Regenerated micro powder cement-based grouting material and preparation method thereof

Abstract

The invention discloses a regenerated micro powder cement-based grouting material and a preparation method thereof, and belongs to the field of civil engineering. The regenerated micro powder cement-based grouting material comprises the following components: 60-90 parts of cement, 5-30 parts of regenerated micro powder, 1-5 parts of an alkali activator, 1-5 parts of an expanding agent, 1-5 parts of an early strength agent, 1-5 parts of a thickening agent and 1-5 parts of a water reducing agent, the cement is Portland cement; the regenerated micro-powder is obtained through the following processes: crushing and screening waste concrete, and crushing waste sand powder through an airflow mill to form regenerated micro-powder with the particle size of less than 75 microns; the alkali activator is prepared by mixing and grinding sodium hydroxide and sodium silicate, and the modulus of the alkali activator is 0.8-2.0. By doping the waste concrete recycled micro powder, the cement consumption is reduced, the problem of solid waste landfill is effectively solved, the preparation process is controllable, the raw materials are low in price and easy to obtain, the product performance is excellent, and the method is suitable for large-scale industrial production and popularization.

Description

Technical Field

[0001] The invention relates to a recycled micropowder cement-based grouting material and a preparation method thereof, and is particularly suitable for resource utilization of recycled micropowder and mix ratio design of recycled micropowder cement-based grouting material, belonging to the field of civil engineering. Background Art

[0002] Infrastructure construction and residential construction activities generate a large amount of demolition waste, especially the amount of waste concrete generated is increasing year by year. At present, the waste concrete is crushed to form recycled coarse aggregate (particle size ≥ 4.75mm), and the recycled coarse aggregate is used to replace natural coarse aggregate to prepare recycled coarse aggregate concrete, which can alleviate the problem of random landfill of waste concrete. However, the remaining sand powder (particle size <4.75mm) after crushing has poor performance and is uncontrollable, so its utilization rate is very low and it is still mainly landfilled.

[0003] The sand powder produced after the crushing of waste concrete is ground to form a powder with a particle size of less than 75μm, commonly known as recycled micropowder. Recycled micropowder contains a large amount of potentially active silicon-aluminum components. Certain methods can be used to stimulate its potential activity, making the recycled micropowder a cementitious material with high hydration characteristics. The production process of cement consumes huge amounts of energy and produces a large amount of greenhouse gases. Each ton of cement product produced emits about 0.85-1 ton of CO2 gas into the atmosphere. Therefore, the complete recycling of recycled coarse aggregate and recycled micropowder from waste concrete can effectively reduce the consumption of natural resources, reduce solid waste landfill and reduce greenhouse gas emissions.

[0004] Cement-based grouting material generally refers to a dry mix composed of raw materials such as cement, mineral admixtures, and admixtures, which are produced by mixing. Among them, mineral admixtures include silica fume, fly ash, slag, etc. Due to coal restrictions, industrial transformation and upgrading, and uneven regional distribution, the difficulty of obtaining silica fume, fly ash, and slag has gradually increased. Replacing the above-mentioned traditional mineral admixtures with recycled micropowder and reducing the amount of cement to prepare a recycled micropowder cement-based grouting material will be very beneficial to solving the shortage of traditional admixtures and promoting efficient carbon reduction in the industry.

[0005] Under the current national dual carbon strategy and circular economy background, the research and application of waste concrete recycled micropowder in cement-based grouting materials, in order to save materials, reduce consumption and reduce carbon, thereby improving the waste utilization and low-carbon green level of the cement-based grouting industry, has become a new direction for the development of my country's civil engineering field. Summary of the invention

[0006] The purpose of the present invention is to provide a recycled micro-powder cement-based grouting material, which has the characteristics of good fluidity, no water seepage, no shrinkage, good sedimentation stability, high early strength, etc. Compared with conventional cement-based grouting materials, the present invention not only reduces the amount of cement by adding recycled micro-powder from waste concrete, but also effectively solves the problem of solid waste landfill, meets the current needs of green environmental protection and sustainable development, and has broad market application prospects.

