrate is calcium nitrate or calcium nitrite, and described organic compound is methyl alcohol or ethanol;
Step 2, ultralow-temperature high-performance pouring concrete: after needing the reinforcing cage colligation of construction concrete structure and prop up a mold process to complete, adopt the concrete casting process of ultralow-temperature high-performance described in concrete pumping equipment completing steps one, obtain the concrete structure of moulding by casting;
During actual cast, when ambient temperature is 0 ℃～-10 ℃, the concrete molding temperature of described ultralow-temperature high-performance is controlled at 5 ℃～10 ℃; When environment temperature is-10 ℃～-20 ℃, the concrete molding temperature of described ultralow-temperature high-performance is controlled at 10 ℃～15 ℃; And when ambient temperature is during lower than-20 ℃, the concrete molding temperature of described ultralow-temperature high-performance is not less than 15 ℃;
Step 3, ultralow-temperature high-performance concrete curing: the concrete structure of moulding by casting in step 2 is carried out to insulated curing.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, first adopt firing equipment that the water of ultralow-temperature high-performance the reinforcement of concrete described in mix is heated to 50 ℃～70 ℃; Afterwards, then by sand, rubble, water, mineral admixture, cement and Concrete admixtures, according to design proportioning by first to the rear evenly mix of throwing in respectively in mixing plant, just obtain the described ultralow-temperature high-performance concrete that mix forms;
Wherein, described Concrete admixtures comprises high efficiency water reducing agent and compound antifreezer.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, need first described compound antifreezer to be prepared, and described compound antifreezer is evenly mixed and forms according to design proportioning by nitrate, organic compound, calcium formate and water;
When described compound antifreezer is prepared, its preparation method is as follows:
Step 101, nitrate and calcium formate preheating: by described nitrate and calcium formate, be heated to respectively 40 ℃～70 ℃;
Step 102, be evenly mixed: by described nitrate and calcium formate after preheating in water and step 101, after mixing according to design proportioning, make described compound antifreezer.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: when sand, rubble, water, mineral admixture, cement and Concrete admixtures are thrown in step 1, the temperature of described sand, rubble, mineral admixture and cement is all not less than 0 ℃, and described high efficiency water reducing agent and compound antifreezer in described Concrete admixtures are liquid state.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: the concrete maximum water-cement ratio of ultralow-temperature high-performance described in step 1 be 0.4 and its sand coarse aggregate ratio be 32%～44%, simultaneously the concrete gel material content of described ultralow-temperature high-performance is not less than 360kg/m 3, unit consumption of water is not more than 165kg/m 3, described high efficiency water reducing agent is polycarboxylic acid series high efficiency water reducing agent.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: while cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, adopt concrete agitation station to carry out mix, the mixing plant rotating speed of described concrete agitation station is 23.5r/min ± 3r/min, and duration of mixing is no less than 120s.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, is characterized in that: the concrete water-cement ratio of described ultralow-temperature high-performance is 0.26～0.4; And in described ultralow-temperature high-performance concrete, the weight ratio of sand and cementitious material is 1.40～1.80.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: while described concrete structure being carried out to insulated curing in step 3, the insulated curing time is no less than 7 days, or described concrete structure insulated curing to its compressive strength need be reached design strength more than 50% till.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, it is characterized in that: in step 3, described concrete structure is carried out in insulated curing process, the temperature difference between described concrete structure inside and external surface is not more than 20 ℃, and the temperature difference between described concrete structure external surface and ambient temperature is not more than 15 ℃.
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of above-mentioned severe cold area, is characterized in that: while described concrete structure being carried out to insulated curing in step 3, when ambient temperature is 0～-10 ℃, adopt double-layer heat insulation method to carry out maintenance; When ambient temperature is-10 ℃～-20 ℃, adopt three layers of thermal-insulating method to carry out maintenance; When ambient temperature is during lower than-20 ℃, adopt auxiliary heating thermal-insulating method to carry out maintenance;
While adopting double-layer heat insulation method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, immediately at described concrete structure outside parcel one deck Polypropylence Sheet, on wrapped up Polypropylence Sheet, wrap up one deck tent cloth more afterwards or cotton pad is incubated;
While adopting three layers of thermal-insulating method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, immediately at described concrete structure outside parcel one deck Polypropylence Sheet, on wrapped up Polypropylence Sheet, wrap up one deck tent cloth more afterwards or cotton pad is incubated, and then wrap up one deck Polypropylence Sheet on wrapped up tent cloth or cotton pad;
Adopt auxiliary heating thermal-insulating method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, first in described concrete structure outside, set up a brooder, and in brooder, be provided with heater, simultaneously also need be at described concrete structure outside parcel one deck Polypropylence Sheet.
The present invention compared with prior art has the following advantages:
1, processing step simple, operate simple and easy and realize conveniently, input cost is lower.
2, the ultralow-temperature high-performance concrete performance adopting is good, no matter is concrete mechanical property and endurance quality after concrete workability and sclerosis, all can reach designing requirement.Simultaneously, this ultralow-temperature high-performance concrete can effectively be suitable for to concreting in cold-weather, and the concrete air content of ultralow-temperature high-performance need be controlled to 3.0%～5.0% during actual mix, the ultralow-temperature high-performance concrete of institute's mix can effectively be suitable for to the varying environment temperature such as 0 ℃～-40 ℃ in addition, and can effectively guarantee construction quality.
3, adopt ultralow-temperature high-performance mix proportion design process simple and optimize conveniently, only need the proportioning etc. of cement and mineral admixture in suitable water-cement ratio, sand coarse aggregate ratio, cementitious material just can be optimized ultralow-temperature high-performance mix proportion.Simultaneously, the present invention has provided the affect rule of each component on performances such as concrete 's air-containing, permeability, crushing resistance, frost resistances in ultralow-temperature high-performance concrete, thereby by the proportioning of respective components in easy adjustment ultralow-temperature high-performance concrete, just can meet different design requirements.
4, ultralow-temperature high-performance concrete mixing, cast and maintaining process are reasonable in design, and workable, and the concrete structure amount of having constructed is good.In concrete mixing process, according to different temperature conditions, to measures such as raw material insulation, heating, improve concrete mix temperature and molding temperature, take the measures such as covering curing, auxiliary heating, improved the maintenance quality of concrete structure, thereby the quality of the concrete structure that further guaranteed to have constructed technique.
5, each component proportion of the compound antifreezer adopting is reasonable in design, easy to prepare and result of use is good, and the nitrate adopting and nitrite are less on concrete durability impact, and can effectively improve concrete endurance quality.During actual use, according to design requirement, and in conjunction with function and the effectiveness of each component in compound antifreezer, and by suitably adjust the proportioning of each component in compound antifreezer, just can prepare the compound antifreezer that meets design requirement and possess diminishing, early strong, bleed and the effect such as antifreeze simultaneously.The alkali-free of this compound antifreezer own, without chlorine, it is in the situation that effectively improving early age strength of concrete, concrete later strength and endurance quality do not reduce, and can meet design requirement, and have overcome the unfavorable disadvantage of traditional antifreezing admixture to concrete durability.
6, there is significant social and economic benefits, for the severe cold area winter construction of railway concrete engineering from now on provides experience for reference, not only guaranteed construction speed, saved the energy, reduced cost, have good application value.
In sum, the present invention is reasonable in design, construction sequence is simple, easy to operate and construction speed is fast, construction cost is low, and the concrete structure quality of having been constructed is good.
Below by drawings and Examples, technical scheme of the present invention is described in further detail.
Accompanying drawing explanation
Fig. 1 is construction technology process block diagram of the present invention.
The specific embodiment
Embodiment 1
The concrete construction technology of ultralow-temperature high-performance for the construction of railways of a kind of severe cold area as shown in Figure 1, comprises the following steps:
Step 1, ultralow-temperature high-performance concrete mixing: cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water are carried out after even mix, and acquisition unit weight is 2350kg/m 3～2450kg/m 3ultralow-temperature high-performance concrete.The concrete maximum water-cement ratio of described ultralow-temperature high-performance and sand coarse aggregate ratio, all according to the design drawing requirement that needs construction concrete structure, and according to construction of railways, by mix proportion method for designing, design, it is conventional railway construction mix proportion method for designing well known to those skilled in the art.
The ratio that described cementitious material is 88～78 ︰ 12～22 by cement and mineral admixture according to weight ratio evenly mixes.During actual use, described mineral admixture is coal dust ash or ground slag powder.In the present embodiment, described mineral admixture is coal dust ash.
The water-reducing rate of described high efficiency water reducing agent is not less than 25%, and the weight ratio of described high efficiency water reducing agent and described cementitious material is 0.5 ︰ 100～1 ︰ 100.
The weight ratio of described compound antifreezer and described cementitious material is 3 ︰ 100～6 ︰ 100; The composition of described compound antifreezer is by weight: nitrate 30%～35%, and organic compound 30%～33%, calcium formate 0.5%～1%, surplus is water; Described nitrate is calcium nitrate or calcium nitrite, and described organic compound is methyl alcohol or ethanol.
In the present embodiment, when ultralow-temperature high-performance mix proportion is designed, the concrete minimum gel material content of ultralow-temperature high-performance and maximum unit water supply volume, all according to the design drawing requirement that needs construction concrete structure, and design by mix proportion method for designing according to construction of railways.
While designing by mix proportion method for designing according to construction of railways, according to (No. (2005) 157, iron construction) < < railway concrete durability design of structure temporary provisions > > and < < design of common concrete proportioning rules > > (JGJ55), design.
