Low-heat early-strength steel fiber mass concrete and preparation process thereof

Abstract

The application discloses a kind of low heat early strength steel fiber mass concrete and its preparation process, belong to building material technical field.It is prepared by cement, mineral admixture, water, fine aggregate, coarse aggregate, steel fiber with the mass ratio of 413:177:147.5:657.3:1050:27.5.By adding steel fiber uniformly, the compressive strength and fluidity of concrete can be improved;Pouring by temperature control, the concrete early rapid hydration can also reduce the temperature inside the structure;The prepared water reducing agent can greatly improve the strength and durability of concrete by introducing various functional monomers, reduce the cracking of mass concrete, and also improve the early strength of concrete, speed up the production cycle;Therefore, the concrete prepared by the application has high early strength, good crack resistance and low hydration heat, and has strong fluidity, and has important application value in the field of building materials technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a low-heat early-strength steel fiber mass concrete and a preparation process thereof. BACKGROUND

[0002] In recent years, with the continuous increase of engineering scale, the reinforced concrete structure needs to bear greater load, and higher requirements are put forward for the strength and durability of the concrete. The temperature crack control and strength growth demand caused by mass concrete pouring become important factors affecting the safety of the project. The hydration heat is greater in the mass concrete, a greater internal and external temperature difference is formed, the early strength of the concrete material is low, and the concrete material is insufficient to bear stress and cracks, and the performance is deteriorated in the later period. In severe cases, other engineering disasters are even induced. Moreover, the hydration heat of the mass concrete also causes the decomposition of the ettringite in the mass concrete, and the ettringite is reformed after the temperature decreases, so that the mass concrete is expanded and damaged, thereby affecting the strength of the mass concrete structure.

[0003] In view of the above problems, the application discloses a low-heat early-strength steel fiber mass concrete and a preparation process thereof. The internal and external temperature difference of the mass pouring structure is reduced by reducing the hydration heat, and the early strength is increased to cope with the temperature stress and other load actions, so as to solve the problem that the mass pouring structure is prone to cracking in major projects, and has important application value in the technical field of building materials. SUMMARY

[0004] The application aims to overcome the defects of the prior art, and provides a low-heat early-strength steel fiber mass concrete and a preparation process thereof.

[0005] The object of the application can be achieved by the following technical solutions.

[0006] A preparation process of a low-heat early-strength steel fiber mass concrete, comprising the following steps:

[0007] The cement, the mineral admixture, the fine aggregate, the coarse aggregate and the steel fiber are uniformly added in a compulsory mixer, and the materials are mixed uniformly for 10-30s, then water is injected, and the stirring is continued for 3-4min, the material is discharged, and the vibration is carried out until the surface of the concrete mixture appears to be covered with a layer of paste, and substantially no air bubbles escape, that is, the compaction is completed, and finally the low-heat early-strength steel fiber mass concrete is obtained by pouring and forming.

[0008] Further, the mass ratio of the cement, the mineral admixture, the water, the fine aggregate, the coarse aggregate and the steel fiber is 413:177:147.5:657.3:1050:27.5.

[0009] Further, the cement is Portland cement, and the percentage of particles of 3-30 microns is more than 90%, and the percentage of particles less than 10 microns is not more than 10%.

[0010] Further, the fine aggregate is II zone sand with fineness modulus of 2.6-3.0.

[0011] Further, the coarse aggregate is processed from basalt raw rock, and the particle size is 5-20 mm with continuous gradation, wherein the content of needle-like particles is not more than 5%, and the crushing value is not more than 8%.

[0012] Further, the steel fiber is end-hook type steel fiber with aspect ratio of 80, length of 50 mm, equivalent diameter of 0.62 mm, and 8037 pieces / kg.

[0013] Further, the pouring temperature is 15-20℃.

[0014] Further, the mineral admixture is prepared by mixing the following raw materials in parts by weight: 40-60 parts of ground slag, 20-30 parts of fly ash, 14-20 parts of silica powder, and 4-12 parts of water reducing agent.

[0015] Further, the ground slag is not less than S95 grade.

