Environment-friendly low-cost grouting material and preparation method thereof

Abstract

The invention discloses an environment-friendly low-cost grouting material and a preparation method thereof, and belongs to the technical field of grouting material preparation, the grouting material comprises the following components by weight: 30-45 parts of cement, 5-15 parts of a mineral admixture, 30-45 parts of machine-made sand, 15-25 parts of foundry waste sand, 0.05-0.15 part of a water reducer, 0.05-0.1 part of an antifoaming agent, 0-1 part of a foundry waste sand treating agent, 0-5 parts of an expanding agent, and 0-0.02 part of an anti-settling agent; during preparation, the functional additives are mixed into the component A, then the component A is mixed with the cementing material and the aggregate, and water is added for stirring for 3-5 minutes. The foundry waste sand and the machine-made sand synergistically replace natural sand, the mineral admixture replaces part of cement, and under the synergistic effect of the functional additive, on the premise that the fluidity, strength, volume stability and other performance of the grouting material meet the standard, the cost is remarkably reduced, solid waste resource utilization is achieved, resource and energy consumption is reduced, and the economic benefit is increased. And economic benefits and social benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of grout preparation technology, specifically to an environmentally friendly, low-cost grout and its preparation method. Background Technology

[0002] my country is the world's largest producer of castings, and the casting process inevitably generates foundry waste sand. Statistics show that tens of millions of tons of foundry waste sand require disposal annually. While most of this waste sand can be recycled through various processes, recycling has its limits, and a large amount of foundry waste sand still exists in actual production. Currently, it is mainly disposed of as waste through landfill, which not only wastes significant land resources but also causes serious environmental pollution. Furthermore, treating foundry waste sand as solid waste incurs high discharge costs, increasing casting production costs. Foundry waste sand is a valuable solid waste. Resource utilization of foundry waste sand can significantly reduce waste sand emissions and the consumption of new sand resources, achieving environmentally friendly production and ensuring the sustainable development of the casting industry. Therefore, finding a reasonable treatment and disposal method for it is urgently needed.

[0003] In recent decades, due to the increasing number of old buildings, my country has gradually shifted its construction focus to the repair, renovation, and reinforcement of old buildings. The building reinforcement and renovation industry has developed rapidly, becoming an important part of the construction industry, and its prosperity and development are increasing. Grouting materials, with their high fluidity, early strength, high strength, and micro-expansion characteristics, play a very important role in building reinforcement and renovation projects. However, traditional grouting materials have the following drawbacks: 1. To achieve the performance requirements of early strength and high strength, a large amount of cement is required. However, the cement production process is not only energy-intensive but also causes a large amount of carbon dioxide and dust emissions, which is inconsistent with the development direction of green building. 2. Good performance depends on high-quality river sand, but natural river sand in my country is becoming increasingly scarce. On the one hand, long-term mining has led to the depletion of natural sand resources; on the other hand, the mining of natural sand causes serious damage to the ecological environment, making the search for new alternative resources urgent. 3. High production costs often prevent large-scale use in projects. This greatly limits its application in reinforcement and renovation projects.

[0004] Given the shortcomings of the existing technologies, there is an urgent need to develop a grouting material that combines environmental protection, low cost, and high performance to solve the problems of resource waste, environmental pollution, and excessive cost. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an environmentally friendly, low-cost grouting material and its preparation method. By synergistically replacing natural sand with foundry waste sand and manufactured sand, replacing part of the cement with mineral admixtures, and with the synergistic effect of functional additives, the cost is significantly reduced while ensuring that the grouting material's fluidity, strength, volume stability and other properties meet the standards, thereby realizing the resource utilization of solid waste.

[0006] This invention is implemented as follows: An environmentally friendly, low-cost grouting material, comprising, by weight: 30-45 parts cement, 5-15 parts mineral admixtures, 30-45 parts manufactured sand, 15-25 parts foundry waste sand, 0.05-0.15 parts water-reducing agent, 0.05-0.1 parts defoamer, 0-1 part foundry waste sand treatment agent, 0-5 parts expansion agent, and 0-0.02 parts anti-settling agent; The manufactured sand is at least two of the following particle sizes: 5-40 mesh, 20-50 mesh, 40-70 mesh, and 70-140 mesh. The particle size of the foundry waste sand is 50~100 mesh; The foundry waste sand treatment agent is at least one of calcium chloride, calcium formate, and calcium nitrate.