[0007] Another object of the present invention is to provide a method for preparing a recycled micro-powder cement-based grouting material, which utilizes the characteristics of uniform fineness, regular shape, and good dispersibility of the recycled micro-powder, further stimulates its potential activity through an alkali activator, and optimizes the admixture after the proportion of each component to form a recycled micro-powder cement-based grouting material with adjustable performance. The method has reliable principles, simple operation, cheap and easy-to-obtain raw materials, controllable preparation process, excellent product performance, and is suitable for large-scale industrial production and promotion.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0009] A recycled micropowder cement-based grouting material, comprising the following components in parts by weight: 60-90 parts of cement, 5-30 parts of recycled micropowder, 1-5 parts of alkali activator, 1-5 parts of expansion agent, 1-5 parts of early strength agent, 1-5 parts of thickener, and 1-5 parts of water reducer; the cement is silicate cement, and the recycled micropowder is obtained by the following process: after crushing and screening waste concrete, waste sand powder with a particle size of less than 4.75 mm is collected, and the waste sand powder is crushed by a jet mill to form recycled micropowder with a particle size of less than 75 μm; the alkali activator is prepared by mixing and grinding sodium hydroxide and sodium silicate, the alkali activator has a modulus of 0.8-2.0, and a particle size of less than 40 μm; the expansion agent, early strength agent, thickener and water reducer are all conventional cement additives.

[0010] Furthermore, the cement is one or more of PO 42.5 ordinary Portland cement, PO 52.5 ordinary Portland cement, P.I 42.5 Portland cement, P.I 52.5 Portland cement, P.II 42.5 Portland cement, and P.II 52.5 Portland cement in any proportion.

[0011] Furthermore, the regenerated micro powder is composed of one or more of 200 mesh, 500 mesh, 800 mesh, 1000 mesh, and 2000 mesh in any proportion, and the particle size is less than 75 μm.

[0012] Furthermore, the waste concrete is crushed by a jaw crusher or an impact crusher, and the waste sand powder is mainly composed of mortar, a certain amount of unhydrated cement particles, sand and gravel aggregate fragments, hydration products and possible mineral admixtures, and the physical phase components include: quartz, limestone, CSH, AFt, CaCO3, Ca(OH)2, etc.

[0013] Furthermore, the jet mill is a machine that uses high-speed airflow to impact, shear and rub waste sand powder, thereby achieving ultra-fine grinding of materials, further exposing unhydrated cement particles in the regenerated micro-powder, reducing the crystallinity of the physical phase in the regenerated micro-powder, and generating lattice defects, thereby increasing the activity of the regenerated micro-powder. At the same time, the jet mill is equipped with a classifier, which can produce regenerated micro-powders of multiple particle size segments at a time, and has the characteristics of high efficiency and energy saving.

[0014] Furthermore, the alkaline activator is composed of sodium hydroxide and sodium silicate, the modulus of sodium silicate is 3.3, and the sodium hydroxide and sodium silicate are mixed and ground to prepare an alkaline activator with a modulus of 0.8-2.0 and a particle size of less than 40 μm. The alkaline activator can break the Si-O and Al-O bonds of the silicon and aluminum components contained in the regenerated micropowder, and reorganize the internal structure, so that the regenerated micropowder is more likely to undergo a polycondensation reaction to generate a gelling substance.

[0015] Furthermore, the expansion agent is an inorganic salt expansion agent, the main components of which are one or more of aluminum sulfate, aluminum oxide, potassium sulfate, and potassium aluminum sulfate in any proportion, and the particle size of the expansion agent after grinding is less than 40 μm, the purpose of which is to prevent the volume shrinkage of the recycled micro-powder cement-based grouting material.

