Functional admixture for prefabricated part concrete and preparation method of functional admixture

Abstract

The invention discloses a functional admixture for prefabricated part concrete and a preparation method thereof. The functional admixture for the prefabricated part concrete is prepared from an adsorption dispersant, a workability regulator, an internal curing agent and a hydration temperature rise control agent. The functional admixture is used in the component concrete stirring process, fine particles in a rubber material are dispersed, the viscosity of the component concrete is reduced, and internal bubbles are more easily discharged; bubbles introduced by continuous reaction of surfactants such as a grinding aid and a water reducing agent of chemical raw materials in the concrete are reduced through internal curing and hydration of a temperature rise inhibitor; in addition, the dispersing agent and the internal curing agent can adjust the softness of the concrete, bubbles generated in the concrete are easily discharged in the vibrating process, the number of the bubbles is reduced, the component forming efficiency is improved, and the surface appearance of the concrete component is achieved.

Description

Technical Field

[0001] The invention belongs to the field of building chemicals and relates to a functional admixture for prefabricated component concrete and a preparation method thereof. Background Art

[0002] Precast concrete components are building components made in advance in factories according to molds using concrete as the basic material, including various beams, slabs, columns and building decoration accessories. As an important building material, precast concrete components have attracted more and more attention due to their shorter construction period, energy saving and environmental protection, and are increasingly widely used in the fields of construction and engineering. However, with the high-strength requirements of key projects, the increase in the amount of concrete adhesives, and the changes in raw materials such as cement, sand and gravel aggregates, the number of bubbles on the surface of precast concrete components is increasing, which seriously affects the quality and appearance of the components and reduces the overall performance of the product, which has an adverse effect on the safety and durability of the building structure. Therefore, how to reduce the number of bubbles on the surface of precast concrete components and improve the quality and stability of the products has always been a hot issue of concern to manufacturers. The fundamental reason for the generation of bubbles in prefabricated components is that the amount of cementitious materials used in concrete is large, the strength is high, the grading of concrete raw materials is unreasonable, and the chemical components of various surfactant additives in cement concrete are introduced. In addition, the viscosity of concrete is too high, and the bubbles in short-term mixing are difficult to discharge. With the vibration of the equipment, the bubbles gather on the surface of the concrete and the surface of the formwork. After demolding, various large and small pores are formed on the surface. These pores give the concrete an unsightly and uneven appearance and even form a honeycomb surface, affecting the strength and durability of prefabricated concrete components.

[0003] Currently, there are two ways to solve the pore problem: first, apply cement slurry to the pores on the surface of the prefabricated concrete components to repair the pores left by the bubbles; second, use a good water-based release agent during the preparation of concrete; third, add a defoaming agent during the preparation of concrete, especially the third method is used more frequently. The existing solution is to apply cement slurry on the surface of the pores of the precast concrete components after forming. The cement slurry will shrink after hardening, and the interface between the new and old cement in the pores is not completely dissolved together. After the slurry is hydrated and hardened, the cement slurry will shrink and fall off, and the appearance problem cannot be completely solved; in addition, the use of water-based release agent can reduce the size of bubbles, but the densely packed small bubbles cannot be solved; the use of defoaming agent can reduce the number of bubbles inside the concrete, but bubbles on the surface of the component can still be generated and gathered, and it is difficult to fundamentally solve the problem, especially when the amount of defoaming agent is small, it is difficult to stir the concrete evenly in a short time. After increasing the amount of defoaming agent, the strength of the concrete is significantly reduced; in addition, physical means such as increasing the vibration time and changing the vibration method will reduce the generation of apparent bubbles, but will cause the concrete aggregate to settle, the slurry to float, the component surface to shrink more, the rebound strength to decrease, and the homogeneity of the component to decrease, so it cannot fundamentally solve the problem. Summary of the invention