[0016] Further, the fly ash is I or II grade F type fly ash.

[0017] Further, the silica ash has SiO2 content of more than 90%, and specific surface area of not less than 15000 m 2 / kg.

[0018] The addition of steel fiber can enhance the load effect of concrete, and also improve the compressive strength of concrete, and the uniform distribution of steel fiber in concrete can prevent the steel fiber from clustering, bending or breaking, and also enhance the fluidity of concrete; the pouring process controls the temperature to ensure early rapid hydration of concrete to increase early strength, and also reduce the maximum internal temperature of the poured structure.

[0019] Further, the water reducing agent is prepared by the following steps:

[0020] S1, in a three-necked flask equipped with stirring device, triethanolamine, 9-decenoic acid and N,N-dimethylformamide (DMF) were stirred and mixed uniformly, dibutyltin oxide (catalyst) and dicyclohexyl carbodiimide (DCC, dehydrating agent) were added, the reaction temperature was controlled at 75℃, and the reaction was kept for 8h, the reaction was continuously stirred during the reaction, after the reaction was completed, part of the solvent was removed by reduced pressure distillation, and then purified by column chromatography (eluent was a mixture of petroleum ether / ethyl acetate, the volume ratio of the two was 5:1), the eluent was removed by rotary evaporation, and the intermediate was obtained; the amount ratio of triethanolamine, 9-decenoic acid, N,N-dimethylformamide, dibutyltin oxide, dicyclohexyl carbodiimide was 16.3g:16.9g:150mL:0.2g:20.6g;

[0021] Under the catalysis of dibutyltin oxide and dicyclohexyl carbodiimide, esterification reaction occurred between the carboxyl group on 9-decenoic acid and the hydroxyl group on triethanolamine, by controlling the molar ratio of the two to be close to 1:1 and the triethanolamine to be slightly excessive, only one hydroxyl group on triethanolamine participated in the reaction, and the intermediate was obtained; the specific reaction process is as follows:

[0022]

[0023] S2, in a three-necked flask, nano-silica, ethanol aqueous solution and hydrochloric acid solution were mixed and ultrasonically treated for 30min, then silane coupling agent KH-570 was added, stirred and heated to 60℃, and kept for 1.5h, then stirred and heated to 80℃, and kept for 5h, the reaction was completed, cooled, filtered, washed with acetone and vacuum dried to obtain modified nano-silica; the amount ratio of nano-silica, ethanol aqueous solution, hydrochloric acid solution and silane coupling agent KH-570 was 1g:100mL:10mL:0.6g;

[0024] The surface of nano-silica contains a large number of hydroxyl groups, which can react with silane coupling agent KH-570 to introduce unsaturated carbon-carbon double bonds on the nano-silica;

[0025] S3, in a three-necked flask, ethylene glycol monovinyl polyoxyethylene ether (EPEG), hydrogen peroxide, modified nano-silica, intermediate and water are mixed to obtain a mixed solution, then acrylic acid and water are mixed to obtain A liquid; 3-mercaptopropionic acid, ascorbic acid and water are mixed to obtain B liquid; under stirring, A liquid and B liquid are slowly added into the mixed solution by dropwise adding method, the dropwise adding time is 1h, the reaction temperature is controlled at 15 DEG C during the dropwise adding process, after the dropwise adding is completed, the reaction is continuously kept for 1h, the reaction is completed, the pH value is adjusted to 5-7 by sodium hydroxide aqueous solution, to obtain a water reducing agent; the amount ratio of ethylene glycol monovinyl polyoxyethylene ether, hydrogen peroxide, modified nano-silica, intermediate, water, acrylic acid, 3-mercaptopropionic acid, ascorbic acid is 30g:5mL:0.3g:1.5g:45mL:3g:0.5g:0.04g;

[0026] Ethylene glycol monovinyl polyoxyethylene ether, modified nano-silica and intermediate all contain unsaturated carbon-carbon double bond, and the water-soluble solution polymerization method is used to obtain the water reducing agent;

