Mechanism sand concrete admixture, preparation method and application thereof

Abstract

This invention relates to a manufactured sand concrete admixture, its preparation method, and its application. The admixture is composed of raw materials comprising the following weight percentages: 10-20% structural filler, 15-25% surface modifier, 10-15% interface optimizer, and 40-65% water. The preparation method includes the following steps: preparing raw materials containing structural filler, surface modifier, interface optimizer, and water according to the specified proportions; dividing the water into three equal parts; dissolving the structural filler, surface modifier, and interface optimizer separately to obtain solutions A, B, and C; slowly adding solutions A and C to solution B; and homogenizing to obtain a milky white admixture. This invention solves the problems of poor fluidity and rapid slump loss in manufactured sand concrete through the synergistic effect of multiple components. It is a concrete workability admixture that effectively inhibits harmful clay adsorption, improves the surface characteristics of manufactured sand particles, and enhances interfacial bonding performance.

Description

Technical Field

[0001] This invention relates to the technical field of concrete, and in particular to a manufactured sand concrete admixture, its preparation method, and its application. Background Technology

[0002] Manufactured sand is a fine aggregate produced by mechanically crushing and screening rocks. Due to its wide availability, low cost, and lack of limitation by natural sand resources, it has become an indispensable raw material for modern concrete preparation. However, manufactured sand has two inherent defects in its production process, severely restricting its widespread application in high-performance concrete. First, the parent rock of manufactured sand often contains a certain amount of layered silicate clay minerals. This clay is difficult to completely remove during crushing, resulting in a clay content of 3% to 8% in the finished manufactured sand. These clay minerals have a unique interlayer structure and strong cation exchange capacity. When they enter the concrete system, they consume a large amount of mixing water and polycarboxylate superplasticizer molecules through intercalation adsorption, leading to a sharp loss of concrete slump. In severe cases, this can cause pumping interruption or even pipe blockage. Second, the mechanical crushing process results in manufactured sand particles with a distinctly angular morphology and high surface roughness. Under the same gradation conditions, the water requirement of manufactured sand concrete increases by 10% to 25% compared to natural sand concrete. This not only exacerbates the risk of shrinkage cracking in concrete, but also directly reduces the initial fluidity of fresh concrete, making construction operations difficult.

[0003] To address the technical challenges posed by manufactured sand, researchers and engineers in related fields have attempted various improvement solutions. The physical coating method uses mineral oil or polymer emulsions to coat the surface of manufactured sand particles, attempting to reduce inter-particle frictional resistance and improve flowability. However, these oily substances form a physical barrier in concrete, hindering effective bonding between cement hydration products and the aggregate surface, leading to a significant 15% to 20% decrease in the 28-day compressive strength of the concrete. The retarding compensation method extends the cement hydration induction period by adding retarding components such as sodium gluconate, thereby maintaining the workability of the concrete for a longer period. However, this method does not address the core contradiction of clay mineral adsorption of water-reducing agents; the slump loss rate of the concrete still exceeds 35%, making it difficult to meet the workability maintenance requirements of modern pumping construction. Traditional anti-mud agents mainly use cationic surfactants such as quaternary ammonium salts to shield the negative charge on the clay surface, thereby reducing its adsorption of water-reducing agents. However, these single-function admixtures can only reduce the adsorption of water-reducing agents by 30% to 50% and do not improve the morphology of manufactured sand particles. More seriously, when traditional anti-mud agents are used in excess, they can easily introduce a large number of air bubble defects into the concrete, causing the concrete strength dispersion coefficient to increase to more than 10%, which seriously endangers the stability of the structural quality.

