Environment-friendly gravel concrete and preparation process thereof

Abstract

The invention provides an environment-friendly gravel concrete preparation process which comprises the following steps: mixing low-clinker gel, modified biomass ash and iron powder, and uniformly stirring to obtain a mixture A; then adding the recycled aggregate and the modified sand grains into the mixture A, and uniformly stirring to obtain a mixture B; adding a water reducing agent into the mixture B, and uniformly stirring to obtain a mixture C; and then adding seawater electrolytic calcium carbonate paste into the mixture C, and uniformly stirring to obtain the environment-friendly gravel concrete. The recycled aggregate is prepared by modifying waste concrete blocks. The environment-friendly gravel concrete has good environmental protection property, mechanical strength and working performance.

Description

Technical Field

[0001] This invention relates to the field of concrete preparation technology, and in particular to an environmentally friendly sand and gravel concrete preparation process. Background Technology

[0002] Concrete, as the world's most widely used building material, relies heavily on natural sand and gravel resources in its traditional production methods, which come at a high environmental cost. Cement production contributes approximately 8% of global carbon dioxide emissions, while the large amounts of waste concrete and bricks generated from building demolition also create enormous environmental pressure.

[0003] While existing technologies have attempted to utilize recycled aggregates or some industrial waste to prepare concrete, most environmentally friendly concrete only achieves material substitution, often leading to problems such as decreased concrete performance and reduced functionality. Therefore, there is an urgent need for a high-performance, environmentally friendly aggregate concrete. Summary of the Invention

[0004] This invention provides an environmentally friendly sand and gravel concrete and its preparation process, which combines good environmental protection, mechanical strength, and workability.

[0005] According to one aspect of the present invention, an environmentally friendly aggregate concrete preparation process is provided, comprising the following steps: mixing low-clinker gel, modified biomass ash, and iron powder, stirring evenly to obtain mixture A; subsequently adding recycled aggregate and modified sand to mixture A, stirring evenly to obtain mixture B; subsequently adding a water-reducing agent to mixture B, stirring evenly to obtain mixture C; subsequently adding seawater electrolytic calcium carbonate paste to mixture C, stirring evenly to obtain environmentally friendly aggregate concrete; the recycled aggregate is prepared from waste concrete blocks through modification treatment. In this invention, by using waste concrete blocks to prepare recycled aggregate, and using modified biomass ash, seawater electrolytic calcium carbonate paste, and modified sand as functional additives, the efficient resource utilization of construction waste and industrial waste is achieved, while effectively reducing cement consumption and carbon emissions, and ensuring the strength and workability of the concrete.

[0006] Preferably, the waste concrete blocks are crushed and screened to obtain screened aggregate. A silane coupling agent is added to the screened aggregate, and the mixture is reacted for 5 to 20 minutes at a speed of 400 to 600 rpm to obtain recycled aggregate.

[0007] Preferably, the recycled aggregate includes recycled aggregate A and recycled aggregate B; the particle size of recycled aggregate A is 5~20mm, and the particle size of recycled aggregate B is 0.15~5mm.

[0008] Preferably, the ratio of recycled aggregate A to recycled aggregate B, calculated by mass percentage, is (60%~70%):(30%~40%). By using recycled aggregate A with a particle size of 5~20mm and recycled aggregate B with a particle size of 0.15~5mm, and by adjusting the ratio of recycled aggregate A to recycled aggregate B, the different particle sizes of recycled aggregate A and recycled aggregate B are interlocked to form a dense packing structure. This minimizes the amount of cement paste required and effectively improves the mechanical strength, durability, and workability of the concrete.

[0009] Preferably, the low-clinker gel comprises silicate cement, fly ash, and granulated blast furnace slag powder, and the mass ratio is calculated as follows: silicate cement: fly ash: granulated blast furnace slag powder = (90~110):(10~20):(10~20). By controlling the proportions of silicate cement, fly ash, and granulated blast furnace slag powder within the above range, while ensuring that the silicate cement provides sufficient mechanical strength, the addition of appropriate amounts of fly ash and granulated blast furnace slag powder can effectively reduce the amount of high-energy-consuming cement used and effectively improve environmental benefits.

