Modified material for improving construction robustness of self-compacting concrete mixture as well as preparation method and application of modified material

Abstract

The invention discloses a modified material for improving construction robustness of a self-compacting concrete mixture as well as a preparation method and application of the modified material, and belongs to the technical field of building materials. The modified material comprises the following components in percentage by mass: 60%-70% of a composite mineral admixture, 15%-20% of zeolite powder, 12%-15.5% of nano calcium carbonate, 0.5%-1% of lignin fibers and 2%-4% of an organic rheology modifier. The modified material for improving the construction robustness of the self-compacting concrete mixture disclosed by the invention can effectively improve the segregation resistance and the water retention capacity of the self-compacting concrete mixture and improve the construction robustness of the self-compacting concrete mixture; the construction performance of the self-compacting concrete mixture can be kept stable under the condition that the water content of the raw materials fluctuates to a certain extent, so that the construction quality of the concrete is guaranteed, and important application value is achieved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a performance-modifying material for concrete mixtures, its preparation method, and its application. Background Technology

[0002] Self-compacting concrete is a new type of concrete with high workability. It can solve the problem of dense pouring of concrete in engineering structures where vibration is not allowed, impossible, or difficult, and has received widespread attention and undergone numerous practical applications. Practice shows that concrete mixtures have high fluidity, making them prone to segregation and bleeding, which negatively impacts construction quality. Meanwhile, with the increasing depletion of natural sand and gravel resources and growing environmental awareness, large quantities of manufactured sand are being used in concrete. Manufactured sand is made from natural rocks, pebbles, mine tailings, industrial slag, and construction waste through crushing and screening. Variations in the parent materials of manufactured sand can easily cause fluctuations in its quality. The sharp edges, irregular surfaces, and discontinuous gradation of manufactured sand, often resulting in gradation breaks, are also important reasons why concrete mixtures are prone to segregation, bleeding, and stratification.

[0003] To address the issues of fluctuating workability in fresh concrete, especially high-flowability, self-compacting concrete mixtures, researchers typically add fine-particle mineral admixtures or high-molecular-weight thickeners such as thermal sizing agents, cellulose ethers, and polyacrylamide. While these measures can alleviate segregation and bleeding to some extent, the overall workability of the concrete mixture remains unsatisfactory, and they can also negatively impact the concrete's strength. Against this backdrop, concrete viscosity modifiers and materials that improve the construction robustness of self-compacting concrete mixtures have gradually become research hotspots.

[0004] Patent CN108863148A discloses a self-compacting concrete viscosity modifier, which is composed of 30%~40% nano-silica, 10%~20% ultrafine mineral powder, 30%~45% heavy calcium carbonate, 2%~8% redispersible latex powder, 2%~8% hydroxypropyl methylcellulose, and 1%~5% polyvinyl alcohol by mass percentage. While this self-compacting concrete viscosity modifier can reduce problems such as bleeding and segregation in concrete mixtures, the large amount of organic thickening materials such as nano-silica, hydroxypropyl methylcellulose, and polyvinyl alcohol in the formulation significantly affects the fluidity of the mixture. Furthermore, nano-silica is very expensive, making it technically uneconomical and difficult to promote. Additionally, this technology does not address how to improve the filler ratio of the finished product.

[0005] Patent CN 117623666 A discloses a concrete viscosity modifier, its preparation method, and its application. This patent mainly involves reacting a 0.1%–3% (w / w) aqueous solution of carboxylated multi-walled carbon nanotubes, a 0.1%–1.5% (w / w) aqueous solution of hydroxyethyl cellulose, and an appropriate amount of p-toluenesulfonic acid at 105–120 °C for 2–3 h. The reaction is followed by centrifugation, washing, and drying to obtain the concrete viscosity modifier. This modifier increases concrete viscosity while reducing its impact on flowability, thus increasing the workability of the concrete. However, carbon nanotubes are expensive and difficult to disperse, resulting in limited overall construction stability of the concrete mixture. Furthermore, this technology does not address how to improve the filler ratio of the finished product.