[0004] Chinese Patent CN115534107B, authorized by CN115534107B, discloses a preparation process for improving the performance of manufactured sand concrete. The process comprises the following steps: S1: A composite admixture is prepared by mixing ether-based water-reducing agent, ether-based slump-preserving water-reducing agent, retarder, mud inhibitor, and water in a ratio of 160:35:20:5:780; S2: 585 parts of manufactured sand are washed using a washing machine, then dried. The treated manufactured sand is then mixed with 200 parts of fine river sand, 25 parts of red mud, and 1050 parts of stone, and stirred for 30-50 seconds to obtain mixture A; S3: 60 parts of fly ash, 60 parts of sludge, and 240 parts of cement are added to mixture A, and stirred for 40-50 seconds to obtain mixture B; S4: 9 parts of the composite admixture and 170 parts of water are added to mixture B, and stirred for 40-50 seconds to obtain manufactured sand concrete. This accelerator uses aluminum sulfate, sodium aluminate, and fluoride salts as its main raw materials, achieving its rapid setting effect by introducing fluoride ions. However, this technology introduces sodium salts and fluoride ions, which may increase the risk of alkali-aggregate reaction in the later stages, affecting the long-term durability of concrete.

[0005] Chinese Patent CN117602888B discloses a design method for manufactured sand concrete to reduce fluidity loss over time. The method includes the following steps: providing a first base material for the concrete, compensating water, and a superabsorbent polymer for adding to the concrete to absorb and slowly release the compensating water. The first base material comprises cement, manufactured sand, crushed stone, admixtures, and water in a preset mass ratio. Based on the 5-minute spread of the mortar mixture prepared with the first base material and the empirical water absorption capacity of the superabsorbent polymer, a first test is conducted to determine the superabsorbent polymer's... The estimated water absorption capacity of the superabsorbent polymer is determined, whereby the estimated water absorption capacity is the mass of compensating water that a unit mass of the superabsorbent polymer can absorb. Based on the estimated water absorption capacity and the 1-hour spread of the second base material (using an equal amount of natural sand to replace manufactured sand), the amount of compensating water is determined through a second test. Based on the amount of compensating water and the estimated water absorption capacity of the superabsorbent polymer, the amount of superabsorbent polymer added to the first base material is determined. Based on the amount of superabsorbent polymer added and the amount of compensating water, the preset mass ratio is adjusted to obtain the design mix ratio of the manufactured sand concrete.

[0006] The shortcomings of the aforementioned existing technologies are as follows: the former uses a combination of water-reducing agents, retarders, and mud inhibitors, while the latter regulates the workability of manufactured sand concrete through measures such as compensating water. However, they are insufficient in regulating the overall integrity of the concrete, lacking a multifunctional composite regulation scheme that can simultaneously achieve pore filling of manufactured sand particles, surface morphology modification, and paste-aggregate interface optimization. Developing a concrete workability admixture that can effectively inhibit harmful clay adsorption, improve the surface properties of manufactured sand particles, and enhance interfacial bonding performance is of significant engineering value and practical importance for solving key technical problems such as poor fluidity, rapid slump loss, and insufficient durability of manufactured sand concrete, and for promoting the widespread application of manufactured sand in high-performance concrete. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the first objective of this invention is to provide a manufactured sand concrete admixture that solves the problems of poor fluidity and rapid slump loss in manufactured sand concrete through the synergistic effect of multiple components. This admixture effectively inhibits harmful clay adsorption, improves the surface characteristics of manufactured sand particles, and enhances interfacial bonding performance.

[0008] The second objective of this invention is to provide a method for preparing a manufactured sand concrete admixture, which has the advantages of simple operation and mild conditions. It can achieve uniform compounding of each component through conventional stirring reaction, without the need for special high temperature and high pressure equipment, making it suitable for continuous industrial production. Moreover, no toxic or harmful substances are generated during the preparation process, which meets the requirements of green chemical development.

[0009] The third objective of this invention is to provide an application of a manufactured sand concrete admixture in the preparation of manufactured sand concrete. By incorporating the admixture into the manufactured sand concrete system in a certain proportion, the initial fluidity of fresh concrete can be significantly improved, the slump loss rate over time can be reduced, and the mechanical properties of hardened concrete can be optimized.

[0010] The third objective of this invention is to provide an application of a manufactured sand concrete admixture, which has the advantages of significantly improving the initial fluidity of fresh concrete, reducing the slump loss rate over time, and optimizing the mechanical properties of hardened concrete.