Wherein, water-cement ratio is the weight ratio of water and cementitious material.The consumption S/ of sand coarse aggregate ratio SP=sand (the consumption S+ rubble consumption G of sand) * 100%, and sand coarse aggregate ratio is mass ratio.Minimum gel material content is the minimum amount of cementitious material in ultralow-temperature high-performance concrete described in every side, and Qie Qi unit is kg/m 3.Unit consumption of water is the concrete water supply volume of ultralow-temperature high-performance described in every side, and Qie Qi unit is kg/m 3.
When reality designs ultralow-temperature high-performance mix proportion, learn after the concrete maximum water-cement ratio of ultralow-temperature high-performance, sand coarse aggregate ratio, minimum gel material content, unit consumption of water and unit weight, just can extrapolate the consumption of ultralow-temperature high-performance concrete medium sand and rubble.
During practice of construction, need the design drawing of construction concrete structure to require conventionally to include various intensity and life requirement, and cross section requirement, reinforcement placement and the cement type of each member, the particle diameter of sand are, the particle diameter of stone etc.In the present embodiment, needing construction concrete structure is cushion cap, pier shaft, abutment body, top cap, pallet, basis, culvert body, pile cover or raft plate, and construction environment temperature is 0 ℃～-40 ℃.
In practice of construction process, the concrete maximum water-cement ratio of ultralow-temperature high-performance be 0.4 and its sand coarse aggregate ratio be 32%～44%, simultaneously the concrete gel material content of described ultralow-temperature high-performance is not less than 360kg/m 3, unit consumption of water is not more than 165kg/m 3.
When specifically ultralow-temperature high-performance mix proportion is designed, the concrete water-cement ratio of ultralow-temperature high-performance is 0.26～0.4.And in described ultralow-temperature high-performance concrete, the weight ratio of sand and cementitious material is 1.40～1.80.
In the present embodiment, the concrete water-cement ratio of described ultralow-temperature high-performance is 0.35, and sand coarse aggregate ratio is 35%, and the weight ratio of sand and cementitious material is 1.5～1.6.The ratio that described cementitious material is 82 ︰ 18 by cement and flyash according to weight ratio evenly mixes.The weight ratio of described compound antifreezer and described cementitious material is 3 ︰ 100, and the weight ratio of described high efficiency water reducing agent and described cementitious material is 0.5 ︰ 100.During practice of construction, can according to specific needs, the weight ratio of weight ratio, described compound antifreezer and described cementitious material of weight ratio, sand and the cementitious material of cement and flyash in water-cement ratio, sand coarse aggregate ratio, described cementitious material and the weight ratio of described high efficiency water reducing agent and described cementitious material be adjusted accordingly.
In the present embodiment, in described compound antifreezer, nitrate used is calcium nitrate, and the composition of described compound antifreezer is by weight: nitrate 30%, and organic compound 33%, calcium formate 0.75%, surplus is water.Described nitrate is calcium nitrate, and described organic compound is methyl alcohol or ethanol.
In the present embodiment, before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, need first described compound antifreezer to be prepared, and described compound antifreezer is evenly mixed and forms according to design proportioning by nitrate, organic compound, calcium formate and water.
When described compound antifreezer is prepared, its preparation method is as follows:
Step 101, nitrate and calcium formate preheating: by described nitrate and calcium formate, be heated to respectively 40 ℃～70 ℃.
In the present embodiment, while nitrate and calcium formate being carried out to preheating in step 101, described nitrate and calcium formate are heated to respectively to 50 ℃.During actual preparation, can according to specific needs, the preheat temperature of described nitrate and calcium formate be adjusted accordingly.
Step 102, be evenly mixed: by described nitrate and calcium formate after preheating in water and step 101, after mixing according to design proportioning, make described compound antifreezer.
In the present embodiment, when water is mixed with described nitrate after preheating in step 101 and calcium formate, adopt circulation compound reactor to mix.
Described circulation compound reactor comprises normal-pressure reaction kettle and is arranged on the liquid circulation line on described normal-pressure reaction kettle, on described liquid circulation line, circulation pump is housed, and described circulation compound reactor evenly mixes to the mode that pumps into circulating fluid in described normal-pressure reaction kettle with described circulation pump.During actual use, also can adopt other mixing apparatus evenly to mix.During actual preparation, also can adopt the material mixing equipment of other type to mix.
In the present embodiment, the internal capacity of described normal-pressure reaction kettle is 10 tons, and the pump output of described circulation pump is 60 tons/hour, and the power of motor of described circulation pump is 5.5 kilowatts, and incorporation time is no less than half an hour.
Before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, first adopt firing equipment that the water of ultralow-temperature high-performance the reinforcement of concrete described in mix is heated to 50 ℃～70 ℃; Afterwards, then by sand, rubble, water, flyash, cement and Concrete admixtures, according to design proportioning by first to the rear evenly mix of throwing in respectively in mixing plant, just obtain the ultralow-temperature high-performance concrete that mix forms; Wherein said Concrete admixtures comprises high efficiency water reducing agent and compound antifreezer.
In the present embodiment, before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water are carried out to even mix, first adopt firing equipment that the water of ultralow-temperature high-performance the reinforcement of concrete described in mix is heated to 60 ℃.During actual preparation, can to the heating-up temperature of ultralow-temperature high-performance concrete water described in mix, adjust accordingly according to specific needs.
In the present embodiment, during mix, the release sequence of each component is different from normal temperature concrete, need according to by first to after order sand, rubble, water, flyash, cement and Concrete admixtures are thrown in successively, be mainly because the higher water of heating-up temperature can be directly contact and produce false set (cement contacts meeting generation false set with more than 60 ℃ hot water) with cement moment.Thereby, after sand, rubble, water and flyash are thrown in, then throw in cement, mixing time should increase 30s than normal temperature concrete, but should be lower than 120s.
In the present embodiment, when sand, rubble, water, flyash, cement and Concrete admixtures are thrown in, the temperature of described sand, rubble, flyash and cement is all not less than 0 ℃, and described high efficiency water reducing agent and compound antifreezer in described Concrete admixtures are liquid state.
That is to say, when sand, rubble, water, flyash, cement and Concrete admixtures are thrown in, should guarantee in described high efficiency water reducing agent and compound antifreezer all without solid-state caking.
In the present embodiment, high efficiency water reducing agent and compound antifreezer should be stored in the storage tank of heat insulating material parcel or covering, guarantee not freeze, and generally should not heat in liquid high efficiency water reducing agent and compound antifreezer.
In actual fabrication process, before sand, rubble, water, flyash, cement and Concrete admixtures are thrown in, when the temperature of described sand, rubble, flyash or cement is during lower than 0 ℃, to temperature, described sand, rubble, flyash or the cement lower than 0 ℃ heats respectively also to need to adopt firing equipment, and temperature after heating is no more than 30 ℃.
While there is caking in described high efficiency water reducing agent or compound antifreezer, also need to adopt firing equipment to existing described high efficiency water reducing agent or the compound antifreezer of caking to heat, until without caking.
In the present embodiment, the cementitious material being comprised of cement and flyash is stored in the outside holding vessel wrapping up with two-layer cotton pad, and two-layer cotton pad therebetween electric blanket, and the temperature of cementitious material is controlled to 0～10 ℃ of left and right, the highest should not be over 40 ℃.
Described fine sand and rubble the previous day must charging canopies in construction, adopt caliduct geothermal heating method, and before mix, the temperature of fine sand and rubble must reach positive temperature, must not have the piece of freezing.
In the present embodiment, in step 1, sand, rubble, water, flyash, cement and Concrete admixtures are carried out in even mix process, the mixeding liquid temperature after sand, rubble and water mix is no more than 40 ℃.
In addition, actual being prepared in process, when described high efficiency water reducing agent and compound antifreezer are thrown in, one first throws in or described high efficiency water reducing agent and compound antifreezer is thrown in simultaneously after one; And while throwing in after one first one, described high efficiency water reducing agent throws in prior to described compound antifreezer or described compound antifreezer is thrown in and all can prior to described high efficiency water reducing agent.
In the present embodiment, when cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water are carried out to even mix, adopt concrete agitation station to carry out mix, and the described mixing plant mixer that is described concrete agitation station.
When reality is carried out even mix to cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water, the rotating speed of described mixing plant is 23.5r/min ± 3r/min, and duration of mixing is no less than 120s.In the present embodiment, the model of described concrete agitation station is HZS120G, and manufacturer is 31 heavy industrys, and the model of described mixing plant is JS2000 type, motor power (output) is 37 kilowatts, and mixing speed is 120 cubes ms/h, and mixer rotating speed is 23.5r/min.
During actual preparation, described high efficiency water reducing agent is polycarboxylic acid series high efficiency water reducing agent.In the present embodiment, described polycarboxylic acid series high efficiency water reducing agent is standard type polycarboxylic acid series high efficiency water reducing agent, is specially the polycarboxylic acid series high efficiency water reducing agent that Sichuan superstar's Admixture Co., Ltd produces.
In the present embodiment, while preparing described ultralow-temperature high-performance concrete, rubble used is that particle diameter (being specially nominal particle diameter) is the graded broken stone of 5mm～31.5mm.Described sand is that the fineness modulus of river sand and described river sand is 2.6～2.9, and the mud content of described rubble is less than 0.5wt%, and the mud content of described river sand is 1.0wt%～1.5wt%.
In actual fabrication process, in test room to after preparing the concrete air content of the ultralow-temperature high-performance that obtains, compressive strength, permeability, frost resistance etc. test.