[0016] Furthermore, the early strength agent is an inorganic salt early strength agent, the main components of which are one or more of calcium chloride, sodium sulfate, calcium sulfate, sodium nitrate, and sodium silicate in any proportion, and after grinding, the particle size of the early strength agent is less than 40 μm, the purpose of which is to improve the early strength of the recycled micropowder cement-based grouting material.

[0017] Furthermore, the thickener is a polymer thickener, the main components of which are one or more of methyl cellulose, hydroxypropyl methyl cellulose, xanthan gum, and weinen gum in any proportion, and after grinding, the thickener particle size is less than 40 μm, the purpose of which is to prevent water seepage from the recycled micro-powder cement-based grouting slurry and improve the slurry sedimentation stability.

[0018] Furthermore, the water reducer is a powdered polycarboxylic acid high-efficiency water reducer with a water reduction rate greater than 10%, the purpose of which is to reduce the amount of water used and adjust the rheological properties of the recycled micro-powder cement-based grouting material slurry.

[0019] Furthermore, in order to reduce the generation of bubbles during the mixing process of the recycled micropowder cement-based grouting material, an appropriate amount of defoaming agent can be added during the mixing process of the grouting material.

[0020] A method for preparing a recycled micropowder cement-based grouting material comprises the following steps in sequence: (1) Crushing and screening the waste concrete with a jaw crusher or an impact crusher to collect waste sand powder with a particle size of less than 4.75 mm; (2) Grinding the waste sand powder by jet mill to form regenerated micro powder with a particle size of less than 75 μm; (3) Weigh 60-90 parts by weight of cement, 5-30 parts by weight of recycled micropowder, 1-5 parts by weight of alkali activator, 1-5 parts by weight of expansion agent, 1-5 parts by weight of early strength agent, 1-5 parts by weight of thickener, and 1-5 parts by weight of water reducer respectively, and stir the above components thoroughly in a mixing tank to mix them evenly to obtain recycled micropowder cement-based grouting material.

[0021] Furthermore, the recycled micro-powder cement-based grouting material and water are mixed and stirred to form a recycled micro-powder cement-based grouting material slurry, and the performance of the slurry is tested; if the slurry performance is qualified, the ratio of each component is directly determined; if the slurry performance is unqualified, the dry mix composition is appropriately adjusted.

[0022] Furthermore, during on-site construction, the recycled micro-powder cement-based grouting material and water are mixed and stirred at a weight ratio of 1:0.4-0.8, and can be used after being stirred evenly.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The regenerated micro powder prepared by the air jet mill has the characteristics of uniform fineness, narrow particle size distribution, regular shape, good dispersibility, high activity and ultra-fine particles, which is conducive to improving the activity of the regenerated micro powder; the nucleation effect, filling effect and volcanic ash effect of the regenerated micro powder are used to achieve partial replacement of cement by the regenerated micro powder. At the same time, the air jet mill has the advantages of high efficiency and energy saving, wide application range, and can produce products of multiple particle sizes at one time;

[0024] (2) By preparing an alkali activator, the potential activity of the regenerated micropowder is stimulated and the reaction degree of the regenerated micropowder is increased, which is beneficial to further improve the mechanical properties of the regenerated micropowder cement-based grouting material; (3) The initial fluidity of the recycled micro-powder cement-based grouting material is greater than 300mm, the 30-minute fluidity is greater than 250mm, and the 3-hour vertical expansion rate is greater than 0.1%; the recycled micro-powder cement-based grouting material has no bleeding, no stratification, and good settlement stability; the compressive strength of the recycled micro-powder cement-based grouting material at 1d, 3d, and 28d is greater than 20MPa, 40MPa, and 60MPa, respectively, meeting the requirements of on-site construction; (4) The construction performance and physical and mechanical properties of recycled micro-powder cement-based grouting materials are adjustable, and the appropriate proportion can be selected according to the actual engineering application requirements; (5) Applying recycled micropowder from waste concrete to cement-based grouting materials can reduce cement consumption, lower material costs, and reduce industry CO2 emissions, which is in line with current energy conservation, emission reduction and sustainable development requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the particle size distribution diagram of regenerated micro powders of different finenesses prepared by air jet milling.