[0011] To achieve the first objective mentioned above, the present invention provides the following technical solution: A manufactured sand concrete admixture is composed of raw materials comprising the following weight percentages: 10-20% structural filler component, 15-25% surface modification component, 10-15% interface optimization component, and 40-65% water.

[0012] Furthermore, the structural filler components include hexadecyltrimethylammonium bromide and sodium tripolyphosphate in a mass ratio of 1:(2~5).

[0013] Furthermore, the surface modification component is selected from polymer emulsions containing siloxane groups.

[0014] Furthermore, the polymer emulsion containing siloxane groups is an acrylate-siloxane copolymer emulsion containing 15-30% siloxane segments.

[0015] Furthermore, the acrylate-siloxane copolymer is polymerized from raw materials comprising γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate and butyl acrylate in a mass ratio of 1:(2~4):(5~7).

[0016] Furthermore, the interface-optimized components include methylcellulose ether and ethylene glycol in a mass ratio of 1:(0.5~2.0).

[0017] Furthermore, the molecular weight of the methylcellulose ether is 10,000 to 50,000 Da.

[0018] To achieve the second objective mentioned above, the present invention provides the following technical solution: A method for preparing a manufactured sand concrete admixture includes the following steps: S1 prepares raw materials containing structural filler components, surface modification components, interface optimization components and water according to the formula, and divides the water into three equal parts, dissolves the structural filler components, surface modification components and interface optimization components respectively to obtain solution A, solution B and solution C; S2 slowly adds solutions A and C to solution B, and after homogenization, a milky white additive is obtained.

[0019] Furthermore, the specific implementation of S1 is as follows: S11 Prepare raw materials containing structural filler components, surface modification components, interface optimization components and water according to the formula, and divide the water into three equal parts; S12 dissolves hexadecyltrimethylammonium bromide and sodium tripolyphosphate in the first portion of water to obtain solution A; S13 involves emulsifying and polymerizing γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate, and butyl acrylate in a second part of water. The emulsification copolymerization is carried out at 75-85°C under the action of a composite emulsifier and initiator, with the pH of the reaction system controlled at 6.0-8.0 and the reaction time at 3-5 hours, to obtain solution B. S14 dissolves methylcellulose ether and ethylene glycol in a third part of water to obtain solution C.

[0020] To achieve the third objective mentioned above, the present invention provides the following technical solution: Application of a manufactured sand concrete admixture in the preparation of manufactured sand concrete.

[0021] In summary, the beneficial technical effects of the present invention are as follows: 1. The structural filler component in the admixture of the present invention can effectively fill the pores of manufactured sand, and the surface modification component can improve its surface properties. The synergistic effect of the components significantly improves the material stability of manufactured sand, reduces performance fluctuations caused by external factors, and provides high-quality and stable aggregate for the preparation of high-performance concrete, making the quality of concrete more guaranteed. 2. The admixture of the present invention can be applied to concrete containing silt-containing manufactured sand, which can greatly improve its workability. The structural filling component, surface modification component and interface optimization component work together to improve the fluidity, plasticity and water retention of concrete, making the concrete easier to operate during construction, reducing construction difficulty and improving construction efficiency. 3. The interface-optimizing component in the admixture of the present invention optimizes the interfacial bonding between manufactured sand and cement paste, reducing the adverse effects of mud on concrete performance; the admixture of the present invention significantly improves the durability of concrete, enhances its resistance to external environmental erosion, extends the service life of concrete structures, and saves on later maintenance costs. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with specific embodiments. Example

[0023] Example 1: A manufactured sand concrete admixture disclosed in this invention is composed of raw materials comprising the following weight percentages: 10% structural filler component, 15% surface modification component, 10% interface optimization component, and 65% water.

[0024] The structural filler components include cetyltrimethylammonium bromide and sodium tripolyphosphate in a mass ratio of 1:3.