While specifically testing, in test room and under room temperature, according to the blending method described in step 1, ultralow-temperature high-performance concrete is carried out to mix, adopt the mono-horizontal shaft forced type concrete mixer of HJW60 to carry out mix herein, and mix complete the measurement of the slump, air content and the moulding of ultralow-temperature high-performance concrete sample to be measured in 5min after completing.After ultralow-temperature high-performance concrete sample to be measured moulding, first in room temperature environment, after standing precuring 4h～5h, be encased in the large-scale refrigerator-freezer that is cooled in advance design temperature and carry out maintenance, curing temperature maintains-14 ℃～-16 ℃, and rate of temperature fall is 3 ℃/h; After negative temperature conservation 7d, from refrigerator-freezer, take out at room temperature form removal after standing 4h～5h, proceed to standard curing room (20 ℃ ± 2 ℃) maintenance to be measured after 28d or 56d.
(1) ultralow-temperature high-performance concrete 's air-containing test:
The assay method adopting is according to GB/T50080-2002 < < Standard for test methods of properties of ordinary concrete mixture standard > > prescriptive procedure, and adopt direct-reading mixing wastewater with air gas content to measure, show that after measured in the present embodiment, the concrete air content of prepared ultralow-temperature high-performance is 3.5%.
Simultaneously, in test room, also need the calcium formate consumption in ultralow-temperature high-performance concrete compound antifreezer used to adjust within the scope of 0～1.0wt%, and adopt direct-reading mixing wastewater with air gas content to test the concrete air content of prepared ultralow-temperature high-performance under different calcium formate consumptions, test draws: because polycarboxylate high performance water-reducing agent contains certain bleed composition, make the air content of normal concrete very high, and calcium formate consumption is during lower than 0.75wt%, the concrete air content minimum of prepared ultralow-temperature high-performance is 1.5% and maximum value only 2.4%, this explanation has reduced the concrete air content of prepared ultralow-temperature high-performance adding of calcium nitrate, and adding of calcium formate increases the concrete air content of ultralow-temperature high-performance, and when the calcium formate consumption in compound antifreezer is 1wt%, the concrete air content of ultralow-temperature high-performance increases to 3.8%, has surpassed the air content 3.0% of normal concrete.
In addition, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and adopt direct-reading mixing wastewater with air gas content to measure, test draws, increase with flyash consumption in cementitious material, the concrete air content of prepared ultralow-temperature high-performance constantly reduces, this explanation, and flyash has the suction-operated compared with intensity to the bubble in prepared ultralow-temperature high-performance concrete.
Thereby in actual fabrication process, can prepare the concrete air content requirement of ultralow-temperature high-performance according to need, and in conjunction with calcium formate consumption in above-mentioned compound antifreezer on ultralow-temperature high-performance concrete (inner containing calcium nitrate) air content affect result and the suction-operated of flyash to bubble in ultralow-temperature high-performance concrete, calcium formate consumption in compound antifreezer is adjusted accordingly in 0.5%～1.0% scope; , flyash consumption in cementitious material is adjusted meanwhile, specifically the weight ratio of cement in cementitious material and flyash is adjusted accordingly in 88～78 ︰ 12～22 scopes.
(2) ultralow-temperature high-performance concrete tensile strength test:
When test room tests the concrete compressive strength of ultralow-temperature high-performance, according to GB/T50081-2002 < < standard for test methods of mechanical properties of ordinary concrete > >, the ultralow-temperature high-performance concrete sample (100mm * 100mm * 100mm) of made is tested, test adopts YES-2000 type digital display hydraulic pressure testing machine, and maximum load capacity is 2000KN.In the present embodiment, when test draws " after negative temperature conservation 7d more positive temperature maintenance 28d ", the compressive strength of prepared ultralow-temperature high-performance concrete sample is 40MPa, and it is 80% that mark is supported compressive strength rate, and benchmark compressive strength rate is 63%; When " after negative temperature conservation 7d more positive temperature maintenance 56d ", the compressive strength of prepared ultralow-temperature high-performance concrete sample is 50MPa, and it is 92% that mark is supported compressive strength rate, and benchmark compressive strength rate surpasses 100%.
Wherein, benchmark compressive strength rate is the compressive strength of ultralow-temperature high-performance concrete sample that draws of experimental test and the ratio of the compressive strength of normal concrete, it is the compressive strength of ultralow-temperature high-performance concrete sample and the ratio of the concrete compressive strength of standard curing that experimental test draws that mark is supported compressive strength rate, and the concrete compressive strength of standard curing is herein for to carry out the compressive strength after standard curing to preparing ultralow-temperature high-performance concrete sample ultralow-temperature high-performance concrete used.
Simultaneously, also need the calcium formate consumption of preparing in ultralow-temperature high-performance concrete sample compound antifreezer used to adjust within the scope of 0～1.0wt%, and adopt YES-2000 type digital display hydraulic pressure testing machine, to made ultralow-temperature high-performance concrete sample at " negative temperature conservation 7d ", the compressive strength in the difference such as " after negative temperature conservation 7d more positive temperature maintenance 28d " and " after negative temperature conservation 7d more positive temperature maintenance 56d " length of time is tested, draw after tested: " negative temperature conservation 7d " (wherein, d is day) and the compressive strength of made ultralow-temperature high-performance concrete sample when " after negative temperature conservation 7d more positive temperature maintenance 28d ", increase along with calcium formate consumption in compound antifreezer used, in fluctuation, slightly rising up and down.And support compressive strength rate for benchmark compressive strength rate and the mark in " negative temperature conservation 7d " and " after negative temperature conservation 7d more positive temperature maintenance 28d " these two length of times, while not mixing calcium formate in compound antifreezer used, the foster compressive strength rate of the benchmark compressive strength rate of made ultralow-temperature high-performance concrete sample and mark is all minimum, wherein the benchmark compressive strength rate of ultralow-temperature high-performance concrete sample and mark are supported compressive strength and are no more than 8% when " negative temperature conservation 7d ", when " after negative temperature conservation 7d more positive temperature maintenance 28d ", the benchmark compressive strength rate of ultralow-temperature high-performance concrete sample and mark are supported compressive strength and are no more than 80%, but the compressive strength of ultralow-temperature high-performance concrete sample when " after negative temperature conservation 7d more positive temperature maintenance 56d ", increase with calcium formate consumption in compound antifreezer used, in fluctuation, slightly declining up and down, and the foster compressive strength rate of the benchmark compressive strength rate of the described ultralow-temperature high-performance concrete sample of this section in length of time and mark is minimum when in compound antifreezer used, calcium formate consumption is 1.0wt%, its mark is supported compressive strength rate and is only had 87.85%.Make a general survey of the development and change of whole age concrete intensity, can obviously find out: when calcium formate consumption is 0.25wt% in compound antifreezer used, the concrete mechanical property of prepared ultralow-temperature high-performance is best; When in compound antifreezer used, calcium formate consumption is 0.75wt%, the concrete mechanical property of prepared ultralow-temperature high-performance is taken second place; And it is all lower in compound antifreezer used, not mix the concrete crushing strength that calcium formate and calcium formate consumption are 1wt%.
Test result by above-mentioned ultralow-temperature high-performance concrete crushing strength also can be found out, adds after calcium nitrate in concrete, and in energy accelerate concrete, the aquation of cementitious material, increases the concrete tensile strength of prepared ultralow-temperature high-performance.Wherein, calcium nitrate is good freezing protection effect not only, and non-toxic, can improve concrete hole gap structure, improves concrete density.Compare with calcium nitrite, the concrete workability of ultralow-temperature high-performance of adding calcium nitrate is more excellent, but it is less to add at low temperatures the concrete slump-loss of ultralow-temperature high-performance of calcium nitrate, can be used for pumping construction technique.But at low temperatures, the concrete strength increase of ultralow-temperature high-performance that adds calcium nitrate is slower, and the volume while effectively reducing freezing point is larger, and later strength loss is also larger.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and adopt YES-2000 type digital display hydraulic pressure testing machine, and according to GB/T50081-2002 < < standard for test methods of mechanical properties of ordinary concrete > >, the tensile strength of made ultralow-temperature high-performance concrete sample is tested, test draws: when in cementitious material used, flyash consumption is 15%, the concrete compressive strength of prepared ultralow-temperature high-performance is the highest, when in cementitious material used, flyash consumption is 20%, the concrete compressive strength of prepared ultralow-temperature high-performance is taken second place, and flyash consumption is 26.5wt% in cementitious material used.Thereby flyash consumption should be controlled at 15%～20% in cementitious material used.
Thereby, in actual fabrication process, can prepare the concrete tensile strength requirement of ultralow-temperature high-performance according to need, and the impact on prepared ultralow-temperature high-performance concrete (inner containing calcium nitrate) tensile strength in conjunction with flyash consumption in calcium formate consumption in above-mentioned compound antifreezer and cementitious material used, calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope, and the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
In addition, for the flyash in cementitious material used, because it is active in clinker, particularly at the maintenance initial stage, there is hardly pozzolanic reaction, therefore in cementitious material used, flyash consumption is larger, can reduce concrete early strength undoubtedly, and this effect is very serious threat for negative temperature concrete.Thereby fly ash content should not surpass 20% in cementitious material used.
(3) ultralow-temperature high-performance concrete permeability test:
When test room tests with the concrete permeability of ultralow-temperature high-performance, adopt direct current measurement method to test.While adopting concrete electric weight method fast detecting permeability, the water saturation circular sample cylinder test specimen of diameter 100mm, a high 50mm is placed on to two ends to be equipped with in the container of liquid, it is 3% NaCl solution that mass concentration is filled in container one end, and the other end is filled the NaOH solution that concentration is 0.3mol/L.In container, add 60V direct current, negative pole is connected with NaCl solution simultaneously, and positive pole is connected with NaOH solution.Wherein, in NaCl solution, electronegative chlorion will be to positive pole migration from sample, and corresponding current potential just increases.Tested concrete permeability is larger, and the chlorion of infiltration is just more, so electric current is just larger.
