Modified recycled aggregate carbon sequestration clear water concrete and preparation method thereof

Abstract

The application discloses a modified recycled aggregate carbon sequestration clear water concrete and a preparation method thereof, and belongs to the field of modified carbon sequestration recycled concrete, and is used for solving the technical problem of increasing multiple processes or equipment and greatly increasing the modification cost of recycled aggregate no matter whether pre-wetting treatment or carbonization treatment is used for modifying the recycled aggregate in different ways; the application comprises the following components according to mass: 140-180 parts of phosphorous slag, 190-230 parts of industrial solid waste composite powder, 30-40 parts of ordinary Portland cement, 710-760 parts of recycled sand, 890-940 parts of recycled gravel, 140-150 parts of water, 7-10 parts of additive, 134-150 parts of carbon sequestration agent and 3-5 parts of GU release agent; the application realizes the recycling use of the alkali-activated industrial solid waste composite powder, reduces the carbon emission in the concrete production process, effectively overcomes the original defects of the recycled aggregate by cooperating with the special carbon sequestration agent, and realizes the simple modification pretreatment process of the recycled aggregate, greatly optimizes the workability, strength, apparent quality and carbon sequestration rate of the recycled aggregate clear water concrete.

Description

Technical Field

[0001] This invention belongs to the field of modified carbon-fixing recycled concrete, and particularly relates to a modified recycled aggregate carbon-fixing fair-faced concrete and its preparation method. Background Technology

[0002] With the development of the concept of recycling resources, these construction wastes, after being crushed, can now generally be used as aggregates in some conventional concrete. However, recycled aggregates themselves have disadvantages such as high water absorption and high crushing value. If we want to further increase the application ratio of recycled aggregates in concrete, it is often necessary to modify the recycled aggregates before application. Currently, in the field of modified carbon-fixing recycled concrete, there are various ways to modify recycled aggregates. However, whether it is pre-wetting treatment or carbonization treatment, it will add multiple processes or equipment, significantly increasing the cost of recycled aggregate modification. How to simplify the modification process of recycled aggregates, reduce the modification cost of recycled aggregates, and realize the large-scale application of recycled aggregates still requires further improvement. Summary of the Invention

[0003] This invention provides a modified recycled aggregate carbon-fixing fair-faced concrete and its preparation method. It significantly simplifies the recycled aggregate modification process by using a carbon-fixing agent to modify the recycled aggregate, effectively improving its performance. Furthermore, the carbon-fixing agent's high adsorption capacity for carbon dioxide allows for rapid carbon fixation, while the characteristics of the recycled aggregate enable efficient carbon fixation and internal curing. This transforms the defects of recycled aggregate into advantages, further enhancing concrete performance. Based on a high proportion of mineral admixtures, it reduces cement usage and lowers carbon emissions, achieving an environmentally friendly, green, and low-carbon modified carbon-fixing recycled aggregate fair-faced concrete preparation technology.

[0004] The technical solution according to this application is as follows:

[0005] Preferably, the modified carbon-fixing recycled aggregate fair-faced concrete comprises the following raw material components in the following mass ratio: 140-180 parts of phosphorus slag; 190-230 parts of industrial solid waste composite powder; 30-40 parts of ordinary silicate cement; 710-760 parts of recycled sand; 890-940 parts of recycled crushed stone; 140-150 parts of water; 7-10 parts of admixture; 134-150 parts of carbon-fixing agent; and 3-5 parts of GU release agent.

[0006] Preferably, the components of the carbon-fixing agent are in the following mass ratio: fumed silica: 25-33 parts; deionized water: 225-300 parts; sodium silicate: 3-5 parts; sodium hydroxide: 1-3 parts.

[0007] Preferably, the fumed silica has a particle size of 10-20 nm and a purity of 99.9%.

[0008] Preferably, the sodium silicate is a white powder with a purity of 98%.

[0009] Preferably, the sodium hydroxide is in the form of flaky crystals with a purity of 95%.

[0010] Preferably, the ordinary silicate cement is one of P·O425 cement, P·O425R cement, P·O525 cement, and P·O525 cement.

[0011] Preferably, the phosphorus slag powder is a white powder with an activity of 93%.

[0012] Preferably, the industrial solid waste composite powder is one or more of the following: fly ash, mineral powder, steel slag, water-quenched slag, metakaolin, electrolytic manganese slag, nickel-iron slag, and copper slag.

[0013] Preferably, the recycled sand is collected during the crushing process of construction solid waste, with a fineness modulus of 2.9, a bottom powder content of 7%, a water absorption rate of 8.1%, and a crushing value of 21.3%.

