Self-waterproof carbon-reducing regenerated concrete and preparation method thereof

Abstract

The present invention provides a self-waterproof carbon-reducing regeneration concrete and a preparation method thereof. The self-waterproof carbon-reducing regeneration concrete is prepared from the following raw materials in parts by weight: 300-450 parts of cement, 1000-1100 parts of coarse aggregate, 500-600 parts of fine aggregate, 200-250 parts of water, and 80-130 parts of admixtures; the admixtures include the following raw materials in parts by weight: 30-60 parts of metakaolin and 50-70 parts of fly ash. The preparation method is to sequentially add coarse aggregate, cement, fine aggregate, metakaolin, and fly ash, mix them evenly, then add water for stirring, and mold and maintain. The self-waterproof carbon-reducing regeneration concrete prepared by the present invention has strong compressive strength and impermeability, and reduces the amount of cement used, which can reduce concrete carbon emissions.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete processing, and in particular relates to a self-waterproof carbon-reducing regenerated concrete and a preparation method thereof. Background Art

[0002] China's carbon emissions reached 11.47 billion tons in 2021. The building materials industry accounted for about 13.2% of the country's carbon dioxide emissions. The cement industry is the largest carbon emission industry in the building materials industry, accounting for 83%. Concrete is mainly composed of cement, admixtures, coarse aggregate, fine aggregate, admixtures and water. Among them, cement is the most critical factor affecting concrete carbon emissions. The task of reducing carbon emissions from cement materials is extremely important.

[0003] Recycled concrete refers to new concrete made by crushing, cleaning, and grading discarded concrete blocks, mixing them with grading in a certain proportion, partially or completely replacing natural aggregates such as sand and gravel (mainly coarse aggregates), and then adding cement, water, etc.

[0004] Since the performance of recycled aggregates is inferior to that of natural aggregates, it has many adverse effects on recycled concrete, resulting in relatively low performance of recycled concrete such as compression resistance and impermeability, among which the impermeability defect cannot be ignored. Summary of the Invention

[0005] The present invention provides a self-waterproof carbon-reducing recycled concrete and a preparation method thereof, the purpose of which is to reduce the carbon emissions of concrete while making it have stronger compressive and anti-permeability properties, which can effectively solve the problems in the background technology.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A self-waterproof and carbon-reducing recycled concrete is prepared from the following raw materials in parts by weight: 300-450 parts of cement, 1000-1100 parts of coarse aggregate, 500-600 parts of fine aggregate, 200-250 parts of water, and 80-130 parts of admixture; the admixture includes the following raw materials in parts by weight: 30-60 parts of metakaolin and 50-70 parts of fly ash.

[0008] Furthermore, it is prepared from the following raw materials in parts by weight: 300-350 parts of cement, 1000-1050 parts of coarse aggregate, 550-600 parts of fine aggregate, 200-220 parts of water, and 100-120 parts of admixture; the admixture includes the following raw materials in parts by weight: 30-50 parts of metakaolin and 60-70 parts of fly ash.

[0009] Preferably, it is prepared from the following raw materials in parts by weight: 334 parts of cement, 1041 parts of coarse aggregate, 562 parts of fine aggregate, 205 parts of water, and 112 parts of admixture; the admixture includes the following raw materials in parts by weight: 45 parts of metakaolin and 67 parts of fly ash.

[0010] Furthermore, the coarse aggregate is wrapped by a composite anti-seepage agent, which is a mixture of epoxy resin, diluent, curing agent and toughening agent in a weight ratio of 60:10:15:9.

[0011] Furthermore, the weight ratio of the coarse aggregate to the epoxy resin is 50:1.

[0012] Furthermore, the coarse aggregate is composed of virgin coarse aggregate and recycled coarse aggregate, and the mixing ratio of virgin coarse aggregate to recycled coarse aggregate is 2-3:7-8; the fine aggregate is zone 2 medium sand with good particle gradation.

[0013] Preferably, the mixing ratio of the virgin coarse aggregate to the recycled coarse aggregate is 3:7.

[0014] Furthermore, the recycled coarse aggregate is prepared by the following method: waste concrete is crushed to obtain waste concrete particles with a particle size of less than 25 mm; the waste concrete particles are collected, cleaned, aired, and sieved to obtain recycled coarse aggregate with a particle size of 5 mm to 25 mm.

