CN116082004A - Regenerated UHPC (ultra high Performance) suitable for saline-alkali areas and preparation method thereof - Google Patents
Regenerated UHPC (ultra high Performance) suitable for saline-alkali areas and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00017—Aspects relating to the protection of the environment
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/34—Non-shrinking or non-cracking materials
- C04B2111/343—Crack resistant materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract
The invention belongs to the technical field of concrete, and relates to regenerated UHPC suitable for a saline-alkali area and a preparation method thereof. The UHPC consists of the following components: gel component, mixing water, regenerated fine aggregate, quartz sand, chemical additive and mixed fiber; 34-50wt% of gelling component, 6.3-13.5wt% of mixing water, 23.75-32.4wt% of recycled fine aggregate and 10-20wt% of quartz sand; water-to-gel ratio: 0.16-0.22, and the sand-cement ratio: 0.475-0.945, chemical additive: 0.42-1.1 wt%, hybrid fiber: 5-12.25wt%. The invention provides a preparation method of multistage preparation and three-time mixing, which effectively regulates and controls the early hydration environment in UHPC by using alkali brine with higher calcium and magnesium ion content and a mode of pre-saturating water treatment on regenerated fine aggregate, relieves the gradient of relative humidity reduction, and simultaneously compensates partial shrinkage due to the reaction of the alkali brine and a cementing material, thereby effectively preventing early cracking; in addition, the water source in the saline-alkali area is fully utilized, and the method is green and environment-friendly, and has profound engineering significance and economic and practical values.
Description
Technical Field
The invention belongs to the technical field of concrete, and particularly relates to a regenerated UHPC (ultra high performance polyethylene) suitable for a saline-alkali area and a preparation method thereof.
Background
Salt lakes and saline soil are extremely widely distributed in China and mainly concentrated in parts of coastal and offshore areas, northwest and inner Mongolia areas, the mineralization degree of the salt lakes is generally about 300g/L, the salt content is high, the components are complex, and most of the salt lakes belong to Na + 、K + 、Mg 2+ 、Cl - 、SO 4 2- The system is a medium environment which is different from a classical seawater system (the mineralization degree is 34-35 g/L) and a salt water lake system (the mineralization degree is 1-20 g/L). Besides the salt-rich groundwater and surface water, even air has a large salt content. The saline soil is mainly distributed in northeast, north China and northwest China, is mainly concentrated in northwest China (Xinjiang, qinghai, tibet and inner Mongolia), and has high salt content. If the saline-alkali water is directly used for preparing concrete and applied to engineering, the durability of the reinforced concrete structure is seriously threatened. Therefore, when the concrete structure is constructed in the saline-alkali area, the mixing water is mostly required to be purified or transported, so that the construction cost is greatly increased, and the construction progress is also restricted. Therefore, the method has important engineering significance in preparing concrete by fully utilizing the alkali brine.
The ultra-high performance concrete (UHPC) is a novel cement-based engineering material with compact microstructure, has ultra-high strength and excellent durability, almost has no carbonization, has very little penetration of chloride ions and sulfate, and provides feasibility for preparing UHPC by directly utilizing saline-alkali water. Meanwhile, UHPC generally uses high-quality quartz sand as fine aggregate, so that the cost is quite high, and how to fully and effectively utilize construction waste and industrial waste is an important problem to be solved when UHPC cost is reduced and environmental damage is slowed down.
Disclosure of Invention
Aiming at the problems, the invention provides the regenerated UHPC suitable for the saline-alkali area based on the existing research results and combined with the current situation that the saline-alkali soil is widely distributed and the building solid waste is difficult to effectively utilize, and according to local conditions, the saline-alkali water is fully utilized, so that the water source for engineering is solved, the water treatment process for concrete in the saline-alkali area is simplified, the long-distance transportation is avoided, the building waste is fully utilized, the environment is protected, the energy is saved, the engineering construction quality is ensured, the construction cost is reduced, and the economic and social benefits are good.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides regenerated UHPC suitable for saline-alkali areas, which consists of the following components: a gelling component, mixing water, recycled fine aggregate, quartz sand, a chemical additive and hybrid fibers; wherein, the mass fraction of the gelling component is as follows: 34-50% of mixing water: 6.3-13.5% of regenerated fine aggregate: 23.75-32.4%, and the mass fraction of quartz sand: 10-20%; mass fraction of chemical additive: 0.42-1.1% of mixed fiber by mass: 5-12.25%;
the cementing component consists of cement, fly ash, microbeads, silica fume and mineral powder;
the mixing water consists of brine and clear water in a saline-alkali area, wherein the consumption of the clear water is 10-30% of the mass of cement, the brine is a water source in a light saline-alkali area, the pH value is 7.2-8.5, and SO in the water 4 2- The content is below 1600mg/L, the chloride content is below 1800mg/L, and the salt alkalinity is below 3%;
the hybrid fiber consists of brass plated steel fiber and organic fiber on the surface;
the chemical additive consists of a water reducing agent, an alkali excitant and a hyperdispersant;
the water-gel ratio of the regenerated UHPC is 0.16-0.22, and the sand-gel ratio is 0.475-0.945.