[0014] Preferably, the recycled crushed stone is 5-25mm crushed stone with a crushing value of 13.4% and a water absorption rate of 6.4%.

[0015] Preferably, the GU release agent is a silane coupling agent or a polyvinyl alcohol-acrylate copolymer.

[0016] Preferably, the process of modifying recycled aggregate with carbon fixation agent is as follows:

[0017] Step 1: Weigh out each raw material in the carbon fixation agent according to the mass ratio. Put the fumed silica into a planetary mixer and start stirring at a speed of 120 r / min. At the same time, use a tube to introduce deionized water into the mixer at a speed of 500 ml / min. Keep the mixer running during the process. After the deionized water is introduced, increase the speed to 600 r / min and keep stirring for 10 to 15 minutes to finally obtain a mixture of powdered fumed silica and deionized water.

[0018] Step 2: Add sodium silicate powder and sodium hydroxide to the mixture obtained in Step 1. Stir the mixture at 120 r / min. During the stirring process, rinse the surface of the stirring pot with water to lower the temperature inside the pot. Stop stirring after 5 to 8 minutes. At this point, the carbon fixation agent is prepared.

[0019] Step 3: Pour the weighed recycled sand and recycled crushed stone into a container, then pour the prepared carbon-fixing agent into the same container. Remix the recycled sand and recycled crushed stone every 30 minutes. After 8 hours, modified recycled sand and modified recycled crushed stone are obtained.

[0020] The preparation principle of the carbon fixation agent is as follows: Nanoscale fumed silica has stable properties and a large number of bonded silanol groups. The presence of these silanol groups gives it significant shear-thinning properties. When stirred at 60 r / min, the fumed silica initially breaks down, encapsulates, and evenly spreads the deionized water. When the speed is increased to 600 r / min, the fumed silica continuously breaks down the deionized water into small droplets. Under the action of the silanol groups, the fumed silica continuously forms a network of aggregates that encapsulate the small droplets, eventually forming a near-powder-like substance. Sodium silicate and sodium hydroxide are then added. During stirring, the sodium silicate and sodium hydroxide rapidly disperse and dissolve into the small droplets. Due to the presence of sodium silicate and sodium hydroxide, the surface tension of the small droplets increases rapidly. At this point, the fumed silica aggregates tightly encapsulate the sodium silicate and sodium hydroxide composite solution droplets, increasing the overall viscosity and weakening the shear-thinning properties. The resulting near-powder-like substance is the carbon fixation agent.

[0021] Preferably, the preparation process of the modified recycled aggregate carbon-fixing fair-faced concrete and its preparation method is as follows:

[0022] Step 1: Weigh the following components according to their mass ratio: phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, modified recycled crushed stone, water, admixtures, carbon fixative, GU release agent, etc.

[0023] Step 2: Add the weighed phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, and modified recycled crushed stone from Step 1 to the mixer and mix for 10-15 seconds to ensure that all powders and aggregates are mixed evenly.

[0024] Step 3: Add the water and admixtures weighed according to the mass ratio of each component in Step 1 to the well-mixed mixture in Step 2. Continue mixing in the mixer for 240-300 seconds. At this time, apply GU release agent evenly to the inner wall of the mold. After the concrete is mixed, pour it into the mold to form the final product.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) In this invention, the amount of ordinary silicate cement is very small, and the raw materials are mainly industrial solid waste. Except for phosphorus slag powder, the main components of industrial solid waste composite powder are CaO, SiO2, Al2O3 and other non-active metal oxides and metals with potential activity. As the cement hydration process progresses, hydrated calcium silicate gel and calcium hydroxide appear in the concrete. After thorough mixing, the carbon-fixing agent added along with the modified recycled aggregate is also dispersed into the concrete. Sodium silicate and sodium hydroxide in the carbon-fixing agent, as well as calcium hydroxide products in the slurry, provide an alkaline environment for the industrial solid waste composite powder. The potential active oxides in the industrial solid waste composite powder quickly undergo hydration reaction to generate hydrated calcium aluminosilicate gel with completely different products, and quickly form a strong structure. In the entire concrete production and preparation process, only a small amount of cement is used, and the rest of the raw materials are industrial solid waste or construction waste, which effectively reduces pollution and carbon emissions in the production process.

