CN112745076B

CN112745076B - Concrete doped with dolomite powder and preparation method thereof

Info

Publication number: CN112745076B
Application number: CN202110013956.5A
Authority: CN
Inventors: 田景松; 刘炳尧; 王雷; 李冬; 庞永龙; 白启帆; 张子翕; 张硕; 李彦昌; 文俊强
Original assignee: Beijing Gaoqiang Concrete Co ltd
Current assignee: Beijing Gaoqiang Concrete Co ltd
Priority date: 2021-01-06
Filing date: 2021-01-06
Publication date: 2022-08-26
Anticipated expiration: 2041-01-06
Also published as: CN112745076A

Abstract

The application relates to the technical field of energy-saving and environment-friendly building materials, and particularly discloses dolomite stone powder doped concrete and a preparation method thereof, wherein the dolomite stone powder doped concrete comprises the following raw materials in parts by weight: 150-400 parts of cement; 150-170 parts of water; 30-50 parts of fly ash; 60-90 parts of granulated blast furnace slag powder; 30-50 parts of dolomite powder; 700-900 parts of medium sand; 900-1061 parts of gravel; 5-10 parts of a polycarboxylic acid water reducing agent. The concrete prepared by the method has excellent mixture performance, mechanical property and durability.

Description

Concrete doped with dolomite powder and preparation method thereof

Technical Field

The application relates to the technical field of energy-saving and environment-friendly building materials, in particular to a dolomite powder doped concrete and a preparation method thereof.

Background

The dolomite fines are dolomite fines with higher purity, the 0.045mm screen residue of which is within 45 percent and is obtained by air separation and dust collection or screening redundant powdery particles in sandstone aggregates in the process of crushing dolomite rocks into dolomite sandstone aggregates, and the dolomite fines are mine wastes and are good inert auxiliary cementing materials.

Common mineral admixtures such as fly ash, ground slag powder and the like are used as important cementing materials in concrete, are applied to a large number of concrete structures, become indispensable important raw materials and form huge market demands. With the adjustment of energy structures in China, the proportion of coal used as thermal power generation and heating is gradually reduced, new energy sources such as nuclear power, water energy, wind energy, solar energy and the like are developed greatly, the new energy sources begin to occupy the most important position in national economy, the utilization amount of coal is reduced year by year even if the traditional coal energy sources are used in parts in North China, the yield of fly ash serving as a product after coal combustion is reduced year by year, a large amount of low-quality fly ash such as desulfurization and denitrification begins to be used in concrete, and the situation that the supply market of the fly ash is incomplete and short in supply appears, so that the quality of the concrete is seriously influenced. Especially, the fly ash is in shortage at the end of the heating season and outside the peak period of power consumption in summer, and the problem of the healthy development of the concrete industry is urgently solved by searching a new product for replacing the fly ash.

The ecological environment of green water of the Qingshan mountain is built, a plurality of areas begin to comprehensively treat river channels and forbid the collection of natural gravels, dry production in the machine-made sand industry is developed vigorously due to the characteristics of water conservation and environmental protection and gradually becomes the mainstream mode of gravels for concrete, a large amount of dust is generated in the process of crushing dolomite rocks to prepare the gravels aggregate, and a dust collector is usually installed in a gravels production crushing workshop for dust collection in order to protect the ecological environment; the dolomite rock powder dust collected by the dust remover has the same mineral material as the rock base material, and can be used as a material for replacing fly ash. However, dolomite fines often suffer from the following difficulties in formulating concrete for practical use: the dolomite powder is singly doped into concrete, the bleeding phenomenon is easy to occur on the surface of the concrete, the flow property and the later period mechanical property of the prepared concrete mixture are lower than those of common concrete with the same cement dosage of the fly ash and the granulated blast furnace slag powder, and the use of the dolomite powder in the concrete industry is further limited.

The mine waste cannot be effectively utilized, so that the mine waste becomes a great problem for restricting the healthy development of dry-method production of sand stones in mines. Therefore, it is necessary to prepare high-performance concrete by using the dolomite powder mine waste which is abundant in reserves and low in price. In view of this, the present application provides a dolomite powder doped concrete and a preparation method thereof, which aims to solve the above problems. Experimental research proves that whether the dolomite powder and the fly ash or the granulated blast furnace slag powder are compounded and doped into concrete or are independently doped into the concrete to replace part of cement, the performance and the mechanical property of a prepared concrete mixture are not as good as those of the mixture obtained by doping the fly ash, the granulated blast furnace slag powder and the dolomite powder into the concrete according to a certain proportion.

Disclosure of Invention

In order to effectively utilize dolomite powder and enable the performance of the dolomite powder doped concrete to be more excellent, the application provides the dolomite powder doped concrete and the preparation method thereof.