[0015] Furthermore, a method for preparing self-waterproof carbon-reducing recycled concrete comprises the following steps:

[0016] (1) Weigh the raw materials according to the weight of 300-450 parts of cement, 1000-1100 parts of coarse aggregate, 500-600 parts of fine aggregate, 200-250 parts of water, 30-60 parts of metakaolin, and 50-70 parts of fly ash, and add coarse aggregate, cement, fine aggregate, metakaolin, and fly ash in sequence and mix them evenly;

[0017] (2) Add water and stir for 4-5 minutes;

[0018] (3) The freshly mixed concrete is molded and cured to obtain self-waterproof and carbon-reducing recycled concrete.

[0019] Compared with the existing technology, the beneficial effects of the present invention are as follows: when preparing concrete, the present invention uses kaolin and fly ash to replace part of the cement. The concrete using the technology of the present invention reduces the amount of cement used, indirectly reduces carbon dioxide emissions, can reduce carbon emissions in the cement industry, and can also ensure the strength while ensuring the impermeability of concrete; it has good social and economic value. Implementation Method

[0020] The following examples are only used to more clearly illustrate the technical solutions of the present invention so that those skilled in the art can better understand and utilize the present invention, but are not intended to limit the scope of protection of the present invention.

[0021] A self-waterproof and carbon-reducing recycled concrete is prepared from the following raw materials in parts by weight: 300-450 parts of cement, 1000-1100 parts of coarse aggregate, 500-600 parts of fine aggregate, 200-250 parts of water, and 80-130 parts of admixture; the admixture includes the following raw materials in parts by weight: 30-60 parts of metakaolin and 50-70 parts of fly ash.

[0022] Furthermore, the coarse aggregate is wrapped by a composite anti-seepage agent, which is a mixture of epoxy resin, diluent, curing agent and toughening agent in a weight ratio of 60:10:15:9.

[0023] Furthermore, the weight ratio of the coarse aggregate to the epoxy resin is 50:1.

[0024] Furthermore, the coarse aggregate consists of virgin coarse aggregate and recycled coarse aggregate, and the mixing ratio of virgin coarse aggregate to recycled coarse aggregate is 2-3:7-8.

[0025] Preferably, the mixing ratio of the virgin coarse aggregate to the recycled coarse aggregate is 3:7.

[0026] Furthermore, the recycled coarse aggregate is prepared by the following method: waste concrete is crushed to obtain waste concrete particles with a particle size of less than 25 mm; the waste concrete particles are collected, cleaned, aired, and sieved to obtain recycled coarse aggregate with a particle size of 5 mm to 25 mm.

[0027] Furthermore, a method for preparing self-waterproof carbon-reducing recycled concrete comprises the following steps:

[0028] (1) Weigh the raw materials according to the weight of 300-450 parts of cement, 1000-1100 parts of coarse aggregate, 500-600 parts of fine aggregate, 200-250 parts of water, 30-60 parts of metakaolin, and 50-70 parts of fly ash, and add coarse aggregate, cement, fine aggregate, metakaolin, and fly ash in sequence and mix them evenly;

[0029] (2) Add water and stir for 4-5 minutes;

[0030] (3) The freshly mixed concrete is molded and cured to obtain self-waterproof and carbon-reducing recycled concrete.

[0031] Example 1

[0032] Preparation method of self-waterproof carbon-reducing recycled concrete

[0033] (1) Weigh 205 g of water, 334 g of cement, 562 g of fine aggregate, 312 g of virgin coarse aggregate, 729 g of recycled coarse aggregate, 67 g of fly ash, 45 g of metakaolin, 20.82 g of epoxy resin, 3.47 g of diluent, 5.21 g of curing agent, and 3.12 g of toughening agent.

[0034] (2) Mix the original coarse aggregate with the recycled coarse aggregate, add epoxy resin, diluent, curing agent and toughening agent and then mix to obtain coarse aggregate coated with a composite anti-seepage agent.

[0035] (3) Add the coarse aggregate wrapped with the composite anti-seepage agent, cement, fine aggregate, metakaolin and fly ash in sequence and mix them evenly.

[0036] (4) Add water and stir for 4-5 minutes, then perform formwork and curing to obtain self-waterproof carbon-reducing recycled concrete.