[0027] (2) In the process of modifying recycled aggregate, firstly, the micro-nano size of the carbon-fixing agent allows it to easily penetrate into the mortar layer gaps on the surface of the recycled aggregate. 95% of the carbon-fixing agent remaining in these mortar layer gaps is water, essentially achieving a "pre-wetting" treatment of the recycled aggregate, thereby rapidly and effectively reducing its water absorption rate. Secondly, after concrete is formed, it will continuously be eroded by carbon dioxide in the air. Based on the micro-nano porous structure of the carbon-fixing agent, this structure has a strong adsorption capacity for carbon dioxide. After carbon dioxide enters the interior of the concrete, it easily enters the gaps in the recycled aggregate and is captured and adsorbed by the carbon-fixing agent. This portion of carbon dioxide will react with the surface of the recycled aggregate. In the surface mortar layer, calcium hydroxide reacts to form calcium carbonate. This calcium carbonate fills the pores between the recycled aggregate mortar layers, thereby further improving the compactness of the recycled aggregate and reducing its crushing value. Thirdly, as the strength of concrete increases, microcracks inevitably form inside the concrete due to shrinkage. Carbon dioxide in the air will preferentially enter the concrete through these microcracks. During this process, the carbon dioxide is directly absorbed by the carbon-fixing agent in the microcracks and reacts directly with sodium hydroxide to form sodium carbonate. Subsequently, sodium carbonate crystals precipitate to fill the gaps, thus allowing the concrete to continuously absorb carbon dioxide and continuously improve its strength and durability throughout its service life.

[0028] (3) In this invention, GU release agent is applied to the template. After the concrete is poured into the template, one end of the silane coupling agent is coupled with the polyvinyl alcohol-acrylate copolymer, and the other end is adsorbed on the concrete surface. The hydrophobic end of the polyvinyl alcohol-acrylate will face away from the concrete surface. When the concrete hardens, the polyvinyl alcohol-acrylate forms a smooth hydrophobic layer on the concrete surface, thereby improving the appearance quality of the concrete. Detailed Implementation

[0029] The technical solution of the present invention will be further illustrated below through specific implementation examples. These examples are intended to explain the present invention and not to limit it.

[0030] Example 1:

[0031] S1: Weigh 25 parts of fumed silica, 225 parts of deionized water, 3 parts of sodium silicate, and 1 part of sodium hydroxide by mass.

[0032] S2: Add the weighed fumed silica from S1 to the mixer. Place the fumed silica into the planetary mixer and start stirring at a speed of 120 r / min. At the same time, use a tube to introduce deionized water into the mixer at a speed of 500 ml / min. Keep the mixer running during the process. After the deionized water is introduced, increase the speed to 600 r / min and keep stirring for 10 minutes to obtain a mixture of powdered fumed silica and deionized water.

[0033] S3: Add sodium silicate powder and sodium hydroxide to the mixture obtained in S2. Stir the mixture at 120 r / min. During the stirring process, rinse the surface of the stirring pot with water to reduce the temperature inside the stirring pot. Stop stirring after 5 minutes. At this time, the carbon fixation agent is prepared.

[0034] S4: Pour the weighed recycled sand and recycled crushed stone into a container, then pour the prepared carbon-fixing agent into the same container. Every 30 minutes, remix the recycled sand and recycled crushed stone. After 8 hours, modified recycled sand and modified recycled crushed stone are obtained.

[0035] S5: By mass, weigh the following raw material components: 140 parts phosphorus slag, 190 parts industrial solid waste composite powder, 30 parts ordinary silicate cement, 710 parts recycled sand, 890 parts recycled crushed stone, 140 parts water, 7 parts admixture, 134 parts carbon fixative, and 3 parts GU release agent.

[0036] S6: Add the weighed phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, and modified recycled crushed stone from S5 according to the mass ratio of each component to the mixer and stir for 10 seconds to mix all powders and aggregates evenly.

[0037] S7: Add the water and admixtures weighed according to the mass ratio of each component in S1 to the well-mixed mixture in S6, and continue mixing in the mixer for 240 seconds. At this time, apply GU release agent evenly to the inner wall of the mold. After the concrete is mixed, pour it into the mold to form the final product.

[0038] Example 2:

[0039] S1: Weigh out 33 parts of fumed silica, 300 parts of deionized water, 5 parts of sodium silicate, and 3 parts of sodium hydroxide by mass.

[0040] S2: Add the weighed fumed silica from S1 to the mixer. Place the fumed silica into the planetary mixer and start stirring at a speed of 120 r / min. At the same time, use a tube to introduce deionized water into the mixer at a speed of 500 ml / min. Keep the mixer running during the process. After the deionized water is introduced, increase the speed to 600 r / min and keep stirring for 15 minutes to obtain a mixture of powdered fumed silica and deionized water.