[0004] In view of the causes and characteristics of bubbles generated in component concrete, the present invention provides a functional admixture for prefabricated component concrete and a preparation method thereof. The present invention adopts an adsorption dispersant, a workability regulator, an internal curing agent and a hydration temperature rise control agent to prepare a functional admixture for prefabricated component concrete. The functional admixture is used in the mixing process of component concrete to disperse fine particles in the adhesive, reduce the viscosity of the component concrete, and make it easier to discharge internal bubbles; through internal curing and hydration temperature rise inhibitors, the bubbles introduced by the continuous reaction of chemical raw material grinding aids, water reducers and other surfactants in the concrete are reduced; in addition, the dispersant and the internal curing agent can adjust the softness of the concrete, and the bubbles generated in the concrete are easily discharged during the vibration process, which reduces the number of bubbles, improves the component molding efficiency, and solves the surface appearance of the concrete component.

[0005] The technical solution of the present invention is: a functional admixture for prefabricated component concrete, characterized in that its components and weight ratio are: 30-40% adsorption dispersant, 30-40% workability regulator, 10-20% internal curing agent, 10-20% hydration temperature rise controller, 5%-10% water, and the functional admixture for prefabricated component concrete is obtained by mixing and stirring the above raw materials evenly.

[0006] Among them, the adsorption dispersant is diethanol monoisopropanolamine methacrylate, which is obtained by mixing methacrylic acid and diethanolamine monoisopropanolamine in a molar ratio of 2.8-3.2:1, adding a catalyst (zinc acetate), and performing reduced pressure distillation and esterification reaction. The temperature is controlled at 110±2°C. After the reaction is completed, diethanol monoisopropanolamine methacrylate is obtained by post-treatment.

[0007] The preparation method of the workability regulator is as follows: add methyl butyl hydroxyethyl polyoxyethylene ether, maleic anhydride, sodium methacrylic acid sulfonate, and hydroxypropyl methacrylate to an initiator for polymerization to obtain the workability regulator. The mass ratio of methyl butyl hydroxyethyl polyoxyethylene ether, maleic anhydride, sodium methacrylic acid sulfonate, and hydroxypropyl methacrylate is 300:30-50:40-60:40-60. Preferably, the initiator is azobisisobutyronitrile and azobisisoheptanenitrile prepared in a mass ratio of 1:1.

[0008] The internal curing agent is a modified polymer obtained by using polyacrylamide as a base polymer and introducing a small monomer propylene oxide; the mass ratio of polyacrylamide to propylene oxide is 7-9: 1, preferably 8: 1. Furthermore, stannous chloride is added as a catalyst and diethylenetriamine is added as a crosslinking agent during the preparation process.

[0009] The components and weight proportions of the hydration temperature rise controller are: 8-12 parts of 1,5-pentanediol, 100 parts of polyethylene glycol, 8-12 parts of oleyl glyceride, 22-27 parts of ferric sulfate, 4-6 parts of pentaerythritol, and 4-6 parts of 2,5-dihydroxybenzoic acid.