In a first aspect, the present application provides a dolomite powder doped concrete, which adopts the following technical scheme:

the dolomite stone powder doped concrete comprises the following raw materials in parts by weight: 150-400 parts of cement; 150-170 parts of water; 30-50 parts of fly ash; 60-90 parts of granulated blast furnace slag powder; 30-50 parts of dolomite powder; 700-900 parts of medium sand; 900-1061 parts of macadam; 5-10 parts of a polycarboxylic acid water reducing agent.

By adopting the technical scheme, the concrete cementing material prepared by the method consists of granulated blast furnace slag powder, dolomite rock powder, fly ash and cement, and the technical route is that the advantages complementary action and synergistic effect of the cement and various admixtures are fully exerted by optimizing the proportion, improving the grain composition by using the dolomite rock powder, improving the micro-bead effect and low-heat property of the fly ash and the low-heat property and strength effect of the mineral powder, so that the concrete has good impermeability, frost resistance, crack resistance and lower hydration heat temperature rise. The dolomite powder is adopted to prepare the concrete, so that the dolomite powder is green and environment-friendly, saves resources and utilizes wastes, and the dolomite powder mainly comprises calcium carbonate, magnesium oxide and silicon dioxide, has good compressive strength and flexural strength, can improve the mechanical property of the concrete, reduce the drying shrinkage and internal stress of the concrete, reduce the expansion of cracks and improve the cracking resistance and impermeability of the concrete. The granulated blast furnace slag powder mainly comprises oxides, mainly contains silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide and the like, has light weight and good dispersibility, can be fully filled in cement slurry, reduces the porosity of concrete, and improves the compactness, impermeability and strength of the concrete. After the polycarboxylic acid high-performance water reducing agent is added into the concrete, an adsorption film is formed on the surface of concrete particles, the hydration speed of the concrete is influenced, the growth of concrete stone crystals is more perfect, so that capillary gaps of water evaporation are reduced, the internal network structure of the concrete is more compact, and the hardness and the structural compactness of the concrete are improved.

Preferably, the weight ratio of the dolomite powder to the fly ash to the granulated blast furnace slag powder is 1:1: 2-3.

By adopting the technical scheme, for the concrete with the same mixing ratio of the double-doped fly ash and the granulated blast furnace slag powder, the fly ash or the slag powder is replaced by the stone powder, the strength values of the concrete can be changed in different degrees, and the influence degree of the replaced fly ash on the strength is smaller; when the weight ratio of the dolomite powder, the fly ash and the granulated blast furnace slag powder is 1:1: 2-3 for the medium-strength concrete, a synergistic effect occurs, and the strength of the concrete is obviously higher than that of the concrete with other mixing ratios.

Preferably, the dolomite fines are dolomite fines with higher purity, which are obtained by winnowing and dust collection of the dolomite rocks or screening redundant powdery particles in the sandstone aggregates by a square-hole sieve with the diameter of 45 mu m in the process of crushing the dolomite rocks into the dolomite sandstone aggregates.

By adopting the technical scheme, the influence of the fineness and the purity of the dolomite powder on the performance of the concrete is large, when the fineness of the dolomite powder particles is large, the performance of the concrete is reduced, the water seepage phenomenon easily occurs in the workability, the strength of the concrete is reduced, and when the fineness (45 mu m screen residue) of the dolomite powder is less than or equal to 45%, the performance of the concrete is greatly improved.

Preferably, the raw materials also comprise the following components in parts by weight: 1-5 parts of an anti-cracking waterproof agent for the expanded fiber, 30-80 parts of a modified polypropylene fiber and 20-50 parts of a dispersing agent.

By adopting the technical scheme, after the expansion fiber anti-cracking waterproof agent is doped into the concrete, a plurality of fibers can be distributed in the concrete on the basis of the modified polypropylene fibers, and the dispersed fibers can reduce the stress of plastic shrinkage of the concrete and improve the anti-cracking performance of the concrete; the fiber network formed by the anti-cracking waterproof agent of the expansive fibers can improve the cohesiveness of the concrete, improve the layering phenomenon of the concrete and improve the segregation resistance of the concrete; in addition, the expansion components in the expansion fiber anti-cracking waterproof agent can be expanded properly to compensate the phenomenon of shrinkage cracking of concrete, so that the anti-cracking and anti-permeability performance of the concrete is improved, and the durability of the concrete is further improved. The expansion fiber anti-cracking waterproof agent not only has hydration reaction with cement in concrete to generate a large amount of ettringite to fill capillary pores of the concrete, cut off the communication between the capillary and other gaps and reduce the pore diameter of the capillary, thereby achieving the purposes of compacting the concrete and improving the impermeability, but also introduces an organic waterproof component, further seals the capillary gaps of the concrete through a film forming principle, and further improves the impermeability of the concrete. The modified polypropylene fiber has high impact strength, can inhibit the occurrence of cracks caused by concrete shrinkage, and ensures that the concrete has good looseness resistance, high residual strength, low abrasion, high permeation pressure resistance and high tensile strength and breaking strength.