[0007] Furthermore, the cement is ordinary Portland cement of strength grade 42.5R; The mineral admixture is one or more of silica fume, secondary fly ash, and S95 mineral powder; The water-reducing agent is a polycarboxylate water-reducing agent; The defoamer is an organosilicone defoamer; The expanding agent is at least one of azodicarbonamide and calcium thioaluminate; The anti-settling agent is at least one of cellulose ether and stabilizer.

[0008] Furthermore, the manufactured sand is composed of manufactured sand with particle sizes of 5-40 mesh and 70-140 mesh, wherein the amount of 5-40 mesh sand is 20-35 parts and the amount of 70-140 mesh sand is 7-15 parts.

[0009] Furthermore, the foundry waste sand treatment agent is calcium formate.

[0010] Furthermore, the mineral admixture is secondary fly ash.

[0011] Furthermore, it includes the following steps: (1) By weight, take 0.05~0.15 parts of water-reducing agent, 0.05~0.1 parts of defoamer, 0~1 parts of foundry waste sand treatment agent, 0~5 parts of expansion agent, and 0~0.02 parts of anti-settling agent, and mix them evenly to form component A; (2) By weight, take 30-45 parts of cement, 5-15 parts of mineral admixture, 30-45 parts of manufactured sand, and 15-25 parts of foundry waste sand, and mix them evenly with component A obtained in step (1); (3) Add 13 to 16 parts of water by total weight to the mixture in step (2), stir for 3 to 5 minutes, and obtain the environmentally friendly low-cost grouting material.

[0012] Furthermore, in step (3), the weight of water added is 14 parts, and the stirring time is 3 minutes.

[0013] The synergistic relationship between the various components in this invention is as follows: Synergistic effect of cement and mineral admixtures in the cementitious system: Cement, as the primary cementitious material, provides early and late core strength; this invention utilizes mineral admixtures to partially replace cement, reducing costs and carbon emissions, and simultaneously fills the capillary pores of cement hydration products through the "micro-aggregate filling effect" and "secondary hydration reaction," optimizing the microstructure and improving the density and durability of the grout. The synergistic effect of these two components ensures that the mechanical properties of the grout are not reduced while decreasing cement usage.

[0014] Synergistic effect of aggregate system of manufactured sand and foundry waste sand: The multi-size combination of manufactured sand and foundry waste sand forms a good gradation, ensuring the fluidity and bulk density of the grout; the surface of foundry waste sand is coated with an inert film, which reacts with cement in the early stage and quickly forms hydration products that are detrimental to strength. By adding a foundry waste sand treatment agent to dissolve the inert film, the adverse effects of foundry waste sand on the early strength of the grout can be compensated. When the two are matched with the particle size and dosage specified in this invention, they can completely replace natural sand, which not only solves the environmental disposal problem of foundry waste sand, but also ensures the load-bearing capacity and fluidity of the aggregate through complementary gradation, and significantly reduces aggregate cost without affecting the strength of the grout.

[0015] Functional additives work synergistically with the main system: water-reducing agents lower the water-cement ratio and improve fluidity, while creating conditions for the close bonding of the cementitious system and aggregates; defoamers eliminate air bubbles and avoid strength reduction and durability degradation caused by porosity; expansion agents compensate for shrinkage during the hydration process of the cementitious system, and anti-settling agents ensure uniform distribution of aggregates. The two work synergistically to improve the volume stability of the grout and prevent cracking and delamination.

[0016] In particular, the use of a foundry waste sand treatment agent in this invention to synergistically treat foundry waste sand can achieve the following effects: First, it releases Ca²⁺ to accelerate cement hydration, solving the problem of insufficient early strength caused by waste sand and ensuring that the 1-day compressive strength meets the standard; second, it modifies the surface of waste sand, dissolving the inert film on the surface of the foundry waste sand and preventing it from participating in hydration to form hydration products that are detrimental to early strength; this makes a 15-25% addition of foundry waste sand feasible, solving existing problems, realizing the resource utilization of solid waste and reducing aggregate costs; and ensuring that the performance of the grouting material meets national standards.

[0017] The present invention has the following advantages: Significant cost reduction: By synergistically replacing natural sand with foundry waste sand and manufactured sand, and by replacing part of the cement with mineral admixtures, the cost of raw materials has been greatly reduced; in addition, the resource utilization of foundry waste sand reduces solid waste treatment costs, further reducing overall costs and facilitating large-scale promotion of the project.

[0018] Significant environmental benefits: It consumes a large amount of foundry waste sand and industrial solid waste (such as fly ash), realizing the resource utilization of solid waste and reducing landfill pollution; it reduces cement consumption and natural sand mining, thereby reducing carbon emissions, energy consumption and ecological damage, which is in line with the development direction of green buildings.