[0027] The prepared water reducing agent contains nano-silica, the nano-particle has high activity and low particle size, can compactly fill and secondarily hydrate and reinforce the concrete, and can enhance the durability, optimize the physical structure and mechanical properties of the concrete; the nano-silica is modified, different functional groups and molecular structures are grafted on the surface of the nano-silica, due to the space steric hindrance between molecules, the dispersibility of the nano-silica is enhanced, and the performance of the nano-silica is fully played; in addition, the prepared water reducing agent is a polycarboxylic acid water reducing agent, has good water reducing property, and also has the functions of retarding and slump maintaining; in addition, the carboxylic acid functional group can adsorb Ca 2+ and SO4 2- , produced by the decomposition of ettringite, so that the free Ca 2+ and SO4 2- are reduced, the amount of ettringite is reduced, the damage of the mass concrete structure can be effectively reduced; in addition, the raw material of the water reducing agent is ethylene glycol monovinyl polyoxyethylene ether, which is a new ether macromonomer, the unsaturated double bond is directly connected with an oxygen atom, the unsaturated activity of the double bond is greatly improved, normal temperature or even low temperature polymerization is realized, and the polymerization time is greatly shortened, and the energy consumption is reduced; finally, the water reducing agent contains an alcohol amine group, can be used as an early strength agent of concrete, accelerates the production cycle, improves the work efficiency, and can improve the frost resistance of the concrete under low temperature conditions, and prevents cracking.

[0028] The beneficial effects of the present application are as follows:

[0029] 1. The prepared concrete can improve the compressive strength and fluidity of the concrete by uniformly adding steel fibers.

[0030] 2. The concrete is poured by controlling the temperature, so that the concrete is rapidly hydrated in early stage, and the temperature inside the pouring structure is reduced;

[0031] 3. The prepared water reducing agent can greatly improve the strength and durability of the concrete, reduce the cracking of mass concrete, and improve the early strength of the concrete and speed up the production cycle by introducing various functional monomers;

[0032] Therefore, the prepared concrete has high early strength, good crack resistance and low hydration heat, and has strong fluidity, and has important application value in the field of building material technology. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0034] Embodiment one

[0035] Preparation of water reducing agent:

[0036] S1, in a three-necked flask equipped with a stirring device, 16.3g of triethanolamine, 16.9g of 9-decenoic acid and 150mL of N,N-dimethylformamide were stirred and mixed uniformly, 0.2g of dibutyl tin oxide and 20.6g of dicyclohexyl carbodiimide were added, the reaction temperature was controlled at 75℃, and the reaction was kept for 8h, the reaction was continuously stirred during the reaction, after the reaction was completed, part of the solvent was removed by reduced pressure distillation, and then the intermediate was purified by column chromatography (eluent: mixed solvent of petroleum ether / ethyl acetate, volume ratio of 5:1), and the eluent was removed by rotary evaporation to obtain the intermediate;

[0037] S2, in a three-necked flask, 1g of nano-silicon dioxide (average particle size D50 of 20nm), 100mL of ethanol aqueous solution (mass fraction of 90%) and 10mL of hydrochloric acid solution (mass fraction of 12%) were mixed and ultrasonically treated for 30min, then 0.6g of silane coupling agent KH-570 was added, stirred and heated to 60℃, and kept for 1.5h, then stirred and heated to 80℃, and kept for 5h, the reaction was completed, cooled, filtered, washed with acetone and vacuum dried to obtain modified nano-silicon dioxide;

[0038] S3, in a three-necked flask, 30 g of ethylene glycol monovinyl polyoxyethylene ether (molecular weight 3000), 5 mL of hydrogen peroxide (mass fraction 27.5%), 0.3 g of modified nano-silica, 1.5 g of intermediate and 15 mL of water were mixed to obtain a mixed solution, then 3 g of acrylic acid and 15 mL of water were mixed to obtain A solution; 0.5 g of 3-mercaptopropionic acid, 0.04 g of ascorbic acid and 15 mL of water were mixed to obtain B solution; under stirring, A solution and B solution were slowly added to the mixed solution by dropwise addition, the dropwise addition time was 1 h, free radical polymerization was carried out, the reaction temperature was controlled at 15°C during the dropwise addition process, after the dropwise addition was completed, the reaction was continued for 1 h, the reaction was completed, the pH value was adjusted to 7 with sodium hydroxide aqueous solution to obtain a water reducing agent.