[0010] The technical principle of the present invention is as follows: (1) The main function of the adsorption dispersant is to produce a repulsive dispersion effect between fine particles such as cementitious materials in component concrete and fine powder (<75um) in machine-made sand. Compared with ordinary dispersants, the carbon chain length of the side chain of diethyl methacrylate monoisopropylamine ester is increased, the molecular layer thickness is large, and it shows a better adsorption and dispersion effect. In addition, the non-polar -CH3 introduced into the compound offsets the polar -OH functional group in cement hydration, reduces the agglomeration phenomenon in the hydration process, and makes the bubbles generated between the fine particles easily discharged from the inside to the surface and burst in a short time during the vibration process; (2) The sulfonic acid group is introduced into the workability regulator, and its hydrophilicity is better than that of functional groups such as carboxyl groups, so The viscosity of this slurry is reduced. At the same time, it acts as a chain transfer agent during the polymerization reaction, which can control the size of the molecular weight, make the molecular weight distribution uniform, and avoid stratification of the slurry inside and outside the concrete. Its function is to reduce the viscosity of high-grade component concrete, improve workability, increase vibration efficiency, and improve the homogeneity and density of concrete, so that the surface and internal structure of the component concrete are the same, and it is difficult to generate large bubbles inside. Only small uniform bubbles are generated and discharged on the surface; (3) The internal curing agent itself can absorb water. When the cementitious material inside the concrete is hydrated and the internal humidity is reduced, capillary tension is formed in the pores, and the internal curing agent releases water to compensate for the reaction and evaporation loss of water, thereby keeping the interior moist. Reduce the friction resistance between particles and avoid "forming local dry areas, which prevent bubbles from escaping and form pores on the surface and shallow layer of concrete"; (4) The hydration temperature rise controller regulates the hydration process of C3S through alcohol hydroxyl groups and iron salts, and reduces the cement hydration rate during the accelerated period through the delay effect of oleic acid glyceride groups, reduces the internal hydration temperature of concrete by more than 10°C, reduces the maximum value of the concrete hydration heat peak, thereby reducing the early hydration heat, changing the hydration process, and preventing chemical grinding aids and water reducers in concrete from forming more bubbles at high temperatures by reducing the heat of the cement hydration process.

[0011] The technical effects of the present invention are as follows: the functional admixture of the present invention can reduce the viscosity of high-grade component concrete, improve the workability of concrete, and make it easy to discharge bubbles in the concrete during vibration; reduce the surface tension of surfactants such as chemical raw material grinding aids and water reducers in concrete, uniformly disperse the glue particles in the concrete, and easily discharge the bubbles between the fine particles to the surface and break, and can improve the construction efficiency; reduce the hydration temperature rise, and reduce the number of bubbles generated by chemical additives in concrete due to the high hydration temperature; the adding method is simple, and there is no need to change the preparation process of the component concrete. DETAILED DESCRIPTION

[0012] The following is an example to illustrate the effect.

[0013] Example 1

[0014] The functional admixture has the following components and weight ratios: 35% adsorption dispersant, 30% workability regulator, 15% internal curing agent, 15% hydration temperature rise controller, and 5% water. The functional admixture for prefabricated concrete is obtained by mixing and stirring the above raw materials.

[0015] The preparation method of the adsorption dispersant (methacrylic acid diethanol monoisopropanolamine ester) is as follows: 258 grams of methacrylic acid and 163 grams of diethanolamine monoisopropanolamine are placed in a three-necked flask, 5 grams of zinc acetate catalyst is added, and vacuum distillation and esterification reaction are carried out. The temperature is controlled at 110 + 2°C, react for 3h, evaporate the generated water and reaction water in the mixed solution to obtain a crude product of diethanol monoisopropanolamine methacrylate. The crude product is dissolved in isooctane solvent, washed with 30% sodium hydroxide aqueous solution and distilled water to remove unreacted methacrylic acid and diethanolamine monoisopropanolamine, and finally the solvent is removed to obtain diethanol monoisopropanolamine methacrylate.

[0016] The preparation method of the workability regulator is as follows: weigh 300g of methyl butyl hydroxyethyl polyoxyethylene ether (CH2=C(CH3)CH2CH2OCH2CH2O(CH2CH2O) n H, n = 10 ~ 60), 40g of maleic anhydride, 50g of sodium methyl propylene sulfonate are poured into a four-necked bottle filled with 200g of water, and the temperature is raised to 60°C after being fully dissolved, 5.5g of initiator (azobisisobutyronitrile and azobisisoheptanenitrile are prepared in a mass ratio of 1:1) is added, and stirred for 10min, 50g of hydroxypropyl methacrylate is added dropwise, and the addition time is 2h. After the addition is completed, the reaction is kept warm for 1h to obtain a workability regulator.