Preferably, in the regenerated UHPC suitable for a saline-alkali region: the mass fraction of the gel component is as follows: 37-42% of mixing water: 7-10% of recycled fine aggregate: 25-30% of quartz sand: 12-15%; water-to-gel ratio: 0.18-0.20, sand cement ratio: 0.65-0.80 mass percent of chemical additive: 0.6-1.0% of mixed fiber mass fraction: 6-12%.
Preferably, the gelling component consists of the following components in mass percent: 40-80% of cement, 0-10% of fly ash, 10-20% of microbeads, 7-40% of silica fume and 2-10% of mineral powder.
Preferably, the mass of the water reducer is 1.6-2.2% of the mass of the gelling component, the mass of the alkali activator is 0.01-0.08% of the mass of the gelling component, and the mass of the hyperdispersant is 0.01-0.08% of the mass of the gelling component.
Preferably, the cement is selected from any one of sulfate-resistant cement, ordinary portland cement, mineral powder cement or aluminoferrite cement.
Preferably, the recycled fine aggregate is obtained by processing and sieving concrete with C50 and original strength more than C50 by a jaw crusher; the particle size of the regenerated fine aggregate is 0.18-0.5 mm, the maximum crushing value is 5-20%, the los Angeles abrasion value is 10-25%, and the apparent density is 2.6-2.9 kg/m 3 The saturated water absorption rate is 7-20%.
Preferably, the steel fibers are straight steel fibers or end hook steel fibers, the diameter of the straight steel fibers is 0.2mm, the length of the straight steel fibers is 13mm, 16mm, 18mm or 20mm, and the length-diameter ratio of the straight steel fibers is 65, 80, 90 or 100; the end hook type steel fiber has the diameter of 0.2mm, the length of 13mm or 16mm and the length-diameter ratio of 65 or 80; the organic fiber is ultra-high molecular weight polyethylene fiber, polyvinyl alcohol fiber or alkali-resistant glass fiber; the length of the organic fiber is 12mm, and the diameter is 14-40 mu m; the UHPC mechanical property improving effect is ordered by different fibers: end hook type steel fiber, straight type steel fiber, ultra-high molecular weight polyethylene fiber, polyvinyl alcohol fiber and alkali-resistant glass fiber.
Further preferably, the steel fiber is a straight steel fiber with the diameter of 0.2mm, the length of 13mm and the length-diameter ratio of 65; the organic fiber is ultra-high molecular weight polyethylene fiber with the diameter of 20 mu m and the length of 12mm, and the mixing ratio of the steel fiber and the organic fiber is 4:1.
Preferably, the hyper-dispersant is polyether hyper-dispersant, sodium carboxymethyl cellulose or sodium polyacrylate; the alkali-activated agent is sodium hydroxide or sodium silicate; the water reducer is a polycarboxylic acid high-efficiency water reducer.
The invention also provides a preparation method of the regenerated UHPC applicable to the saline-alkali area, which comprises the following steps:
step one: carrying out clear water saturation treatment on quartz sand, and carrying out water saturation treatment on the regenerated fine aggregate by using saline-alkali water;
step two: uniformly mixing the rest clear water with cement, 1/3 of water reducer, 1/2 of alkali excitant and 1/2 of hyper-dispersant to prepare cement paste;
step three: mixing and stirring the rest saline alkali water, 1/3 water reducer, the rest 1/2 hyper-dispersant, 1/2 alkali excitant, silica fume, fly ash, micro beads and mineral powder to obtain gelled slurry;
step four: mixing and uniformly stirring quartz sand subjected to water saturation treatment in the step II with the cement paste to obtain mixed mortar;
step five: mixing the regenerated fine aggregate subjected to the water saturation treatment of the saline-alkali water in the first step with the gelling slurry obtained in the third step, and stirring for 2-3 minutes to prepare gelling system mortar;
step six: mixing and stirring the mixed mortar in the fourth step and the mortar in the cementing system in the fifth step for 2-3 minutes, then adding steel fibers, slowly adding organic fibers after stirring for 1 minute, adding the rest 1/3 of water reducer after the fibers are uniformly dispersed, and continuously stirring for 3-5 minutes to obtain the regenerated UHPC suitable for the saline-alkali areas.
The invention uses silica fume and a large amount of active mineral admixture to replace part of cement; the preparation process of multi-stage preparation and three-time mixing is provided; the water-gel ratio, the sand-gel ratio, the material quality of the regenerated fine aggregate, the grain diameter, the crushing value and the water absorption rate requirements of UHPC (ultra high performance concrete) are given; the composition mixing ratio range of the regenerated UHPC component of the saline-alkali water is defined.