[0006] CN 104829160 B discloses a method for preparing a novel viscosity modifier for CRTSⅢ type self-compacting concrete, which is uniformly mixed from fumed silica, calcium carbonate, low-viscosity hydroxyethyl cellulose, high-viscosity hydroxyethyl cellulose, thixotropic modifier, and water-soluble polymer powder. This patent is specifically designed for a viscosity modifier of CRTSⅢ type self-compacting concrete, significantly improving the viscosity of the self-compacting concrete mixture and effectively reducing bleeding and segregation. However, the use of multiple organic modifiers, such as low-viscosity hydroxyethyl cellulose, high-viscosity hydroxyethyl cellulose, thixotropic modifier, and water-soluble polymer powder, can easily lead to increased air bubble content in the concrete mixture, weakened robustness, and reduced hardened concrete strength. Furthermore, its technical, economic, and ecological benefits urgently need improvement. Additionally, this technology does not address how to increase the filler ratio of the finished product. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a modified material and its preparation method for improving the construction robustness of self-compacting concrete mixtures. This material can effectively improve the anti-segregation and water retention properties of self-compacting concrete mixtures, significantly enhance their construction robustness, and maintain stable construction performance of self-compacting concrete mixtures even under conditions of fluctuating raw material moisture content, thereby effectively ensuring good construction quality of concrete.

[0008] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0009] A modified material for improving the construction robustness of self-compacting concrete mixtures, characterized in that it comprises the following components by mass percentage: 60-70% composite mineral admixture, 15-20% zeolite powder, 12-15.5% nano-calcium carbonate, 2-4% organic rheology modifier, and 0.5-1% lignin fiber.

[0010] The above-mentioned composite mineral admixture is prepared by mixing slag, gypsum dihydrate powder, and yellow phosphorus slag powder in a mass ratio of (50~60):(15~20):(25~30) and then grinding them. The specific surface area of ​​the composite mineral admixture is greater than or equal to 500 m². 2 / kg, preferably (500~600)m 2 / kg, the gypsum dihydrate powder contains ≥90wt% CaSO4·2H2O, and the yellow phosphorus slag powder contains ≥80wt% (CaO+SiO2). The activity index of the composite mineral admixture is ≥0.80. The slag is S95 slag and / or S105 slag. During the technical exploration, S75 slag was also tried, but the effect was too poor.

[0011] This invention requires the slag powder used to have a fineness greater than or equal to 500 μm. 2 / kg, fineness range of yellow phosphorus slag powder 400~600 μm 2 / kg.

[0012] Preferably, in the composite mineral admixture, the mass percentage of S95 slag is (55~60)%, the mass percentage of dihydrate gypsum powder is 15%, and the mass percentage of yellow phosphorus slag powder is (25~30)%, and the three are mixed and ground together to obtain the product.

[0013] Preferably, the specific surface area of ​​the composite mineral admixture is (550~650) m². 2 / kg. This invention controls the specific surface area of ​​the composite mineral admixture to be greater than or equal to 500 m². 2 / kg, preferably (500~600)m 2 / kg, further preferably (550~650)m 2 The / kg fineness range is because this range allows for gradation with other powder components and ensures appropriate slurry viscosity. If the specific surface area is too low, it can lead to low slurry viscosity, bleeding of the mixture, and segregation. In practical applications, an excessively high specific surface area increases costs and can cause agglomeration.

[0014] Preferably, the dihydrate gypsum powder used in the composite mineral additive can be derived from desulfurized gypsum or phosphogypsum, wherein CaSO4·2H2O ≥ 90wt% and moisture content ≤ 2%. In industrial applications, the particle size of the dihydrate gypsum powder is greater than or equal to 200 mesh.

[0015] Preferably, the yellow phosphorus slag powder contains ≥80wt% (CaO+SiO2) and the SiO2 / CaO (mass ratio) is ≥0.82. For industrial applications, the particle size of the yellow phosphorus slag powder is preferably 500~600 μm. 2 / kg.

[0016] Preferably, the activity index of the composite mineral admixture is ≥0.85.

[0017] The zeolite powder mentioned above is a white powder, wherein the SiO2 content is ≥60wt% (and the active SiO2 content is ≥15wt%), the Al2O3 content is (10~20)wt%, and the specific surface area is not less than 500m² / g, which of course includes not less than 500~700m² / g.

