CN1128118C - Preparation and application of high-performance concrete admixture - Google Patents

Abstract

The invention relates to a preparation method and application of a high-performance concrete admixture. It takes limestone as the main material and grinds it to a certain specific surface area powdery material, and can be mixed with a small amount of gypsum and slag to improve performance. The raw materials have certain quality requirements; Grinding, control a certain fineness and specific surface area to make the product. The admixture can be used to prepare concrete. When preparing concrete with the same grade, it can replace less than 30% of cement, and the excess substitution coefficient is 1.1-1.4. The invention has simple production process, wide sources of raw materials, low power consumption, low cost, and the prepared concrete has high flexural strength, high early compressive strength, small drying shrinkage, low heat of hydration, good impermeability and carbonation resistance, etc. advantage.

Description

Preparation method and application of high performance concrete admixture

The invention relates to a preparation method and application of a high-performance concrete admixture, which belongs to the production and application technology of the concrete admixture.

With the rapid development of concrete technology and concrete industry, the role and status of fine admixtures, the sixth component of concrete materials, have been increasingly valued by the material research and production departments. As a kind of aggregate, the fine admixture is mixed into concrete, which mainly plays three roles: (1) water reducing effect, (2) filling effect, (3) active effect. The use of admixtures can reduce the production cost of concrete, improve the working performance and mechanical properties of concrete, reduce the heat of hydration of concrete, and improve the volume stability and durability of concrete. At present, there are many types of domestic admixtures, such as fly ash, finely ground slag, silica fume, zeolite powder, etc. The functions of various mineral admixtures in concrete are roughly the same, but the prices vary greatly. There are few sources of silica fume, and the price is 3,000 to 12,000 yuan/ton; finely ground zeolite powder has a large internal specific surface area, and it is easy to increase the unit water consumption when mixed into concrete; finely ground slag consumes high power, resulting in use costs The game is too high. The largest consumption is still the fly ash discharged from thermal power plants. If the quality of fly ash can meet the requirements of Class I and Class II ash stipulated in the national standard, its effect in concrete is very obvious. However, for traditional ash or Class III ash, due to its relatively large water demand, large loss on ignition or coarse fineness, which affects its water reduction, filling and activation effects, the effect is often poor. The commercial concrete industry in Guangzhou is developing rapidly. There are more than 40 commercial concrete mixing stations in the city, with an annual production capacity of 4.2 million cubic meters of concrete. Calculated by using fly ash to replace 20% of cement, the annual consumption of fly ash is about 300,000 tons. Due to the limited power resources near Guangzhou, the annual ash discharge is difficult to meet the needs of the development of the commercial concrete industry. In the future, the country will implement power transmission from west to east, so it is less likely to build a power plant. Calcination quality decline, insufficient calcination, etc., the quality of fly ash will gradually decline. At present, the supply of Class I and Class II fly ash in Guangzhou is very limited. Most commercial concrete mixing plants use unified ash or Class III fly ash. The quality of ash fluctuates greatly, which may easily cause commercial concrete failure. quality fluctuations. Every year during the peak season of power plant maintenance or concrete production, even if it is unified ash or Class III fly ash, there will still be insufficient supply of fly ash, and the production cost of commercial concrete mixing plants will increase significantly. In the 21st century, human beings need further sustainable development and are faced with three major problems: population expansion, environmental degradation and resource shortage. In order to achieve sustainable development of material science and technology, in addition to the technical and economical requirements of materials, it is also required to have environmental coordination, that is to say, it needs to be developed from the perspective of energy saving, resource saving, high durability and recycling new material. The two important directions of the current concrete technology development are: one is to develop high-strength and high-performance concrete, that is, HPC (high performance concrete), and the other is to make ordinary concrete high-performance, so that its service life is extended from 40 to 45 years to 60 to 70 years . The material basis for the development of concrete along these two directions is the multifunctional high-efficiency water reducer and high-performance admixtures.