As shown in figure 1 of the specification, the preparation process of the regenerated UHPC has the following characteristics:
1) Multistage preparation: uniformly stirring cement and clear water to prepare cement paste, and then adding water-saturated quartz sand to prepare mixed mortar; uniformly stirring cementing materials such as silica fume, fly ash, microbeads and the like, brine, chemical additives and the like to prepare cementing slurry, and then adding regenerated fine aggregate which is treated by brine by using brine to prepare cementing system mortar;
2) Mixing for three times: mixing cement paste and recycled fine aggregate to prepare mixed mortar, mixing the gelled slurry and quartz sand to prepare gelled system mortar, and mixing the mixed mortar and the gelled system mortar to prepare the saline-alkali water recycled UHPC.
Wherein the fractional preparation is employed because: 1. pre-saturating water treatment is carried out on the recycled fine aggregate and quartz sand, so that the recycled fine aggregate and quartz sand play an internal curing role in UHPC after molding and pouring, the structure is compact, and the transmission of harmful media is reduced; 2. the saline alkali water contains more Na + 、K + 、Mg 2+ 、Cl - 、SO 4 2- If the ion is directly added, the early strength of cement is easy to be caused, the fluidity of UHPC is reduced, and the risk of occurrence of durability diseases is increased.
Compared with the prior art, the invention has the following advantages:
(1) The use of the alkali brine in the invention can enhance the early strength of concrete and improve the later strength of concrete.
(2) The raw materials of the invention comprise cementing materials (cement, fly ash, silica fume and mineral powder) and aggregates, and the particle sizes of the components are different, so that continuous grading can be formed, and the compactness of the material is improved; in addition, under the action of an alkaline excitant, the active silicon dioxide in the mineral admixture with large doping amount is exposed, so that the pozzolan reaction can be accelerated, and the main reaction principle is as follows:
SiO 2 +Ca(OH) 2 +H 2 O→CaO-SiO 2 -H 2 O
2（2CaO-SiO 2 ）+ 4H 2 O=3CaO-2SiO 2 -3H 2 O + Ca(OH) 2 。
(3) The UHPC additive has larger mixing amount, low water-gel ratio and large dosage of cementing materials and mineral admixtures, so that shrinkage problems are easy to occur in early stage, and early cracking is caused; according to the invention, by using the saline alkali water with higher calcium and magnesium ion content and the mode of carrying out clear water pre-saturation water treatment on the regenerated fine aggregate, the early hydration environment in the UHPC is effectively regulated and controlled, the relative humidity gradient is relieved, meanwhile, the reaction of the saline alkali water and the cementing material compensates for partial shrinkage, and early cracking is effectively prevented.
(4) The regenerated UHPC can reasonably utilize industrial waste, fully utilizes water sources in the saline-alkali area, solves the problem of water sources for engineering, simplifies the water treatment process for concrete in the saline-alkali area, avoids long-distance transportation, reduces engineering cost on the premise of ensuring strength, is environment-friendly, has profound engineering significance and economic and practical values, and also provides a development direction for reasonable utilization of the saline-alkali water.
(5) In the preparation method of the invention, firstly, the reclaimed fine aggregate and the quartz sand are subjected to pre-saturation water treatment, so that the reclaimed fine aggregate and the quartz sand can play an internal curing role in UHPC after being molded and poured, and the structure is compact, thereby being beneficial to reducing the transmission of harmful media; the saline alkali water is not directly added into the cement, so that the fluidity of UHPC can be improved, and the risk of durable diseases is reduced.
Drawings
FIG. 1 is a flow chart of the preparation of UHPC for regenerating saline-alkali water in the embodiment of the invention;
FIG. 2 is a graph showing the fluidity test result of the saline-alkali water regenerated UHPC according to example 1 of the present invention;
FIG. 3 is a graph showing the results of the test of the compressive strength and the flexural strength of the saline-alkali water regenerated UHPC according to the embodiment 1 of the invention;
FIG. 4 is a graph showing the fluidity test result of the saline-alkali water regenerated UHPC according to example 2 of the present invention;
FIG. 5 is a graph showing the results of the test of the compressive strength and the flexural strength of the regenerated UHPC of the saline-alkali water in example 2 of the present invention;
FIG. 6 is a graph showing the fluidity test result of UHPC regenerated saline-alkali water in example 3 of the present invention;
FIG. 7 is a graph showing the results of the test of the compressive strength and the flexural strength of the regenerated UHPC of the saline-alkali water in example 3 of the present invention;
FIG. 8 is a graph showing the results of the fluidity test of regenerated UHPC in comparative example 1 of the present invention;
FIG. 9 is a graph showing the results of the compressive strength and flexural strength test of the regenerated UHPC of comparative example 1 of the present invention;
FIG. 10 is a graph showing the results of the flowability test of regenerated UHPC according to comparative example 2 of the present invention;
FIG. 11 is a graph showing the results of the test of the compressive strength and the flexural strength of the regenerated UHPC of comparative example 2 of the present invention.
Detailed Description
The advantages and features of the present invention will become more apparent from the following description, in which reference is made to the ultra-high performance concrete (UHPC) specification given by a certain yellow river bridge, in conjunction with the specific embodiments. The embodiments are merely exemplary and do not limit the scope of the invention in any way. It will be understood by those skilled in the art that various changes and substitutions of details and forms of the technical solution of the present invention may be made without departing from the spirit and scope of the present invention, but these changes and substitutions fall within the scope of the present invention.
