CN110304860B - Concrete flexibilizer and concrete - Google Patents

Abstract

The invention relates to a concrete flexibilizer and concrete, belongs to the technical field of concrete, and solves the problems of high concrete rigidity and insufficient deformation capability in the prior art. The concrete flexibilizer comprises the following components in percentage by mass: 10 to 50 percent of organic cementing material, 5 to 40 percent of expanding material, 0.5 to 4 percent of superplasticizer, 0.3 to 2 percent of water-retaining thickener, 0.3 to 3 percent of air entraining agent, 0.5 to 3 percent of defoamer, 0.5 to 5 percent of pour regulator, 0.5 to 30 percent of shrinkage reducer and the balance of filler. The concrete comprises the following components in percentage by mass: cement: river sand: crushing stone: water: fly ash: the concrete flexibilizer is 380-420: 650-700: 1200-1220: 140-150: 60-75: 40 to 50. The concrete flexibilizer is used for reducing the rigidity of concrete and improving the deformation capability of the concrete.

Description

Concrete flexibilizer and concrete

Technical Field

The invention relates to the technical field of concrete, in particular to a concrete flexibilizer and concrete.

Background

Concrete is the most widely used and most used building material in the world at present. It plays an irreplaceable role in the engineering construction fields of buildings, highways, civil aviation, water conservancy and hydropower and the like. However, with the wide application of concrete structures, the problem of concrete cracks is more and more prominent, and a continuous steel bridge with 245m of a certain main span in China has serious midspan deformation, the maximum deflection reaches 32cm and is accompanied by a large amount of concrete cracks; the Hengyang Xiangjiang second bridge was completed in 1988, but the roof plate, the web plate and the diaphragm plate of the bridge box girder have the problem of cracks in 1989; the Fengling yellow river highway bridge is finished and driven in 1994, the bridge has cracks in different degrees after driving, the maximum width of the web cracks is 0.75mm, and the top plate and the bottom plate have cracks in different degrees; the new Ma chest bridge in Tongzhou district of Beijing is a dangerous bridge after 6 years of traffic in 2011 in 2005 when traffic is in transit; in 1978 of the United states, the Parrots ferry bridge built by adopting a cantilever assembly method is a prestressed lightweight aggregate concrete continuous steel bridge with the longest span at the time, and after 12 years of use, a main span of 195m sags by 63.5cm, and simultaneously, a large amount of concrete cracks are also accompanied.

Concrete cracks can be divided into cracks caused by load and cracks caused by deformation (non-load factors) according to the generation reasons, and the domestic and foreign investigation data show that the cracks caused by the deformation account for about 80 percent and the cracks caused by the load account for about 20 percent.

Aiming at the crack problem caused by load, the crack problem mainly shows bending cracks, shearing cracks and torsion cracks, and all the cracks are formed by pulling the concrete by external force exceeding the deformation tolerance of the concrete; and when the cracks caused by non-load factors are expressed that the deformation of the concrete is restrained by various types, the tensile stress is generated in the concrete, and when the tensile stress exceeds the deformation tolerance of the concrete, various crack problems can be generated. The crack problem of various concrete can be seen, and the reason is directly related to the large rigidity and insufficient deformability of the concrete.

One method for improving the crack problem of concrete is to increase the tensile strength of concrete and increase the resistance of concrete to cracking stress, but the tensile strength of concrete is only one tenth to one twentieth of the compressive strength of concrete, and the proportion is reduced along with the increase of the compressive strength, and the improvement of the crack resistance is not facilitated by simply increasing the strength grade of concrete. At present, the more effective way for improving the tensile strength of concrete is to add fibers into the concrete, although the addition of the fibers increases the breaking tensile strength of the concrete and obviously reduces the width of a crack, the bond stress difference between the fibers and the concrete is larger and unstable, after the fiber concrete is stressed, visible or invisible microcracks often exist in the concrete, the crack resistance of the concrete is not fundamentally changed, and the microcracks influence the long-term bearing capacity and durability of the concrete.

The other method for improving the concrete crack problem is to reduce the compression elastic modulus of concrete, reduce the rigidity of concrete, relatively increase the deformation capacity of concrete and improve the crack resistance of concrete, for example, the elastic modulus of concrete can be reduced to a certain extent by using lightweight aggregate concrete, but the compressive strength of concrete is greatly reduced, the bearing capacity is greatly influenced, data show that the compressive strength of lightweight aggregate concrete produced in the nineties of China is only 5.0-25 MPa, the strength difference of structural concrete required by engineering is large, and the lightweight aggregate concrete can only be used for building block filling walls of frame structures and cannot be used for bearing structures. With the development of the lightweight aggregate concrete industry in China, the lightweight aggregate concrete with the grade of CL30-CL60 can be produced in China at present, but with the improvement of the strength grade, the mold pressure ratio (namely the ratio of the elastic modulus to the compressive strength) is not reduced, and the crack resistance is not fundamentally changed.