[0041] S3: Add sodium silicate powder and sodium hydroxide to the mixture obtained in S2. Stir the mixture at 120 r / min. During the stirring process, rinse the surface of the stirring pot with water to reduce the temperature inside the stirring pot. Stop stirring after 8 minutes. At this time, the carbon fixation agent is prepared.

[0042] S4: Pour the weighed recycled sand and recycled crushed stone into a container, then pour the prepared carbon-fixing agent into the same container. Every 30 minutes, remix the recycled sand and recycled crushed stone. After 8 hours, modified recycled sand and modified recycled crushed stone are obtained.

[0043] S5: Weigh the following raw material components by mass: 180 parts phosphorus slag, 230 parts industrial solid waste composite powder, 40 parts ordinary silicate cement, 760 parts recycled sand, 940 parts recycled crushed stone, 150 parts water, 10 parts admixture, 150 parts carbon fixative, and 5 parts GU release agent.

[0044] S6: Add the weighed phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, and modified recycled crushed stone from S5 according to the mass ratio of each component to the mixer and stir for 15 seconds to mix all powders and aggregates evenly.

[0045] S7: Add the water and admixture weighed according to the mass ratio of each component in S1 to the well-mixed mixture in S6, and continue mixing in the mixer for 300 seconds. At this time, apply GU release agent evenly to the inner wall of the mold. After the concrete is mixed, pour it into the mold to form the final product.

[0046] Example 3:

[0047] S1: Weigh out 29 parts of fumed silica, 263 parts of deionized water, 4 parts of sodium silicate, and 2 parts of sodium hydroxide by mass.

[0048] S2: Add the weighed fumed silica from S1 to the mixer. Place the fumed silica into the planetary mixer and start stirring at a speed of 120 r / min. At the same time, use a tube to introduce deionized water into the mixer at a speed of 500 ml / min. Keep the mixer running during the process. After the deionized water is introduced, increase the speed to 600 r / min and keep stirring for 12.5 min to obtain a mixture of powdered fumed silica and deionized water.

[0049] S3: Add sodium silicate powder and sodium hydroxide to the mixture obtained in S2. Stir the mixture at 120 r / min. During the stirring process, rinse the surface of the stirring pot with water to reduce the temperature inside the stirring pot. Stop stirring after 6.5 min. At this time, the carbon fixation agent is prepared.

[0050] S4: Pour the weighed recycled sand and recycled crushed stone into a container, then pour the prepared carbon-fixing agent into the same container. Every 30 minutes, remix the recycled sand and recycled crushed stone. After 8 hours, modified recycled sand and modified recycled crushed stone are obtained.

[0051] S5: By mass, weigh the following raw material components: 160 parts of phosphorus slag, 210 parts of industrial solid waste composite powder, 35 parts of ordinary silicate cement, 735 parts of recycled sand, 925 parts of recycled crushed stone, 145 parts of water, 8 parts of admixture, 142 parts of carbon fixative, and 4 parts of GU release agent.

[0052] S6: Add the weighed phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, and modified recycled crushed stone from S5 according to the mass ratio of each component to the mixer and stir for 12 seconds to mix all powders and aggregates evenly.

[0053] S7: Add the water and admixture weighed according to the mass ratio of each component in S1 to the well-mixed mixture in S6, and continue mixing in the mixer for 270 seconds. At this time, apply GU release agent evenly to the inner wall of the template. After the concrete is mixed, pour it into the mold to form the final product.

[0054] Comparative Example 1:

[0055] The difference between this comparative example and Example 3 is that no carbon-fixing agent was added, and recycled aggregate was used directly to prepare concrete.

[0056] Comparative Example 2:

[0057] The difference between this comparative example and Example 3 is that in step S4, no carbon-fixing agent was used to modify the recycled aggregate; the carbon-fixing agent was directly added to the concrete in step S5.

[0058] Comparative Example 3:

[0059] The difference between this comparative example and Example 3 is that in step S7, the template was not coated with GU release agent;

[0060] Comparative Example 4:

[0061] The difference between this comparative example and Example 3 is that, in step S6, the carbon-fixing agent of this patent is not added, and the recycled aggregate is pre-wetted and drained before trial mixing.