[0019] Stable and reliable performance: The initial fluidity of the grout is ≥330mm, the fluidity remains good after 30 minutes, the vertical expansion rate is ≥0.5% after 3 hours, the drying shrinkage is low after 28 days, the compressive strength is ≥24MPa after 1 day, ≥45MPa after 3 days, and ≥65MPa after 28 days. It fully complies with the requirements of the national standard GB / T50448-2015 and has excellent construction performance, mechanical properties and volume stability. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially. Example 1

[0021] The raw materials, by weight, are as follows: 30 parts cement, 8 parts fly ash, 33 parts 5-40 mesh manufactured sand (basalt), 15 parts foundry sand, 12 parts 70-140 mesh manufactured sand, 0.12 parts polycarboxylate superplasticizer, 0.02 parts defoamer, 0.5 parts calcium formate, 0.02 parts plastic expansion agent, 2 parts expansion agent, and 0.01 parts stabilizer. Example 2

[0022] The raw materials, by weight, are as follows: 30 parts cement, 8 parts fly ash, 29 parts 5-40 mesh manufactured sand (basalt), 20 parts foundry sand, 11 parts 70-140 mesh manufactured sand, 0.12 parts polycarboxylate superplasticizer, 0.02 parts defoamer, 0.5 parts calcium formate, 0.02 parts plastic expansion agent, 2 parts expansion agent, and 0.01 parts stabilizer. Example 3

[0023] The raw materials are as follows by weight: 30 parts cement, 8 parts fly ash, 25 parts 5-40 mesh manufactured sand (basalt), 25 parts foundry sand, 10 parts 70-140 mesh manufactured sand, 0.12 parts polycarboxylate superplasticizer, 0.02 parts defoamer, 0.5 parts calcium formate, 0.02 parts plastic expansion agent, 2 parts expansion agent, and 0.01 parts stabilizer.

[0024] The preparation process of Examples 1-3 is as follows: First, polycarboxylate superplasticizer, silicone defoamer, calcium formate, plastic expansion agent, calcium sulfoaluminate expansion agent and stabilizer are mixed evenly to form component A; then cement, secondary fly ash, two kinds of manufactured sand with different particle sizes and foundry waste sand are mixed evenly with component A; 14% water is added and stirred for 3 minutes to obtain grouting material.

[0025] Comparative Example 1: The difference from Example 3 is that calcium formate is not added, that is, the foundry waste sand is used directly without treatment, and the rest is the same as Example 3.

[0026] Comparative Example 2: The difference from Example 3 is that all the sand was replaced with quartz sand, while the rest was the same as in Example 3.

[0027] Comparative Example 3: The difference from Example 3 is that all fly ash was replaced with cement, while the rest was the same as Example 3.

[0028] The grouting materials prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to grouting material performance tests according to the national standard GB / T50448-2015 "Technical Specification for Application of Cement-based Grouting Materials". The test results are shown in the table below:

[0029] As shown in the table above, in Examples 1-3, as the amount of foundry waste sand increased from 15 parts to 25 parts, the initial flowability of the grout was above 330 mm, the flowability remained good after 30 minutes, the vertical expansion rate after 3 hours was above 0.5, the drying shrinkage after 28 days was low, the 1-day compressive strength was between 24 and 26 MPa, the 3-day compressive strength exceeded 45 MPa, and the 28-day compressive strength exceeded 65 MPa, meeting the grout indicators for different types of grouts in the national standard GB / T 50448-2015 "Technical Specification for Application of Cement-Based Grouting Materials". This indicates that the formulation system of the present invention has good construction performance, mechanical properties, and volume stability, and within the reasonable proportion range of the present invention, the performance of the grout is relatively stable. The formulation can be flexibly adjusted according to different needs to meet engineering requirements.

[0030] Comparative Example 1: While the fluidity, volume stability, and later-stage strength of foundry waste sand treated without the addition of a foundry waste sand treatment agent met the standard requirements, the early-stage strength was too low (1-day compressive strength only 18 MPa), failing to meet the early-stage strength requirements of the grout. This is because foundry waste sand may have residual foundry binders (such as resin, clay, etc.) on its surface, or its own activity is low. Direct addition of this material will slow down the early hydration rate of cement. Cement hydration requires sufficient Ca²⁺ to generate CSH gel and calcium hydroxide, and the "inertness" of foundry waste sand will indirectly consume the active components in the grout, resulting in insufficient early-stage strength. Simultaneously, the inert layer or impurities on the surface of the foundry waste sand will weaken the interfacial bonding between it and the cement grout (cementing system), forming "interfacial porosity defects." Even if the later-stage strength meets the standard, the interface may become a potential cracking hazard, affecting the durability of the grout.