Disclosure of Invention

In view of the above analysis, the present invention aims to provide a concrete flexibilizer and a concrete, which solve the problems of large rigidity and insufficient deformability of the concrete in the prior art.

The invention is mainly realized by the following technical scheme:

on one hand, the invention provides a concrete flexibilizer, which comprises the following components in percentage by mass: 10 to 50 percent of organic cementing material, 5 to 40 percent of expanding material, 0.5 to 4 percent of superplasticizer, 0.3 to 2 percent of water-retaining thickener, 0.3 to 3 percent of air entraining agent, 0.5 to 3 percent of defoamer, 0.5 to 5 percent of pour regulator, 0.5 to 30 percent of shrinkage reducer and the balance of filler.

Further, the viscosity of the water-retaining thickener is 5000-200000 mPa.s.

In another aspect, the present invention provides a method for preparing a concrete flexibilizer, comprising the steps of:

step 1, weighing organic cementing materials, expanding materials, fillers, superplasticizers, water-retention thickeners, air entraining agents, defoaming agents, coagulation regulators and shrinkage reducers according to mass percentage;

step 2, starting a mixer, then sequentially adding the expansion material, the filler and the organic cementing material, and after the materials are put into the mixer, uniformly mixing the materials;

step 3, sequentially adding a superplasticizer, a water retention thickener, an air entraining agent, a defoaming agent, a thickening time control agent and a shrinkage reducing agent into the uniformly mixed material in the step 2; and (3) after the materials are put into the mixer, mixing and stirring the materials for 3-5 minutes to finish the preparation of the concrete flexibilizer.

The invention also provides a cement paste, which comprises a concrete flexibilizer, cement and water, wherein the cement paste comprises the following components in percentage by mass: cement: water: the concrete flexibilizer is 1: 0.3-0.35: 0.1 to 0.15.

The invention also provides concrete, which comprises the following components in percentage by mass: cement: river sand: crushing stone: water: fly ash: the concrete flexibilizer is 380-420: 650-700: 1200-1220: 140-150: 60-75: 40 to 50.

Further, the crushed stone comprises a first crushed stone and a second crushed stone, and the particle size of the first crushed stone is smaller than that of the second crushed stone.

Further, the particle size of the first crushed stone is 4.75-9.5 mm, and the particle size of the second crushed stone is more than 9.5mm and less than or equal to 19 mm.

Further, the mass ratio of the first crushed stone to the second crushed stone is as follows: 840-850: 360-370.

The invention also provides a preparation method of the concrete, which comprises the following steps:

s1, weighing cement, river sand, first crushed stone, second crushed stone, water, fly ash and a concrete flexibilizer according to mass percentage;

s2, sequentially adding the first crushed stone, the second crushed stone, river sand, cement, fly ash and the concrete flexibilizer into the concrete mixer, starting the mixer, firstly dry-mixing, then adding water, and continuously stirring for 60-120S until the mixture is uniformly stirred.

Further, in the step S2, the dry mixing time is 25 to 35S.

Compared with the prior art, the invention can realize at least one of the following beneficial effects:

a) the concrete flexibilizer provided by the invention is prepared by adding the organic cementing material, the water-retention thickening agent, the superplasticizer, the shrinkage reducing agent, the coagulation regulating agent, the air entraining agent and the defoaming agent in specific mass percentages, selecting the specific expansion material and the type and the dosage of the filler and adopting a specific preparation method, and adding the concrete flexibilizer into the cement paste can obviously improve the deformation capacity of the cement paste (the maximum deformation is improved from 3mm to 42 mm).

b) According to the concrete provided by the invention, the concrete flexibilizer with a specific mass percentage is added, so that the 28d compression strength and 28d bending strength of the concrete can be improved; the elastic modulus of the concrete 28d can be obviously reduced, and the deformation performance of the concrete under external load is improved; can obviously improve the bonding strength of concrete interfaces and improve the bonding performance between concrete layers.

c) The concrete flexibilizer provided by the invention has the advantages of simple components, simple preparation process, short preparation period and lower cost, can be used immediately after being prepared, and does not influence the use effect after being placed for a certain time; the concrete flexibilizer is nontoxic and environment-friendly.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the present application may be realized and attained by the instrumentalities and combinations particularly pointed out in the written description.