[0018] Preferably, the zeolite powder contains 65-70 wt% SiO2 (with an active SiO2 content ≥15 wt%) and ≥10 wt% active Al2O3.

[0019] Preferably, the specific surface area of ​​the zeolite powder is (550~650) m² / g.

[0020] The CaCO3 content in the above-mentioned nano-calcium carbonate is not less than 95wt%, the average particle size is not greater than 50nm, and the maximum particle size is not greater than 90nm.

[0021] The above-mentioned composite organic rheology modifier is composed of 30-40 (parts by weight) of ethylene-vinyl acetate copolymer renewable latex powder, 45-50 parts of guar gum ether, and 15-20 parts of hydroxypropyl methylcellulose.

[0022] Preferably, in the composite organic rheology modifier, 30-35 parts of ethylene-vinyl acetate copolymer renewable latex powder, 50 parts of guar gum ether, and 15-20 parts of hydroxypropyl methylcellulose are present.

[0023] Preferably, the viscosity of guar gum ether is 400~800; and the viscosity of hydroxypropyl methylcellulose is 20000~40000.

[0024] The lignin fibers mentioned above have a length of no more than 2.5 mm, a particle size of less than 0.15 mm, an ash content of no more than 10%, and a moisture content of no more than 5%.

[0025] The aforementioned modified material for improving the construction robustness of self-compacting concrete mixtures is prepared using a two-stage high-efficiency mixing process, and the specific preparation method is as follows:

[0026] The first step involves loading nano-calcium carbonate, organic rheology modifier, and lignin fiber into the hopper of the first-stage mixing system, weighing them according to the above proportions using a precise metering system (accuracy not less than 0.5%), and then discharging them into the first-stage twin-shaft zero-gravity paddle mixer for dispersion and mixing for no less than 3 minutes until a uniform mixture is formed.

[0027] The second step involves placing the composite mineral additive into the silo of the second-stage mixing system and weighing it according to the above proportion using a precise metering system (accuracy not less than 1%). The mixture is then discharged into the second-stage twin-shaft zero-gravity paddle mixer. Simultaneously, the homogeneous mixture from the first-stage twin-shaft zero-gravity paddle mixer is also discharged into the second-stage twin-shaft zero-gravity paddle mixer system in proportion to form a multi-component mixture. This mixture is then dispersed and mixed for at least 5 minutes until a homogeneous modified material is formed.

[0028] The present invention relates to the application of a modified material for improving the construction robustness of self-compacting concrete mixtures, the application including its use in self-compacting concrete.

[0029] As a preferred option, 30-33 kg of modified material is added to each cubic meter of self-compacting concrete.

[0030] In engineering applications, the other components of self-compacting concrete can be basically the same as those in existing technologies. Of course, as a preferred method, the amount of each substance added per cubic meter of self-compacting concrete can be:

[0031] 325 kg of cement, 125 kg of mineral powder, 44 kg of expanding agent, 850 kg of medium sand, 315 kg of 5-10 mm crushed stone, 480 kg of 10-16 mm crushed stone, 6.0 kg of water-reducing agent, 165 kg of water, and 32 kg of the modified material developed in this invention.

[0032] The mineral powder can specifically be at least one of S95 slag powder and S105 slag powder.

[0033] The expanding agent can be a type II expanding agent (or a type II expanding agent).

[0034] The water-reducing agent may be at least one of the following: a carboxylic acid-based high-efficiency water-reducing agent with a water reduction rate of not less than 25%.