Preferably, the modified polypropylene fiber is prepared by the following method:

(1) dispersing 30 wt% of nano titanium nitride into ethylene glycol, uniformly mixing terephthalic acid and antimony trioxide, and adding the mixture into a polymerization kettle, wherein the mass ratio of the ethylene glycol to the terephthalic acid to the antimony trioxide is 1: 2.75: 0.02, sealing the polymerization kettle, pressurizing to 0.25MPa, heating to 250 ℃, stirring at the speed of 100r/min, and carrying out esterification reaction for 1.5 hours to obtain an intermediate product;

(2) carrying out polycondensation treatment on the intermediate product to ensure that the vacuum degree is increased to 20Pa, controlling the temperature at 270 ℃, adjusting the stirring speed to 240r/min, and reacting for 1.5h to obtain a nano titanium nitride/PET polycondensate;

(3) and (3) adjusting the pressure to normal pressure, adjusting the temperature to 50 ℃, adjusting the stirring speed to 130r/min, adding polypropylene resin accounting for 35 percent of the total amount of the nano titanium nitride/PET polycondensate into the reaction kettle in the step (2), uniformly stirring and mixing the polypropylene resin with the nano titanium nitride/PET polycondensate, discharging, cooling and granulating, and spinning the master batch to obtain the modified polypropylene fiber.

By adopting the technical scheme, the PET has good mechanical property, particularly tensile property, and stable property and strong tolerance; the nano titanium nitride is compounded with the polypropylene fiber, so that the polypropylene fiber has a certain heat absorption effect, and the inner surface temperature difference during concrete hydration is reduced, so that the temperature stress is reduced, and the possibility of generating temperature cracks in the concrete is reduced; PET, nano titanium nitride and polypropylene fiber are compounded, so that the concrete has a reinforcing effect, the concrete has tensile strength for resisting larger temperature stress, and the generation condition of concrete cracks is improved.

Preferably, the dispersant is sodium methylene bis (methyl) naphthalene sulfonate.

By adopting the technical scheme, the sodium methylene bis (methyl naphthalene) sulfonate is taken as a dispersing agent, is easy to dissolve in water, has excellent diffusion performance, and simultaneously has affinity with the modified polypropylene fiber, so that the modified polypropylene fiber can be diffused into concrete, and the strength of the concrete is improved.

Preferably, the raw materials also comprise the following components in parts by weight: 7-10 parts of ethylene-vinyl acetate copolymer, 0.1-0.3 part of 4- (4-pyridyloxy) -benzenesulfonic acid and 1-2 parts of perylene-3, 4,9, 10-tetracarboxylic acid.

By adopting the technical scheme, the ethylene-vinyl acetate copolymer, the 4- (4-pyridyloxy) -benzenesulfonic acid and the perylene-3, 4,9, 10-tetracarboxylic acid are compounded, so that the tensile strength, the compressive strength and the flexibility of concrete are enhanced, the cohesiveness of the concrete can be improved, and the layering phenomenon of the concrete is improved, so that the concrete is not easy to crack, and the condition that the impervious concrete cracks is improved.

Preferably, the raw materials also comprise the following components in parts by weight: 2-15 parts of sodium alginate and 10-30 parts of guar gum.

By adopting the technical scheme, the sodium alginate is easy to dissolve in water and can form a viscous liquid, so that the sodium alginate has certain bonding capacity on the modified polypropylene fiber, the modified polypropylene fiber is fully mixed with cement, granulated blast furnace slag powder, fly ash and the like, raw materials can be fully mixed, and meanwhile, the sodium alginate also has certain hygroscopicity, so that the modified polypropylene fiber also has a crack prevention effect in the later use process of concrete, so that the service life and the strength of the concrete are improved, the sodium alginate can generate a synergistic effect with ethylene-vinyl acetate copolymer, 4- (4-pyridyloxy) -benzenesulfonic acid, perylene-3, 4,9, 10-tetracarboxylic acid, the cohesive force and the cohesiveness of the concrete can be improved, the separation rate of material components is reduced, and the homogeneity, the workability and the permeability of the concrete are improved, The setting time of the concrete is adjusted, so that the impermeability of the concrete is further improved. Guar gum is as water-soluble macromolecular substance, can be mutually soluble with water, and guar gum and modified polypropylene fiber have certain affinity simultaneously to guar gum has excellent dispersion properties in cold water, effectively prevents the modified polypropylene fiber and reunites the phenomenon in the in-process of stirring, improves polypropylene fiber's utilization ratio.

Preferably, the raw materials also comprise the following components in parts by weight: 5-8 parts of mesoporous molecular sieve and 5-10 parts of pumice powder.