[0039] Example two

[0040] Preparation of water reducing agent:

[0041] S1, in a three-necked flask equipped with stirring device, 32.6 g of triethanolamine, 33.8 g of 9-decenoic acid and 300 mL of N,N-dimethylformamide were stirred and mixed uniformly, 0.4 g of dibutyltin oxide and 41.2 g of dicyclohexyl carbodiimide were added, the reaction temperature was controlled at 75°C, and the reaction was kept for 8 h, the reaction was continuously stirred during the reaction, after the reaction was completed, part of the solvent was removed by reduced pressure distillation, then the intermediate was purified by column chromatography (eluent: mixed solvent of petroleum ether / ethyl acetate, volume ratio 5:1), and the eluent was removed by rotary evaporation to obtain the intermediate;

[0042] S2, in a three-necked flask, 2 g of nano-silica (average particle size D50 of 20 nm), 200 mL of ethanol aqueous solution (mass fraction 90%) and 20 mL of hydrochloric acid solution (mass fraction 12%) were mixed and ultrasonically treated for 30 min, then 1.2 g of silane coupling agent KH-570 was added, stirred and heated to 60°C, kept for 1.5 h, then stirred and heated to 80°C, kept for 5 h, the reaction was completed, cooled, filtered, washed with acetone and vacuum dried to obtain modified nano-silica;

[0043] S3, in a three-necked flask, 60 g of ethylene glycol monovinyl polyoxyethylene ether (molecular weight 3000), 10 mL of hydrogen peroxide (mass fraction 27.5%), 0.6 g of modified nano-silica, 3.0 g of intermediate and 30 mL of water were mixed to obtain a mixed solution, then 6 g of acrylic acid and 30 mL of water were mixed to obtain A solution; 1.0 g of 3-mercaptopropionic acid, 0.08 g of ascorbic acid and 30 mL of water were mixed to obtain B solution; under stirring, A solution and B solution were slowly added to the mixed solution by dropwise addition, the dropwise addition time was 1 h, free radical polymerization was carried out, the reaction temperature was controlled at 15°C during the dropwise addition process, after the dropwise addition was completed, the reaction was continued for 1 h, the reaction was completed, the pH value was adjusted to 7 with sodium hydroxide aqueous solution to obtain a water reducing agent.

[0044] Example Three

[0045] In a compulsory mixer, 413 g of P·O5 52.5 Portland cement (more than 90% of particles of 3-30 μm, no more than 10% of particles less than 10 μm), 177 g of mineral admixture, 657.3 g of fine aggregate (II zone medium sand with fineness modulus of 2.6), 1050 g of coarse aggregate (5 mm continuous grading, with needle-like content no more than 5%, crushing value no more than 8%), and 27.5 g of steel fiber (aspect ratio 80, length 50 mm, equivalent diameter 0.62 mm, 8037 roots / kg of end-hook type steel fiber) were uniformly added, the materials were mixed uniformly by stirring for 10 s, then 147.5 g of water was injected, and stirring was continued for 3 min, the material was discharged, and vibration was carried out until the surface of the concrete mixture appeared to be floated, substantially no bubbles escaped, then the material was tamped, and finally was cast into a mold (mold temperature 15 °C) to obtain low-heat early-strength steel fiber concrete;

[0046] The mineral admixture was prepared by mixing 40 g of ground slag (S95 grade), 20 g of fly ash (I or II F class), 14 g of silica fume (SiO2 content of silica fume is 90%, specific surface area is 15000 m 2 / kg), and 4 g of the water reducing agent prepared in Example One in a mixer.