The purpose of the present invention is to overcome and solve the problem that the existing concrete fine admixture has a large internal specific surface area, the water consumption increases too much when it is mixed into concrete, some grinding power consumption is high, and the use cost remains high; Some have large fluctuations in their own quality, and are likely to cause shortcomings and problems such as fluctuations in the quality of concrete or problems with the source of raw materials. The preparation and application of a high-performance concrete admixture has been researched and invented. It uses limestone as the main raw material and can be used It is a powder material prepared by compounding a small amount of gypsum, grinding and controlling a certain fineness and specific surface area; the concrete admixture can improve the working performance of concrete, increase the flexural and early compressive strength of concrete, and reduce the It is a good material to realize the high performance of ordinary concrete; on the basis of finely ground limestone high-performance admixture, compound a small amount of finely ground slag, and can also produce high-strength high-performance concrete series of admixture products. The invention has wide sources of raw materials, simple production process, stable and controllable product quality, and low production cost. When used for preparing concrete, the performance can be improved and the production cost of concrete can be reduced.

The present invention is realized through the following technical scheme: the preparation method of the high-performance concrete admixture is based on limestone as the main raw material, compounded with a small amount of gypsum and slag, and is processed by grinding to control a certain fineness and specific surface area, and is prepared into For powdery materials, the mass percentages of the three materials are:

Limestone: 50-100%

Gypsum: 0-8%

Slag: 0-50% Within the range of the above formula, a series of high-performance concrete admixtures with different functions can be produced, such as: ordinary type LS-FA (95-100% limestone, 0-5% gypsum) and high-strength type LS-FA (limestone 50-95%, gypsum 0-8%, slag 5-50%); raw material quality requirements: limestone CaO, MgO content is not limited, aluminum oxide Al ₂ O ₃ content is less than 2.5%; gypsum The content of sulfur trioxide _SO3 is 25-45%; the alkalinity coefficient of slag is greater than 1; the production process is as follows: limestone and gypsum are crushed, measured separately with slag, and then ground to control the fineness to 0.045mm square hole sieve Sieve residue ≤ 20%, SO ₃ content 0-3.0%, specific surface area 330-600m ² /kg; the high-performance concrete admixture produced according to the above preparation method has been experimentally applied to the production of construction engineering concrete, and Received the expected effect of the purpose of the present invention, common type LS-FA can replace less than 30% of cement when preparing concrete with the same designation, and the excess substitution coefficient is 1.1 to 1.4, and the performance of the prepared concrete is better than that of the benchmark concrete (concrete prepared with the same grade of pure cement) to make ordinary concrete high-performance; high-strength LS-FA, that is, on the basis of limestone content of 50-95%, compound 0-8% gypsum and 5-50% gypsum Slag can be used to prepare high-strength concrete with a strength grade above C50. Compared with the reference concrete, it can also replace cement within 30%, and the excess substitution coefficient is 1.1-1.4; this series of admixtures has water-reducing effect, filling effect and The active effect can improve the working performance of the concrete mixture, increase the flexural strength and early compressive strength of the concrete, reduce the heat of hydration of the concrete, reduce the shrinkage of the concrete, and significantly reduce the cracking of the concrete; in addition, the admixture’s The application can also reduce the production cost of concrete and fully achieve the purpose of the present invention.

