Low-carbon regenerated cement-based pervious concrete and preparation method thereof

Abstract

The invention relates to a low-carbon regenerated cement-based pervious concrete and a preparation method thereof, and belongs to the technical field of concrete.The low-carbon regenerated cement-based pervious concrete is prepared from, by weight, 220-260 parts of cement, 0-80 parts of regenerated micro powder, 900-1100 parts of aggregate, 110-130 parts of water, 90-110 parts of slag and 5-10 parts of a water reducing agent; the aggregate comprises at least one of recycled aggregate and natural aggregate. Waste concrete blocks are effectively treated, CO2 emission is reduced, cyclic utilization of resources is achieved, accumulation of building waste is reduced, the production cost is reduced, the environmental protection performance of the pervious concrete is improved, and low-carbon and sustainable city construction is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to a low-carbon recycled cement-based permeable concrete and a preparation method thereof. Background Art

[0002] With the acceleration of urbanization, the widespread use of impermeable materials such as cement and asphalt has led to a sharp increase in the hardening rate of urban surfaces. This has severely hindered the natural infiltration of rainwater, increased pressure on stormwater pipe networks, and triggered a series of ecological and environmental problems, such as frequent urban flooding, insufficient groundwater recharge, an intensified urban heat island effect, and water pollution. Permeable concrete, a functional building material with interconnected pores, effectively promotes rapid rainwater infiltration. It plays a vital role in alleviating these problems, building sponge cities, and improving water circulation. It has become a key material in the construction of modern green infrastructure.

[0003] At the same time, recycling discarded concrete blocks and using recycled cement and aggregate in concrete not only achieves resource recycling but also significantly reduces energy consumption and emissions. Research has shown that recycled aggregates, due to their porous, rough, and irregular shapes, contribute to the formation of more developed pore channels when used in permeable concrete, potentially achieving superior permeability compared to natural aggregates.

[0004] However, the resource utilization of fine powder generated during the crushing of waste concrete faces even greater challenges. Recycled micropowder, primarily composed of incompletely hydrated cement particles, hydration products, and stone dust, is significantly less active than ordinary Portland cement. Directly replacing cement in concrete can easily lead to insufficient hydration activity, increased water storage, and a loose internal concrete structure. Therefore, ensuring the high permeability, sufficient strength, and excellent durability required of permeable concrete is a pressing technical challenge. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-carbon recycled cement-based permeable concrete and a preparation method thereof, which solves the key technical problems that the low activity of recycled micropowder from waste concrete leads to insufficient mechanical strength and durability of permeable concrete, and the low resource utilization rate of waste concrete restricts the low-carbon and environmentally friendly performance of permeable concrete.

[0006] On the one hand, the present invention provides a low-carbon recycled cement-based permeable concrete, which adopts the following technical solution:

[0007] A low-carbon recycled cement-based permeable concrete comprising the following raw materials in parts by weight:

[0008] 220-260 parts of cement, 0-80 parts of recycled micro powder, 900-1100 parts of aggregate, 110-130 parts of water, 90-110 parts of slag, 5-10 parts of water reducer;

[0009] The aggregate includes at least one of recycled aggregate and natural aggregate.

[0010] Preferably, the particle size of the aggregate is 3-20 mm;

[0011] The mass ratio of the aggregate with a particle size of 3-5 mm, the aggregate with a particle size of 6-10 mm, and the aggregate with a particle size of 11-20 mm is 1: (1.8-2.4): 1.2.

[0012] Preferably, the recycled aggregate comprises the following preparation steps:

[0013] The recycled aggregate comprises the following preparation steps:

[0014] S1, taking waste concrete and placing it in a screening device to remove impurities;

[0015] S2. The waste concrete treated in step S1 is placed in a crusher for crushing to obtain concrete particles, and the concrete particles are placed in a screening device for screening to obtain aggregate particles with particle sizes of 3-5 mm, 6-10 mm, and 11-20 mm, respectively;

[0016] S3. The aggregate particles obtained in step S2 are placed in a cleaning device, rinsed, and then compounded to obtain recycled aggregate.