[0035] This invention, for the first time, utilizes a variety of solid waste mineral materials with relatively stable quality and complementary properties. Through mechanical and physical mixing and grinding, a composite mineral admixture component is prepared, which physically retains water and thickens while chemically enhancing phase transformation. This is then further combined with appropriate amounts of active zeolite powder and nano-calcium carbonate particles, which significantly adsorb, store, and slowly release free aqueous solutions, to enhance the water retention capacity of the concrete mixture. Furthermore, an appropriate amount of multi-component gradient-modified composite organic rheology modifier with excellent water absorption, swelling, thickening, and thixotropic properties is incorporated. Simultaneously, an appropriate amount of lignin fiber is added to form a reinforced spatial network support system, effectively reducing the settling tendency of different density components such as paste, sand, and stone in the concrete, and enhancing the suspension stability and anti-segregation performance of solid particles in the system. The resulting modified material, which improves the construction robustness of self-compacting concrete mixtures, exhibits excellent construction stability and good compatibility with existing high-efficiency water-reducing agents. It can significantly improve the stability and anti-segregation properties of the mixture while ensuring the high fluidity of the self-compacting concrete mixture.

[0036] In summary, the modified material of this invention, which enhances the construction robustness of self-compacting concrete mixtures, is prepared through a four-level gradient regulation of complementary multi-component composite mineral admixtures, zeolite powder with good absorption and release regulation due to its layered pore structure, nano-calcium carbonate particles, composite organic rheology modifiers, and cellulose fibers. It effectively solves the problems of unstable performance and large fluctuations in construction quality in traditional self-compacting concrete mixtures, such as easy exudation of free water, easy floating of slurry, and excessive sedimentation and segregation of sand and gravel. It not only significantly improves the construction robustness of self-compacting concrete mixtures but also ensures the strength and other properties of self-compacting concrete after hardening, demonstrating excellent technical advantages.

[0037] Compared with the prior art, the advantages of the present invention are:

[0038] (1) The modified material of the present invention for improving the construction robustness of self-compacting concrete mixtures, in conjunction with physicochemical principles, employs complementary multi-component composite mineral admixtures, porous zeolite powder with good absorption and release control, nano-calcium carbonate particles, composite organic modifiers, and lignin fibers. This not only effectively adsorbs excess free water and enhances the viscosity of the liquid phase, but also increases the solid-phase skeleton content and packing density in the slurry through micro- and nano-scale mineral particles, thereby improving the solid-liquid ratio and slurry density. Simultaneously, the porous zeolite powder particles with good absorption and release properties can control the consistency of the liquid phase, and the lignin fibers further strengthen the spatial network support capacity of the system, ensuring the suspension stability of sand and stone aggregate particles. Therefore, the modified material of the present invention significantly improves the performance stability of self-compacting concrete mixtures, reduces system bleeding and segregation, and especially improves the performance stability of the system under conditions of fluctuating external moisture, ensuring stable construction quality.

[0039] (2) This invention uses multi-component composite mineral admixtures, porous active zeolite powder, nano-calcium carbonate and other multi-scale mineral powders to make full use of the chemical activity of slag and yellow phosphorus slag, and the fluidization and activation effect of gypsum powder. In the system, it plays the role of physical compaction and chemical modification and strengthening phase, improves the pore structure, compactness and impermeability of the system, and synergistically improves the workability of self-compacting concrete mixture and the strength and durability after hardening, significantly improving the long-term performance of self-compacting concrete.

[0040] (3) The modified material of this invention is the first to utilize a suitable amount of slag powder, desulfurized gypsum or phosphogypsum, yellow phosphorus slag and other diverse solid waste resources. At the same time, the zeolite powder and nano-calcium carbonate particles used are relatively inexpensive. Moreover, a large amount of renewable latex powder and guar gum ether are also used in the composite organic rheology modifier, which has outstanding cost performance and ecological benefits. In addition, the preparation process of the modified material of this invention is relatively simple and convenient. Overall, the modified material of this invention has excellent safety, ecological and environmental protection characteristics. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The present invention discloses a modified material for improving the construction robustness of self-compacting concrete mixtures, comprising the following components by mass percentage: 60-70% composite mineral admixture, 15-20% zeolite powder, 12-15.5% nano-calcium carbonate, 2-4% organic rheology modifier, and 0.5-1% lignin fiber. The mixture is prepared by two-stage high-efficiency mixing as follows: (1) First, nano-calcium carbonate, organic rheology modifier and lignin fiber are loaded into the silo of the first-stage mixing system and weighed by a precise metering system according to the above proportion (accuracy not less than 0.5%). The mixture is then discharged into the first-stage twin-shaft gravity-free paddle mixer for dispersion and mixing for no less than 3 minutes until a uniform mixture is formed; (2) Then, the composite mineral additive is placed into the silo of the second-stage mixing system and weighed by a precise metering system according to the above proportion (accuracy not less than 1%). The mixture is then discharged into the second-stage twin-shaft gravity-free paddle mixer. At the same time, the uniform mixture in the first-stage twin-shaft gravity-free paddle mixer is also discharged into the second-stage twin-shaft gravity-free paddle mixing system according to the proportion to form a multi-component mixture. The mixture is then dispersed and mixed for no less than 5 minutes until a uniform modified material is formed.