[0026] Figure 2 This is the particle size distribution diagram of 500 mesh regenerated micro powder. DETAILED DESCRIPTION

[0027] The present invention is further described below with reference to the accompanying drawings and examples, so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, they are all protected.

[0028] The preparation process of the recycled micro-powder cement-based grouting material of the present invention is as follows: (1) Use a jaw crusher or an impact crusher to crush and screen the waste concrete and collect waste sand powder with a particle size of less than 4.75 mm; (2) The waste sand powder is crushed by the air jet mill, and the classifier attached to the air jet mill is used to produce regenerated micro powders with finenesses of 200 mesh, 500 mesh, 800 mesh, 1000 mesh and 2000 mesh at one time. The particle size distribution of regenerated micro powders with different finenesses is as follows: Figure 1 As shown; (3) Design the proportion of each component of the recycled micropowder cement-based grouting material according to the on-site application requirements. The recycled micropowder cement-based grouting material is composed of 60-90 parts by weight of cement, 5-30 parts by weight of recycled micropowder, 1-5 parts by weight of alkali activator, 1-5 parts by weight of expansion agent, 1-5 parts by weight of early strength agent, 1-5 parts by weight of thickener and 1-5 parts by weight of water reducer;

[0029] (4) Weigh different raw materials, and use a mixing tank to fully and evenly mix the raw materials to obtain a dry mix of recycled micro-powder cement-based grouting material.

[0030] After the preparation is completed, the dry mix and water are mixed and stirred in a weight ratio of 1:0.4-0.8 to form a grouting slurry.

[0031] The recycled micropowder cement-based grouting material of Examples 1-7 comprises the following components: 66-85 parts by weight of cement, 5-20 parts by weight of recycled micropowder, 3 parts by weight of alkali activator, 2 parts by weight of expansion agent, 2-4 parts by weight of early strength agent, 1 part by weight of thickener, and 2-4 parts by weight of water reducing agent. The cement is PO 52.5 ordinary Portland cement; the recycled micropowder is 500 mesh recycled micropowder from waste concrete (particle size distribution see Figure 2 ); the alkali activator has a modulus of 1.6 and is prepared from sodium hydroxide and sodium silicate; the expansion agent is prepared from aluminum sulfate and aluminum oxide in a weight ratio of 50:50; the early strength agent is prepared from calcium chloride, calcium sulfate and sodium silicate in a weight ratio of 30:20:20; the thickener is prepared from xanthan gum and Wenlun gum in a weight ratio of 50:50; the water reducer is a powdered polycarboxylic acid high-efficiency water reducer with a water reduction rate greater than 15%.

[0032] According to the above scheme, 7 groups of different proportions of recycled micropowder cement-based grouting materials were designed. The main components of the recycled micropowder cement-based grouting materials are shown in Table 1.

[0033] The recycled micro-powder cement-based grouting material and water in Table 1 were mixed and stirred at a weight ratio of 1:0.54 to form a recycled micro-powder cement-based grouting material slurry, and the basic properties of the slurry were tested. The basic properties of different recycled micro-powder cement-based grouting materials are shown in Table 2.

[0034] It can be seen from the performance test results of Examples 1-7 that the basic properties of the above-mentioned recycled micropowder cement-based grouting materials all meet the requirements of "Technical Specifications for Application of Cement-based Grouting Materials" GB / T50448-2015. Examples 1-3 show that with the increase of the amount of recycled micropowder, the truncated cone fluidity of the recycled micropowder cement-based grouting material decreases slightly, and the compressive strength shows a downward trend. Examples 3-5 show that with the increase of early strength agent, the fluidity of the recycled micropowder cement-based grouting material decreases, but the compressive strength increases. Examples 5-7 show that with the increase of water reducer, the fluidity of the recycled micropowder cement-based grouting material increases, the early compressive strength decreases, but the 28d compressive strength does not change much. It can be seen from the examples that the various properties of the recycled micropowder cement-based grouting material are controllable, and the performance can be optimized according to the actual needs of the site, and the best mix ratio can be selected.