The inventor started from the study of the action mechanism of the admixture in concrete, and through laboratory research and experiments, invented finely ground limestone (LS-FA: lime-stone-Fine-aggregate) as a high-performance admixture for concrete, and The preparation method and application of this high-performance concrete admixture have been successfully studied. And has been put into experimental production and engineering trial. When the admixture is formulated with 95-100% limestone and 0-5% gypsum, the prepared concrete admixture is a common type LS-FA, which can be used to prepare concrete with a strength level below C50; when preparing concrete with a strength level above C50 For high-grade concrete, 5-50% of slag can be compounded to produce high-strength LS-FA admixture, which can meet the requirements. The admixture can be made into a series of admixture products suitable for concrete of various strength grades according to market needs. From the results of many experiments, the effect of this kind of admixture on the working performance, mechanical properties and durability of concrete is better than that of reference concrete, and the early compressive strength, flexural strength and shrinkage resistance of concrete are better than those of II Concrete prepared with grade fly ash. The role of the admixture in concrete is mainly reflected in: (1) Its own water demand is small, and it has a certain water-reducing effect; (2) The fine particles have a good filling effect, which is conducive to making the interface structure of the concrete more dense, and can Improve the flexural strength and impermeability of concrete and reduce the drying shrinkage and cracking of concrete; (3) The chemical activity effect of limestone is mainly reflected in the early stage, and the calcium carbonate in limestone can form hydrated aluminum carbonate with the hydration product of cement , can significantly improve the early compressive strength of concrete; (4) can reduce the heat of hydration of concrete, and use finely ground limestone to replace less than 30% of cement when preparing concrete, which can greatly reduce the heat of hydration of concrete and reduce the heat of hydration of concrete. Shrink and crack. In addition, because limestone is easy to grind, the power consumption of grinding is low, the stability is good, and the quality fluctuation is small, using it to replace less than 30% of cement to prepare concrete can improve the performance of concrete and greatly reduce the cost of concrete. production cost.

Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) the present invention mixes finely ground limestone powder (the limestone content can reach 95% to 100%) into ordinary concrete in large quantities as a kind of fine admixture Among them, the amount of cement replaced can reach within 30%, and the performance of the prepared concrete is better than that of the reference concrete prepared with the same grade of pure cement. Even if the performance of ordinary concrete is improved, the production cost of concrete is reduced; (2) this Invented on the basis of limestone content of 50-95%, combined with 0-8% gypsum and 5-50% slag, high-strength LS-FA series products can be produced, which are used to prepare high-strength and high-performance concrete, replacing 30% % cement, the performance of the prepared concrete is better than the same label reference concrete, to meet the requirements of high strength and high performance; (3) the present invention can apply common type and high strength type LS-FA products to the concrete of actual construction projects (4) The production process of the present invention is simple, and the source of raw materials is wide; (5) The concrete admixture prepared by the present invention is compared with finely ground slag in terms of grinding power consumption (6) Compared with fly ash, the concrete admixture prepared by the present invention has stable and controllable product quality, and the early compressive strength, flexural strength and shrinkage resistance of the prepared concrete are more excellent; (7) Compared with the reference concrete of the same label, the concrete prepared with the admixture prepared by the present invention has high early strength, high flexural strength, small drying shrinkage value of concrete, low heat of hydration and impermeability, anti-carbonation performance Good and other advantages.

The inventor has gone through many years of research and scientific experiments, and there are many examples of successful laboratory and engineering trial applications. Moreover, the admixture prepared by the method of the present invention has been trial-produced at 600 tons in Guangzhou Jiahua Cement Factory, wherein the common type LS -300 tons of FA (ratio: 98% limestone, 2% gypsum), 300 tons high-strength LS-FA (ratio: 64% limestone, 6% gypsum, 30% slag) Concrete Co., Ltd. has successfully applied it to actual construction projects. The commercial concrete prepared with LS-FA high-performance admixture in the construction of Guangdong Supply and Marketing Cooperative Project and Yudean Building Project is nearly 1,000 cubic meters, and the concrete strength grade is C20~C50 , the production and construction units are satisfied with the quality of this batch of concrete, the working performance fully meets the construction requirements, and the performance tests of the samples retained on the construction site all meet the design requirements. Below only enumerate following several embodiments to illustrate:

Example 1:

The contriver prepares the test result of C30 concrete with the series product A13 of common type SL-FA high-performance admixture prepared by the present invention as shown in table 1～2: (the admixture formula of numbering A13 is: 98% limestone, 2 % gypsum; specific surface area is 350m ² /kg)