Detailed Description

The preferred embodiments of the present invention are described in detail below:

the invention provides a concrete flexibilizer which comprises the following components in percentage by mass: 10 to 50 percent of organic cementing material, 5 to 40 percent of expanding material, 0.5 to 4 percent of superplasticizer, 0.3 to 2 percent of water-retaining thickener, 0.3 to 3 percent of air entraining agent, 0.5 to 3 percent of defoamer, 0.5 to 5 percent of pour regulator, 0.5 to 30 percent of shrinkage reducer and the balance of filler.

The organic cementing material is re-dispersible latex powder, and can be one or more of vinyl acetate homopolymer, acrylate, ethylene-vinyl acetate copolymer, vinyl acetate-vinyl versatate copolymer, acrylate-styrene copolymer, styrene-butadiene copolymer, ethylene-vinyl chloride-vinyl laurate copolymer, and vinyl acetate-ethylene-methyl methacrylate copolymer. The organic cementing material plays a role in increasing bonding, improving cracking resistance and reducing compressive strength, and if the addition amount is too low, the bonding force is lower and the cracking resistance is poor, and if the addition amount is too high, the compressive strength is reduced too much and the cracking resistance is also poor. Therefore, the content of the organic cementing material is controlled to be 10-50 percent.

The expanding material may be one or more of sulphoaluminate clinker type expanding agent, calcium oxide type expanding agent, magnesium oxide type expanding agent and gypsum type expanding agent. The expansion material plays a role in compensating shrinkage and improving the compactness of the concrete flexibilizer, the addition content is too low, so that the shrinkage of the concrete flexibilizer is increased, the cracking resistance is not facilitated, and the concrete flexibilizer can expand in the later period due to too high content, so that expansion cracks are easily caused. Therefore, the content of the expansion material is controlled to be 5-40 percent.

The superplasticizer can be one or more than two of polycarboxylic acid high-performance water reducing agent, sulfamate water reducing agent and melamine water reducing agent. The water reducing rate should be not less than 20%. The superplasticizer plays the roles of reducing water, enhancing and improving the fluidity of the concrete flexibilizer, the low addition content can cause the low strength and the low cohesive force of the concrete flexibilizer, the too high addition content can reduce the construction performance, and the problems of segregation, bleeding and the like of the concrete flexibilizer occur. Therefore, the content of the superplasticizer is controlled to be 0.5 to 4 percent.

The water-retaining thickener can be one or more of hydroxypropyl methyl cellulose ether, hydroxyethyl cellulose ether, polyvinyl alcohol and polyacrylamide. The viscosity should be 5000 to 200000 mPa.s. The water-retaining thickener has the functions of water retention, thickening and anti-sagging, the water retention rate of the concrete softener is reduced when the adding content is too low, sagging is generated, and the concrete softener is sticky and inconvenient to construct when the adding content is too high. Therefore, the content of the water-retaining thickening agent is controlled to be 0.3-2 percent.

The air entraining agent can be one or more of rosin resins, alkyl and alkyl arene sulfonates and saponins. The air entraining agent plays a role of introducing micro closed bubbles into the concrete flexibilizer, the mortar gas content is low due to too low addition content, and the compressive strength of the concrete flexibilizer is reduced due to too high addition content. Therefore, the content of the air entraining agent is controlled to be 0.3-3 percent.

The defoaming agent can be one or more of silicone oil, polyether and higher alcohol. The defoaming agent plays a role in eliminating bubbles in the concrete flexibilizer, the low addition content can cause the high gas content and insufficient compressive strength of the concrete flexibilizer, and the high addition content can reduce the gas content, so that the antifreezing property and the salt freezing resistance are not facilitated. Therefore, the content of the defoaming agent is controlled to be 0.5 to 3 percent.

Because the gas content in the concrete flexibilizer is too high to be beneficial to the compressive strength and too low to be beneficial to the freezing resistance and the salt freezing resistance, the dosage of the air entraining agent and the defoaming agent needs to be comprehensively coordinated.