Claims

1. A recycled micro-powder cement-based grouting material, comprising the following components in parts by weight: 60-90 parts of cement, 5-30 parts of regenerated micropowder, 1-5 parts of alkali activator, 1-5 parts of expansion agent, 1-5 parts of early strength agent, 1-5 parts of thickener, and 1-5 parts of water reducer; the cement is silicate cement, and the regenerated micropowder is obtained by the following process: after crushing and screening waste concrete, waste sand powder with a particle size of less than 4.75 mm is collected, and the waste sand powder is crushed by a jet mill to form regenerated micropowder with a particle size of less than 75 μm; the alkali activator is prepared by mixing and grinding sodium hydroxide and sodium silicate, the alkali activator has a modulus of 0.8-2.0, and a particle size of less than 40 μm; the expansion agent, early strength agent, thickener and water reducer are all conventional cement additives.

2. A recycled micro-powder cement-based grouting material as claimed in claim 1, characterized in that: The regenerated micro powder is composed of one or more of 200 mesh, 500 mesh, 800 mesh, 1000 mesh and 2000 mesh in any proportion, and the particle size is less than 75 μm.

3. A recycled micro-powder cement-based grouting material as claimed in claim 1, characterized in that: The jet mill is a machine that uses high-speed airflow to impact, shear and rub waste sand powder to achieve ultra-fine grinding of materials; at the same time, the jet mill is equipped with a classifier to produce recycled micro powder of multiple particle size segments at one time.

4. A recycled micro-powder cement-based grouting material as claimed in claim 1, characterized in that: The expansion agent is one or more of aluminum sulfate, aluminum oxide, potassium sulfate, and potassium aluminum sulfate.

5. A recycled micro-powder cement-based grouting material as claimed in claim 1, characterized in that: The early strength agent is one or more of calcium chloride, sodium sulfate, calcium sulfate, sodium nitrate, and sodium silicate.

6. A recycled micro-powder cement-based grouting material as claimed in claim 1, characterized in that: The thickener is one or more of methyl cellulose, hydroxypropyl methyl cellulose, xanthan gum and wenan gum.

7. A recycled micro-powder cement-based grouting material as claimed in claim 1, characterized in that: The water reducer is a polycarboxylic acid high efficiency water reducer.

8. A method for preparing a recycled micropowder cement-based grouting material as claimed in claim 1, 2, 3, 4, 5, 6 or 7, comprising the following steps in sequence: (1) Crushing and screening the waste concrete with a jaw crusher or an impact crusher to collect waste sand powder with a particle size of less than 4.75 mm; (2) Grinding the waste sand powder by jet mill to form regenerated micro powder with a particle size of less than 75 μm; (3) Weigh 60-90 parts by weight of cement, 5-30 parts by weight of recycled micropowder, 1-5 parts by weight of alkali activator, 1-5 parts by weight of expansion agent, 1-5 parts by weight of early strength agent, 1-5 parts by weight of thickener, and 1-5 parts by weight of water reducer respectively, and stir the above components thoroughly in a mixing tank to mix them evenly to obtain a dry mix of recycled micropowder cement-based grouting material.

9. The method according to claim 8, characterized in that The recycled micro-powder cement-based grouting material and water are mixed and stirred to form a recycled micro-powder cement-based grouting material slurry, and the performance of the slurry is tested; if the slurry performance is qualified, the proportion of each component of the recycled micro-powder cement-based grouting material is directly determined; if the slurry performance is unqualified, the composition of the dry mix is ​​adjusted.

10. The method according to claim 9, characterized in that The recycled micro-powder cement-based grouting material and water are mixed and stirred at a weight ratio of 1:0.4-0.8, and can be used after being stirred evenly.

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