Table 1: Mixing ratio of raw materials and concrete used in the test experiment material cement water sand 5-16mm stone grain 5-25mm stone grain FDN-5 (water reducer) Admixture fly ash LS-FA Origin, brand Zhujiang Factory Yuexiu Brand tap water Beijianghe Wanggang Stone Field Wanggang Stone Field Zhanjiang Admixture Factory Guangzhou Power Plant A13 Variety, Grade PII.42.5R / Fineness modulus Mx=2.3 / / Retarded high-efficiency superplasticizer Gray / Mixing ratio of admixture to concrete (Kg/m ³ ) fly ash 287 203 751 120 923 5.02 99 / A13 287 195 751 120 923 5.02 / 99 Reference concrete mix (Kg/m ³ ) 363 200 725 120 923 5.02 /

Table 2: Comparative test results of concrete prepared with Guangzhou Power Plant fly ash and A13 admixture and benchmark concrete sample Liquidity (mm) Bulk density(kg/m ³ ) Portability Description Compressive strength (Mpa) Flexural strength (Mpa) Impermeability grade Slump Expansion 3d 7d 28d 7d 28d fly ash 165 290 2335 Thick pulp 17.4 25.5 37.4 2.4 3.3 S9 A13 180 370 2405 Thick pulp 23.1 33.1 40.2 3.1 4.2 S9 benchmark concrete 145 260 2420 Thick pulp 19.8 27.9 38.8 2.5 3.4 S7

From the above experimental results, it can be seen that: (1) LS-FA admixture has a better water-reducing effect. In the case of small unit water consumption, the initial slump and expansion are greater than the reference concrete, and are also better than powder Concrete prepared with coal ash shows better flow performance, and if the same working performance as the reference concrete is guaranteed, the water-cement ratio can also be reduced; (2) The compressive strength of concrete prepared with LS-FA admixture The performance is obviously better than that of the benchmark concrete. The strength of 3d (3 days) is increased by 3.3Mpa, the strength of 7d is increased by 5.2Mpa, and the strength of 28d is increased by 1.4Mpa. 24%, 28d flexural strength increased by 0.8Mpa, 23.5% higher than the benchmark concrete. Moreover, its compressive strength and flexural strength are significantly higher than the concrete prepared with fly ash; (3) The impermeability is better than that of the reference concrete.

Example 2

The inventor used the series product A12 of high-strength LS-FA high-performance concrete admixture prepared by the present invention (the formula of number A12 is: limestone 64%, gypsum 6%, slag 30%, specific surface area 370m ² /kg) to prepare C60 The concrete test results are shown in Tables 3 to 5 below:

Table 3. Raw materials and concrete mix ratio used in the test

Table 4. Contrast test results of benchmark concrete and the A12 admixture prepared concrete prepared by the present invention sample Slump (mm) Bulk density(kg/m ³ ) Portability Description Compressive strength (Mpa) Flexural strength (Mpa) The impermeability label reaches S12 average water seepage height (cm) oh 1.0h 3d 7d 28d 7d 28d benchmark concrete 17.0 13.5 2430 Workability is better 48.8 53.0 67.6 / 6.3 2.4 A12 20.0 17.5 2430 Workability is good 50.8 59.1 69.0 / 6.7 2.1

Table 5. The shrinkage test comparative results of the A12 admixture prepared concrete prepared by the reference concrete and the present invention sample Drying shrinkage value 1×10 ^-6 (mm) 3d 7d 28d 45d 60d 90d benchmark concrete 180 300 470 480 490 500 A12 27 180 340 360 393 440

From the above test results, it can be seen that the initial slump of C60 concrete prepared with high-strength LS-FA admixture is larger than that of the reference concrete, the loss of slump after 1 hour is smaller than that of the reference concrete, and the work performance is better than that of the reference concrete. The 3-day, 7-day, and 28-day compressive strength of the concrete is high, the 28-day flexural strength is high, and the impermeability is good. The drying shrinkage of the concrete within 90 days is smaller than that of the benchmark concrete, and the early shrinkage is smaller.