[0025] The surface modification component is selected from polymer emulsions containing siloxane groups; the polymer emulsion containing siloxane groups is an acrylate-siloxane copolymer emulsion containing 15-30% siloxane segments; the acrylate-siloxane copolymer is polymerized from raw materials containing γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate and butyl acrylate in a mass ratio of 1:3:6.

[0026] The interface optimization components include methylcellulose ether and ethylene glycol in a mass ratio of 1:1.5; the molecular weight of methylcellulose ether is 30,000 Da.

[0027] This invention also discloses a method for preparing a manufactured sand concrete admixture, comprising the following steps: S1 prepares raw materials containing structural filler components, surface modification components, interface optimization components and water according to the formula, and divides the water into three equal parts, dissolves the structural filler components, surface modification components and interface optimization components respectively to obtain solution A, solution B and solution C; S11 Prepare raw materials containing structural filler components, surface modification components, interface optimization components and water according to the formula, and divide the water into three equal parts; S12 dissolves hexadecyltrimethylammonium bromide and sodium tripolyphosphate in the first portion of water to obtain solution A; S13 emulsifies and polymerizes γ-methacryloxypropyltrimethoxysilane, hydroxyethyl methacrylate, and butyl acrylate in the second part of water. The emulsification copolymerization is carried out at 75-85℃ under the action of a composite emulsifier and initiator. The pH of the reaction system is controlled at 7.0 and the reaction time is 4h to obtain solution B. S14 dissolves methylcellulose ether and ethylene glycol in a third part of water to obtain solution C; S2 slowly adds solutions A and C to solution B, and after homogenization, a milky white additive is obtained.

[0028] This invention also discloses the application of a manufactured sand concrete admixture in the preparation of manufactured sand concrete. Preferably, it is applied to C40 concrete prepared based on silty manufactured sand, wherein the manufactured sand concrete is composed of the following raw materials in parts by weight: 14 parts cement, 7 parts water, 32 parts manufactured sand, 47 parts crushed stone, 0.15 parts water-reducing agent, and 1 part admixture.

[0029] Example 2: This invention discloses a manufactured sand concrete admixture, which differs from Example 1 in that it is composed of raw materials comprising the following weight percentages: 10% structural filler component, 15% surface modification component, 10% interface optimization component, and 65% water.

[0030] Example 3: This invention discloses a manufactured sand concrete admixture, which differs from Example 1 in that it is composed of raw materials comprising the following weight percentages: 10% structural filler component, 15% surface modification component, 10% interface optimization component, and 65% water.

[0031] Example 4: This invention discloses a manufactured sand concrete admixture, which differs from Example 1 in that it is composed of raw materials comprising the following weight percentages: 10% structural filler component, 15% surface modification component, 10% interface optimization component, and 65% water.

[0032] Example 5: This invention discloses a manufactured sand concrete admixture, which differs from Example 1 in that it is composed of raw materials comprising the following weight percentages: 10% structural filler component, 15% surface modification component, 10% interface optimization component, and 65% water.

[0033] The structural filler components include cetyltrimethylammonium bromide and sodium tripolyphosphate in a mass ratio of 1:2.

[0034] The surface modification component is selected from polymer emulsions containing siloxane groups; the polymer emulsion containing siloxane groups is an acrylate-siloxane copolymer emulsion containing 15-30% siloxane segments; the acrylate-siloxane copolymer is polymerized from raw materials containing γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate and butyl acrylate in a mass ratio of 1:2:5.

[0035] The interface optimization components include methylcellulose ether and ethylene glycol in a mass ratio of 1:0.5; the molecular weight of methylcellulose ether is 10000 Da.

[0036] Example 6: This invention discloses a manufactured sand concrete admixture, which differs from Example 1 in that it is composed of raw materials comprising the following weight percentages: 10% structural filler component, 15% surface modification component, 10% interface optimization component, and 65% water.

[0037] The structural filler components include cetyltrimethylammonium bromide and sodium tripolyphosphate in a mass ratio of 1:2.