[0017] The preparation method of the internal curing agent is as follows: add 10g of propylene oxide to every 80g of polyacrylamide, add 0.5g of stannous chloride as a catalyst, add 2g of diethylenetriamine as a crosslinking agent, react at 50°C for 4h, and obtain a modified polymer internal curing agent.

[0018] Among them, the preparation method of the hydration temperature rise control agent is as follows: 10g of 1,5-pentanediol, 100g of polyethylene glycol, 10g of olein, 25g of ferric sulfate, 5g of pentaerythritol, and 5g of 2,5-dihydroxybenzoic acid are stirred and dissolved.

[0019] Effect verification of the functional admixture prepared in Example 1 of the present invention

[0020] 1. Comparison of the application of defoamer and functional admixture in concrete C55 of the present invention

[0021] The test method refers to GB / T50082 "Standard for test methods of long-term performance and durability of ordinary concrete"; GB / T50081 "Standard for test methods of physical and mechanical properties of concrete" and GB / T50080 "Test methods of ordinary concrete mixtures"

[0022] The C55 mix of component concrete is shown in Table 1, and the test indicators are shown in Table 2.

[0023] Table 1: The C55 mix ratio of component concrete is as follows (Kg / m 3 )

[0024]

[0025] Note: (1) Cement is PI52.5, mineral powder is S95, fly ash is Class I, machine-made sand fineness modulus is 2.4, crushed stone particle size is 5-20mm, admixture (polycarboxylic acid admixture, preparation method: 20% polycarboxylic acid water reducer + 2.0% sodium gluconate + 78% water) solid content is 10 + 1%, water reduction rate ≥25%, defoamer concentration is 0.5%, and the ingredient is polyoxyethylene polyoxypropanolamine ether.

[0026] Table 2 Component concrete test indicators

[0027]

[0028]

[0029] Result analysis:

[0030] (1) The defoamer used in component concrete 1 reduced the total number of bubbles and the number of large bubbles in the concrete; the functional admixture was used in component concrete 2, and the bubbles were significantly reduced, especially the number of large bubbles was zero;

[0031] (2) The defoamer was used in component concrete 1 to reduce the bubbles in the concrete, but the performance and strength were reduced. However, the functional admixture was used in component concrete 2, and the performance and strength were improved, especially the emptying time of the inverted slump bucket. After the defoamer was used, the emptying time was longer, indicating that the viscosity of the concrete was larger. However, after the functional admixture was used, the emptying time of the inverted concrete was significantly shortened, indicating that the viscosity was significantly reduced, thereby improving the production efficiency of the concrete.

[0032] (3) In terms of durability, after using the functional admixture of the present invention, the bubbles inside the component concrete 2 are reduced, the interior of the concrete is dense, and the number of freeze-thaw cycles of the concrete is significantly improved.

[0033] 2. Comparison of application in plastering mortar for component concrete

[0034] The test reference standard is GB / T25281-2019 "Premixed Mortar".

[0035] The proportion of M10 plastering mortar for component concrete is shown in Table 3, and the properties of plastering mortar are shown in Table 4.

[0036] Table 3 M10 proportion of mortar for component concrete (Kg / m 3 )

[0037]

[0038] Note: (1) Ordinary cement, fly ash, machine-made sand, admixtures and defoaming agent used are the same as those in Table 1.

[0039] Table 4: Plastering mortar properties

[0040]

[0041]

[0042] Result analysis:

[0043] (1) A defoamer is used in the component concrete facing mortar (comparative mortar 1) to reduce the total number of bubbles and the number of large bubbles in the component concrete facing mortar; after using the functional admixture of the present invention (test mortar 1), the bubbles in the component concrete facing mortar are significantly reduced, especially the number of large bubbles is zero;

[0044] (2) While the defoamer reduces the bubbles in the plastering mortar for component concrete, the consistency, fluidity and strength are reduced. However, after the functional admixture of the present invention is used, the performance and strength of the plastering mortar for component concrete are improved, especially the coating rate of the plastering mortar is reduced, the construction performance of the mortar is improved, and the cost performance is improved;

[0045] (3) After using the functional admixture of the present invention, the bubbles inside the plastering mortar for component concrete are reduced, the inside of the mortar is dense, and the number of freeze-thaw cycles of the plastering mortar for component concrete is significantly improved.