Example 3

The contriver uses the test result of the series product A13, A12 of the LS-FA high-performance admixture prepared by the present invention to be applied in engineering pilot application (the formula of numbering A13 is: limestone 98%, gypsum 2%, specific surface area 350m ² /kg ; The formula of number A12 is: limestone 64%, gypsum 6%, slag 30%, specific surface area 370m ² /kg) as shown in Table 6-9.

Table 6. The materials and concrete mix ratio of C35 pumped concrete in Yudean Building Project Material Red cotton P042.5R cement Admixture A13 Xijiang river sand (gradation zone II, fineness modulus Mx=2.4) Kawashi (particle size 5 ~ 16m) AP-1 Admixture water Mixing ratio(kg/m ³ ) 290 120 704 1101 8.20 185

Table 7. On-site sample test results of Yudean Building Slump when leaving the mixing station (mm) Slump when arriving at the construction site (mm) Work site and workability description 7d compressive strength (Mpa) 28d compressive strength (Mpa) 200 185 Workability is good 34.2 47.2

Table 8. Material and concrete mix ratio of C50 concrete used in the construction site of Guangdong Supply and Marketing Cooperative Material Red cotton P042.5R cement Admixture A12 Xijiang river sand (gradation zone II, fineness modulus Mx=2.4) Kawashi (particle size 5 ~ 16m) AP-1 Admixture water Mixing ratio(kg/m ³ ) 345 95 690 1084 11.20 175

Table 9. Test results of on-site samples of Guangdong supply and marketing cooperatives Slump when leaving the mixing station (mm) Slump when arriving at the construction site (mm) Work site and workability description 7d compressive strength (Mpa) 28d compressive strength (Mpa) 180 160 Workability is good 46.2 59.2

As can be seen from Tables 6 to 9, the effect of the admixture prepared by the present invention in the engineering pilot application is better, and the workability and mechanical properties of the commercial concrete prepared by the series of products of the admixture can fully reach the engineering design. and construction requirements.

Claims (2)

1, a kind of preparation method of high-performance concrete admixture, it is characterized in that: take limestone as main raw material, compound a small amount of gypsum and slag, through grinding process, control certain fineness and specific surface area, be prepared into grinding material, The weight percentages of the three materials are: Limestone: 50-100% Gypsum: 0-8% Slag: 0-50% Within the range of the above formula, a series of high-performance concrete admixtures with different functions can be produced, common type LS-FA, that is, limestone 95-100%, gypsum 0-5% and high-strength type LS-FA FA, that is, limestone 50-95%, gypsum 0-8%, slag 5-50%; raw material quality requirements: the content of calcium oxide CaO and magnesium oxide MgO in limestone is not limited, and the content of aluminum oxide Al ₂ O ₃ is less than 2.5% The content of sulfur trioxide _SO3 in gypsum is 25-45%; the alkalinity coefficient of slag is greater than 1; the production process is: limestone and gypsum are crushed, measured separately with slag, and then ground to control the fineness to 0.045mm The residual amount of the square hole sieve is ≤20%, the SO ₃ content is 0-3.0%, and the specific surface area is 330-600m ² /kg. 2. The prepared concrete admixture can be used to prepare concrete by the preparation method of the high-performance concrete admixture described in claim 1, and the common type LS-FA admixture can replace within 30% when preparing concrete with the same label High-strength cement, the excess substitution coefficient is 1.1-1.4, and the performance of the prepared concrete is better than that of the reference concrete, which makes the ordinary concrete high-performance; high-strength LS-FA admixture, that is, when the limestone content reaches 50-95%. On the basis of 0-8% gypsum and 5-50% slag, it can be used to prepare high-strength concrete with a strength grade above C50, which can replace less than 30% of cement, and the excess substitution coefficient is 1.1-1.4. The performance of the prepared concrete is better than that of the reference concrete, meeting the requirements of high strength and high performance.