During actual test, adopt NEL-PEU type concrete charge pass analyzer to test the concrete permeability of ultralow-temperature high-performance, its test process is as follows: first the side of ready ultralow-temperature high-performance concrete sample (100mm * 100mm * 50mm) is adopted after paraffin sealing, adopt again the water pretreatment of satisfying of the full wetting system of NEL-NVJ concrete intelligent vacuum, then test specimen is arranged on the special-purpose fixture with red and black electrodes, in the red jack one side battery case of battery clamp, inject the NaOH solution of 0.3mol/L, the NaCl solution that in black jack one side battery case, implantation quality concentration is 3.0%, after solution injects, with wire exact connect ion on the corresponding position of analyzer, open instrument, setting-up time, open channel, the every 15min of analyzer gathers a secondary data, tested and needed altogether 6h.
In the present embodiment, described in when test draws " after negative temperature conservation 7d more positive temperature maintenance 28d ", the concrete electric flux value of ultralow-temperature high-performance is 1280C, when " after negative temperature conservation 7d more positive temperature maintenance 56d " described in the concrete electric flux value of ultralow-temperature high-performance be 730C.
And, also need the calcium formate consumption of preparing in ultralow-temperature high-performance concrete sample compound antifreezer used to adjust within the scope of 0～1.0wt%, and adopt NEL-PEU type concrete charge pass analyzer to test the concrete permeability of ultralow-temperature high-performance, according to test result, draw: along with calcium formate consumption in compound antifreezer used constantly increases within the scope of 0～1.0wt%, the concrete permeability of prepared ultralow-temperature high-performance first reduces then to increase, when wherein in compound antifreezer used, calcium formate consumption is 0.75wt%, the concrete permeability of prepared ultralow-temperature high-performance reaches minimum, especially when " after negative temperature conservation 7d more positive temperature maintenance 56d ", the concrete electric flux value of prepared ultralow-temperature high-performance is 730C, and its electric flux increment is negative value, now the concrete permeability of prepared ultralow-temperature high-performance lower than normal concrete.In addition, the electric flux of electric flux when test draws " after negative temperature conservation 7d more positive temperature maintenance 56d " during than " after negative temperature conservation 7d more positive temperature maintenance 28d " obviously reduces a lot, and this is that the secondary reaction of hydration product of later stage flyash is filled due to space.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and adopt NEL-PEU type concrete charge pass analyzer to test the tensile strength of made ultralow-temperature high-performance concrete sample, test draws: with the increase of flyash consumption in cementitious material used, the permeability of prepared ultralow-temperature high-performance concrete when " after negative temperature conservation 7d more positive temperature maintenance 28d " all increases gradually.According to the viewpoint of Berry Malhotra, at the aquation initial stage, as the flyash of cementitious material, can reduce the bonding between aggregate and cement paste, the moisture film of fly ash grain adsorption will make the transition region porous more that becomes, therefore under negative temperature conservation condition, flyash in cementitious material used has negative effect to concrete permeability, and this effect is serious all the more along with the increase of flyash consumption.Therefore, for the higher negative temperature concrete structure of life requirement, mixing of flyash should be prudent, mixes less or fly ash not, to guarantee the life-span of engineering as far as possible.
Thereby, in actual fabrication process, can prepare the concrete permeability requirement of ultralow-temperature high-performance according to need, and in conjunction with flyash consumption in calcium formate consumption in above-mentioned compound antifreezer and cementitious material used on the infiltrative impact of prepared ultralow-temperature high-performance concrete (inner containing calcium nitrate), calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope, and the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
(4) ultralow-temperature high-performance concrete frost resistance test:
According to the quick-freeze method of GB/T50082-2009 < < Standard for test methods of longterm performance and durability of ordinary concrete standard > >, carry out frost resistance test.Quick-freeze Fa Yi U.S. ASTM C666 (A) method is basis, and the freezing and melt all of ultralow-temperature high-performance concrete sample carried out in water.Concrete prism test specimen is carried out to water and freeze aqueous fusion, whole process need complete in 2h～4h.Using concrete dynamic modulus of elasticity, mass loss rate and relative durability factor as evaluation index, the mass loss rate of usining reach 5% or relative dynamic elastic modulus drop to 60% threshold as concrete through freeze-thaw test, and regulation using relative dynamic elastic modulus drop to 60% or the freezing-thawing cycles of mass loss while reaching 5% as concrete freeze proof label, with this, evaluate concrete frost resistance.
Adopting TDR-1 concrete fast freeze-thaw test equipment to carry out fast freeze-thaw test to concrete prism test specimen (100mm * 100mm * 400mm), is-17 ℃～8 ℃ from freezing to its center range of temperature of thawing end of a period, and whole Circulation calendar is through 3h～4h.One-shot measurement is made in every 25 freeze thawing circulation, until that the loss of concrete dynamic modulus of elasticity is down to is original 60% below or when mass loss reaches 5%, and test termination.Dynamic modulus of elasticity and relative dynamic elastic modulus adopt NM-4B nonmetal ultrasonic detection analyzer to test post analysis and draw.In the present embodiment, after 225 freeze thawing circulation, the mass loss rate of ultralow-temperature high-performance concrete sample is 3.5%, and relative dynamic elastic modulus drops to 57%, and test specimen can stand the freeze thawing circulation destruction of 200 times～225 times.
And, also need the calcium formate consumption of preparing in ultralow-temperature high-performance concrete sample compound antifreezer used to adjust within the scope of 0～1.0wt%, and adopt above-mentioned antifreezing test method to test the frost resistance of prepared ultralow-temperature high-performance concrete sample, test result is as follows: for the ultralow-temperature high-performance concrete that is added with calcium nitrate for inside, no matter in compound antifreezer used, calcium formate consumption is arbitrary value within the scope of 0～1.0wt%, when test specimen reaches destruction, its mass loss does not all surpass 5%, and relative dynamic elastic modulus drops to below 60%, that is to say that ultralow-temperature high-performance concrete that inside is added with calcium nitrate is in standing freeze thawing circulation destructive process, it is even more serious that inner spalling damages outside spalling damage.Similar to permeability, do not mix the ultralow-temperature high-performance concrete that inside that calcium formate and calcium formate consumption are 1wt% is added with calcium nitrate, in freeze thawing cyclic process mass loss maximum, frost resistance is also the poorest.From the situation of peeling off on surface, mixing calcium formate has certain inhibitory action to the freezing-thawing damage of concrete surface, but along with the increase of calcium formate consumption, this inhibitory action weakens gradually; From inner degree of impairment, except not mixing the ultralow-temperature high-performance concrete of calcium formate, other curves are more level and smooth, do not occur the phenomenon of bursting apart, and inside concrete evenly destroys.
Because concrete freeze-thaw damage comes from the inner bulbs of pressure that produce, should analyze that to cause the expansion force of ultralow-temperature high-performance concrete destruction be that diffusion due to water has caused the relatively volume growth of the ice of smallest number, the diffusion of water is to produce due to osmotic pressure, and osmotic pressure is owing to not freezing due to water intermediate ion concentration increases.
In addition, the oneself factor that affects ultralow-temperature high-performance concrete frost resistance quality is mainly concrete compactness and internal pore structure.And pore structure is the main cause that affects this concrete frost resistance, the a small amount of calcium formate of admixture is not enough to guarantee that pore structure when ultralow-temperature high-performance concrete hardens under subzero temperature suffers freezing and destroys, and the excessive calcium formate of admixture increases intercommunicating pore in the rear concrete of its sclerosis, two kinds of effects interlaced, makes concrete pore structure complicated and changeable.Thereby reply calcium formate consumption accurately limits.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and tackle mutually the concrete frost resistance of prepared ultralow-temperature high-performance and test, test draws: flyash has a great impact the frost resistance of negative temperature concrete, with the increase of flyash consumption in cementitious material, the concrete frost resistance of prepared ultralow-temperature high-performance obviously reduces.Wherein, in cementitious material, flyash consumption is 10%, and it is best that inside is added with the concrete frost resistance of ultralow-temperature high-performance of calcium nitrate, after 300 freeze thawing circulation its relatively with modulus of elasticity still higher than 60%, but its mass loss is also maximum, after 300 freeze thawing circulation, approach 5%.
Flyash to the unfavorable factor of negative temperature concrete mainly from two aspects: first, the introducing of flyash can affect concrete bubble structure, in Concrete process, thinner fly ash grain usually can adsorb air entraining agent molecule (containing bleed composition in polycarboxylate water-reducer), the in the situation that of identical bleed composition volume, will make the concrete air bubble content of ultralow-temperature high-performance reduce; Secondly, the activity of flyash is far away from cement, extremely slow at maintenance initial stage hydration reaction, especially under negative temperature conservation, flyash equivalent replaces cement, not only can postpone concrete and reach freeze proof critical intensity, and make to contain more and can freeze the water yield in concrete, make inside concrete produce larger ice crystal stress, destroy concrete structure.Although to the maintenance later stage, the secondary hydration product of flyash has some improvement to the pore structure of inside concrete, the moulding of concrete internal construction, it improves DeGrain.
Thereby, in actual fabrication process, can prepare the concrete frost resistance requirement of ultralow-temperature high-performance according to need, and the impact on prepared ultralow-temperature high-performance concrete (inner containing calcium nitrate) frost resistance in conjunction with flyash consumption in calcium formate consumption in above-mentioned compound antifreezer and cementitious material used, calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope, and the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
In sum, for inside, be added with the ultralow-temperature high-performance concrete of calcium nitrate, the calcium nitrate adding can reduce concrete air content, and being added in of calcium formate increased the concrete air content of ultralow-temperature high-performance to a certain extent, but the increase along with calcium formate consumption, its air content slightly reduces, and when calcium formate consumption is 1wt%, air content increases to 3.8%; With the increase of calcium formate consumption, the concrete compressive strength of ultralow-temperature high-performance fluctuates to some extent, but calcium formate consumption is while being 0.75wt%, and concrete mechanical property is comparatively desirable; With the increase of calcium formate consumption, after first reducing, the concrete permeability of ultralow-temperature high-performance raises again; In standing freeze thawing circulation destructive process, it is even more serious that the spalling of test specimen inside damages outside spalling damage, and in freeze thawing cyclic process, be inner evenly destruction.