[0010] Preferably, the preparation process of modified biomass ash includes the following steps: burning rice husks for 1 to 3 hours at a temperature of 550 to 650°C with oxygen introduced to obtain rice husk ash; then grinding the rice husk ash to obtain rice husk ash powder; and then adding a silane coupling agent to the rice husk ash powder for surface treatment.

[0011] Preferably, the specific surface area of ​​the rice husk ash powder is denoted as x, which satisfies x ≥ 400 m². 2 / kg. Rice husk ash is treated with controlled oxygen combustion and ball milling to achieve a specific surface area ≥400 m² / kg, and then modified with a silane coupling agent to give it both pozzolanic activity and interface enhancement function.

[0012] Preferably, the preparation process of modified sand particles includes the following steps: under a temperature of 55~65℃, recycled aggregate B, ethanol, catalyst and desiccant are mixed and reacted for 45~55 hours.

[0013] Preferably, the catalyst includes potassium hydroxide, and the desiccant includes dimethoxypropane. Potassium hydroxide is chosen as the catalyst because it can efficiently catalyze the esterification reaction between ethanol and the silanol groups on the surface of sand particles. Adding dimethoxypropane as a desiccant can promptly remove the reaction byproduct (water), promoting the chemical reaction to continue towards the formation of tetraalkoxysilane, effectively improving the synthesis efficiency of the modified sand particles.

[0014] Preferably, the preparation process of seawater electrolytic calcium carbonate paste includes the following steps: under the condition of a current of 24V, the pH value of seawater is raised to 10-12 to obtain intermediate product A; then carbon dioxide is introduced into intermediate product A to lower the pH value of intermediate product A to 6-7, a white precipitate is precipitated, and the white precipitate is dehydrated to obtain seawater electrolytic calcium carbonate paste.

[0015] Preferably, the solid content of the seawater electrolytic calcium carbonate paste is 65% to 70%.

[0016] Preferably, the stirring speed is 20-40 rpm during the preparation of mixture A.

[0017] Preferably, the stirring speed is 20-40 rpm during the preparation of mixture B.

[0018] Preferably, during the preparation of mixture C, the stirring speed is 100~140 rpm.

[0019] Preferably, when adding seawater electrolytic calcium carbonate paste to the mixture C and stirring until homogeneous, the stirring speed is 100~140 rpm.

[0020] According to another aspect of the present invention, an environmentally friendly aggregate concrete is provided, which is prepared by an environmentally friendly aggregate concrete preparation process. Detailed Implementation

[0021] Example 1 This embodiment provides an environmentally friendly sand and gravel concrete preparation process, including the following steps: Mix 130 kg of low-clinker gel, 10 kg of modified biomass ash, and 5 kg of iron powder in a mixer and stir at 30 rpm for 8 minutes until homogeneous to obtain mixture A. Then add 100 kg of recycled aggregate (composed of 65 kg of recycled aggregate A and 35 kg of recycled aggregate B) and 20 kg of modified sand to mixture A and stir at 30 rpm for 10 minutes to obtain mixture B. Then add 2 kg of water-reducing agent to mixture B and increase the mixer speed to 120 rpm for 4 minutes to obtain mixture C. Then add seawater electrolytic calcium carbonate paste to mixture C and continue stirring at 120 rpm for 5 minutes to obtain environmentally friendly sand and gravel concrete.

[0022] The low clinker gel is prepared by mixing 100 kg of silicate cement, 15 kg of fly ash, and 15 kg of granulated blast furnace slag powder.

[0023] The preparation process of modified biomass ash is as follows: Rice husks are burned for 2 hours at a temperature of 600℃ with oxygen introduced, yielding a specific surface area of ​​450 m². 2 / kg rice husk ash; then the rice husk ash was ground to obtain rice husk ash powder; then 1.5wt% of silane coupling agent was added to the rice husk ash powder, and surface treatment was carried out at a temperature of 60℃ for 5 minutes.