[0047] Example Four

[0048] In a compulsory mixer, 413 g of P·O5 52.5 Portland cement (more than 90% of particles of 3-30 μm, no more than 10% of particles less than 10 μm), 177 g of mineral admixture, 657.3 g of fine aggregate (II zone medium sand with fineness modulus of 2.6), 1050 g of coarse aggregate (5 mm continuous grading, with needle-like content no more than 5%, crushing value no more than 8%), and 27.5 g of steel fiber (aspect ratio 80, length 50 mm, equivalent diameter 0.62 mm, 8037 roots / kg of end-hook type steel fiber) were uniformly added, the materials were mixed uniformly by stirring for 10 s, then 147.5 g of water was injected, and stirring was continued for 3 min, the material was discharged, and vibration was carried out until the surface of the concrete mixture appeared to be floated, substantially no bubbles escaped, then the material was tamped, and finally was cast into a mold (mold temperature 15 °C) to obtain low-heat early-strength steel fiber concrete;

[0049] The mineral admixture was prepared by mixing 40 g of ground slag (S95 grade), 20 g of fly ash (I or II F class), 14 g of silica fume (SiO2 content of silica fume is 90%, specific surface area is 15000 m 2 / kg), and 4 g of the water reducing agent prepared in Example One in a mixer.

[0050] Example Five

[0051] In a compulsory mixer, 413 g of P·O5 2.5 Portland cement (more than 90% of particles of 3-30 μm, no more than 10% of particles less than 10 μm), 177 g of mineral admixture, 657.3 g of fine aggregate (II zone medium sand with fineness modulus of 3.0), 1050 g of coarse aggregate (20 mm continuous grading, with needle-like content no more than 5%, crushing value no more than 8%), and 27.5 g of steel fiber (aspect ratio 80, length 50 mm, equivalent diameter 0.62 mm, 8037 hooks per kg of end-hook type steel fiber) were uniformly added, stirred for 30 s to mix the materials uniformly, then 147.5 g of water was injected, and stirring was continued for 4 min, the material was discharged, and vibration was carried out until the surface of the concrete mixture appeared to be floated, substantially no bubbles escaped, then it was tamped, and finally it was poured into a mold (the mold temperature was 20 ℃) to obtain low-heat early-strength steel fiber reinforced mass concrete;

[0052] The mineral admixture was prepared by mixing 60 g of finely ground slag (S95 grade), 30 g of fly ash (I or II F class), 20 g of silica fume (SiO2 content of silica ash is 90%, specific surface area is 15000 m 2 / kg) and 12 g of the water reducing agent prepared in Example One in a mixer.

[0053] Comparative Example One

[0054] A commercially available polycarboxylic acid type water reducing agent was used to replace the water reducing agent in Example Five, and the remaining steps were the same as those in Example Five to prepare the concrete.

[0055] Comparative Example Two

[0056] A commercially available concrete was used.

[0057] The concrete prepared in Examples Three, Four, Five, Comparative Examples One and Two was tested for the following properties:

[0058] The fluidity was determined according to the national standard GB / T 8077-2012 “Concrete Admixture Homogeneity Test Method”;

[0059] The compressive strength after 3 d and 28 d of test curing was determined according to the national standard GB / T 50081-2019 “Standard for Testing Methods of Mechanical Properties of Ordinary Concrete”;

[0060] The hydration heat after 3 d of test curing was determined by a hydration heat tester;

[0061] The results are shown in the following table:

[0062]

[0063] From the above table, the early strength of the concrete prepared by the embodiment of the application is high, the hydration heat is low, and the fluidity is strong, and the application value in the building material technical field is high.

[0064] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0065] The above is only an example and description of the application, and those skilled in the art can make various modifications or supplements or replace with similar ways, as long as it does not deviate from the invention or exceed the scope defined by the claims, which shall belong to the protection scope of the application.