For inside, be added with the ultralow-temperature high-performance concrete of calcium nitrate, along with the increase of flyash consumption in cementitious material, the concrete air content of ultralow-temperature high-performance obviously reduces; In cementitious material, flyash consumption is 20% when following, and the concrete early strength function of ultralow-temperature high-performance is more remarkable; Under negative temperature conservation condition, flyash has adverse effect to the concrete permeability of ultralow-temperature high-performance, and influence degree increases along with the increase of flyash consumption.Compound antifreezer that the present invention adopts has not only been avoided the detrimental effect of part inorganic salts to concrete frost resistance, and by adjusting its inner each amounts of components, to the concrete frost resistance of ultralow-temperature high-performance, also can increase.
When reality is prepared ultralow-temperature high-performance concrete, the cement adopting is 42.5 grades low alkali Portland cements, alkali content 0.59%, and chloride ion content 0.003%, other technical indicator meets the regulation of [2009] No. 152 files of iron construction.The water demand ratio of the flyash adopting is not more than 95%, alkali content 2.10%, and chloride ion content 0.003%, all the other technical indicators meet the regulation of [2009] No. 152 files of iron construction.The river sand adopting is the river sand of 5 constant virtues La Linhe, fineness modulus 2.6～2.9, and mud content 1.0%～1.5%, chloride ion content 0.0001%, active without potential alkali reaction, all the other technical indicators meet [2009] No. 152 files specify of iron construction.The rubble adopting is that limestone gravel is produced in Yuquan, parent rock compressive strength is 96MPa, particle diameter is 5～31.5mm, pin, sheet-like particle content are 5%～7%, mud content is below 0.5%, chloride ion content 0.0001%, without potential alkali active reaction aggregate, all the other technical indicators all meet the regulation requirement of [2009] No. 152 files of iron construction.The high efficiency water reducing agent adopting is standard type polycarboxylic acid series high efficiency water reducing agent, alkali content 2.64%, and sodium sulphate 1.5%, chloride ion content 0.12%, all the other technical indicators meet [2009] No. 152 files specify of iron construction.The water adopting is mixing water, alkali content 0.04677%, sodium sulphate 1.5%, chloride ion content 0.00293%.In actual fabrication process, also can adopt the cement of other label and the river sand in other place of production, rubble.
When reality designs described ultralow-temperature high-performance mix proportion, according to code requirement, need improve a strength grade, for high performance concrete, as long as measures is guaranteed, do not need to improve intensity intensity level, still can guarantee the sclerosis quality of high performance for concrete structure.Determine after optimum mix proportion, effectively control concrete coagulating time, guarantee that concrete can reach the more than 40% of design strength (critical intensity before requirement is endured cold) in 48h, 56d mechanical performance of concrete and endurance quality reach designing requirement.
Railway high performance concrete design concept is high-durability energy, the realization of high-durability energy need to be mixed high efficiency water reducing agent and flyash, the major function of flyash in concrete is to improve the interfacial structure of cement slurry and aggregate, replace a certain amount of cement, make the speed that produces the heat of hydration delay, extend concrete time of setting, participate in the pore of aquation fill concrete, improve impervious, reduce folk prescription concrete harmful substance contents, can effectively suppress alkali-aggregate reaction, but early age strength of concrete is on the low side to some extent.
Frost-resistant concrete is general only need to consider that early strength reaches certain value, but early strength concrete is larger on later strength impact, ordinary concrete need to improve a strength grade and just can meet design requirement, high-performance frost-resistant concrete not only requires early strength high, and the growth of later strength can not be subject to large impact, otherwise cannot meet life requirement.Flyash plays retarding action to concrete early hydration, this requires high frost-resistant concrete to early strength is contradiction, and flyash is one of high performance concrete quality principal security condition, in order to meet antifreeze high performance concrete early strength, increase requirement, make it not be subject to low temperature freezing-disaster under certain condition, and later strength growth is not subject to large impact, and indices must reach high performance concrete quality requirement.
Through test, find, the consumption of compound antifreezer, not only directly affects concrete time of setting, also concrete mechanical property and endurance quality is produced to significant impact.As can be seen from the test results, the consumption of compound antifreezer should be controlled at 3%～4% (with the percentage by weight of cementitious material) and be advisable, the impact of the main critical-temperature of considering to endure cold, determining of critical intensity will be determined according to environment temperature, generally, in the time of-15 ℃, require critical intensity to reach 40% of design strength and just can meet the critical intensity requirement of enduring cold, and the critical intensity of-20 ℃ should be brought up to more than 50% and is advisable, can improve the quality guarantee rate of concrete structure like this, reduce the risk of enduring cold.But early strength is too high, larger on concrete later strength impact, on the impact of durability also clearly, therefore, compound antifreezer consumption should be controlled in a comparatively rational scope.
Mixing flyash master is in order to reduce the heat of hydration, delay concrete time of setting, improve workability of concrete, reduce concrete shrinkage, to improve concrete anti-permeability performance etc.But it is very fast that the concrete of winter construction needs early strength to increase, and the initial setting time must be done sth. in advance by a relatively large margin, and this need to mix compound antifreezer and realize, and this contradicts with fly ash.If fly ash not, concrete can not meet high performance requirement, its main cause is: the one, and folk prescription higher alkali content surpasses required standard, and the 2nd, to mix merely early-strength antifreezing admixture late strength of concrete and had a strong impact on, endurance quality can not meet the demands.Therefore, in order to reach should early strength high, can not produce significant impact to later strength again, but also must meet the intrinsic technical requirements of high performance concrete, must regulate the concrete property indices of ultralow-temperature high-performance with flyash.
When described ultralow-temperature high-performance concrete transports after having prepared, the concrete delivery truck outside that transport point is used must be incubated with heat insulating material parcel, and guarantee the coast is clear in transportation, transportation and the dead time arriving behind cast place should not surpass 60min, prevent that heat waste is excessive, environment temperature is during lower than-30 ℃, described ultralow-temperature high-performance is concrete go out tank temperature should be lower than 20 ℃.
Step 2, ultralow-temperature high-performance pouring concrete: after needing the reinforcing cage colligation of construction concrete structure and prop up a mold process to complete, adopt the concrete casting process of ultralow-temperature high-performance described in concrete pumping equipment completing steps one, obtain the concrete structure of moulding by casting.
Actual while carrying out reinforcing cage colligation and formwork, according to reinforcing cage colligation and the mold method of conventional reinforced concrete structure, construct.
During actual cast, when ambient temperature is 0 ℃～-10 ℃, the concrete molding temperature of described ultralow-temperature high-performance is controlled at 5 ℃～10 ℃; When environment temperature is-10 ℃～-20 ℃, the concrete molding temperature of described ultralow-temperature high-performance is controlled at 10 ℃～15 ℃; And when ambient temperature is during lower than-20 ℃, the concrete molding temperature of described ultralow-temperature high-performance is not less than 15 ℃.
In the present embodiment, before described ultralow-temperature high-performance pouring concrete, should be according to the supporting situation of environment temperature, wind-force, wind direction and plant equipment, the cast personnel of rationalization, shorten the duration of pouring as far as possible, in order to avoid excessive cast (the entering mould) temperature requirement that can not meet of temperature loss.
When described ultralow-temperature high-performance concrete transports building site to, filling car is run up after 5s～10s and carries out workability detection, meet the demands, pour into immediately, if because of certain reason, concrete slump loss is excessive, in the time of can not meeting instillation process requirement, the volume that preprepared high efficiency water reducing agent and compound antifreezer should be provided by test room carries out secondary interpolation, 10s～the 30s that concrete tank should be run up after secondary adds, confirms that concrete mixing evenly and after reaching instillation process requirement can pour into.
Step 3, ultralow-temperature high-performance concrete curing: the concrete structure of moulding by casting in step 2 is carried out to insulated curing.
In the present embodiment, when described concrete structure is carried out to insulated curing, the insulated curing time is no less than 7 days, or described concrete structure insulated curing to its compressive strength need be reached design strength more than 50% till.
When the ultralow-temperature high-performance concrete of immersion under Freezing-Melting Condition starts to endure cold, described concrete structure insulated curing to its compressive strength need be not less than design strength 80% till.
In the present embodiment, reality is carried out in insulated curing process described concrete structure, and the temperature difference between described concrete structure inside and external surface is not more than 20 ℃, and the temperature difference between described concrete structure external surface and ambient temperature is not more than 15 ℃.
In practice of construction process, after described ultralow-temperature high-performance pouring concrete, covering and heat insulating immediately, answers cast limit, limit to cover for concrete in mass (as roadbed raft plate etc.), prevents from suffering freeze injury at lower temperature condition soffit.
In the present embodiment, while described concrete structure being carried out to insulated curing in step 3, when ambient temperature is 0～-10 ℃, adopt double-layer heat insulation method to carry out maintenance; When ambient temperature is-10 ℃～-20 ℃, adopt three layers of thermal-insulating method to carry out maintenance; When ambient temperature is during lower than-20 ℃, adopt auxiliary heating thermal-insulating method to carry out maintenance.
While adopting double-layer heat insulation method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, immediately at described concrete structure outside parcel one deck Polypropylence Sheet, on wrapped up Polypropylence Sheet, wrap up one deck tent cloth more afterwards or cotton pad is incubated.