[0024] The preparation process of recycled aggregate A and recycled aggregate B is as follows: waste concrete blocks are crushed to obtain recycled aggregate intermediates. 0.5 wt% of silane coupling agent is added to the recycled aggregate intermediates and reacted for 10 minutes at a speed of 500 rpm. The mixture is then sieved to obtain recycled aggregate A with a particle size of 5~20 mm and recycled aggregate B with a particle size of 0.15~5 mm.

[0025] The preparation process of modified sand particles is as follows: 20 kg of recycled aggregate B, 40 kg of ethanol, 0.4 kg of potassium hydroxide and 1 kg of dimethoxypropane are mixed at a temperature of 60℃ and reacted for 50 hours. The reaction product is then filtered and dried to obtain modified sand particles.

[0026] The preparation process of seawater electrolytic calcium carbonate paste is as follows: Under the condition of 24V current, the pH value of seawater is raised to 11 to obtain intermediate product A; then carbon dioxide is introduced into intermediate product A to lower the pH value of intermediate product A to 6.5, and a white precipitate is precipitated. The white precipitate is then dehydrated to obtain seawater electrolytic calcium carbonate paste with a solid content of 68%.

[0027] Example 2 This embodiment provides an environmentally friendly sand and gravel concrete preparation process, including the following steps: Mix 130 kg of low-clinker gel, 10 kg of modified biomass ash, and 5 kg of iron powder in a mixer and stir at 30 rpm for 8 minutes until homogeneous to obtain mixture A. Then add 100 kg of recycled aggregate (composed of 65 kg of recycled aggregate A and 35 kg of recycled aggregate B) and 20 kg of modified sand to mixture A and stir at 30 rpm for 10 minutes to obtain mixture B. Then add 2 kg of water-reducing agent to mixture B and increase the mixer speed to 120 rpm for 4 minutes to obtain mixture C. Then add seawater electrolytic calcium carbonate paste to mixture C and continue stirring at 120 rpm for 5 minutes to obtain environmentally friendly sand and gravel concrete.

[0028] The low clinker gel is prepared by mixing 100 kg of silicate cement, 15 kg of fly ash, and 15 kg of granulated blast furnace slag powder.

[0029] The preparation process of modified biomass ash is as follows: Rice husks are burned for 3 hours at a temperature of 650℃ with oxygen introduced, yielding a specific surface area of ​​600 m². 2 / kg rice husk ash; then the rice husk ash was ground to obtain rice husk ash powder; then 1.5wt% of silane coupling agent was added to the rice husk ash powder, and surface treatment was carried out at a temperature of 60℃ for 5 minutes.

[0030] The preparation process of recycled aggregate A and recycled aggregate B is as follows: waste concrete blocks are crushed to obtain recycled aggregate intermediates. 0.5 wt% of silane coupling agent is added to the recycled aggregate intermediates and reacted for 10 minutes at a speed of 500 rpm. The mixture is then sieved to obtain recycled aggregate A with a particle size of 5~20 mm and recycled aggregate B with a particle size of 0.15~5 mm.

[0031] The preparation process of modified sand particles is as follows: 20 kg of recycled aggregate B, 40 kg of ethanol, 0.4 kg of potassium hydroxide and 1 kg of dimethoxypropane are mixed at a temperature of 65℃ and reacted for 55 hours. The reaction product is then filtered and dried to obtain modified sand particles.

[0032] The preparation process of seawater electrolytic calcium carbonate paste is as follows: Under the condition of 24V current, the pH value of seawater is raised to 12 to obtain intermediate product A; then carbon dioxide is introduced into intermediate product A to lower the pH value of intermediate product A to 6, and a white precipitate is precipitated. The white precipitate is then dehydrated to obtain seawater electrolytic calcium carbonate paste with a solid content of 70%.