The above-mentioned coagulation regulator can be one or several kinds of zinc salt, boric acid, saccharide compound, hydroxycarboxylic acid and its salt, polyalcohol, phosphate, sodium carbonate, lithium carbonate, ferric chloride, lithium chloride, ferric hydroxide and lithium hydroxide. The setting regulator plays a role in adjusting the setting time of the mortar by promoting cement hydration or inhibiting cement hydration, the too low or too high addition content can cause too short or too long mortar setting time, the too short setting time is not beneficial to field construction operation, and the too long setting time can cause long-time non-setting, so that cracking, compressive strength reduction and freezing resistance reduction are caused. Therefore, the content of the coagulation regulator is controlled to be 0.5 to 5 percent.

The shrinkage reducing agent may be polyether or polyol, such as polypropylene glycol, ethylene oxide cycloalkyl addendum, ethylene oxide dimethylamino addendum, or their mixture. The shrinkage reducing agent has the effects of reducing mortar shrinkage and improving the crack resistance of the mortar by reducing the surface tension of aqueous solution in the mortar, and if the addition content is too low, the shrinkage reducing agent has no effect on reducing the shrinkage and improving the crack resistance, and if the addition content is too high, the setting time of the mortar is prolonged, and the compressive strength is reduced. Therefore, the content of the shrinkage-reducing agent is controlled to be 0.5-30 percent.

The filler can be one or more of fly ash, slag powder, zeolite powder, limestone powder and silica fume. Wherein the specific surface area of the fly ash, the slag powder, the zeolite powder and the limestone powder is not less than 350m²Per kg, the specific surface area of the silica fume is not less than 18000m²In terms of/kg. The filler plays roles of filling, secondary hydration and the like, and the compactness, the strength and the long-term performance of the concrete flexibilizer can be reduced when the adding content is too low or too high.

The invention also provides a preparation method of the concrete flexibilizer, which comprises the following steps:

step 1, weighing the organic cementing material, the expanding material, the filler, the superplasticizer, the water-retention thickener, the air entraining agent, the defoaming agent, the coagulation regulator and the shrinkage reducing agent according to the mass percentage.

And 2, starting a mixer, then sequentially adding the expansion material, the filler and the organic cementing material, and stirring the mixture for 3-5 minutes after the materials are put into the mixer.

And 3, sequentially adding the superplasticizer, the water-retention thickening agent, the air entraining agent, the defoaming agent, the thickening agent and the shrinkage reducing agent into the uniformly mixed material obtained in the step 2. And (3) after the materials are put into the mixer, mixing and stirring the materials for 3-5 minutes to finish the preparation of the concrete flexibilizer.

The invention also provides a cement paste, which comprises the following components in percentage by mass: cement: water: the concrete flexibilizer is 1: 0.3-0.35: 0.1 to 0.15; preferably, the ratio of cement: water: the concrete flexibilizer is 1: 0.3: 0.1. the water quantity can reduce the compressive strength and the pliability of the cement paste too much, so that the flexibility test data is distorted, the water quantity can increase the compressive strength and the flexibility discreteness of the cement paste too little, and the flexibility test data can be distorted.

The invention also provides concrete, which comprises the following components in percentage by mass: cement: river sand: crushing stone: water: fly ash: the concrete flexibilizer is 380-420: 650-700: 1200-1220: 140-150: 60-75: 40 to 50. The concrete prepared according to the proportion can obviously improve the 28d compressive strength and the 28d flexural strength of the concrete; the elastic modulus of the concrete 28d can be obviously reduced, and the deformation performance of the concrete under external load is improved; can obviously improve the bonding strength of concrete interfaces and improve the bonding performance between concrete layers.

The crushed stone comprises a first crushed stone with the grain diameter of 4.75-9.5 mm and a second crushed stone with the grain diameter of more than 9.5mm and less than or equal to 19 mm. In order to make the crushed stone void ratio in the concrete low, the skeleton effect is outstanding, improves concrete strength performance, and the quality ratio of control first crushed stone and second crushed stone is: 840-850: 360-370.

The invention also provides a preparation method of the concrete, which comprises the following steps:

s1, weighing cement, river sand, first crushed stone, second crushed stone, water, fly ash and a concrete flexibilizer according to mass percentage;

s2, sequentially adding the first gravel, the second gravel, river sand, cement, fly ash and the concrete flexibilizer into a concrete mixer, starting the mixer, firstly, dry-mixing for 25-35S, then, slowly adding water, and continuously stirring for 60-120S until the mixture is uniformly stirred.

Preferably, in S2, the mixture is first dry-mixed for 30S.