[0017] Preferably, the regenerated micropowder comprises the following preparation steps:

[0018] S1, taking waste concrete and placing it in a screening device to remove impurities;

[0019] S2, placing the waste concrete processed in step S1 in a crusher for crushing to obtain concrete particles, and grinding the concrete particles in a grinder to obtain concrete powder with a particle size ranging from 1 to 100 μm;

[0020] S3, removing metal impurities from the concrete powder obtained in step S2, and then placing it in a screening device to remove particles with a particle size greater than 100 μm;

[0021] S4. The concrete powder processed in step S3 is placed in a high-temperature furnace for calcination, cooled and ground to obtain regenerated micropowder with a particle size ranging from 1 to 100 μm.

[0022] Preferably, the calcination temperature in step S4 is 1000°C.

[0023] Preferably, the water reducer is a polycarboxylic acid water reducer.

[0024] Preferably, the slag is S95 grade high-grade slag.

[0025] On the other hand, the present invention also provides a method for preparing the above-mentioned low-carbon recycled cement-based permeable concrete, which adopts the following technical solution:

[0026] A method for preparing low-carbon recycled cement-based permeable concrete comprises the following steps:

[0027] S1. Add aggregate and 10% of the total water into a mixer and stir for 20-30 seconds to obtain a first mixture;

[0028] S2. Add recycled micropowder, slag, cement, and water reducer to the first mixture prepared in step S1, and stir for 20-30 seconds to obtain a second mixture;

[0029] S3. Add the remaining water to the second mixture prepared in step S2, stir for 1 minute, and obtain concrete slurry; inject the prepared concrete slurry into a mold, cure at room temperature for 24 hours, and continue curing after demolding to finally obtain low-carbon recycled cement-based permeable concrete.

[0030] In summary, the present invention has the following beneficial technical effects:

[0031] 1. The present invention includes cement, recycled micropowder, aggregate, water, slag and water reducing agent. Since the activity of recycled micropowder is relatively low, slag is added to improve its hydration characteristics; aggregate usually has a certain rough surface and irregular shape, which helps to form more tiny pores and enhance the water permeability of concrete.

[0032] 2. The combined use of recycled micropowder, recycled aggregate and slag can enhance the hydration capacity and chemical corrosion resistance of concrete, improve the long-term stability and durability of permeable concrete. Under the influence of climate change, recycled cement-based permeable concrete has better frost resistance, sulfate corrosion resistance and other properties, which can extend its service life. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0034] Preparation Example

[0035] Preparation Example 1

[0036] The preparation steps of recycled aggregate are as follows:

[0037] 1) Take the waste concrete and place it in the screening equipment to remove impurities such as steel bars, wood, bricks, and plastic;

[0038] 2) placing the waste concrete treated in step 1) in a crusher for crushing to obtain concrete particles, placing the concrete particles in a screening device for screening to obtain aggregate particles with particle sizes of 3-5 mm, 6-10 mm, and 11-20 mm, respectively;

[0039] 3) The aggregate particles obtained in step 2) are placed in a cleaning device, rinsed, and then mixed with aggregate particles with a particle size of 3-5 mm, aggregate particles with a particle size of 6-10 mm, and aggregate particles with a particle size of 11-20 mm in a mass ratio of 1:1.8:1.2 to obtain recycled aggregate.

[0040] Preparation Example 2

[0041] The preparation steps of the recycled aggregate are different from those of Preparation Example 1, except that in step 3), aggregate particles with a particle size of 3-5 mm, aggregate particles with a particle size of 6-10 mm, and aggregate particles with a particle size of 11-20 mm are mixed in a mass ratio of 1:2.4:1.2, and the remaining steps are the same as those of Preparation Example 1.