Ultra-high performance concrete technical index table
| Index (I) | Technical requirements | Inspection standard |
| 28d flexural strength/MPa | ≥20 | GB/T 31387-2015 |
| 28d cube compressive strength/MPa | ≥100 | GB/T 31387-2015 |
| Modulus of elasticity/Gpa | ≥40 | GB/T 50081-2002 |
| Slump extension/mm | ≥500 | GB/T 50080-2016 |
| Apparent density/kg/m 3 | ≤2750 | GB/T 50080-2016 |
In all examples and comparative examples:
the fly ash is national standard class I class C fly ash, the particle size is 7-9 mu m, the fineness is less than or equal to 12, the water demand ratio is less than or equal to 95%, the activity index is more than or equal to 80, the ignition loss is less than or equal to 5, and the sulfur dioxide content is less than or equal to 3;
the average particle size of the microbeads is about 4-7 mu m, the water demand ratio is less than or equal to 95%, and the activity index is more than or equal to 80;
the silica fume is an industrial smelting byproduct, is micro silicon powder, has a loss on ignition of less than 2.8, an average particle size of 0.1-0.3 mu m, a silicon content of more than 90%, an activity index of 110-125 and a specific surface area of 20-28 m 2 /g；
The specification of the mineral powder is S95 grade mineral powder, and the fineness is more than or equal to 350m 2 /kg；
The saline alkali water is a water source in a slight saline-alkali area, the pH value is 7.2-8.5, and SO in the water 4 2- The content is below 1600mg/L, the chloride content is below 1800mg/L, and the salt alkalinity is below 3%;
the quartz sand is refined quartz sand with 24-40 meshes.
Example 1
The regenerated UHPC suitable for the saline-alkali area and the preparation method thereof are provided, wherein the UHPC comprises the following components:
511kg of cement, 39 kg of fly ash, 147 kg of microbeads, 200kg of silica fume, 102 kg of mineral powder, 70kg of clear water, 130 kg of saline-alkali water, 670 kg of recycled fine aggregate, 335kg of quartz sand, 21 kg of polycarboxylic acid type high-efficiency water reducer, 0.5kg of sodium carboxymethyl cellulose, 0.5kg of sodium hydroxide, 132.6 kg of steel fiber and 5.2 kg of organic fiber.
The water-gel ratio was 0.2 and the sand-gel ratio was 0.67.
The cement is ordinary silicate cement, the label is more than or equal to 52.5, and the specific surface area is more than or equal to 300m 2 Per kg, magnesium oxide content less than or equal to 5%, trioxygenThe content of sulfur is less than or equal to 3 percent;
the particle size of the regenerated fine aggregate is 0.2-0.3 mm, the maximum crushing value is 8%, the los Angeles abrasion value is 13%, and the apparent density is 2.7kg/m 3 The saturated water absorption was 11%.
The steel fiber is brass-plated steel fiber with the surface, and flat steel fiber with the diameter of 0.2mm, the length of 13mm and the length-diameter ratio of 65 is selected; the organic fiber is ultra-high molecular weight polyethylene fiber with the diameter of 20 mu m and the length of 12mm, and the mixing ratio of the steel fiber and the organic fiber is 4:1.
The mass fraction of the gelling component in this example: 42.3% of mixing water: 8.5 percent of regenerated fine aggregate: 28.3% of quartz sand: 14.2% of chemical additive: 0.9 percent of mixed fiber mass fraction: 5.8%.
The mass of the water reducing agent is 2.1% of the mass of the gelling component, the mass of the alkali-activated agent is 0.05% of the mass of the gelling component, and the mass of the hyper-dispersant is 0.05% of the mass of the gelling component.
The gel component comprises the following components in percentage by mass: 51% of cement, 4% of fly ash, 15% of microbeads, 20% of silica fume and 10% of mineral powder.
The mass of the clean water is 13.7 percent of the mass of the cement.
The preparation method of the regenerated UHPC suitable for the saline-alkali areas comprises the following steps:
step one: putting 335kg quartz sand into clear water (35 kg) for water saturation treatment; placing 670 kg regenerated fine aggregate in saline alkali water (70 kg) for water saturation treatment;
step two: mixing and stirring 511 and kg cement, 7 and kg water reducing agent, 250g sodium carboxymethyl cellulose, 250g sodium hydroxide and the rest clear water (35 kg) to prepare cement paste;
step three: mixing and stirring 39 kg fly ash, 147 kg micro beads, 200kg silica fume, 102 kg mineral powder, 7kg water reducer, 250g sodium carboxymethyl cellulose, 250g sodium hydroxide and the rest saline alkali water to prepare gelled slurry;
step four: mixing and stirring clear water saturated quartz sand and the cement slurry obtained in the step two to obtain mixed mortar;
step five: mixing and stirring the saline-alkali water saturated regenerated fine aggregate obtained in the first step and the gelling slurry obtained in the third step to obtain gelling system mortar;
step six: mixing and stirring the mixed mortar and the mortar of the gel system for 2-3 minutes; adding steel fibers, stirring for 1min, slowly adding organic fibers, adding the rest 7kg water reducer after the fibers are uniformly dispersed, and continuously stirring for 3-5 min to obtain the regenerated UHPC suitable for saline-alkali areas.