By adopting the technical scheme, the mesoporous molecular sieve and the pumice powder can increase the stacking density of the stone aggregates in a limited way, thereby increasing the compressive strength and the impermeability of the concrete. The mesoporous molecular sieve and the pumice powder are both porous materials, and have the characteristics of high adsorption capacity due to the action of an electric field and polarity inside holes of the mesoporous molecular sieve and the pumice powder, and water is a molecule with strong polarity, so that the mesoporous molecular sieve and the pumice powder can be easily absorbed in the concrete mixing process, and along with the extension of the hydration age, the water absorbed by the mesoporous molecular sieve and the pumice powder can be continuously released to supplement capillary water inside the concrete, so that the capillary water and the relative humidity inside the concrete are improved, the negative pressure of the capillary is reduced, and the self-shrinkage of the concrete can be effectively reduced. And the modified polypropylene fiber enters or partially enters the mesoporous molecular sieve and the pumice powder and is adsorbed in the pore diameters of the mesoporous molecular sieve and the pumice powder, and the mesoporous molecular sieve and the pumice powder play a role in connecting nodes, so that the modified polypropylene fiber forms a network structure in a cementing layer. When concrete is stressed, the modified polypropylene fiber tends to be separated from the mesoporous molecular sieve and the pumice powder, and the adsorption force between the mesoporous molecular sieve and the pumice powder on the modified polypropylene fiber prevents the modified polypropylene fiber from being separated from the mesoporous molecular sieve and the pumice powder, so that the strength of the concrete is improved.

In a second aspect, the present application provides a method for preparing a dolomite powder doped concrete, which adopts the following technical scheme:

a preparation method of dolomite powder doped concrete is characterized by comprising the following steps: the method comprises the following steps:

step 1: mixing the medium sand, the broken stone and 2/3 water according to a set proportion, and uniformly stirring to form a premix; step 2: according to a set proportion, cement, fly ash, granulated blast furnace slag powder, dolomite powder, modified polypropylene fiber, an expansion fiber anti-cracking waterproof agent, a dispersing agent, an ethylene-vinyl acetate copolymer, 4- (4-pyridyloxy) -benzenesulfonic acid, perylene-3, 4,9, 10-tetracarboxylic acid, sodium alginate, guar gum, a polycarboxylic acid water reducing agent, a mesoporous molecular sieve, pumice powder and the rest water are added into the premix and continuously stirred uniformly to form a mixture;

and step 3: and (3) uniformly stirring the mixture to prepare the concrete mixture doped with dolomite powder.

By adopting the technical scheme, the medium sand, the broken stone and the modified polypropylene fiber are mixed, then a certain amount of water is added, so that water is adhered to the surfaces of the medium sand, the broken stone and the modified polypropylene fiber, then cement, fly ash, granulated blast furnace slag powder, dolomite powder, a polycarboxylic acid water reducing agent, guar gum and sodium alginate are added, and the absorption of the cement, the blast furnace slag powder and the like to the water is reduced, so that the water amount is reduced.

In summary, the present application has the following beneficial effects:

1. the technical route of the concrete cementing material is that the concrete cementing material is prepared from granulated blast furnace slag powder, dolomite powder, coal ash and cement by optimizing the proportion, improving the grain composition by using the dolomite powder, and fully exerting the complementary advantages and the synergistic effects of the cement and various admixtures by using the micro-bead effect and the low-heat characteristic of the coal ash and the low-heat characteristic and the strength effect of the mineral powder, so that the concrete has good impermeability, frost resistance, crack resistance and lower hydration heat temperature rise;

2. the modified polypropylene fiber has higher impact strength, can inhibit the concrete from cracking due to dry shrinkage, and ensures that the concrete has better loosening resistance, higher residual strength, smaller abrasion, higher seepage pressure resistance and increased tensile strength and breaking strength;

3. for the concrete with the same mixing proportion of the double-doped fly ash and the granulated blast furnace slag powder, the fly ash or the slag powder is replaced by the stone powder, the strength values of the concrete can be changed in different degrees, and the influence degree of the replaced fly ash on the strength is smaller; for medium strength concrete, the ratio of dolomite fines to fly ash is 1:1, a synergistic effect appears, and the concrete strength is obviously higher than that of other mix proportion concrete;

4. the dolomite rock powder is mixed into the concrete, and the drying shrinkage of the concrete and the hydration heat of the concrete are obviously reduced under the condition of the same cement consumption. By doping dolomite powder into concrete for preparing mass concrete and self-compacting concrete, the advantages of low shrinkage, low hydration heat and the like are utilized, and the long-term performance and the durability of the concrete can be greatly improved.

Drawings

FIG. 1 is a graph comparing adiabatic temperature rise curves of concrete in comparative example 3 and comparative example 4 of the present application.

FIG. 2 is a graph showing the non-contact shrinkage of concrete in comparative examples 5 to 8 of the present application.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples.

The raw materials in the application are all purchased from the market.