In the present embodiment, actual while carrying out maintenance, first with Polypropylence Sheet by described concrete structure surface coverage or wrap up tightly, then cover or parcel with tent cloth or cotton pad, afterwards with weight by surrounding with to have joint to press tight.Wherein, every layer of necessary parcel is tight, must not have cold air to permeate into, otherwise not reach natural thermal insulation effect.
While adopting three layers of thermal-insulating method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, immediately at described concrete structure outside parcel one deck Polypropylence Sheet, on wrapped up Polypropylence Sheet, wrap up one deck tent cloth more afterwards or cotton pad is incubated, and then wrap up one deck Polypropylence Sheet on wrapped up tent cloth or cotton pad.
In the present embodiment, actual while carrying out maintenance, first floor with Polypropylence Sheet by described concrete structure surface coverage or wrap up tight, tent cloth or cotton pad covers or parcel for the second layer, the 3rd layer is sealed whole concrete structure surface with Polypropylence Sheet again.Wherein, every layer of necessary parcel is tight, must not have cold air to permeate into, otherwise not reach natural thermal insulation effect.
Adopt auxiliary heating thermal-insulating method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, first in described concrete structure outside, set up a brooder, and in brooder, be provided with heater, simultaneously also need be at described concrete structure outside parcel one deck Polypropylence Sheet.
In the present embodiment, brooder material adopts tent cloth or cotton pad, heater adopts honeycomb briquette stove or electrical heating, auxiliary heating method of curing must have people on duty by 24h before concrete reaches critical intensity, guarantee temperature of shed, make as far as possible temperature of shed reach balance, prevent that local temperature difference is excessive, will prevent that especially part is in subzero temperature and endures cold.To take care in addition, fire prevention, anti-gas poisoning.
Meanwhile, in maintenance processes, should take necessary temperature control measures.In the present embodiment, while carrying out ultralow-temperature high-performance pouring concrete in step 2, the reserved thermometer hole that described concrete structure internal temperature is monitored.The position of described thermometer hole should be from more than concrete structure edge 1m, general every 100m 2reserved 2 thermometer holes, the degree of depth should be imbedded from the bottom 20cm of concrete structure and be advisable, in 24h, temperature detection monitoring is no less than 2 times, while finding that difference that described concrete structure difference inner and surface temperature surpasses 20 ℃ or surface and environment temperature is over 15 ℃, take immediate steps, guarantee that temperature is in prescribed limit.For concrete smallest cross-sectional, be less than the concrete structure of 1m, can not reserve thermometer hole, directly survey surface temperature of concrete.Temperature measuring device can be used infrared thermometer, wired or wireless temperature detection monitoring instrument etc.Environment temperature, molding temperature when on-the-spot thermometric record comprises cast, internal temperature, surface temperature, environment temperature after hardening of concrete.The monitoring of concrete internal and external temperature should continue to monitor and be no less than 72h from having watered 12h, and concrete in mass is no less than 96h.
Embodiment 2
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of described ultralow-temperature high-performance is 0.3, the weight ratio of sand and cementitious material is 1.4～1.5, sand coarse aggregate ratio is 32%, in cementitious material, the weight ratio of cement and flyash is 88 ︰ 12, the weight ratio of compound antifreezer and cementitious material is 4 ︰ 100, and the weight ratio of high efficiency water reducing agent and cementitious material is 0.8 ︰ 100; The compound antifreezer adopting is as different from Example 1: the composition of described compound antifreezer is by weight: nitrate 35%, and organic compound 30%, calcium formate 0.5%, surplus is water.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 3
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of described ultralow-temperature high-performance is 0.4, the weight ratio of sand and cementitious material is 1.7～1.8, sand coarse aggregate ratio is 38%, in cementitious material, the weight ratio of cement and flyash is 78 ︰ 22, the weight ratio of compound antifreezer and cementitious material is 5 ︰ 100, and the weight ratio of high efficiency water reducing agent and cementitious material is 1 ︰ 100; The compound antifreezer that adopts as different from Example 1: the composition of described compound antifreezer is by weight: nitrate 32%, organic compound 32%, calcium formate 0.8%, surplus is water.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 4
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of ultralow-temperature high-performance is 0.32, the weight ratio of sand and cementitious material is 1.5～1.6, sand coarse aggregate ratio is 40%, in cementitious material, the weight ratio of cement and flyash is 85 ︰ 15, the weight ratio of compound antifreezer and cementitious material is 3.5 ︰ 100, and the weight ratio of high efficiency water reducing agent and cementitious material is 0.7 ︰ 100; The compound antifreezer adopting is as different from Example 1: the composition of described compound antifreezer is by weight: nitrate 34%, and organic compound 32%, calcium formate 1%, surplus is water.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 5
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of described ultralow-temperature high-performance is 0.26, the weight ratio of sand and cementitious material is 1.5～1.6, sand coarse aggregate ratio is 44%, in cementitious material, the weight ratio of cement and flyash is 84 ︰ 16, the weight ratio of compound antifreezer and cementitious material is 6 ︰ 100, and the weight ratio of high efficiency water reducing agent and cementitious material is 0.75 ︰ 100; The compound antifreezer adopting is as different from Example 1: the composition of described compound antifreezer is by weight: nitrate 34%, and organic compound 32%, calcium formate 0.65%, surplus is water.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 6
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of ultralow-temperature high-performance is 0.394, the weight ratio of sand and cementitious material is 1.75, sand coarse aggregate ratio is 40%, in cementitious material, the weight ratio of cement and flyash is 331 ︰ 85, the weight ratio of compound antifreezer and cementitious material is 4 ︰ 100, the weight ratio of high efficiency water reducing agent and cementitious material is 1 ︰ 100, it is C35 that mix forms the concrete strength grade of ultralow-temperature high-performance, and the slump is 160mm～180mm.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 7
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of ultralow-temperature high-performance is 0.334, the weight ratio of sand and cementitious material is 1.637, sand coarse aggregate ratio is 38.8%, in cementitious material, the weight ratio of cement and flyash is 340 ︰ 90, the weight ratio of compound antifreezer and cementitious material is 4 ︰ 100, the weight ratio of high efficiency water reducing agent and cementitious material is 1 ︰ 100, it is C40 that mix forms the concrete strength grade of ultralow-temperature high-performance, and the slump is 160mm～180mm.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 8
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the concrete water-cement ratio of ultralow-temperature high-performance is 0.324, the weight ratio of sand and cementitious material is 1.546, sand coarse aggregate ratio is 37.9%, in cementitious material, the weight ratio of cement and flyash is 346 ︰ 95, the weight ratio of compound antifreezer and cementitious material is 4 ︰ 100, the weight ratio of high efficiency water reducing agent and cementitious material is 1 ︰ 100, it is C45 that mix forms the concrete strength grade of ultralow-temperature high-performance, and the slump is 160mm～180mm.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 9
In the present embodiment, in step 1, the ultralow-temperature high-performance concrete of institute's mix as different from Example 1: the mineral admixture in described cementitious material is ground slag powder.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
Embodiment 10
In the present embodiment, in step 1 the compound antifreezer that adopts as different from Example 1: the composition of described compound antifreezer is by weight: nitrate 30%, organic compound 33%, calcium formate 0.85%, surplus is water.Described nitrate is calcium nitrite, and organic compound is methyl alcohol or ethanol.
In the present embodiment, concrete all the other component proportions of the ultralow-temperature high-performance that adopts with and processing step and the technological parameter of construction technology all identical with embodiment 1.
In the present embodiment, in test room, the concrete air content of obtained ultralow-temperature high-performance, compressive strength, permeability, frost resistance etc. are tested.During actual test, in test room, the method for mix low-temperature concrete and making low-temperature concrete test specimen is all identical with embodiment 1.
(1) ultralow-temperature high-performance concrete 's air-containing test:
In the present embodiment, the air content method of testing adopting is identical with embodiment 1, and mensuration show that in the present embodiment, the concrete air content of prepared ultralow-temperature high-performance is 3.8%.
Simultaneously, in test room, also need the calcium formate consumption of preparing in ultralow-temperature high-performance concrete compound antifreezer used to adjust at 0～1.0wt%, and adopt direct-reading mixing wastewater with air gas content to test the concrete air content of prepared ultralow-temperature high-performance under different calcium formate consumptions, test draws: when admixture calcium formate not, the concrete air content of prepared ultralow-temperature high-performance only has 2.6%, also lower than the air content 3% of normal concrete mixture, but the continuous increase along with calcium formate consumption in compound antifreezer, the concrete air content of prepared ultralow-temperature high-performance obviously raises.And when in compound antifreezer, calcium formate consumption is 0.25wt%, the concrete air content of prepared ultralow-temperature high-performance increases to 3.3%, higher than normal concrete air content 3%, and the concrete air content of prepared ultralow-temperature high-performance continues along with the increase of calcium formate consumption in compound antifreezer to raise, until when in compound antifreezer, calcium formate consumption is 0.75wt%, the concrete air content of prepared ultralow-temperature high-performance is 3.6%.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and adopt direct-reading mixing wastewater with air gas content to test, test draws, increase with flyash consumption in cementitious material used, the concrete air content of prepared ultralow-temperature high-performance constantly reduces, this explanation, flyash has the suction-operated compared with intensity to the bubble in prepared ultralow-temperature high-performance concrete.