[0037] Preferably, the fine aggregate is zone 2 medium sand with good particle gradation, and the cement is P·O 42.5 cement.

[0038] When filling the mold, clean the mold to make it neat and free of foreign matter, moisten the mold and ensure that there is no water accumulation on the surface, and apply a release agent inside the mold; load the concrete into the mold in three layers, and vibrate each layer to ensure that the concrete is naturally solid and evenly dense after vibration; the vibration should be straight up and down, with fast insertion and slow withdrawal layer by layer, and the surface should be filled with slurry.

[0039] Before curing, clean the curing box and check the water level in the humidifier to ensure the temperature is 20±2°C and the relative humidity is greater than 95% to ensure proper operation of the curing box. After the concrete formwork is complete, place it in the curing box and remove it from the formwork after 24 hours before continuing with curing.

[0040] Example 2

[0041] Compressive resistance test of self-waterproof carbon-reducing recycled concrete

[0042] 1. Experimental Design

[0043] According to the mix proportions in Table 1, control groups A1 and A2 were designed without adding metakaolin and fly ash. The coarse aggregate of A1 was all virgin coarse aggregate, and the coarse aggregate of A2 was all recycled coarse aggregate. The experimental groups were designed to replace part of the cement with fly ash and metakaolin, and the coarse aggregate was a combination of virgin coarse aggregate and recycled coarse aggregate. In experimental groups B1, B2, and B3, fly ash accounted for 10%, 15%, and 20% of the total amount of cement, fly ash, and metakaolin, respectively, and the ratio of virgin coarse aggregate to recycled coarse aggregate was 1:9. In experimental groups C1 and C2, virgin coarse aggregate accounted for 20% and 30% of the coarse aggregate, respectively, and the ratio of virgin coarse aggregate to recycled coarse aggregate was 2:8 and 3:7, respectively, and fly ash accounted for 15% of the total amount of cement, fly ash, and metakaolin. The water-cement ratio of both the control and experimental groups was 0.46, and the sand content was 35%.

[0044] Table 1 Experimental mix ratios of various concrete

[0045] project Water / g Cement / g Fine aggregate / g Primary coarse aggregate / g Recycled coarse aggregate / g Fly ash / g Metakaolin / g Group A1 205 446 577 1068 0 0 0 Group A2 205 446 562 0 1041 0 0 Group B1 205 357 562 104 937 45 45 Group B2 205 334 562 104 937 67 45 Group B3 205 312 562 104 937 89 45 Group C1 205 334 562 208 833 67 45 Group C2 205 334 562 312 729 67 45

[0046] Using the above-mentioned method for preparing self-waterproof recycled concrete, concrete was prepared according to the raw materials in different proportions of 1, and was respectively loaded into molds of 100 mm×100 mm×100 mm for curing, and then the compressive strength was tested.

[0047] Take a concrete block that has been cured for 7 days, and use the sides when it was formed as the upper and lower pressure-bearing surfaces to measure the area of ​​the upper pressure-bearing surface. The test instrument is a DYE-2000 electro-hydraulic pressure testing machine. Place the block in the center of the test machine's pressure plate, adjust the upper pressure plate to touch the block's upper pressure-bearing surface, start the instrument, and when the force value no longer increases, it means the block has been destroyed. Record the failure load and turn off the instrument. The compressive strength is calculated according to the following formula:

[0048] P=F / S×0.95

[0049] P--compressive strength of concrete test blocks, MPa

[0050] F--Failure load when the block is crushed, N

[0051] S--Bearing surface area of ​​the block, mm 2

[0052] The conversion factor for 100mm×100mm×100mm specimen is 0.95.

[0053] 2. Experimental results

[0054] The compressive strength of each block under different mix ratios after curing for 7 days is shown in Table 2.

[0055] Table 2 Compressive strength of concrete under different mix ratios

[0056]

[0057] It can be seen from Table 2 that under the experimental mix ratios of 10%, 15% and 20% fly ash, the fly ash content of 15% can play its maximum role in ensuring the strength of concrete; the proportion of different primary coarse aggregates will affect the strength of recycled concrete. When the primary coarse aggregate accounts for 30% of the coarse aggregate, the strength of recycled concrete is greatly improved. It is expected that the concrete strength can reach 30 MPa after 28 days of curing.