[0031] Comparative Example 2: Although the overall performance is also relatively good, the price of quartz sand is much higher than that of foundry waste sand and manufactured sand. Using quartz sand completely will greatly increase the cost of grouting material, affecting the promotion and large-scale application of grouting material.

[0032] Comparative Example 3: Although using all cement to replace mineral admixtures resulted in higher mechanical properties, it also resulted in poorer fluidity and a 28-day drying shrinkage of 428 × 10⁻⁶. -6 This means that shrinkage increases significantly, which can easily lead to cracking problems in actual use. Furthermore, the increased cement usage leads to higher costs and carbon emissions, which does not meet environmental protection requirements.

[0033] In summary, this invention, by treating foundry waste sand and rationally combining it with manufactured sand, completely replaces quartz sand. Simultaneously, it uses mineral admixtures to replace a portion of the cement, significantly reducing the cost of the grout while maintaining its performance. This formula not only boasts excellent performance and low cost, making it highly suitable for the widespread application of grout in reinforcement projects, but also possesses the advantages of being environmentally friendly, consuming minimal resources and energy, and enabling the resource utilization of solid waste, resulting in significant economic and social benefits.

[0034] In summary, this invention, through the rational selection, optimized proportioning, and synergistic effects of its components, achieves the dual goals of low cost and environmental protection while ensuring the performance of the grout meets the standards. It has significant practical value and promotional significance.

[0035] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An environmentally friendly, low-cost grouting material, characterized in that: The grouting material, by weight, comprises: 30-45 parts cement, 5-15 parts mineral admixtures, 30-45 parts manufactured sand, 15-25 parts foundry waste sand, 0.05-0.15 parts water-reducing agent, 0.05-0.1 parts defoamer, 0-1 part foundry waste sand treatment agent, 0-5 parts expansion agent, and 0-0.02 parts anti-settling agent; The manufactured sand is at least two of the following particle sizes: 5-40 mesh, 20-50 mesh, 40-70 mesh, and 70-140 mesh. The particle size of the foundry waste sand is 50~100 mesh; The foundry waste sand treatment agent is at least one of calcium chloride, calcium formate, and calcium nitrate.

2. The environmentally friendly, low-cost grouting material according to claim 1, characterized in that: The cement is ordinary Portland cement of strength grade 42.5R; The mineral admixture is one or more of silica fume, secondary fly ash, and S95 mineral powder; The water-reducing agent is a polycarboxylate water-reducing agent; The defoamer is an organosilicone defoamer; The expanding agent is at least one of azodicarbonamide and calcium thioaluminate; The anti-settling agent is at least one of cellulose ether and stabilizer.

3. The environmentally friendly, low-cost grouting material according to claim 1, characterized in that: The manufactured sand is composed of manufactured sand with a particle size of 5-40 mesh and 70-140 mesh, wherein the amount of 5-40 mesh sand is 20-35 parts and the amount of 70-140 mesh sand is 7-15 parts.

4. The environmentally friendly, low-cost grouting material according to claim 1, characterized in that: The foundry waste sand treatment agent is calcium formate.

5. The environmentally friendly, low-cost grouting material according to claim 1, characterized in that: The mineral admixture is secondary fly ash.

6. A method for preparing an environmentally friendly, low-cost grouting material according to any one of claims 1-5, characterized in that: Includes the following steps: (1) By weight, take 0.05~0.15 parts of water-reducing agent, 0.05~0.1 parts of defoamer, 0~1 parts of foundry waste sand treatment agent, 0~5 parts of expansion agent, and 0~0.02 parts of anti-settling agent, and mix them evenly to form component A; (2) By weight, take 30-45 parts of cement, 5-15 parts of mineral admixture, 30-45 parts of manufactured sand, and 15-25 parts of foundry waste sand, and mix them evenly with component A obtained in step (1); (3) Add 13 to 16 parts of water by total weight to the mixture in step (2), stir for 3 to 5 minutes, and obtain the environmentally friendly low-cost grouting material.

7. The method for preparing an environmentally friendly, low-cost grouting material according to claim 6, characterized in that: In step (3), the weight of water added is 14 parts, and the stirring time is 3 minutes.

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