The cement is P.O42.5 ordinary portland cement; the fly ash is F-class II fly ash, the fineness is 15.4%, the water demand ratio is 95%, the ignition loss is 2.5%, and the 28-day compressive strength ratio is 88%; the medium sand is natural medium sand in a II area with the fineness modulus of 2.9, the mud content of the medium sand is less than or equal to 0.6 percent, and the mud block content is less than or equal to 0.1 percent; the continuous size fraction of the crushed stone is 5-20mm, the mud content of the crushed stone is 0.5%, the mud block content is 0.1%, the needle-shaped content is 2%, the crushing value is 5.5%, and the apparent density is 2760kg/m ³ The compressive strength of rock is 113 MPa; the granulated blast furnace slag powder is S95-grade slag powder, the flow rate ratio of the mortar is 106 percent, and the specific surface area is 428m ² /kg。

In recent years, the most widely used resources of the concrete, such as the fly ash, the mineral powder and the like, are gradually in shortage along with the scale construction of high-speed railways, hydraulic engineering, nuclear power stations and the like, and particularly, the fly ash has smaller and smaller coal burning amount and smaller output, so that a mineral admixture resource which is rich in resources, low in price and easy to control in quality is urgently needed to be sought. The research on carbonate rock powder as a concrete admixture is more and more, the carbonate rock powder mainly comprises limestone powder and dolomite rock powder, the standard of the limestone powder as the concrete admixture is published and implemented, but the understanding of the dolomite rock powder is less, and the reason is that the following aspects exist: 1. people do not sufficiently study the dolomite powder as the concrete admixture in tests, and the dolomite powder is rarely used in the industry. 2. No relevant product standard specification exists, so that the dolomite powder used as the mineral admixture in the engineering cannot be subjected to field inspection and engineering acceptance. Further testing of dolomite fines is necessary to enhance the understanding of dolomite fines. The dolomite powder is dolomite powder dust collected by a dust remover, the mineral material is the same as the rock base material, the fineness is 20-45% according to 0.045mm screen residue, the water demand ratio is 95-100%, and the methylene blue MB value is 0.20-0.75. According to the application, the dolomite powder is used for replacing fly ash and granulated blast furnace slag powder with different proportions, and the influence of the dolomite powder on the workability, the mechanical property and the durability of concrete is researched, so that the dolomite powder is effectively utilized in the concrete, and the resource waste and the environmental pollution are reduced.

Preparation examples of raw materials

Preparation example 1

The preparation method of the modified polypropylene fiber comprises the following steps:

(2) carrying out polycondensation treatment on the intermediate product to ensure that the vacuum degree is increased to 20MPa, controlling the temperature at 270 ℃, adjusting the stirring speed to 240r/min, and reacting for 1.5h to obtain a nano titanium nitride/PET polycondensate;

Examples

Example 1

The dolomite powder doped concrete is prepared by the following steps:

step 1: respectively taking 700kg of medium sand, 900kg of broken stone and 100kg of water, mixing according to a set proportion, adding into a stirrer, and uniformly stirring to form a premix;

step 2: 150kg of cement, 30kg of fly ash, 90kg of granulated blast furnace slag powder, 30kg of dolomite powder, 5kg of polycarboxylic acid water reducing agent and 50kg of the rest water are added into the premix in the stirrer and are continuously stirred uniformly to form a mixture.

And step 3: and (3) uniformly stirring the mixture to prepare the concrete mixture doped with the dolomite powder.

The remaining examples are different from example 1 in the raw materials and the amounts of the raw materials added, and are specifically shown in tables 1 and 2.

TABLE 1 Components and amounts of Components added for examples 1-10

TABLE 2 Components and amounts of Components added for examples 11-16

Composition of	Example 11	Example 12	Example 13	Example 14	Example 15	Example 16
							Cement	228	228	228	228	228	228
Water (W)	163	163	163	163	163	163
							Fly ash	38	38	38	38	38	38
Granulated blast furnace slag powder	76	76	76	76	76	76
							Dolomite powder	38	38	38	38	38	38
Medium sand	768	768	768	768	768	768
							Breaking stone	1061	1061	1061	1061	1061	1061
Polycarboxylic acid water reducing agent	7.6	7.6	7.6	7.6	7.6	7.6
							Anti-cracking waterproof agent for expansion fiber	5	5	5	5	5	5
Modified polypropylene fiber	80	80	80	80	80	80
							Dispersing agent	50	50	50	50	50	50
Ethylene-vinyl acetate copolymer	10	10	10	10	10	10
							4- (4-pyridyloxy) -benzenesulfonic acid	0.3	0.3	0.3	0.3	0.3	0.3
Perylene-3, 4,9, 10-tetracarboxylic acids	2	2	2	2	2	2
							Sodium alginate	2	9.5	15	15	15	15
Guar gum	10	20	30	30	30	30
							Mesoporous molecular sieve	/	/	/	5	6.5	8
Pumice powder	/	/	/	5	7.5	10

Comparative example

Comparative examples 1-8 are compared to example 4 with the difference that the components and component levels are different, as shown in table 3.