[0033] Example 3 This embodiment provides an environmentally friendly sand and gravel concrete preparation process, including the following steps: Mix 130 kg of low-clinker gel, 10 kg of modified biomass ash, and 5 kg of iron powder in a mixer and stir at 30 rpm for 8 minutes until homogeneous to obtain mixture A. Then add 100 kg of recycled aggregate (composed of 65 kg of recycled aggregate A and 35 kg of recycled aggregate B) and 20 kg of modified sand to mixture A and stir at 30 rpm for 10 minutes to obtain mixture B. Then add 2 kg of water-reducing agent to mixture B and increase the mixer speed to 120 rpm for 4 minutes to obtain mixture C. Then add seawater electrolytic calcium carbonate paste to mixture C and continue stirring at 120 rpm for 5 minutes to obtain environmentally friendly sand and gravel concrete.

[0034] The low clinker gel is prepared by mixing 100 kg of silicate cement, 15 kg of fly ash, and 15 kg of granulated blast furnace slag powder.

[0035] The preparation process of modified biomass ash is as follows: Rice husks are burned for 1 hour at a temperature of 550℃ with oxygen introduced, yielding a specific surface area of ​​400 m². 2 / kg rice husk ash; then the rice husk ash was ground to obtain rice husk ash powder; then 1.5wt% of silane coupling agent was added to the rice husk ash powder, and surface treatment was carried out at a temperature of 60℃ for 5 minutes.

[0036] The preparation process of recycled aggregate A and recycled aggregate B is as follows: waste concrete blocks are crushed to obtain recycled aggregate intermediates. 0.5 wt% of silane coupling agent is added to the recycled aggregate intermediates and reacted for 10 minutes at a speed of 500 rpm. The mixture is then sieved to obtain recycled aggregate A with a particle size of 5~20 mm and recycled aggregate B with a particle size of 0.15~5 mm.

[0037] The preparation process of modified sand particles is as follows: 20 kg of recycled aggregate B, 40 kg of ethanol, 0.4 kg of potassium hydroxide and 1 kg of dimethoxypropane are mixed at a temperature of 55℃ and reacted for 45 hours. The reaction product is then filtered and dried to obtain modified sand particles.

[0038] The preparation process of seawater electrolytic calcium carbonate paste is as follows: Under the condition of 24V current, the pH value of seawater is raised to 10 to obtain intermediate product A; then carbon dioxide is introduced into intermediate product A to lower the pH value of intermediate product A to 7, and a white precipitate is precipitated. The white precipitate is then dehydrated to obtain seawater electrolytic calcium carbonate paste with a solid content of 65%.

[0039] Example 4 This embodiment describes the preparation of an environmentally friendly aggregate concrete using the same process as in Example 1. The difference lies in the particle size of recycled aggregate A (10-15 mm) and recycled aggregate B (0.5-1 mm). Aside from these differences, the materials, formulation ratios, and preparation procedures used in this embodiment are strictly consistent with those in Example 1.