[0042] Preparation Example 3

[0043] 1) Take the waste concrete and place it in the screening equipment to remove impurities such as steel bars, wood, bricks, and plastic;

[0044] 2) crushing the waste concrete treated in step 1) in a crusher to obtain concrete particles, and grinding the concrete particles in a grinder to obtain concrete powder;

[0045] 3) removing metal impurities from the concrete powder obtained in step 2) by magnetic separation or manual sorting, and then placing the concrete powder in a screening device to remove overly coarse or overly fine particles;

[0046] 4) The concrete powder treated in step 3) is placed in a high-temperature furnace and calcined at 1000° C., and after cooling, cement clinker is obtained, which is ground to obtain recycled fine powder.

[0047] Example

[0048] Example 1

[0049] A method for preparing low-carbon recycled cement-based permeable concrete comprises the following steps:

[0050] 1) Add 100 kg of the recycled aggregate prepared in Preparation Example 1 and 12 kg of water into a mixer and stir for 20-30 seconds to obtain a first mixture;

[0051] 2) Add 60 kg of the recycled micropowder prepared in Preparation Example 3, 120 kg of slag, 240 kg of cement, and 6 kg of a polycarboxylic acid-based water reducer to the first mixture prepared in step 1), and stir for 20-30 seconds to obtain a second mixture;

[0052] The slag is S95 grade blast furnace slag that meets all the indicators of "Granulated blast furnace slag powder for cement, mortar and concrete" (GB / T1596-2017);

[0053] 3) adding 108 kg of water to the second mixture prepared in step 2) and stirring for 1 minute to obtain a concrete slurry; injecting the prepared concrete slurry into a mold, curing at room temperature for 24 hours, and after demolding, curing in a standard curing room at a temperature of 20±2° C. and a relative humidity greater than 95% for 28 days to obtain a low-carbon recycled cement-based permeable concrete.

[0054] Example 2

[0055] A method for preparing low-carbon recycled cement-based permeable concrete, which differs from Example 1 in that the recycled aggregate in step 1) is replaced by an equal weight portion of recycled aggregate prepared in Preparation Example 2, and the remaining steps are the same as in Example 1.

[0056] Example 3

[0057] A method for preparing low-carbon recycled cement-based permeable concrete, which differs from Example 1 in that the recycled aggregate in step 1) is replaced with equal parts by weight of natural aggregate, and the natural aggregate is prepared by mixing aggregate with a particle size of 3-5 mm, aggregate with a particle size of 6-10 mm, and aggregate with a particle size of 11-20 mm in a mass ratio of 1:1.8:1.2. The remaining steps are the same as in Example 1.

[0058] Example 4

[0059] A method for preparing low-carbon recycled cement-based permeable concrete, which differs from Example 1 in that the natural aggregate in step 1) is prepared by mixing aggregate with a particle size of 3-5 mm, aggregate with a particle size of 6-10 mm, and aggregate with a particle size of 11-20 mm in a mass ratio of 1:2.4:1.2; the remaining steps are the same as in Example 1.

[0060] Example 5

[0061] A method for preparing low-carbon recycled cement-based permeable concrete, which differs from Example 1 in that the mass of cement in step 2) is 300 kg, and no recycled micropowder is added, and the remaining steps are the same as Example 1.

[0062] Example 6

[0063] A method for preparing low-carbon recycled cement-based permeable concrete, which is different from Example 2 in that the mass of cement in step 2) is 300 kg, and no recycled micropowder is added. The remaining steps are the same as Example 2.

[0064] Example 7

[0065] A method for preparing low-carbon recycled cement-based permeable concrete, which differs from Example 5 in that the recycled aggregate in step 1) is replaced with equal parts by weight of natural aggregate, and the natural aggregate is prepared by mixing aggregate with a particle size of 3-5 mm, aggregate with a particle size of 6-10 mm, and aggregate with a particle size of 11-20 mm in a mass ratio of 1:1.8:1.2. The remaining steps are the same as in Example 5.

[0066] Example 8

[0067] A method for preparing low-carbon recycled cement-based permeable concrete, which differs from Example 7 in that the natural aggregate in step 1) is prepared by mixing aggregate with a particle size of 3-5 mm, aggregate with a particle size of 6-10 mm, and aggregate with a particle size of 11-20 mm in a mass ratio of 1:2.4:1.2. The remaining steps are the same as in Example 7.