TABLE 3 Components and component amounts of comparative examples 1-8

Composition of	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5	Comparative example 6	Comparative example 7	Comparative example 8
									Cement	228	228	266	266	284	284	246	246
Water (W)	163	163	163	163	163	163	163	163
									Fly ash	76	76	/	/	/	95	/	132
Granulated blast furnace slag powder	76	38	/	/	/	/	/	/
									Dolomite powder	/	38	114	179	95	/	132	/
Medium sand	768	768	768	780	847	847	847	847
									Crushing stone	1061	1061	1061	992	994	994	994	994
Polycarboxylic acid water reducing agent	7.6	7.6	7.6	8.9	7.58	7.58	7.56	7.56

Performance test

Detection method

The concrete mixtures prepared by stirring in the embodiments 1 to 16 and the comparative examples 1 to 8 are subjected to concrete performance detection, and the slump, the expansion, the compressive strength, the concrete adiabatic temperature rise and the non-contact drying shrinkage indexes of the concrete mixtures are respectively measured by detecting according to standard methods in GB/T50080-2016 (standard for testing the performance of common concrete mixtures) and GB/T50081-2019 (standard for testing the physical and mechanical properties of concrete), DL/T5150-2017 (test procedure for hydraulic concrete), GB/T50082-2009 (standard for testing the long-term performance and the durability of common concrete) and the non-contact drying shrinkage indexes.

Testing and detecting concrete slump, expansion and mechanical properties according to GB/T50080-2016 (Standard for testing methods of Performance of common concrete mixtures) and GB/T50081-2019 (Standard for testing methods of physical and mechanical Properties of concrete), wherein when the slump and the expansion of the concrete are detected, a slump tester for the slump test is required to meet the requirements of JG/T248 (Standard for concrete slump tester) in the existing industry standard, the inner wall and the bottom plate of the slump cone are required to be wetted without clear water, the bottom plate is required to be placed on a solid horizontal plane, the slump cone is arranged in the center of the bottom plate, foot pedals on two sides are stepped by feet, and the slump cone is required to be kept at a fixed position during loading; concrete mixture sample should divide the three-layer uniformly to pack into in the slump section of thick bamboo, every dress a layer concrete mixture, use the tamper from the edge to the even interpolation of center spiral 25 times, every layer should be 1/3 that the section of thick bamboo is high after the tamping, should run through whole degree of depth when inserting the bottom, should run through this layer to lower floor top surface when vibrating upper strata and middle level. Removing peripheral impurities, vertically pulling out a slump cone, placing the slump cone on the same horizontal plane of the mixture, measuring the difference between the top end of the slump cone and the height of the slump cone to be used as a slump value, and accurately measuring the slump value to 1mm and repairing the slump cone to about 5 mm; measuring the maximum diameter at which diffusion is no longer occurring or has taken place for 50s using a straight steel ruler and the diameter perpendicular to the maximum diameter; the result of the test of the expansibility is taken as the arithmetic mean value of two diameters with the difference of less than 50mm, the result is accurate to 1mm, and the result is reduced to 5 mm.

When carrying out concrete compressive strength test, should once only pack into the examination mould with concrete mixture, use the spatula to insert along the examination mould inner wall and smash during the loading to make the mixture go out the examination mould upper orifice, use the shaking table vibration closely knit, go out the thick liquid and do not have the big bubble and spill over to the surface. Standing for 1-2d at 20 + -5 deg.C and relative humidity of more than 50%; and (4) after hardening, removing the test piece, demolding, and then placing the test piece in a standard curing box or a standard curing room for curing to the specified age. Firstly measuring the size of a sample to be accurate to 1mm, calculating the pressed area of the sample, continuously and uniformly loading the sample by adopting a hydraulic testing machine at the speed of 10 +/-1 mm/min until the sample is damaged, and recording the damage load to be accurate to 10N. The compressive strength of the concrete is calculated as fcc ═ F/A, where: fcc is the compressive strength of the concrete cubic test piece, MPa; f is the specimen failure load, N; a is the pressed area of the test piece, mm ² 。

3 test pieces are used as a compression strength test group, and the compression strength detection value is accurate to 0.1 MPa. The compressive strength value can be selected in three ways: (1) after the 3 groups of detection values are detected, when the maximum value or the minimum value is compared with the difference value of the intermediate strength and exceeds 15 percent of the difference value, the intermediate value is taken as the detected compressive strength value of the small group of test pieces; (2) referring to the above detection and calculation method, if the maximum and minimum values are within 15% of the median, the arithmetic mean of the 3 test pieces in the group is taken as the detected compressive strength value of the group; (3) once the maximum value and the minimum value of the 3 data are both out of the range of 15% of the intermediate value, the set of experimental data cannot be used, and the test piece should be considered again and tested, and the test results are shown in table 4.