[0038] The surface modification component is selected from polymer emulsions containing siloxane groups; the polymer emulsion containing siloxane groups is an acrylate-siloxane copolymer emulsion containing 15-30% siloxane segments; the acrylate-siloxane copolymer is polymerized from raw materials containing γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate and butyl acrylate in a mass ratio of 1:4:7.

[0039] The interface optimization components include methylcellulose ether and ethylene glycol in a mass ratio of 1:2.0; the molecular weight of methylcellulose ether is 50,000 Da. Comparative Example

[0040] Comparative Example 1: This is an application of the present invention in the preparation of manufactured sand concrete. The difference from Example 1 is that no admixtures are used in the manufactured sand concrete.

[0041] Comparative Example 2: This is an application of the present invention in the preparation of manufactured sand concrete. The difference from Example 1 is that a mud inhibitor is used instead of an admixture in the manufactured sand concrete. Performance testing

[0042] The performance of the manufactured sand concrete obtained in Examples 1-4 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0043] Table 1

[0044] As can be seen from Table 1, the fluidity and 28-day compressive strength of Examples 1-4 are higher than those of Comparative Examples 1-2, indicating that the admixture provided by the present invention can improve the workability and compressive strength of concrete and reduce the porosity of concrete. The admixture can improve the concrete's ability to prevent mud blockage and reduce the performance degradation of manufactured sand, which is beneficial to the formation of hydration products.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A manufactured sand concrete admixture, characterized in that: It is composed of raw materials containing the following weight percentages: 10-20% structural filler, 15-25% surface modification component, 10-15% interface optimization component, and 40-65% water.

2. The manufactured sand concrete admixture according to claim 1, characterized in that: The structural filler components include hexadecyltrimethylammonium bromide and sodium tripolyphosphate in a mass ratio of 1:(2~5).

3. The manufactured sand concrete admixture according to claim 1, characterized in that: The surface modification component is selected from polymer emulsions containing siloxane groups.

4. The manufactured sand concrete admixture according to claim 3, characterized in that: The polymer emulsion containing siloxane groups is an acrylate-siloxane copolymer emulsion containing 15-30% siloxane segments.

5. The manufactured sand concrete admixture according to claim 4, characterized in that: The acrylate-siloxane copolymer is polymerized from raw materials comprising γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate and butyl acrylate in a mass ratio of 1:(2~4):(5~7).

6. The manufactured sand concrete admixture according to claim 1, characterized in that: The interface optimization components include methylcellulose ether and ethylene glycol in a mass ratio of 1:(0.5~2.0).

7. The manufactured sand concrete admixture according to claim 6, characterized in that: The molecular weight of the methylcellulose ether is 10,000 to 50,000 Da.

8. The method for preparing a manufactured sand concrete admixture according to claim 1, characterized in that: Includes the following steps, S1 prepares raw materials containing structural filler components, surface modification components, interface optimization components and water according to the formula, and divides the water into three equal parts, dissolves the structural filler components, surface modification components and interface optimization components respectively to obtain solution A, solution B and solution C; S2 slowly adds solutions A and C to solution B, and after homogenization, a milky white additive is obtained.

9. The method for preparing a manufactured sand concrete admixture according to claim 1, characterized in that: The specific implementation of S1 is as follows: S11 Prepare raw materials containing structural filler components, surface modification components, interface optimization components and water according to the formula, and divide the water into three equal parts; S12 dissolves hexadecyltrimethylammonium bromide and sodium tripolyphosphate in the first portion of water to obtain solution A; S13 involves emulsifying and polymerizing γ-methacryloyloxypropyltrimethoxysilane, hydroxyethyl methacrylate, and butyl acrylate in a second part of water. The emulsification copolymerization is carried out at 75-85°C under the action of a composite emulsifier and initiator, with the pH of the reaction system controlled at 6.0-8.0 and the reaction time at 3-5 hours, to obtain solution B. S14 dissolves methylcellulose ether and ethylene glycol in a third part of water to obtain solution C.

10. The application of the manufactured sand concrete admixture according to claim 1 in the preparation of manufactured sand concrete.

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