[0040] Example 5 This embodiment prepares an environmentally friendly aggregate concrete using the preparation process provided in Example 1. The difference between this embodiment and Example 1 is that the recycled aggregate A used in this embodiment has a particle size of 20-25 mm, and the recycled aggregate B has a particle size of 5-10 mm. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0041] Example 6 This embodiment refers to the preparation process provided in Example 1 to prepare an environmentally friendly aggregate concrete. The difference between this embodiment and Example 1 is that the total amount of recycled aggregate is kept constant during the preparation process. The amount of recycled aggregate A is adjusted to 55 kg, and the amount of recycled aggregate B is adjusted to 45 kg, so that the mass percentage of recycled aggregate A to recycled aggregate B is 55% to 45%. Apart from the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0042] Example 7 This embodiment refers to the preparation process provided in Embodiment 1 to prepare an environmentally friendly aggregate concrete. The difference between this embodiment and Embodiment 1 is that, in the preparation of the environmentally friendly aggregate concrete, the total amount of recycled aggregate is kept constant. The amount of recycled aggregate A is adjusted to 60 kg, and the amount of recycled aggregate B is adjusted to 40 kg, so that, calculated by mass percentage, the ratio of recycled aggregate A to recycled aggregate B is 60% to 40%. Apart from the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0043] Example 8 This embodiment refers to the preparation process provided in Example 1 to prepare an environmentally friendly aggregate concrete. The difference between this embodiment and Example 1 is that the total amount of recycled aggregate is kept constant during the preparation process. The amount of recycled aggregate A is adjusted to 70 kg, and the amount of recycled aggregate B is adjusted to 30 kg, so that the mass percentage of recycled aggregate A to recycled aggregate B is 70% to 30%. Apart from the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0044] Example 9 This embodiment refers to the preparation process provided in Embodiment 1 to prepare an environmentally friendly aggregate concrete. The difference between this embodiment and Embodiment 1 is that, in the preparation of the environmentally friendly aggregate concrete, the total amount of recycled aggregate is kept constant. The amount of recycled aggregate A is adjusted to 75 kg, and the amount of recycled aggregate B is adjusted to 25 kg, so that, calculated by mass percentage, the ratio of recycled aggregate A to recycled aggregate B is 75% to 25%. Apart from the above differences, the materials, formula ratios, and preparation operations used in this embodiment are strictly consistent with those in Embodiment 1.

[0045] Comparative Example 1 This comparative example prepares an environmentally friendly aggregate concrete using the preparation process provided in Example 1. The difference between this comparative example and Example 1 is that, in the preparation of the environmentally friendly aggregate concrete, an equal mass of unmodified biomass ash is used instead of the modified biomass ash in Example 1. Apart from the above differences, the materials, formulation ratios, and preparation operations used in this comparative example are strictly consistent with those in Example 1.

[0046] Comparative Example 2 This comparative example prepares an environmentally friendly aggregate concrete using the preparation process provided in Example 1. The difference between this comparative example and Example 1 is that an equal mass of calcium carbonate is used to replace the seawater electrolytic calcium carbonate paste in Example 1 during the preparation of the environmentally friendly aggregate concrete. Apart from the above differences, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0047] Comparative Example 3 This comparative example prepares an environmentally friendly aggregate concrete using the preparation process provided in Example 1. The difference between this comparative example and Example 1 is that an equal mass of natural river sand is used to replace the modified sand particles in Example 1 during the preparation of the environmentally friendly aggregate concrete. Apart from the above differences, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0048] Comparative Example 4 This comparative example prepares an environmentally friendly aggregate concrete using the preparation process provided in Example 1. The difference between this comparative example and Example 1 is that an equal mass of natural crushed stone is used to replace the waste concrete blocks in Example 1 during the preparation of the environmentally friendly aggregate concrete. Apart from the above differences, the materials, formulation ratios, and preparation procedures used in this comparative example are strictly consistent with those in Example 1.

[0049] Test case 1. Test subjects: The environmentally friendly sand and gravel concrete provided in Examples 1-9 and Comparative Examples 1-4 were used as test subjects.

[0050] 2. Test items: (1) Comprehensive utilization rate of construction waste: The comprehensive utilization rate of construction waste was tested in accordance with the "GB / T 50640-2010 Evaluation Standard for Green Construction of Building Engineering".

[0051] (2) Mechanical strength: The compressive strength of the test object was tested in accordance with GB / T 50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete. The concrete compressive strength test was conducted by molding and curing 150mm or 100mm cube specimens using standard methods, loading them at a specific rate until failure under standard test conditions, and dividing the maximum load by the bearing area of ​​the specimen.

[0052] (3) Workability: The slump and slump spread of the test objects were tested in accordance with GB / T 50080-2016 Standard for Test Methods of Performance of Ordinary Concrete Mixtures. The concrete mixture was placed into the slump cone in three layers, and each layer was tamped 25 times. After smoothing, the cone was lifted vertically. The height difference between the cone height and the highest point of the specimen after slump was measured as the slump. At the same time, the maximum diameter of the mixture after unfolding and its vertical diameter were measured as the slump spread.