As shown in fig. 1, in the application, a concrete adiabatic temperature rise test is performed according to a standard method in DL/T5150-2017, namely hydraulic concrete test regulations, and a concrete mixture is placed in a room with the temperature of 20 +/-5 ℃ for 24 hours before the test, so that the temperature of the concrete mixture is consistent with the room temperature, and the initial temperature is recorded; measuring the temperature of the concrete mixture, then loading the concrete mixture into an insulated temperature rise container in two layers, embedding a temperature measuring pipe in the center of the container according to the instruction of the instrument, feeding the sample container into an insulated chamber, and loading the sample container into the temperature measuring pipe through a temperature measuring element; starting an adiabatic temperature rise instrument to start a test; the 7d or 28d adiabatic temperature rise curves were determined as required for the test. The adiabatic temperature rise value was calculated as follows. And drawing the temperature rise process curve graphs of the concrete in the comparative example 3 and the concrete in the comparative example 4 by taking the time as an abscissa and the temperature rise as an ordinate.

In the formula: thetan < - - - -n-day age concrete adiabatic temperature rise value, DEG C;

θ _n -temperature rise, c, recorded by an n-day age instrument;

θ ₀ -initial temperature of the concrete mix, c;

C _k -the product of the mass of the concrete specimen and the average specific heat capacity of the concrete, kJ/deg.c;

C _m -total heat capacity of adiabatic calorimeter, supplied by the manufacturer, kJ/c;

as shown in FIG. 2, the concrete of comparative example 5, comparative example 6, comparative example 7 and comparative example 8 was subjected to non-contact shrinkage test according to the non-contact shrinkage standard method of GB/T50082-2009 Standard test method for Long-term Performance and durability of ordinary concrete. The test piece is a prism test piece with the side length of 100 multiplied by 515mm, and each group comprises 3 test pieces; the test is carried out in the environment with the temperature of 20 +/-2 ℃ and the humidity of 60 +/-5 percent, the test piece is tested with a mold, and the concrete mixture is loaded into the test mold and then is immediately transferred into a constant-temperature constant-humidity curing room with the mold; the initial setting time of the concrete is measured at the same time of forming the test piece, the initial setting time is consistent with the early shrinkage test environment, the initial readings of the left side and the right side of the test piece are measured during the initial setting of the concrete, and then the deformation readings of the test piece are measured at least every 1 h; the test instrument has the function of automatically acquiring test data; the arithmetic average value of the test results of 3 test pieces in each group is taken as the early-age contraction value of the group, and the calculation and the record are accurate to 1.0 multiplied by 10 < -6 >.

The results are shown in Table 4.

TABLE 4

It can be seen by combining examples 1-4 and comparative examples 1-4 with table 4 that the strength of the concrete doped with dolomite rock powder instead of 50% fly ash is significantly higher than that of comparative example 1, comparative example 2 and comparative example 3 under the condition that the slump and the extension of the mixture are approximately the same, and through data analysis, the dolomite rock powder and the fly ash have a synergistic effect on improving the strength performance of the concrete. Furthermore, as can be seen from example 4, the weight ratio of dolomite fines, fly ash and granulated blast furnace slag powder was 1: when the ratio is 1:2, the dolomite powder doped concrete has excellent mechanical properties.

According to the analysis of the adiabatic temperature rise curve diagrams of the comparative example 3 and the comparative example 4 in the figure 1, compared with the comparative example 3, in the case of the same cement dosage, the comparative example 4 is doped with more dolomite dust, the time of the adiabatic temperature rise peak value is late, the temperature peak value is lower, the control of the adiabatic temperature rise peak value and the delay of the time of the peak value of the mass concrete are facilitated, and the cracking trend caused by the temperature rise is reduced. This advantage can be fully exploited in the formulation of large volumes of concrete.

According to the analysis of the data of the non-contact shrinkage experiment in FIG. 2, the shrinkage value of the concrete doped with 95kg of dolomite powder in the comparative example 5 and the shrinkage value of the concrete doped with 95kg of fly ash in the comparative example 6 are slightly lower; the concrete doped with 132kg of dolomite powder in the comparative example 7 and the concrete doped with 132kg of fly ash in the comparative example 8 have slightly higher shrinkage values in the early stage and are basically equal in the later stage, and experiments show that the influence of the dolomite powder on the shrinkage performance is similar to the effect of the fly ash, and the dolomite powder can be used for crack-sensitive parts commonly used by the fly ash.