The fluidity of the regenerated UHPC of this example was tested according to the standard of the conventional concrete mix Performance test method (GB/T50080-2002); and if the fluidity meets the requirement, performing in-situ casting construction or prefabricating the component.
7 groups of UHPCs (numbered 1-7) were prepared under the conditions of this example, and the flowability of the 7 groups of UHPCs was tested, and the result is shown in FIG. 2, with an expansion degree of 550-600.
When the regenerated UHPC is used for in-situ casting construction or prefabricated components, steam maintenance is needed for the reinforced concrete structure; for structural skin maintenance, standard maintenance or steam maintenance may be employed.
The test results of other properties such as compressive strength and flexural strength are shown in FIG. 3, the compressive strength is 115-125 MPa, and the flexural strength is 20-30 MPa.
Example 2
The regenerated UHPC suitable for the saline-alkali area and the preparation method thereof are provided, wherein the UHPC comprises the following components:
550kg of cement, 100kg of microbeads, 247 and kg of silica fume, 100 and kg of mineral powder, 70 and kg of clear water, 130 and kg of saline-alkali water, 670 and kg of recycled fine aggregate, 335kg of quartz sand, 21 and kg of water reducer, 0.5 and kg of sodium carboxymethyl cellulose, 0.5 and kg of sodium hydroxide, 132.6 and kg of steel fiber, 5.2 and kg of organic fiber and 2.1 percent of mixed fiber volume.
In the regenerated UHPC composition, the water-to-gel ratio is as follows: 0.2, sand gum ratio: 0.67.
the types and specifications of the cement, the recycled fine aggregate, the steel fiber and the organic fiber were the same as in example 1.
The mass fraction of the gelling component in this example: 42.2% of mixing water: 8.5 percent of regenerated fine aggregate: 28.4% of quartz sand: 14.2% of chemical additive: 0.9 percent of mixed fiber mass fraction: 5.8%.
The mass of the water reducing agent is 2.1% of the mass of the gelling component, the mass of the alkali-activated agent is 0.05% of the mass of the gelling component, and the mass of the hyper-dispersant is 0.05% of the mass of the gelling component.
The gel component comprises the following components in percentage by mass: 55.2% of cement, 10.0% of micro-beads, 24.8% of silica fume and 10.0% of mineral powder.
The mass of the clear water is 12.7 percent of the mass of the cement.
The preparation method comprises the following steps:
step one: putting 335kg quartz sand into clear water (35 kg) for water saturation treatment; placing 670 kg regenerated fine aggregate in saline alkali water (70 kg) for water saturation treatment;
step two: mixing and stirring 550kg of cement, 7kg water reducer, 250g of sodium carboxymethyl cellulose, 250g of sodium hydroxide and the rest of clear water (35 kg) to prepare cement paste;
step three: mixing and stirring 100kg of microbeads, 247 kg silica fume, 100kg mineral powder, 7kg water reducing agent, 250g of sodium carboxymethyl cellulose, 250g of sodium hydroxide and the rest of saline alkali water to prepare gelled slurry;
step four: mixing and stirring clear water saturated quartz sand and the cement slurry obtained in the step two to obtain mixed mortar;
step five: mixing and stirring the saline-alkali water saturated regenerated fine aggregate obtained in the step one and the slurry obtained in the step three to obtain a gel system mortar;
step six: mixing and stirring the mixed mortar and the mortar of the gel system for 2-3 minutes; adding steel fibers, stirring for 1min, slowly adding organic fibers, adding the rest 7kg water reducer after the fibers are uniformly dispersed, and continuously stirring for 3-5 min to obtain the regenerated UHPC suitable for saline-alkali areas.
The fluidity of the regenerated UHPC of this example was tested according to the standard of the conventional concrete mix Performance test method (GB/T50080-2002); and if the fluidity meets the requirement, performing in-situ casting construction or prefabricating the component.
7 sets of UHPCs were prepared under the conditions of this example, and the flowability of the 7 sets of UHPCs was tested, and the results are shown in FIG. 4: the expansion degree is 450-500.
When the regenerated UHPC is used for in-situ casting construction or prefabricated components, steam maintenance is needed for the reinforced concrete structure; for structural skin maintenance, standard maintenance or steam maintenance may be employed.
The test results of other properties such as compressive strength and flexural strength are shown in fig. 5: the compressive strength is 120-140 MPa, and the flexural strength is 20-30 MPa.
Example 3
A regenerated UHPC suitable for use in saline-alkaline areas, said UHPC consisting of:
592kg of cement, 59 kg of fly ash, 177kg of microbeads, 236 kg of silica fume, 118 kg of mineral powder, 177kg of clear water, 59 kg of saline-alkali water, 561kg of recycled fine aggregate, 237kg of quartz sand, 21 kg of polycarboxylic acid high-efficiency water reducer, 0.5kg of sodium carboxymethyl cellulose, 0.5kg of sodium hydroxide, 100kg of steel fiber and 25kg of polyvinyl alcohol fiber.