[0068] Comparative Example 1

[0069] A method for preparing low-carbon recycled cement-based permeable concrete. The difference from Example 1 is that no cement is added, the mass of the recycled micropowder is 300 kg, and the remaining steps are the same as those in Example 1.

[0070] Comparative Example 2

[0071] A method for preparing low-carbon recycled cement-based permeable concrete. The difference from Example 2 is that no cement is added, the mass of the recycled micropowder is 300 kg, and the remaining steps are the same as Example 2.

[0072] Comparative Example 3

[0073] A method for preparing low-carbon recycled cement-based permeable concrete, which is different from Example 3 in that the amount of water added is 120 kg, the amount of slag added is 100 kg, and the remaining steps are the same as Example 3.

[0074] Comparative Example 4

[0075] A method for preparing low-carbon recycled cement-based permeable concrete. Unlike Comparative Example 3, the natural aggregate is prepared by mixing aggregate with a particle size of 3-5 mm, aggregate with a particle size of 6-10 mm, and aggregate with a particle size of 11-20 mm in a mass ratio of 1:2.4:1.2. The remaining steps are the same as those in Comparative Example 3.

[0076] Performance testing

[0077] Test Method

[0078] According to CJJ / T 135-2009, "Technical Specification for Permeable Cement Concrete Pavements," permeable concrete specimens with a diameter of 100 mm and a height of 50 mm were prepared according to the methods of Examples 1-8 and Comparative Examples 1-4, respectively. The sides of the specimens were wrapped with sealing materials such as water-stopping tape or transparent film to prevent water from passing only through the upper and lower surfaces of the specimens. The specimens were placed on a constant head device and evacuated with a vacuum pump for 2-5 minutes. After removal, the specimens were quickly immersed in (20±2)°C water, with the top surface of the specimen approximately 20 mm above the water surface. After immersion for (24±0.25) hours, the specimens were removed, any surface water was wiped off, and the specimens were quickly mounted on the permeable device for testing. Water at (20±2)°C was poured into a water storage cylinder. When the water level in the cylinder rose to the overflow port, the overflowing water was collected in a small beaker and discarded to eliminate any bubbles in the device. Immediately fill the water storage cylinder to the specified level. Start a stopwatch and record the time. Measure the water volume in the cylinder every 30 seconds for three consecutive readings. Calculate the water permeability coefficient using Darcy's law. Take the average of the three test results as the water permeability coefficient for the specimen.

[0079] In accordance with GB / T 50081-2019, "Test Methods for Physical and Mechanical Properties of Concrete," permeable concrete cubes with a side length of 100 mm were prepared according to the methods of Examples 1-8 and Comparative Examples 1-4. These cubes were placed on the loading platform of a universal testing machine and subjected to uniaxial compression tests at a loading rate of 0.5 MPa / s. Three tests were performed, and the average value was taken as the compressive strength of the permeable concrete.

[0080] According to JC / T 2558-2020 "Permeable Concrete", permeable concrete cube specimens with a side length of 100 mm were prepared according to the methods of Examples 1-8 and Comparative Examples 1-4, the surface was wiped dry, and the appearance inspection and initial mass and relative dynamic elastic modulus were measured. After the measurement, the specimen was placed in a freezer and frozen at (-15±2)°C for 4 hours. Then it was taken out and placed in a thawing water tank and thawed in water at (20±2)°C. 4 hours was a freeze-thaw cycle, and a total of 25 freeze-thaw cycles were performed. During the test, the appearance changes of the specimens were observed, and the mass loss rate and relative dynamic elastic modulus decrease rate of the specimens were measured to evaluate the frost resistance of the permeable concrete.

[0081] The low-carbon recycled cement-based permeable concrete prepared by Examples 1-8 and Comparative Examples 1-4 were respectively subjected to permeability coefficient performance tests, compressive strength tests, and frost resistance tests. The test results are shown in Table 1.