Example 1

A concrete flexibilizer comprises the following components in percentage by mass: 25% of Wake re-dispersible latex powder, 30% of sulphoaluminate clinker type expanding agent, 3% of polycarboxylic acid water reducing agent, 0.5% of hydroxypropyl methyl cellulose, 0.7% of triterpenoid saponin, 0.2% of polyether defoaming agent, 3% of potassium aluminate, 5% of polypropylene glycol and the balance of 32.6% of fly ash.

The concrete flexibilizer is processed according to the preparation method of the concrete flexibilizer.

Example 2

A cement paste comprising a concrete flexibilizing agent such as that of example 1, the cement paste having the composition: 500g of cement, 150g of water and 50g of concrete flexibilizer.

And adding the cement, the concrete flexibilizer and the water into a stirrer at one time, and quickly stirring for 120s to prepare the cement paste.

Manufacturing the cement paste into a 200 x 100 x 10mm cement paste sheet, curing for 28 days under standard curing conditions, fixing one end of the cement paste sheet by 100mm, applying a load to the other end of the cement paste sheet, and taking the maximum deformation amount generated before the cement paste sheet breaks as the deformation capacity of the cement paste sheet.

Example 3

A concrete comprising a concrete flexibilizing agent such as that of example 1, the concrete having the following components by mass: 400g of cement, 680g of river sand, 363g of first broken stone with the thickness of 4.75-9.5 mm, 846g of second broken stone with the thickness of more than 9.5mm and less than or equal to 19mm, 146g of water, 70g of fly ash and 47g of concrete flexibilizer.

Comparative example 1

Comparative example 1 is a cement paste prepared without adding a concrete flexibilizer on the basis of example 2, and the cement paste of comparative example 1 has the following components: 500g of cement and 150g of water.

Comparative example 2

The concrete without the concrete flexibilizer is added, but 0.45 percent of the polycarboxylic acid water reducing agent in the flexibilizer is added, and the slump of the mixed concrete is similar to that of the concrete in the embodiment 3.

The results of the test for deformability of the cement paste sheets of example 2 and comparative example 1 are shown in table 1, and it can be seen from table 1 that the deformability of the cement paste to which the concrete flexibilizer is added is remarkably improved.

The performance of the concrete of example 3 and comparative example 2 is shown in table 2, and it can be seen from table 2 that the slump of the concrete added with the concrete flexibilizer is obviously increased, because the organic cementing material component, the air-entraining agent component, the shrinkage-reducing agent component and the like in the concrete flexibilizer can be automatically dispersed into fresh concrete in the stirring process, and can not be agglomerated with cement particles, and can play a role in lubricating, so that the concrete has good fluidity, can play a role in reducing water agent under the same concrete slump condition, and reduce the water consumption and water-cement ratio of the concrete, and has a certain contribution to improving the strength and durability of the concrete. In addition, a part of micro bubbles can be brought in during the concrete mixing process to form closed air holes in the concrete, and the closed air holes can improve the air content of the concrete and increase the durability of the concrete to a certain degree; meanwhile, the brought closed bubbles play a roll ball role in the fresh concrete, so that the fluidity of the concrete can be improved to a certain extent, and further the construction performance of the concrete is improved.

As can be seen from the table 2, the compressive strength of the concrete can be properly improved by adding the concrete flexibilizer, the 28d compressive strength of the concrete flexibilizer is improved from 49MPa to 52.7MPa, and the compressive strength of the concrete is improved by 7.6 percent; the 28d flexural strength is improved from 6.4MPa to 7.4MPa, and is increased by 15.6 percent; the improvement of the flexural strength is more obvious than the improvement of the compressive strength.

As can be seen from Table 2, the 28d elastic modulus of the concrete after the concrete flexibilizer is doped is obviously reduced, the elastic modulus is reduced from 49.5GPa to 37.9GPa, and the reduction amplitude reaches 23.4%; the elasticity-compression ratio is reduced from 1010 to 719, and is reduced by 28.8%, which shows that the introduction of the concrete flexibilizer has a relatively obvious effect on reducing the compression elastic modulus of the concrete.

As can be seen from Table 2, the bonding strength can be greatly improved by adding the concrete flexibilizer, the bonding strength is improved from 0.15MPa to 0.5MPa, and the improvement rate reaches more than 300%.