[0062] Performance testing: The results of testing the modified carbon-fixing recycled aggregate fair-faced concrete prepared in Examples 1-3 and Comparative Examples 1-4, including its discharge condition, compressive strength after 28 days of curing, apparent quality, and carbon fixation rate (the ratio of solidified carbon dioxide to concrete mass) after 180 days of curing in 150mm specimens, are as follows:

[0063] Table 1. Results of concrete performance testing

[0064]

[0065] Data Analysis: Examples 1-3 show that the modified recycled aggregate carbon-fixing fair-faced concrete and its preparation method prepared by this invention cover multiple concrete strength grades. When the variation range of each raw material is within the design range, the concrete consistently maintains good workability and compressive strength, and has good appearance quality. Furthermore, it is evident that the carbon content of the modified carbon-fixing recycled aggregate fair-faced concrete increases with the increase of the concrete strength grade. Comparative Examples 1-4 show that regardless of changes in process conditions or adjustments to the formula beyond the specified range, the workability, strength, appearance quality, and carbon fixation rate of the concrete in Example 3 are higher than those of the comparative examples, except that the workability is lower than that of directly pre-wetted recycled aggregate. Moreover, this invention uses phosphorus slag and industrial solid waste composite powder as raw materials, achieving the circular application of bulk industrial solid waste through recycling, reducing the amount of cement added, and reducing carbon emissions during concrete production, thus meeting green and low-carbon environmental protection requirements.

[0066] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A modified recycled aggregate carbon-fixing fair-faced concrete, characterized in that, The concrete raw material components are as follows by mass ratio: 140-180 parts phosphorus slag; 190-230 parts industrial solid waste composite powder; 30-40 parts ordinary silicate cement; 710-760 parts recycled sand; 890-940 parts recycled crushed stone; 140-150 parts water; 7-10 parts admixture; 134-150 parts carbon-fixing agent; and 3-5 parts GU release agent. The carbon-fixing agent components are as follows by mass ratio: fumed silica: 25-33... The composition is as follows: 225-300 parts deionized water, 3-5 parts sodium silicate, and 1-3 parts sodium hydroxide. The fumed silica has a particle size of 10-20 nm and a purity of 99.9%. The industrial solid waste composite powder is one or more of the following: fly ash, mineral powder, steel slag, water-quenched slag, metakaolin, electrolytic manganese slag, nickel-iron slag, and copper slag. The GU release agent is a silane coupling agent or a polyvinyl alcohol-acrylate copolymer. The process of modifying recycled aggregate with carbon fixation agent is as follows: Step 1: Weigh out each raw material in the carbon fixation agent according to the mass ratio. Put the fumed silica into a planetary mixer and start stirring at a speed of 120 r / min. At the same time, use a tube to introduce deionized water into the mixer at a speed of 500 ml / min. Keep the mixer running during the process. After the deionized water is introduced, increase the speed to 600 r / min and keep stirring for 10 to 15 minutes to finally obtain a mixture of powdered fumed silica and deionized water. Step 2: Add sodium silicate powder and sodium hydroxide to the mixture obtained in Step 1. Stir the mixture at 120 r / min. During the stirring process, rinse the surface of the stirring pot with water to reduce the temperature inside the stirring pot. Stop stirring after 5-8 minutes. At this time, the carbon fixation agent is prepared. Step 3: Pour the weighed recycled sand and recycled crushed stone into a container, then pour the prepared carbon fixation agent into the same container. Every 30 minutes, remix the recycled sand and recycled crushed stone. After 8 hours, the modified recycled sand and modified recycled crushed stone are obtained.

2. The modified recycled aggregate carbon-fixing fair-faced concrete according to claim 1, characterized in that, The ordinary silicate cement is one of P·O425 cement, P·O425R cement, and P·O525 cement.

3. The modified recycled aggregate carbon-fixing fair-faced concrete according to claim 1, characterized in that, The recycled sand is collected during the crushing of construction solid waste, with a fineness modulus of 2.9, a bottom powder content of 7%, a water absorption rate of 8.1%, and a crushing value of 21.3%. The recycled crushed stone is 5-25mm crushed stone with a crushing value of 13.4% and a water absorption rate of 6.4%.

4. A method for preparing modified recycled aggregate carbon-fixing fair-faced concrete according to any one of claims 1-3, characterized in that, The preparation process of the modified recycled aggregate carbon-fixing fair-faced concrete is as follows: Step 1: Weigh the following components according to their mass ratio: phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, modified recycled crushed stone, water, admixtures, carbon fixative, GU release agent, etc. Step 2: Add the weighed phosphorus slag, industrial solid waste composite powder, ordinary silicate cement, modified recycled sand, and modified recycled crushed stone from Step 1 to the mixer and mix for 10-15 seconds to ensure that all powders and aggregates are mixed evenly. Step 3: Add the water and admixtures weighed according to the mass ratio of each component in Step 1 to the well-mixed mixture in Step 2. Continue mixing in the mixer for 240-300 seconds. At this time, apply GU release agent evenly to the inner wall of the mold. After the concrete is mixed, pour it into the mold to form the final product.

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