In the regenerated UHPC composition, the water-to-gel ratio is as follows: 0.2, sand gum ratio: 0.475.
the types and specifications of the cement, the recycled fine aggregate, the steel fiber and the organic fiber were the same as in example 1.
The mass fraction of the gelling component in this example: 50.02% of mixing water: 9.99% of regenerated fine aggregate: 23.74% of quartz sand: 10.03% of chemical additive: 0.93% of mixed fiber mass fraction: 5.29%.
The mass of the water reducing agent is 1.78% of the mass of the gelling component, the mass of the alkali-activated agent is 0.042% of the mass of the gelling component, and the mass of the hyperdispersant is 0.042% of the mass of the gelling component.
The gel component comprises the following components in percentage by mass: 50.1% of cement, 5.0% of fly ash, 15.0% of microbeads, 20.0% of silica fume and 10.0% of mineral powder.
The mass of the clear water is 0.30 percent of the mass of the cement.
The preparation method is as described in the specification, and specifically comprises the following steps:
step one: carrying out water saturation treatment on 237 and kg quartz sand by using 25kg clear water, and carrying out water saturation treatment on 561kg of regenerated fine aggregate by using 58.6 kg saline alkali water;
step two: uniformly mixing the rest clear water with cement, 7kg of water reducer, 250g of alkali excitant and 250g of hyper-dispersant to prepare cement paste;
step three: mixing and stirring the rest saline alkali water, 7kg water reducer, 250g hyperdispersant, 250g alkali excitant, silica fume, fly ash, microbeads and mineral powder to obtain gelled slurry;
step four: mixing and uniformly stirring quartz sand subjected to water saturation treatment in the step II with the cement paste to obtain mixed mortar;
step five: mixing the regenerated fine aggregate subjected to the water saturation treatment of the saline-alkali water in the first step with the gelling slurry obtained in the third step, and stirring for 2-3 minutes to prepare gelling system mortar;
step six: mixing and stirring the mixed mortar in the fourth step and the mortar in the cementing system in the fifth step for 2-3 minutes, then adding steel fibers, slowly adding organic fibers after stirring for 1 minute, adding the rest 1/3 of water reducer after the fibers are uniformly dispersed, and continuously stirring for 3-5 minutes to obtain the regenerated UHPC suitable for the saline-alkali areas.
The fluidity of the regenerated UHPC of this example was tested according to the standard of the conventional concrete mix Performance test method (GB/T50080-2002); and if the fluidity meets the requirement, performing in-situ casting construction or prefabricating the component.
7 sets of UHPCs were prepared under the conditions of this example, and the flowability of the 7 sets of UHPCs was tested, and the results are shown in FIG. 6: the expansion degree is 600-622.
When the regenerated UHPC is used for in-situ casting construction or prefabricated components, steam maintenance is needed for the reinforced concrete structure; for structural skin maintenance, standard maintenance or steam maintenance may be employed.
The test results of other properties such as compressive strength and flexural strength are shown in fig. 7: the compressive strength is 119-126 MPa, and the flexural strength is 20-24 MPa.
Comparative example 1
A regenerated UHPC and a method of making the same, the regenerated UHPC comprising the following components:
cement 511kg, fly ash 39 kg, microbeads 147 kg, silica fume 200kg, mineral powder 102 kg, clear water 200kg, recycled fine aggregate 670 kg, quartz sand 335kg, water reducer 21 kg, sodium carboxymethylcellulose 0.5kg, sodium hydroxide 0.5kg, steel fibers 132.6 kg, polyvinyl alcohol fibers 5.2 kg, and mixed fiber volume mixing amount 2.1%.
The cement, recycled fine aggregate, water reducer, steel fiber, and polyvinyl alcohol fiber described in this comparative example were the same as in example 1, except that the same amount of saline-alkali water was replaced with clean water.
The preparation method comprises the following steps:
step one: putting 335kg quartz sand into clear water (35 kg) for water saturation treatment; placing 670 kg recycled fine aggregate in clear water (70 kg) for water saturation treatment;
step two: mixing and stirring 511 and kg cement, 7 and kg water reducing agent, 250g sodium carboxymethyl cellulose, 250g sodium hydroxide and clear water (35 kg) to prepare cement paste;
step three: 39 kg fly ash, 147 kg micro beads, 200kg silica fume, 102 kg mineral powder, 7kg water reducing agent, 250g sodium carboxymethyl cellulose, 250g sodium hydroxide and clear water (60 kg) are mixed and stirred to prepare gelled slurry;
step four: mixing and stirring clear water saturated quartz sand and the cement slurry obtained in the step two to obtain mixed mortar;
step five: mixing and stirring the clean water saturated recycled fine aggregate obtained in the first step and the gelling slurry obtained in the third step to obtain gelling system mortar;
step six: mixing and stirring the mixed mortar and the mortar of the gel system for 2-3 minutes;
step seven: adding the steel fiber, stirring for 1min, slowly adding the organic fiber, adding the rest 7kg water reducer, and continuously stirring for 3-5 min after the fiber is uniformly dispersed, thus obtaining the regenerated UHPC.