[0043] In the following specific embodiments, the mass ratio of S95 slag: dihydrate phosphogypsum powder: yellow phosphorus slag powder in the composite mineral admixture is 55:15:30, and the specific surface area of ​​the composite mineral admixture is approximately 600 m². 2 / kg, phosphogypsum with CaSO4·2H2O ≥ 90wt%, moisture content ≤ 2%, yellow phosphorus slag powder with (CaO + SiO2) 81wt%, and SiO2 / CaO (mass ratio) 0.82, S95 mineral powder with a specific surface area of ​​600 m² 2 / kg, wherein the content of CaO is ≥ 45wt%, the content of SiO2 is ≥ 25wt%, the content of Al2O3 is ≥ 10wt%, and the 28-day activity index is ≥ 95%; the above zeolite powder is a white powder with a specific surface area of ​​500 m² / kg. 2 / kg, wherein the SiO2 content is ≥60wt% (and the active SiO2 content is ≥15wt%), the Al2O3 content is ≥10wt%, and the specific surface area is not less than 550m² / g. The CaCO3 content in the above-mentioned nano-calcium carbonate is not less than 95wt%, the average particle size is not greater than 50nm, and the maximum particle size is not greater than 80nm. The composite organic rheology modifier is composed of 35 (weight percentage) parts of ethylene-vinyl acetate copolymer renewable latex powder, 50 parts of guar gum ether, and 15 parts of hydroxypropyl methylcellulose. The viscosity of guar gum ether is 500; the viscosity of hydroxypropyl methylcellulose is 40000; the lignin fiber has a length not greater than 2 mm, a particle size less than 0.15 mm, an ash content not greater than 8%, and a moisture content of 5%.

[0044] Example 1

[0045] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 60% composite mineral admixture, 20% zeolite powder, 15.5% nano-calcium carbonate, 4% organic rheology modifier, and 0.5% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing process to prepare the modified material.

[0046] Example 2

[0047] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 70% composite mineral admixture, 15% zeolite powder, 12% nano-calcium carbonate, 2% organic rheology modifier, and 1% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing process to prepare the modified material.

[0048] Example 3

[0049] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 65% composite mineral admixture, 15% zeolite powder, 15.5% nano-calcium carbonate, 4% organic rheology modifier, and 0.5% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing process to prepare the modified material.

[0050] Example 4

[0051] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 65% composite mineral admixture, 20% zeolite powder, 12% nano-calcium carbonate, 2% organic rheology modifier, and 1% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing process to prepare the modified material.

[0052] Comparative Example 1

[0053] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 60% composite mineral admixture, 20% zeolite powder, 15.6% nano-calcium carbonate, 4% organic rheology modifier, and 0.4% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing method to prepare the modified material.

[0054] Comparative Example 2

[0055] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 70% composite mineral admixture, 14% zeolite powder, 11% nano-calcium carbonate, 5% organic rheology modifier, and 0% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing method to prepare the modified material.

[0056] Comparative Example 3

[0057] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 67% composite mineral admixture, 15% zeolite powder, 15.9% nano-calcium carbonate, 1% organic rheology modifier, and 1.1% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing method to prepare the modified material.

[0058] Comparative Example 4

[0059] A modified material for improving the construction robustness of self-compacting concrete mixtures has the following composition (mass percentage): 64% composite mineral admixture, 21% zeolite powder, 12.5% ​​nano-calcium carbonate, 2% organic rheology modifier, and 0.5% lignin fiber. The above components are accurately weighed and mixed using the above two-stage high-efficiency mixing method to prepare the modified material.