Claims

1. A low-heat, early-strength, steel-fiber-reinforced mass concrete, prepared from cement, mineral admixtures, water, fine aggregate, coarse aggregate, and steel fiber in a mass ratio of 413:177:147.5:657.3:1050:27.5, characterized in that... The mineral admixture is prepared by mixing the following raw materials in parts by weight: 40-60 parts ground slag, 20-30 parts fly ash, 14-20 parts silica fume and 4-12 parts water-reducing agent; The water-reducing agent is prepared through the following steps: S1. Triethanolamine, 9-decenoic acid and N,N-dimethylformamide were stirred and mixed evenly. Dibutyltin oxide and dicyclohexylcarbodiimide were added. The mixture was reacted at 75°C for 8 hours with constant stirring during the reaction. After the reaction was completed, the intermediate was obtained by vacuum distillation, column chromatography purification and rotary evaporation. S2. Add nano-silica, ethanol aqueous solution and hydrochloric acid solution to a three-necked flask, mix and sonicate for 30 min, add silane coupling agent KH-570, stir and heat to 60℃, keep the reaction at 1.5 h, then stir and heat to 80℃, keep the reaction at 80℃ for 5 h, the reaction is complete, cool, filter, wash and dry to obtain modified nano-silica; S3. Mix ethylene glycol monovinyl polyoxyethylene ether, hydrogen peroxide, modified nano silica, intermediate and water to obtain a mixture. Then mix acrylic acid and water to obtain solution A. Then mix 3-mercaptopropionic acid, ascorbic acid and water to obtain solution B. Under stirring, add solution A and solution B dropwise to the mixture over 1 hour. During the dropwise addition, control the reaction temperature at 15°C. After the dropwise addition is complete, continue to keep the reaction at this temperature for 1 hour. Once the reaction is complete, adjust the pH to 5-7 to obtain the water-reducing agent.

2. The low-heat, early-strength steel fiber reinforced concrete of mass production according to claim 1, characterized in that, In step S1, the ratio of triethanolamine, 9-decenoic acid, N,N-dimethylformamide, dibutyltin oxide, and dicyclohexylcarbodiimide is 16.3g:16.9g:150mL:0.2g:20.6g.

3. The low-heat, early-strength steel fiber reinforced mass concrete according to claim 1, characterized in that, In step S2, the ratio of nano-silica, aqueous ethanol solution, hydrochloric acid solution, and silane coupling agent KH-570 is 1g:100mL:10mL:0.6g.

4. The low-heat, early-strength steel fiber reinforced concrete of mass production according to claim 1, characterized in that, In step S3, the ratio of the amounts of ethylene glycol monovinyl polyoxyethylene ether, hydrogen peroxide, modified nano silica, intermediate, water, acrylic acid, 3-mercaptopropionic acid, and ascorbic acid is 30g:5mL:0.3g:1.5g:45mL:3g:0.5g:0.04g.

5. The low-heat, early-strength steel fiber reinforced concrete of mass production according to claim 1, characterized in that, The cement is silicate cement, with particles of 3-30μm accounting for more than 90% and particles smaller than 10μm accounting for no more than 10%.

6. The low-heat, early-strength steel fiber reinforced concrete of mass production according to claim 1, characterized in that, The fine aggregate is medium sand in zone II with a fineness modulus of 2.6-3.

0.

7. The low-heat, early-strength steel fiber reinforced concrete of mass production according to claim 1, characterized in that, The coarse aggregate is processed from basalt rock, with a continuous gradation of 5-20mm particle size, of which the content of needle-like and flaky particles is no more than 5% and the crushing value is no more than 8%.

8. The low-heat, early-strength steel fiber reinforced concrete of mass production according to claim 1, characterized in that, The steel fibers used are hook-shaped steel fibers with an aspect ratio of 80, a length of 50 mm, an equivalent diameter of 0.62 mm, and 8037 fibers / kg.

9. The preparation process of low-heat, early-strength steel fiber reinforced mass concrete according to claim 1, characterized in that, Includes the following steps: Cement, mineral admixtures, fine aggregates, coarse aggregates, and steel fibers are uniformly added to a forced mixer and stirred until the materials are evenly mixed. Water is then added, and stirring continues. The mixture is discharged, vibrated, and compacted until it is tamped. Finally, it is poured into molds to obtain low-heat, early-strength steel fiber mass concrete.

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