[0046] Example 2

[0047] The functional admixture has the following components and weight ratios: 40% adsorption dispersant, 30% workability regulator, 10% internal curing agent, 10% hydration temperature rise controller, and 10% water. The functional admixture for prefabricated concrete is obtained by mixing and stirring the above raw materials.

[0048] Example 3

[0049] The functional admixture has the following components and weight ratios: 30% adsorption dispersant, 30% workability regulator, 20% internal curing agent, 15% hydration temperature rise controller, and 5% water. The functional admixture for prefabricated concrete is obtained by mixing and stirring the above raw materials.

Claims

1. A functional admixture for precast concrete, characterized in that: Its components and weight ratio are: adsorption dispersant 30-40%, workability regulator 30-40%, internal curing agent 10-20%, hydration temperature rise controller 10-20%, water 5%-10%; The adsorption dispersant is diethanol monoisopropanolamine methacrylate; The preparation method of the workability regulator is as follows: adding methyl butyl hydroxyethyl polyoxyethylene ether, maleic anhydride, sodium methacrylate sulfonate and hydroxypropyl methacrylate to an initiator for polymerization reaction to obtain the workability regulator; The internal curing agent is: a modified polymer obtained by using polyacrylamide as a base polymer and introducing a small monomer propylene oxide; The components and weight proportions of the hydration temperature rise controller are: 8-12 parts of 1,5-pentanediol, 100 parts of polyethylene glycol, 8-12 parts of oleyl glyceride, 22-27 parts of ferric sulfate, 4-6 parts of pentaerythritol, and 4-6 parts of 2,5-dihydroxybenzoic acid.

2. A functional admixture for precast concrete as claimed in claim 1, characterized in that: The preparation method of the adsorption dispersant is as follows: methacrylic acid and diethanolamine monoisopropanolamine are mixed at a molar ratio of 2.8-3.2:1, a catalyst is added, and reduced pressure distillation and esterification reaction are performed to obtain the adsorption dispersant. The temperature is controlled at 110±2° C. After the reaction is completed, diethanolamine monoisopropanolamine methacrylate is obtained through post-treatment.

3. A functional admixture for precast concrete as claimed in claim 2, characterized in that: The catalyst is zinc acetate.

4. The functional admixture for precast concrete as claimed in claim 1, characterized in that: In the preparation method of the workability regulator, the mass ratio of methyl butyl hydroxyethyl polyoxyethylene ether, maleic anhydride, sodium methacrylate sulfonate and hydroxypropyl methacrylate is 300:30-50:40-60:40-60.

5. The functional admixture for precast concrete as claimed in claim 1, characterized in that: In the preparation method of the workability regulator, the initiator is azobisisobutyronitrile and azobisisoheptanenitrile prepared in a mass ratio of 1:

1.

6. The functional admixture for precast concrete as claimed in claim 1, characterized in that: The mass ratio of polyacrylamide and propylene oxide used in the preparation of the internal curing agent is 7-9:

1.

7. The functional admixture for precast concrete as claimed in claim 1, characterized in that: During the preparation of the internal curing agent, stannous chloride is added as a catalyst and diethylenetriamine is added as a cross-linking agent.

8. The method for preparing the functional admixture for precast concrete according to any one of claims 1 to 7, characterized in that: The functional admixture for precast concrete is obtained by mixing and stirring the adsorption dispersant, workability regulator, internal curing agent, hydration temperature rise controller and water evenly.

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