[0060] Comparative Example 5

[0061] The other conditions are the same as in Example 1, except that the mass ratio of S95 slag, dihydrate phosphogypsum powder, and yellow phosphorus slag powder in the composite mineral additive is 65:10:25.

[0062] Comparative Example 6

[0063] The other conditions are the same as in Example 1, except that the composite organic rheology modifier is composed of 25 (by weight) parts of ethylene-vinyl acetate copolymer renewable latex powder, 30 parts of guar gum ether, and 45 parts of hydroxypropyl methylcellulose.

[0064] The modified materials prepared above were subjected to performance tests. The viscosity ratio, water content sensitivity, and difference in spread were tested according to TB / T 3275-2018 Railway Concrete. The normal pressure bleeding rate and compressive strength ratio were tested according to GB 8076. The test results are shown in Table 1.

[0065]

[0066] All performance indicators of the modified materials prepared in Examples 1 to 4 meet the standard requirements. Compared with Example 1, the composite mineral additive and lignin fiber were increased in Example 2, while the dosage of zeolite powder, nano-calcium carbonate, and modified material was reduced. The viscosity ratio, water sensitivity, and slump spread difference were all reduced, while the compressive strength ratio was improved. In Examples 3 and 4, the composite mineral additive was kept at 65, and the content of zeolite powder, nano-calcium carbonate, organic rheology modifier, and lignin fiber were adjusted within the corresponding range. Overall, the viscosity ratio, water sensitivity, and slump spread difference of the modified materials were different from those mentioned above, but the changes were not significant, and all met the corresponding requirements. Moreover, the strength ratios of the four sets of examples were also relatively high.

[0067] Compared with Example 1, the lignin fiber content in Comparative Example 1 was lower; the zeolite powder and nano-calcium carbonate content in Comparative Example 2 were below the required range, while the organic rheology modifier content was above the required range, and no lignin fiber was added; the nano-calcium carbonate and lignin fiber content in Comparative Example 3 were both above the required range, while the organic rheology modifier content was below the required value; the zeolite powder content in Comparative Example 4 was too high, and the organic rheology modifier content was too low; the composition of the composite mineral additive and the organic rheology modifier in Comparative Examples 5 and 6 were changed, respectively. Overall, the viscosity ratios of each comparative group met the requirements. The spread and 3d strength ratio of Comparative Group 1 did not meet the requirements; the spread difference and 28d shrinkage ratio of Comparative Group 2 did not meet the requirements; the water sensitivity and 56d compressive strength ratio of Comparative Groups 3 and 4 did not meet the requirements; the viscosity ratio, spread difference, and shrinkage ratio of Comparative Groups 5 and 6 were too high.

[0068] Application testing

[0069] The modified materials prepared in Examples 1-4 and Comparative Examples 1-6 were applied to self-compacting concrete (the mix proportions are shown in Table 2 below), and the performance of the self-compacting concrete was tested, corresponding to Examples 1-4 and Comparative Examples 1-4 respectively. The test methods were all carried out in accordance with the provisions of "Self-compacting Concrete for High-speed Railway Slab Track" (QC-R596-2017). The performance test results are shown in Table 3.

[0070]

[0071] The mineral powder is S95 slag powder, the expanding agent is a type II expanding agent, and the water-reducing agent is a carboxylic acid-based high-efficiency water-reducing agent with a water reduction rate of not less than 25%.

[0072]

[0073] As shown in Table 3, the self-compacting concrete prepared using the modified materials of this invention, namely Examples 1 to 4, meets the requirements of QCR 596-2017 "Self-compacting Concrete for High-Speed ​​Railway Slab Track" standard in all performance indicators. Comparative Examples 1, 2, 3, 4, 5, and 6, due to fluctuations in the viscosity ratio, water sensitivity, and spread of the modified materials used, exhibit lower or higher slump spread, larger differences in J-ring barrier spread, and lower L-shaped fill ratios in the self-compacting concrete. Macroscopically, this results in the self-compacting concrete system's rheological properties failing to meet requirements, leading to higher shrinkage after hardening and making it difficult to guarantee the construction robustness and performance stability of the self-compacting concrete.