Thereby in actual fabrication process, can prepare the concrete air content requirement of ultralow-temperature high-performance according to need, and in conjunction with calcium formate consumption in above-mentioned compound antifreezer on prepared ultralow-temperature high-performance concrete (inner containing calcium nitrite) air content affect result and flyash has the suction-operated compared with intensity to the bubble in ultralow-temperature high-performance concrete, calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope; , flyash consumption in described cementitious material is adjusted meanwhile, specifically the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
(2) ultralow-temperature high-performance concrete tensile strength test:
In the present embodiment, the tensile strength method of testing adopting is identical with embodiment 1, when test draws " after negative temperature conservation 7d more positive temperature maintenance 28d ", the compressive strength of prepared ultralow-temperature high-performance concrete sample is 48MPa, and it is 97% that mark is supported compressive strength rate, and benchmark compressive strength rate is 100%; When " after negative temperature conservation 7d more positive temperature maintenance 56d ", the compressive strength of prepared ultralow-temperature high-performance concrete sample is 50MPa, and it is 100% that mark is supported compressive strength rate, and benchmark compressive strength rate surpasses 102%.
And, also need the calcium formate consumption of preparing in ultralow-temperature high-performance concrete sample compound antifreezer used to adjust at 0～1.0wt%, and adopt YES-2000 type digital display hydraulic pressure testing machine, to made ultralow-temperature high-performance concrete sample at " negative temperature conservation 7d ", the compressive strength in the difference such as " after negative temperature conservation 7d more positive temperature maintenance 28d " and " after negative temperature conservation 7d more positive temperature maintenance 56d " length of time is tested, draw after tested: the compressive strength of made ultralow-temperature high-performance concrete sample when " after negative temperature conservation 7d more positive temperature maintenance 28d ", increase with calcium formate consumption in compound antifreezer used slightly increases, and from this in length of time section mark support compressive strength rate and benchmark compressive strength recently, gain in strength in this length of time is very fast, mark is supported compressive strength rate and has all been surpassed 85%, when particularly in compound antifreezer, calcium formate consumption is 1wt%, the foster compressive strength rate of its mark and benchmark compressive strength rate are all over 100%.The compressive strength of made ultralow-temperature high-performance concrete sample when " after negative temperature conservation 7d more positive temperature maintenance 56d ", in compound antifreezer, not the ultralow-temperature high-performance concrete of admixture calcium formate, the ultralow-temperature high-performance concrete crushing strength of all the other each calcium formate consumptions is all in 50MPa left and right; And support under condition at mark, only have the ultralow-temperature high-performance concrete crushing strength that in compound antifreezer, calcium formate consumption is 1wt% to surpass normal concrete.Thereby as a whole, at " after negative temperature conservation 7d more positive temperature maintenance 28d ", before this length of time, with calcium formate consumption in compound antifreezer, constantly reduce, the growth rate of prepared ultralow-temperature high-performance concrete crushing strength is slower; And after negative temperature conservation 7d positive temperature maintenance 28d to 56d time again, with calcium formate consumption in compound antifreezer, constantly reduce, the growth rate of prepared ultralow-temperature high-performance concrete crushing strength is faster.This explanation: calcium formate can improve the inner concrete early strength development of ultralow-temperature high-performance that is added with nitrous acid, and this raising is accelerated along with the increase of calcium formate consumption in compound antifreezer.Relatively comprehensive, when in compound antifreezer, calcium formate consumption is 1wt%, the concrete mechanical property of prepared ultralow-temperature high-performance is ideal; When in compound antifreezer, calcium formate consumption is 0.25wt%, the concrete mechanical property of prepared ultralow-temperature high-performance is taken second place; While not mixing calcium formate in compound antifreezer, the concrete mechanical property of prepared ultralow-temperature high-performance is the poorest.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and adopt YES-2000 type digital display hydraulic pressure testing machine, and according to GB/T50081-2002 < < standard for test methods of mechanical properties of ordinary concrete > >, the concrete tensile strength of made ultralow-temperature high-performance is tested, test draws: when in cementitious material used, flyash consumption is 15%, the concrete compressive strength of prepared ultralow-temperature high-performance is the highest.
Thereby, in actual fabrication process, can prepare the concrete tensile strength requirement of ultralow-temperature high-performance according to need, and the impact on prepared ultralow-temperature high-performance concrete (inner containing calcium nitrite) tensile strength in conjunction with flyash consumption in calcium formate consumption in above-mentioned compound antifreezer and cementitious material used, calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope, and the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
In addition, from above-mentioned tension test result, the inside adopting in the present embodiment is added with the inner ultralow-temperature high-performance concrete that is added with calcium nitrate in the ultralow-temperature high-performance concrete of calcium nitrite and embodiment 1 early potent fruit, but the inner concrete early strength function of ultralow-temperature high-performance that is added with calcium nitrite is more remarkable.
(3) ultralow-temperature high-performance concrete permeability test:
In the present embodiment, the permeability test method adopting is identical with embodiment 1.According to test result, draw, compare with the inner ultralow-temperature high-performance concrete that adds calcium nitrate in embodiment 1, the ultralow-temperature high-performance concrete that inside adds calcium nitrite generally increases.
In the present embodiment, described in when test draws " after negative temperature conservation 7d more positive temperature maintenance 28d ", the concrete electric flux value of ultralow-temperature high-performance is 1680C, when " after negative temperature conservation 7d more positive temperature maintenance 56d " described in the concrete electric flux value of ultralow-temperature high-performance be 1230C.
There is above-mentioned testing permeability result known, although the ultralow-temperature high-performance concrete that adds calcium nitrite inner is better than the inner concrete morning potent use of ultralow-temperature high-performance that adds calcium nitrate in embodiment 1, but calcium nitrite to the alligatoring effect of negative temperature concrete pore structure also clearly, with playing certain improvement effect adding of calcium formate, but after its sclerosis, concrete permeability is still undesirable.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and adopt NEL-PEU type concrete charge pass analyzer to test the tensile strength of made ultralow-temperature high-performance concrete sample, test draws: with the increase of flyash consumption in cementitious material used, the permeability of prepared ultralow-temperature high-performance concrete when " after negative temperature conservation 7d more positive temperature maintenance 28d " all increases gradually.According to the viewpoint of Berry Malhotra, at the aquation initial stage, as the flyash of cementitious material, can reduce the bonding between aggregate and cement paste, the moisture film of fly ash grain adsorption will make the transition region porous more that becomes, therefore under negative temperature conservation condition, flyash in cementitious material used has negative effect to concrete permeability, and this effect is serious all the more along with the increase of flyash consumption.Therefore, for the higher negative temperature concrete structure of life requirement, mixing of flyash should be prudent, mixes less or fly ash not, to guarantee the life-span of engineering as far as possible.In addition, owing to adopting the inner concrete permeability of ultralow-temperature high-performance that adds calcium nitrite in the present embodiment, the concrete permeability of ultralow-temperature high-performance that adds calcium nitrate than inside in embodiment 1 is much bigger, thereby the inner ultralow-temperature high-performance concrete that adds calcium nitrite is subject to the impact of flyash side effect also even more serious.
Thereby, in actual fabrication process, can prepare the concrete permeability requirement of ultralow-temperature high-performance according to need, and in conjunction with flyash consumption in calcium formate consumption in above-mentioned compound antifreezer and cementitious material used on the infiltrative impact of prepared ultralow-temperature high-performance concrete (inner containing calcium nitrite), calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope, and the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
(4) ultralow-temperature high-performance concrete frost resistance test:
In the present embodiment, the frost resistance method of testing adopting is identical with embodiment 1, draws after tested: after 225 freeze thawing circulation, the mass loss rate of ultralow-temperature high-performance concrete sample is 2.5%, and relative dynamic elastic modulus drops to 40%; And test specimen can stand the freeze thawing circulation destruction of 175 times～200 times.
And, also need the calcium formate consumption of preparing in ultralow-temperature high-performance concrete sample compound antifreezer used to adjust at 0～1.0wt%, and adopt above-mentioned antifreezing test method to test the frost resistance of prepared ultralow-temperature high-performance concrete sample, test result is as follows: compare with the inner ultralow-temperature high-performance concrete that is added with calcium nitrate in embodiment 1, the inside adopting in the present embodiment is added with the ultralow-temperature high-performance concrete of calcium nitrite when standing freeze thawing ringing, not only freezing tolerance is poor, and inner mode of failure is also not quite similar, especially at concrete dynamic modulus of elasticity, drop to below 80%, while standing freeze-thaw damage again, its relative dynamic elastic modulus acutely declines, internal construction is burst apart.During admixture calcium formate, inside is not added with the concrete frost resistance extreme difference of ultralow-temperature high-performance of calcium nitrite, and after 75 freeze thawing circulation, its relative dynamic elastic modulus just drops to 56%, and mass loss reaches 2.8%.Mix after calcium formate, the concrete frost resistance of ultralow-temperature high-performance that inside is added with to calcium nitrite increases, the amount of peeling off on surface obviously reduces, and calcium formate consumption is while being 0.75wt%, it is best that inside is added with the ultralow-temperature high-performance concrete antifreezing performance of calcium nitrite, and the freeze thawing circulation that can stand 175 times～200 times destroys.
Simultaneously, also need to adjust preparing flyash consumption in ultralow-temperature high-performance concrete cementitious material used (being the percentage that flyash weight accounts for cementitious material gross weight), and tackle mutually the concrete frost resistance of prepared ultralow-temperature high-performance and test, test draws: with the increase of flyash consumption in cementitious material, the concrete frost resistance of prepared ultralow-temperature high-performance obviously reduces.Wherein, in cementitious material, flyash consumption is 10%, and it is best that inside is added with the concrete frost resistance of ultralow-temperature high-performance of calcium nitrite.But, compare with the inner ultralow-temperature high-performance concrete that is added with calcium nitrate in embodiment 1, in the present embodiment, adopt inside to be added with the concrete frost resistance of ultralow-temperature high-performance of calcium nitrite poor.When in cementitious material, flyash consumption is 10%, the freezing-thawing cycles that can stand also only has 200 times～225 times, and its mass loss is little; In addition, when flyash consumption is 20%～25%, its frost resistance changes little, and its freeze thawing circulation destroys number of times between 100～125 times, and mass loss is maximum.