The fluidity of the regenerated UHPC of this example was tested according to the standard of the conventional concrete mix Performance test method (GB/T50080-2002); and if the fluidity meets the requirement, performing in-situ casting construction or prefabricating the component.
7 sets of UHPCs were prepared under the conditions of this comparative example, and the flowability of the 7 sets of UHPCs was tested, and the results are shown in FIG. 8: the expansion degree is 600-630, and compared with the embodiment 1, the expansion degree is reduced by about 10% when the saline-alkali water is used compared with the whole clean water.
When the regenerated UHPC is used for in-situ casting construction or prefabricated components, steam maintenance is needed for the reinforced concrete structure; for structural skin maintenance, standard maintenance or steam maintenance may be employed.
The compressive strength and flexural strength of the obtained UHPC are shown in FIG. 9: the compressive strength is 120-135 MPa, the flexural strength is 20-30 MPa, and compared with the embodiment 1, the compressive strength is reduced by about 8% compared with the total use of clear water by using saline-alkali water, and the flexural strength is basically the same.
With reference to the technical indexes of the ultra-high performance concrete given by the design document, both the examples 1 and 2 and the comparative example 1 meet the design requirements, and the examples 1 and 2 have the advantages by comprehensively considering the economical efficiency and the construction difficulty in the saline-alkali area.
Comparative example 2
The regenerated UHPC suitable for the saline-alkali area consists of the following components:
511kg of cement, 39 kg of fly ash, 147 kg of microbeads, 200kg of silica fume, 102 kg of mineral powder, 70kg of clear water, 130 kg of saline-alkali water, 670 kg of recycled fine aggregate, 335kg of quartz sand, 21 kg of polycarboxylic acid high-efficiency water reducer, 0.5kg of sodium carboxymethyl cellulose, 0.5kg of sodium hydroxide, 132.6 kg of steel fiber, 5.2 kg of polyvinyl alcohol fiber and 2.1 percent of mixed fiber by volume.
The water-gel ratio was 0.2 and the sand-gel ratio was 0.67.
The cement, recycled fine aggregate, water reducing agent, steel fiber, polyvinyl alcohol fiber described in this comparative example were the same as in example 1, except for the production method.
The preparation method of the regenerated UHPC suitable for the saline-alkali areas comprises the following steps:
step one: 511kg of cement, 39 kg of fly ash, 147 kg of microbeads, 200kg of silica fume, 102 kg of mineral powder, 670 kg of recycled fine aggregate, 335kg of quartz sand, 0.5kg of sodium carboxymethyl cellulose and 0.5kg of sodium hydroxide are mixed and stirred for 2 minutes;
step two: adding clear water 70kg, saline-alkali water 130 kg and polycarboxylic acid high-efficiency water reducer 21 kg, mixing and stirring for 3-5 minutes;
step three: and adding the steel fibers, stirring for 1min, slowly adding the polyvinyl alcohol fibers, and continuously stirring for 3-5 min after the fibers are uniformly dispersed, so as to obtain the regenerated UHPC suitable for the saline-alkali areas.
The fluidity of the regenerated UHPC of this example was tested according to the standard of the conventional concrete mix Performance test method (GB/T50080-2002); and if the fluidity meets the requirement, performing in-situ casting construction or prefabricating the component.
7 groups of UHPCs were prepared under the conditions of the comparative example, and the flowability of the 7 groups of UHPCs was tested, and the expansion degree was 480 to 502 as shown in FIG. 10.
When the regenerated UHPC is used for in-situ casting construction or prefabricated components, steam maintenance is needed for the reinforced concrete structure; for structural skin maintenance, standard maintenance or steam maintenance may be employed.
The test results of other properties such as compressive strength and flexural strength are shown in FIG. 11, the compressive strength is 94-102 MPa, and the flexural strength is 17-21 MPa.
As can be seen from the comparative example, the preparation method of multistage preparation and three-time mixing is not adopted, the expansion degree of the prepared cement is obviously reduced, on one hand, the powder cannot be fully dispersed, on the other hand, the reaction of alkaline water and cement can be accelerated by direct stirring, the expansion degree is negatively influenced, and the possibility of generating defects in the concrete is further increased by the reduction of the expansion degree.
Claims (10)
1. The regenerated UHPC suitable for the saline-alkali area is characterized by comprising the following components: a gelling component, mixing water, recycled fine aggregate, quartz sand, a chemical additive and hybrid fibers; wherein, the mass fraction of the gelling component is as follows: 34-50% of mixing water: 6.3-13.5% of regenerated fine aggregate: 23.75-32.4%, and the mass fraction of quartz sand: 10-20% of chemical additive: 0.42-1.1% of mixed fiber by mass: 5-12.25%;
the cementing component consists of cement, fly ash, microbeads, silica fume and mineral powder;
the mixing water consists of brine and clear water in a saline-alkali area, wherein the mass of the clear water is 10-30% of that of cement; the saline alkali water is a water source in a slight saline-alkali area, the pH value is 7.2-8.5, and SO in the water 4 2- The content is below 1600mg/L, the chloride content is below 1800mg/L, and the salt alkalinity is below 3%;
the hybrid fiber consists of brass plated steel fiber and organic fiber on the surface;
the chemical additive consists of a water reducing agent, an alkali excitant and a hyperdispersant;
the water-gel ratio of the regenerated UHPC is 0.16-0.22, and the sand-gel ratio is 0.475-0.945.