TABLE 1 deformation Capacity of Cement paste sheets of example 2 and comparative example 1

Table 2 concrete properties of example 3 and comparative example 2

In conclusion, the concrete flexibilizer provided by the invention can obviously improve the performance of the concrete flexibilizer by adding specific contents of organic cementing materials, expansion materials, superplasticizers, water-retention thickeners, air-entraining agents, defoaming agents, pour point regulators, shrinkage reducers and fillers, and can obviously improve the deformation capacity of cement paste by adding the concrete flexibilizer into the cement paste, wherein the maximum deformation is increased from 3mm to 42 mm; the concrete flexibilizer is added into concrete according to a specific proportion, so that the 28d compressive strength and 28d flexural strength of the concrete can be improved to a certain extent, the 28d flexural strength is increased more obviously than the 28d compressive strength, the flexural-compressive ratio is obviously improved, and the toughness of the concrete is improved; the elastic modulus of the concrete 28d can be obviously reduced, and the deformation performance of the concrete under external load is improved; can obviously improve the bonding strength of concrete interfaces and improve the bonding performance between concrete layers.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (6)

1. The concrete is characterized in that the mass ratio of each component of the concrete is as follows: cement: river sand: first gravel crushing: and (3) second stone crushing: water: fly ash: the concrete flexibilizer is 400: 680: 363: 846: 146: 70: 47; the concrete flexibilizer comprises the following components in percentage by mass: 25% of Wake re-dispersible latex powder, 30% of sulphoaluminate clinker type expanding agent, 3% of polycarboxylic acid type water reducing agent, 0.5% of hydroxypropyl methyl cellulose, 0.7% of triterpenoid saponin, 0.2% of polyether defoaming agent, 3% of potassium aluminate, 5% of polypropylene glycol and the balance of 32.6% of fly ash;

the particle size of the first crushed stone is 4.75-9.5 mm, and the particle size of the second crushed stone is more than 9.5mm and less than or equal to 19 mm;

the water reducing rate of the polycarboxylic acid water reducing agent is not less than 20 percent;

the 28d compressive strength of the concrete reaches 52.7 MPa; the 28d flexural strength reaches 7.4 MPa.

2. The concrete according to claim 1, wherein the viscosity of the hydroxypropylmethylcellulose is 5000 to 200000 mPa.s.

3. The preparation method of the concrete flexibilizer is characterized in that the concrete flexibilizer comprises the following components in percentage by mass: 25% of Wake re-dispersible latex powder, 30% of sulphoaluminate clinker type expanding agent, 3% of polycarboxylic acid type water reducing agent, 0.5% of hydroxypropyl methyl cellulose, 0.7% of triterpenoid saponin, 0.2% of polyether defoaming agent, 3% of potassium aluminate, 5% of polypropylene glycol and the balance of 32.6% of fly ash;

the preparation method comprises the following steps:

step 1, weighing organic cementing materials, expanding materials, fillers, superplasticizers, water-retention thickeners, air entraining agents, defoaming agents, coagulation regulators and shrinkage reducers according to mass percentage;

step 2, starting a mixer, then sequentially adding the expansion material, the filler and the organic cementing material, and after the materials are put into the mixer, uniformly mixing the materials;

step 3, sequentially adding a superplasticizer, a water retention thickener, an air entraining agent, a defoaming agent, a thickening time control agent and a shrinkage reducing agent into the uniformly mixed material in the step 2; and (3) after the materials are put into the mixer, mixing and stirring the materials for 3-5 minutes to finish the preparation of the concrete flexibilizer.

4. The cement paste is characterized in that the mass ratio of each component of the cement paste is as follows: cement: water: the concrete flexibilizer is 500: 150: 50;

the concrete flexibilizer comprises the following components in percentage by mass: 25% of Wake re-dispersible latex powder, 30% of sulphoaluminate clinker type expanding agent, 3% of polycarboxylic acid type water reducing agent, 0.5% of hydroxypropyl methyl cellulose, 0.7% of triterpenoid saponin, 0.2% of polyether defoaming agent, 3% of potassium aluminate, 5% of polypropylene glycol and the balance of 32.6% of fly ash.

5. A method for preparing concrete, for preparing the concrete according to claim 1 or 2, comprising the steps of:

s1, weighing cement, river sand, first crushed stone, second crushed stone, water, fly ash and a concrete flexibilizer according to the mass ratio;

s2, sequentially adding the first crushed stone, the second crushed stone, river sand, cement, fly ash and the concrete flexibilizer into the concrete mixer, starting the mixer, firstly dry-mixing, then adding water, and continuously stirring for 60-120S until the mixture is uniformly stirred.

6. The method for producing concrete according to claim 5, wherein the dry-mixing time in S2 is 25 to 35 seconds.