[0053] 3. Test Results: Table 1. Relevant performance test results of the test subjects

[0054] The test results of the environmentally friendly aggregate concrete provided in Examples 1-9 and Comparative Examples 1-4 are shown in Table 1. The environmentally friendly aggregate concrete provided in Examples 1-10 exhibits good environmental friendliness, mechanical strength, durability, and workability. This demonstrates that by using waste concrete blocks to prepare recycled aggregate and using modified biomass ash, seawater electrolytic calcium carbonate paste, and modified sand particles as functional additives, the efficient resource utilization of construction waste and industrial waste can be achieved while effectively reducing cement consumption and carbon emissions, and ensuring the strength and workability of the concrete.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An environmentally friendly process for preparing sandstone concrete, characterized by, The method comprises the following steps: The low-clinker gel, modified biomass ash and iron powder are mixed and stirred to obtain a mixture A; then the recycled aggregate and modified sand are added into the mixture A and stirred to obtain a mixture B; then the water reducing agent is added into the mixture B and stirred to obtain a mixture C; and then the seawater electrolysis calcium carbonate paste is added into the mixture C and stirred to obtain the environment-friendly sandstone concrete. The recycled aggregate is prepared from waste concrete blocks through modification.

2. The eco-friendly sand-coated concrete production process according to claim 1, wherein, The recycled aggregate comprises recycled aggregate A and recycled aggregate B; the particle size of the recycled aggregate A is 5-20 mm, and the particle size of the recycled aggregate B is 0.15-5 mm.

3. The eco-friendly sand-coated concrete production process according to claim 2, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. According to the mass percentage, the recycled aggregate A and the recycled aggregate B are in a mass ratio of (60%-70%):(30%-40%).

4. The eco-friendly sand-coated concrete production process according to claim 1, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. The low-clinker gel comprises Portland cement, fly ash and granulated blast furnace slag powder, and the Portland cement, the fly ash and the granulated blast furnace slag powder are in a mass ratio of (90-110):(10-20):(10-20).

5. The eco-friendly sand-coated concrete production process according to claim 1, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. The preparation process of the modified biomass ash comprises the following steps: rice husk is burned for 1-3 hours at a temperature of 550-650 DEG C with oxygen being introduced to obtain rice husk ash; then the rice husk ash is ground to obtain rice husk ash powder; and then the rice husk ash powder is treated with a silane coupling agent.

6. The eco-friendly sand-coated concrete production process according to claim 1, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. The specific surface area of the rice hull ash powder is denoted as x, and satisfies x≥400 m 2 / kg.

7. The eco-friendly sand-coated concrete production process according to claim 1, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. The preparation process of the modified sand comprises the following steps: the recycled aggregate B, ethanol, a catalyst and a water absorption agent are mixed at a temperature of 55-65 DEG C, and the mixture is reacted for 45-55 hours.

8. The eco-friendly sand-coated concrete production process according to claim 1, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. The preparation process of the seawater electrolysis calcium carbonate paste comprises the following steps: the pH value of seawater is increased to 10-12 under the condition of an electric current of 24 V to obtain an intermediate product A; then carbon dioxide is introduced into the intermediate product A to reduce the pH value of the intermediate product A to 6-7, and white precipitates are separated out; and then the white precipitates are dehydrated to obtain the seawater electrolysis calcium carbonate paste.

9. The eco-friendly sand-coated concrete production process according to claim 1, wherein the sand-coated concrete is produced by mixing the sand-coated aggregate with cement, water, and a superplasticizer. The solid content of the seawater electrolysis calcium carbonate paste is 65%-70%. 10.An environment-friendly sandstone concrete prepared by the environment-friendly sandstone concrete preparation process according to any one of claims 1-9.

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