By combining examples 4-7 and table 4, it can be seen that after the expansion fiber anti-cracking waterproof agent, the modified polypropylene fiber and the dispersant are added, the adiabatic temperature rise of the concrete (the smaller the adiabatic temperature rise, which indicates that the smaller the difference between the internal stress and the external stress of the concrete, the less likely the concrete will crack), the drying shrinkage is significantly reduced, and the 28d and 60d compressive strength of the concrete is significantly improved; the fiber network formed by the expansion fiber anti-cracking waterproof agent can improve the cohesiveness of the concrete, improve the layering phenomenon of the concrete and improve the segregation resistance of the concrete; in addition, the expansion components in the expansion fiber anti-cracking waterproof agent can be expanded properly to compensate the phenomenon of shrinkage cracking of concrete, so that the anti-cracking and anti-permeability performance of the concrete is improved, the durability of the concrete is further improved, and the strength is improved. Meanwhile, the impact strength of the modified polypropylene fiber is high, the compression strength of concrete can be improved, the modified polypropylene fiber has a thermal effect, and the difference value of the internal temperature and the external temperature of the concrete is reduced, so that the difference of the internal stress and the external stress of the concrete is reduced, cracks in the concrete caused by dry shrinkage can be inhibited, the looseness resistance of the concrete is good, the residual strength is high, the abrasion is low, the permeation pressure resistance is high, and the compression strength and the breaking strength are increased.

As can be seen by combining examples 7-10 and Table 4, the compressive strength of the concrete can be further improved by adding the ethylene-vinyl acetate copolymer, 4- (4-pyridyloxy) -benzenesulfonic acid and perylene-3, 4,9, 10-tetracarboxylic acid to the concrete;

by combining examples 10-13 and table 4, it can be seen that the addition of sodium alginate and guar gum to the concrete can effectively improve the compressive strength of the concrete without affecting the workability of the concrete;

it can be seen from the combination of examples 13-16 and table 4 that the compressive strength of concrete can be further enhanced by adding the mesoporous molecular sieve and the pumice powder into the concrete, and the stacking density between the stone aggregates can be increased in a limited way by the mesoporous molecular sieve and the pumice powder, so that the compressive strength and the impermeability of the concrete are increased. Meanwhile, the mesoporous molecular sieve and the pumice powder are both porous materials, the modified polypropylene fibers enter or partially enter the mesoporous molecular sieve and the pumice powder and are adsorbed in the pore diameters of the mesoporous molecular sieve and the pumice powder, and the mesoporous molecular sieve and the pumice powder play a role in connecting nodes, so that the modified polypropylene fibers form a net structure in a cementing layer. When concrete is stressed, the modified polypropylene fiber tends to be separated from the mesoporous molecular sieve and the pumice powder, and the adsorption force between the mesoporous molecular sieve and the pumice powder on the modified polypropylene fiber prevents the modified polypropylene fiber from being separated from the mesoporous molecular sieve and the pumice powder, so that the strength of the concrete is improved.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The dolomite stone powder doped concrete is characterized by comprising the following raw materials in parts by weight: 150-400 parts of cement; 150-170 parts of water; 30-50 parts of fly ash; 60-90 parts of granulated blast furnace slag powder; 30-50 parts of dolomite powder; 700-900 parts of medium sand; 900-1061 parts of macadam; 5-10 parts of a polycarboxylic acid water reducing agent; 1-5 parts of an anti-cracking waterproof agent for expanded fibers, 30-80 parts of modified polypropylene fibers, 20-50 parts of a dispersing agent, 7-10 parts of an ethylene-vinyl acetate copolymer, 0.1-0.3 part of 4- (4-pyridyloxy) -benzenesulfonic acid, 1-2 parts of perylene-3, 4,9, 10-tetracarboxylic acid, 2-15 parts of sodium alginate, 10-30 parts of guar gum, 5-8 parts of a mesoporous molecular sieve and 5-10 parts of pumice powder; the weight ratio of the dolomite powder, the fly ash and the granulated blast furnace slag powder is 1:1: 2-3; the modified polypropylene fiber is prepared by the following method:

2. The dolomite stone powder doped concrete according to claim 1, wherein: the dolomite powder is prepared by air separation and dust collection of dolomite rock in the process of crushing the dolomite rock into dolomite sandstone aggregate or by sieving redundant powdery particles in the sandstone aggregate by a square-hole sieve with the particle size of 45 mu m until the residue is within 45 percent.

3. The dolomite stone powder doped concrete according to claim 1, wherein: the dispersant is sodium methylene bis (methyl) naphthalene sulfonate.

4. A method for preparing a dolomite powder doped concrete as claimed in any one of claims 1 to 3, wherein: the method comprises the following steps:

step 1: mixing the medium sand, the broken stone and 2/3 water according to a set proportion, and uniformly stirring to form a premix;

step 2: according to a set proportion, adding cement, fly ash, granulated blast furnace slag powder, dolomite powder, modified polypropylene fiber, an expansion fiber anti-cracking waterproof agent, a dispersing agent, an ethylene-vinyl acetate copolymer, 4- (4-pyridyloxy) -benzenesulfonic acid, perylene-3, 4,9, 10-tetracarboxylic acid, sodium alginate, guar gum, a polycarboxylic acid water reducing agent, a mesoporous molecular sieve, pumice powder and the rest water into the premix, and continuously stirring uniformly to form a mixture;

and 3, step 3: and (3) uniformly stirring the mixture to prepare the concrete mixture doped with dolomite powder.