Thereby, in actual fabrication process, can prepare the concrete frost resistance requirement of ultralow-temperature high-performance according to need, and the impact on prepared ultralow-temperature high-performance concrete (inner containing calcium nitrite) frost resistance in conjunction with flyash consumption in calcium formate consumption in above-mentioned compound antifreezer and cementitious material used, calcium formate consumption in described compound antifreezer is adjusted accordingly in 0.5%～1.0% scope, and the weight ratio of cement and flyash in described cementitious material is adjusted accordingly in 88～78 ︰ 12～22 scopes.
In sum, be added with the ultralow-temperature high-performance concrete of calcium nitrite for inside, the concrete air content of ultralow-temperature high-performance increases with the increase of calcium formate consumption, and when calcium formate consumption is 0.75wt%, air content reaches peak; At " after negative temperature conservation 7d more positive temperature maintenance 28d ", before this length of time, calcium formate consumption is less, and the concrete compressive strength growth rate of ultralow-temperature high-performance is slower, and after negative temperature conservation 7d again during positive temperature maintenance 28d to 56d, just contrary; And calcium formate add the development that has improved early age strength of concrete, this raising is accelerated along with the increase of its volume; With the increase of calcium formate consumption, after the concrete permeability of ultralow-temperature high-performance first reduces, raise again, and it is relatively better in embodiment 1, to adopt inside to be added with the concrete permeability of ultralow-temperature high-performance of calcium nitrate; In standing freeze thawing circulation destructive process, it is even more serious that inner spalling damages outside spalling damage.
For inside, be added with the ultralow-temperature high-performance concrete of calcium nitrite, increase along with flyash consumption in cementitious material, the concrete air content of ultralow-temperature high-performance obviously reduces, and in the present embodiment, adopts the reduction amplitude of the inner ultralow-temperature high-performance concrete 's air-containing that is added with calcium nitrite relatively large; In cementitious material, flyash consumption is 20% when following, and the concrete early strength function of ultralow-temperature high-performance is more remarkable; Under negative temperature conservation condition, flyash has adverse effect to the concrete permeability of ultralow-temperature high-performance, and influence degree increases along with the increase of flyash consumption.Compound antifreezer of the present invention has not only been avoided the detrimental effect of part inorganic salts to concrete frost resistance, and by adjusting its inner each amounts of components, to the concrete frost resistance of ultralow-temperature high-performance, also can increase.
The above; it is only preferred embodiment of the present invention; not the present invention is imposed any restrictions, every any simple modification of above embodiment being done according to the technology of the present invention essence, change and equivalent structure change, and all still belong in the protection domain of technical solution of the present invention.

Claims (10)

1. a ultralow-temperature high-performance concrete construction technology for the construction of railways of severe cold area, is characterized in that this technique comprises the following steps:
Step 1, ultralow-temperature high-performance concrete mixing: cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water are carried out after even mix, and acquisition unit weight is 2350kg/m 3～2450kg/m 3ultralow-temperature high-performance concrete; The concrete maximum water-cement ratio of described ultralow-temperature high-performance and sand coarse aggregate ratio, all according to the design drawing requirement that needs construction concrete structure, and design by mix proportion method for designing according to construction of railways; Described ultralow-temperature high-performance concrete refers to that being applicable to environment temperature is the high performance concrete of constructing under 0 ℃～-40 ℃ conditions;
The ratio that described cementitious material is 88～78 ︰ 12～22 by cement and mineral admixture according to weight ratio evenly mixes;
The water-reducing rate of described high efficiency water reducing agent is not less than 25%, and the weight ratio of described high efficiency water reducing agent and described cementitious material is 0.5 ︰ 100～1 ︰ 100;
The weight ratio of described compound antifreezer and described cementitious material is 3 ︰ 100～6 ︰ 100; The composition of described compound antifreezer is by weight: nitrate 30%～35%, and organic compound 30%～33%, calcium formate 0.5%～1%, surplus is water; Described nitrate is calcium nitrate or calcium nitrite, and described organic compound is methyl alcohol or ethanol;
Step 2, ultralow-temperature high-performance pouring concrete: after needing the reinforcing cage colligation of construction concrete structure and prop up a mold process to complete, adopt the concrete casting process of ultralow-temperature high-performance described in concrete pumping equipment completing steps one, obtain the concrete structure of moulding by casting;
During actual cast, when ambient temperature is 0 ℃～-10 ℃, the concrete molding temperature of described ultralow-temperature high-performance is controlled at 5 ℃～10 ℃; When environment temperature is-10 ℃～-20 ℃, the concrete molding temperature of described ultralow-temperature high-performance is controlled at 10 ℃～15 ℃; And when ambient temperature is during lower than-20 ℃, the concrete molding temperature of described ultralow-temperature high-performance is not less than 15 ℃;
Step 3, ultralow-temperature high-performance concrete curing: the concrete structure of moulding by casting in step 2 is carried out to insulated curing.
2. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area claimed in claim 1, it is characterized in that: before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, first adopt firing equipment that the water of ultralow-temperature high-performance the reinforcement of concrete described in mix is heated to 50 ℃～70 ℃; Afterwards, then by sand, rubble, water, mineral admixture, cement and Concrete admixtures, according to design proportioning by first to the rear evenly mix of throwing in respectively in mixing plant, just obtain the described ultralow-temperature high-performance concrete that mix forms;
Wherein, described Concrete admixtures comprises high efficiency water reducing agent and compound antifreezer.
3. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area described in claim 1 or 2, it is characterized in that: before cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, need first described compound antifreezer to be prepared, and described compound antifreezer is evenly mixed and forms according to design proportioning by nitrate, organic compound, calcium formate and water;
When described compound antifreezer is prepared, its preparation method is as follows:
Step 101, nitrate and calcium formate preheating: by described nitrate and calcium formate, be heated to respectively 40 ℃～70 ℃;
Step 102, be evenly mixed: by described nitrate and calcium formate after preheating in water and step 101, after mixing according to design proportioning, make described compound antifreezer.
4. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area claimed in claim 2, it is characterized in that: when sand, rubble, water, mineral admixture, cement and Concrete admixtures are thrown in step 1, the temperature of described sand, rubble, mineral admixture and cement is all not less than 0 ℃, and described high efficiency water reducing agent and compound antifreezer in described Concrete admixtures are liquid state.
5. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area described in claim 1 or 2, it is characterized in that: the concrete maximum water-cement ratio of ultralow-temperature high-performance described in step 1 be 0.4 and its sand coarse aggregate ratio be 32%～44%, simultaneously the concrete gel material content of described ultralow-temperature high-performance is not less than 360kg/m 3, unit consumption of water is not more than 165kg/m 3, described high efficiency water reducing agent is polycarboxylic acid series high efficiency water reducing agent.
6. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area described in claim 1 or 2, it is characterized in that: while cementitious material, sand, rubble, high efficiency water reducing agent, compound antifreezer and water being carried out to even mix in step 1, adopt concrete agitation station to carry out mix, the mixing plant rotating speed of described concrete agitation station is 23.5r/min ± 3r/min, and duration of mixing is no less than 120s.
7. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area claimed in claim 5, it is characterized in that: the concrete water-cement ratio of described ultralow-temperature high-performance is 0.26～0.4; And in described ultralow-temperature high-performance concrete, the weight ratio of sand and cementitious material is 1.40～1.80.
8. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area described in claim 1 or 2, it is characterized in that: while described concrete structure being carried out to insulated curing in step 3, the insulated curing time is no less than 7 days, or described concrete structure insulated curing to its compressive strength need be reached design strength more than 50% till.
9. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area described in claim 1 or 2, it is characterized in that: in step 3, described concrete structure is carried out in insulated curing process, the temperature difference between described concrete structure inside and external surface is not more than 20 ℃, and the temperature difference between described concrete structure external surface and ambient temperature is not more than 15 ℃.
10. according to the concrete construction technology of ultralow-temperature high-performance for the construction of railways of severe cold area described in claim 1 or 2, it is characterized in that: while described concrete structure being carried out to insulated curing in step 3, when ambient temperature is 0～-10 ℃, adopt double-layer heat insulation method to carry out maintenance; When ambient temperature is-10 ℃～-20 ℃, adopt three layers of thermal-insulating method to carry out maintenance; When ambient temperature is during lower than-20 ℃, adopt auxiliary heating thermal-insulating method to carry out maintenance;
While adopting double-layer heat insulation method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, immediately at described concrete structure outside parcel one deck Polypropylence Sheet, on wrapped up Polypropylence Sheet, wrap up one deck tent cloth more afterwards or cotton pad is incubated;
While adopting three layers of thermal-insulating method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, immediately at described concrete structure outside parcel one deck Polypropylence Sheet, on wrapped up Polypropylence Sheet, wrap up one deck tent cloth more afterwards or cotton pad is incubated, and then wrap up one deck Polypropylence Sheet on wrapped up tent cloth or cotton pad;
Adopt auxiliary heating thermal-insulating method to carry out maintenance, after completing the concrete casting process of described ultralow-temperature high-performance in step 2, first in described concrete structure outside, set up a brooder, and in brooder, be provided with heater, simultaneously also need be at described concrete structure outside parcel one deck Polypropylence Sheet.
CN201210319814.2A 2012-08-31 2012-08-31 Construction technique for ultralow-temperature high-property concrete for railway construction in frigid areas Active CN102797358B (en)

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