[0074] In summary, the modified material prepared by this invention for improving the construction robustness of self-compacting concrete mixtures possesses excellent rheological properties, can synergistically modify the flowability and anti-segregation performance of self-compacting concrete mixtures, and has low sensitivity to fluctuations in water content, resulting in strong construction robustness. It effectively ensures that the strength and shrinkage deformation of the corresponding self-compacting concrete after hardening meet the requirements, and has significant practical value.

[0075] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A modified material for improving the construction robustness of self-compacting concrete mixtures, characterized in that, The composition includes the following components by mass percentage: 60-70% composite mineral additives, 15-20% zeolite powder, 12-15.5% nano-calcium carbonate, 2-4% organic rheology modifiers, and 0.5-1% lignin fiber; The composite mineral admixture is prepared by mixing slag, gypsum dihydrate powder, and yellow phosphorus slag powder in a mass ratio of (50~60):(15~20):(25~30) and then grinding them. The specific surface area of ​​the composite mineral admixture is not less than 500 m². 2 / kg; the slag is S95 slag and / or S105 slag; The composite organic rheology modifier, by mass, is composed of 30-40 parts of ethylene-vinyl acetate copolymer renewable latex powder, 45-50 parts of guar gum ether, and 15-20 parts of hydroxypropyl methylcellulose.

2. The modified material for improving the construction robustness of self-compacting concrete mixtures according to claim 1, characterized in that: In the composite mineral admixture, the mass percentages of S95 slag are (55~60)%, gypsum dihydrate powder is 15%, and yellow phosphorus slag powder is (25~30)%. These three are mixed and ground together to obtain the final product, which has a specific surface area of ​​(500~600) m². 2 / kg.

3. The modified material for improving the construction robustness of self-compacting concrete mixtures according to claim 1, characterized in that, The zeolite powder is a white powder, wherein the active silicon content is not less than 15wt%, the active aluminum content is not less than 10wt%, and the specific surface area is not less than 500m² / g.

4. The modified material for improving the construction robustness of self-compacting concrete mixtures according to claim 1, characterized in that: The CaCO3 content in the nano-calcium carbonate is not less than 95wt%, the average particle size is not greater than 50nm, and the maximum particle size is not greater than 90nm.

5. The modified material for improving the construction robustness of self-compacting concrete mixtures according to claim 1, characterized in that: Guar gum has a viscosity of 400~800, and hydroxypropyl methylcellulose has a viscosity of 20000~40000.

6. The modified material for improving the construction robustness of self-compacting concrete mixtures according to claim 1, characterized in that: The lignin fibers have a length of no more than 2.5 mm, a size of less than 0.15 mm, an ash content of no more than 10 wt%, and a moisture content of no more than 5 wt%.

7. The composite mineral admixture according to claim 2, characterized in that, The dihydrate gypsum powder is derived from one or both of desulfurized gypsum and phosphogypsum, wherein CaSO4·2H2O ≥ 90wt% and moisture content ≤ 2%.

8. The modified material for improving the construction robustness of self-compacting concrete mixtures according to claim 1, characterized in that: It is produced by a two-stage high-efficiency mixing process, wherein the two-stage high-efficiency mixing process includes: The first step involves loading nano-calcium carbonate, organic rheology modifier, and lignin fiber into the hopper of the first-stage mixing system, weighing them according to the set ratio, and feeding them into the first-stage twin-shaft zero-gravity paddle mixer for dispersion and mixing for no less than 3 minutes until a uniform mixture is formed. The second step involves placing the composite mineral additive into the hopper of the second-stage mixing system, weighing it according to the set ratio, and then feeding it into the second-stage twin-shaft zero-gravity paddle mixer. At the same time, the uniform mixture in the first-stage twin-shaft zero-gravity paddle mixer is also fed into the second-stage twin-shaft zero-gravity paddle mixer system according to the ratio, and dispersed and mixed for no less than 5 minutes until a uniform modified material is formed.

9. The application of a modified material for improving the construction robustness of self-compacting concrete mixtures as described in any one of claims 1-7, characterized in that: The applications include its use in self-compacting concrete.

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