[0058] Example 3

[0059] Test of impermeability of self-waterproof carbon-reducing recycled concrete

[0060] Self-waterproof carbon-reduced recycled concrete was prepared according to the mix ratio of Group C2 in Table 1. Concrete specimens that had been cured for 28 days were subjected to an anti-permeability test using an HS-4 concrete permeameter to observe whether there was water seepage on the end face. After normal operation, the concrete was pressurized at 0.1 MPa every 8 hours. The formula for calculating the concrete anti-permeability grade is as follows:

[0061] P=10H-1

[0062] P——Concrete impermeability grade

[0063] H——water pressure when 3 out of 6 specimens are leaking, MPa

[0064] The water permeability of the specimens (no water seepage "×", water seepage "○") is shown in Table 3.

[0065] Table 3 Impermeability of self-waterproof carbon-reducing recycled concrete

[0066] Pressurization time Water pressure H (MPa) 1 2 3 4 5 6 June 28, 14:30 0.2 × × × × × × June 28, 22:30 0.3 × × × × × × June 29, 6:30 0.4 × × × × × × June 29, 14:30 0.5 × × × × × × June 29, 22:30 0.6 × × × × × × June 30, 6:30 0.7 × × × × × × June 30, 14:30 0.8 × × × × × × June 30, 22:30 0.9 × × × × × × July 1, 6:30 1.0 × × × × × × July 1, 14:30 1.1 × × × × × × July 1, 22:30 1.2 × × × × × × July 2, 6:30 1.3 × × × × × × July 2nd 14:30 1.4 × × × × × × July 2nd 22:30 1.5 × × × × × × July 3, 6:30 1.6 × × × × × × July 3rd 14:30 1.7 × × × × × × July 3, 22:30 1.8 × × × × × × July 4, 6:30 1.9 × × × × × × July 4th 14:30 2.0 × × × × × × July 4, 22:30 2.1 × × × × × × July 5, 6:30 2.2 × × × × × × July 5, 14:30 2.3 × × × × × × July 5, 22:30 2.4 × × × × × × July 6, 6:30 2.5 × × × × × × July 6th 14:30 2.6 × × × × × × July 6, 22:30 2.7 × × × × × × July 7, 6:30 2.8 × × × × × × July 7, 14:30 2.9 × × × × × × July 7, 22:30 3.0 × × × × × ×

[0067] As can be seen from Table 3, the self-waterproof carbon-reducing recycled concrete provided by the present invention does not have water seepage and has strong anti-seepage performance.

Claims

1. A self-waterproof carbon-reducing recycled concrete, characterized by: It is prepared from the following raw materials in parts by weight: 334 parts cement, 1041 parts coarse aggregate, 562 parts fine aggregate, 205 parts water, 112 parts admixture; The admixture comprises the following raw materials in parts by weight: 45 parts of metakaolin and 67 parts of fly ash; The coarse aggregate is composed of virgin coarse aggregate and recycled coarse aggregate in a mass ratio of 3:7; The coarse aggregate is wrapped by a composite anti-seepage agent, which is prepared by mixing epoxy resin, diluent, curing agent and toughening agent in a weight ratio of 60:10:15:

9. The weight ratio of the coarse aggregate to the epoxy resin is 50:

1.

2. The self-waterproof carbon-reducing recycled concrete according to claim 1, characterized in that: The recycled coarse aggregate is prepared by the following method: waste concrete is crushed to obtain waste concrete particles; the waste concrete particles are collected, cleaned, aired, and sieved to obtain recycled coarse aggregate with a particle size of 5mm-25mm.

3. The method for preparing the self-waterproof carbon-reducing recycled concrete according to claim 2, characterized in that: The following steps are involved: (1) Weigh water, cement, fine aggregate, virgin coarse aggregate, recycled coarse aggregate, fly ash, metakaolin, epoxy resin, diluent, curing agent, and toughening agent in proportion; (2) Mixing the original coarse aggregate with the recycled coarse aggregate, adding epoxy resin, diluent, curing agent and toughening agent and then mixing to obtain the coarse aggregate coated with the composite anti-seepage agent; (3) Add the coarse aggregate coated with the composite anti-seepage agent, cement, fine aggregate, metakaolin, and fly ash in sequence and mix them evenly; (4) Add water and stir for 4-5 minutes, then perform formwork and curing to obtain self-waterproof carbon-reducing recycled concrete.

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