2. The regenerated UHPC suitable for saline-alkali regions according to claim 1, wherein the regenerated UHPC comprises the following gel components in mass percent: 37-42% of mixing water: 7-10% of recycled fine aggregate: 25-30% of quartz sand: 12-15% of chemical additives, 0.6-1.0% of mixed fibers, and 6-12% of mixed fibers; water-to-gel ratio: 0.18-0.20, sand cement ratio: 0.65 to 0.80.
3. A regenerated UHPC suitable for use in saline-alkaline areas according to claim 1, characterised in that the gelling component consists of the following components in mass percent: 40-80% of cement, 0-10% of fly ash, 10-20% of microbeads, 7-40% of silica fume and 2-10% of mineral powder.
4. The regenerated UHPC suitable for saline-alkali areas according to claim 1, wherein the mass of the water reducer is 1.6-2.2% of the mass of the gelling component, the mass of the alkali activator is 0.01-0.08% of the mass of the gelling component, and the mass of the hyperdispersant is 0.01-0.08% of the mass of the gelling component.
5. A recycled UHPC suitable for use in saline-alkali areas according to claim 1, wherein the cement is selected from any one of sulphate-resistant cement, portland cement, mineral powder cement or aluminoferrite cement.
6. The regenerated UHPC suitable for saline-alkali areas according to claim 1, wherein the regenerated fine aggregate is obtained by processing and sieving concrete with C50 and above original strength by a jaw crusher;
the particle size of the regenerated fine aggregate is 0.18-0.5 mm, the maximum crushing value is 5-20%, the los Angeles abrasion value is 10-25%, and the apparent density is 2.6-2.9 kg/m 3 The saturated water absorption rate is 7-20%.
7. The regenerated UHPC suitable for use in saline-alkali regions according to claim 1, wherein the steel fibers are straight steel fibers or end hook steel fibers, the straight steel fibers have a diameter of 0.2mm, a length of 13mm, 16mm, 18mm or 20mm, and an aspect ratio of 65, 80, 90 or 100; the end hook type steel fiber has the diameter of 0.2mm, the length of 13mm or 16mm and the length-diameter ratio of 65 or 80; the organic fiber is ultra-high molecular weight polyethylene fiber, polyvinyl alcohol fiber or alkali-resistant glass fiber; the organic fiber has a length of 12mm and a diameter of 14-40 μm.
8. The regenerated UHPC suitable for saline-alkali areas according to claim 7, wherein the steel fiber is a flat steel fiber with a diameter of 0.2mm, a length of 13mm and an aspect ratio of 65; the organic fiber is ultra-high molecular weight polyethylene fiber with the diameter of 20 mu m and the length of 12mm, and the mixing ratio of the steel fiber and the organic fiber is 4:1.
9. The regenerated UHPC suitable for use in saline-alkali soil areas according to claim 1, wherein the hyperdispersant is a polyether hyperdispersant, sodium carboxymethyl cellulose or sodium polyacrylate; the alkali-activated agent is sodium hydroxide or sodium silicate; the water reducer is a polycarboxylic acid high-efficiency water reducer.
10. A process for the preparation of regenerated UHPC suitable for use in saline-alkaline areas as claimed in any one of claims 1 to 9, comprising the steps of:
step one: carrying out clear water saturation treatment on quartz sand, and carrying out water saturation treatment on the regenerated fine aggregate by using saline-alkali water;
step two: uniformly mixing the rest clear water with cement, 1/3 of water reducer, 1/2 of alkali excitant and 1/2 of hyper-dispersant to prepare cement paste;
step three: mixing and stirring the rest saline alkali water, 1/3 water reducer, the rest 1/2 hyper-dispersant, 1/2 alkali excitant, silica fume, fly ash, micro beads and mineral powder to obtain gelled slurry;
step four: mixing and uniformly stirring quartz sand subjected to water saturation treatment in the step II with the cement paste to obtain mixed mortar;
step five: mixing the regenerated fine aggregate subjected to the water saturation treatment of the saline-alkali water in the first step with the gelling slurry obtained in the third step, and stirring for 2-3 minutes to prepare gelling system mortar;
step six: mixing and stirring the mixed mortar in the fourth step and the mortar in the cementing system in the fifth step for 2-3 minutes, then adding steel fibers, slowly adding organic fibers after stirring for 1 minute, adding the rest 1/3 of water reducer after the fibers are uniformly dispersed, and continuously stirring for 3-5 minutes to obtain the regenerated UHPC suitable for the saline-alkali areas.
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