[0082] Table 1 Performance test results of a low-carbon recycled cement-based permeable concrete

[0083] Group 28d compressive strength (MPa) 28d splitting strength (MPa) KS120 compression / flexural and corrosion resistance coefficient <![CDATA[Coefficient of permeability (cm·s -1 )]]> Strength / mass loss rate after 25 freeze-thaw cycles Grinding pit length (mm) Example 1 14 3.2 1.08 / 1.11 4.9 19% / 4% 29 Example 2 15 3.2 1.09 / 1.13 5.1 20%5% 27 Example 3 20 4.3 1.15 / 1.11 4.1 16% / 3.3% 21 Example 4 22 4.3 1.16 / 1.13 4.2 17% / 3.45% 19 Example 5 15 3.2 1.11 / 1.03 5.7 20% / 5% 26 Example 6 16 3.3 1.14 / 1.09 5.8 20% / 5% 25 Example 7 22 4.1 1.17 / 1.12 4.5 18% / 4% 20 Example 8 23 4.2 1.20 / 1.16 4.6 17% / 5% 18 Comparative Example 1 10 3 1.21 / 1.11 5.4 16%4% 30 Comparative Example 2 12 3 1.22 / 1.13 5.5 16%5% 28 Comparative Example 3 24 4.4 1.00 / 0.99 4 21% / 5% 20 Comparative Example 4 24 4.4 1.03 / 1.00 4.1 21% / 6% 17

[0084] According to the test results shown in Table 1, the water permeability coefficient of Example 1-2 is higher than that of Example 3-4. The recycled aggregate is porous and has a rough surface, so its water permeability is better than that of the natural aggregate. When no recycled micropowder is added, the water permeability is further improved because the pore filling effect of the recycled micropowder is weakened; the compressive strength and splitting strength of Example 3-4 are significantly higher than those of Example 1-2. The strength of the natural aggregate is higher than that of the recycled aggregate, and the strength of Example 1-2 is lower than that of Examples 5-6. Recycled micropowder replacing cement will reduce the strength. The strength of Comparative Example 1-2 is only 10-12 MPa, indicating that the activity of the recycled micropowder is lower than that of cement; the freeze-thaw loss rate of Example 3-4 is lower than that of Example 1-2, indicating that the slag and cement synergistically improve the frost resistance and corrosion resistance. The freeze-thaw loss rate of the natural aggregate group is lower than that of the recycled aggregate group, and the corrosion resistance coefficient is greater than 1, reflecting the chemical corrosion resistance of the slag.

[0085] The above are all preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low-carbon recycled cement-based permeable concrete, characterized in that: The raw materials include the following parts by weight: 220-260 parts of cement, 0-80 parts of recycled micro powder, 900-1100 parts of aggregate, 110-130 parts of water, 90-110 parts of slag, and 5-10 parts of water reducer; The aggregate includes at least one of recycled aggregate and natural aggregate.

2. The low-carbon recycled cement-based permeable concrete according to claim 1, characterized in that: The particle size of the aggregate is 3-20 mm; The mass ratio of the aggregate with a particle size of 3-5 mm, the aggregate with a particle size of 6-10 mm, and the aggregate with a particle size of 11-20 mm is 1:(1.8-2.4):1.

2.

3. The low-carbon recycled cement-based permeable concrete according to claim 2, characterized in that: The recycled aggregate comprises the following preparation steps: S1, taking waste concrete and placing it in a screening device to remove impurities; S2. The waste concrete treated in step S1 is placed in a crusher for crushing to obtain concrete particles, and the concrete particles are placed in a screening device for screening to obtain aggregate particles with particle sizes of 3-5 mm, 6-10 mm, and 11-20 mm, respectively; S3. The aggregate particles obtained in step S2 are placed in a cleaning device, rinsed, and then compounded to obtain recycled aggregate.

4. The low-carbon recycled cement-based permeable concrete according to claim 1, characterized in that: The regenerated micropowder comprises the following preparation steps: S1, taking waste concrete and placing it in a screening device to remove impurities; S2, placing the waste concrete processed in step S1 in a crusher for crushing to obtain concrete particles, and grinding the concrete particles in a grinder to obtain concrete powder with a particle size ranging from 1 to 100 μm; S3, removing metal impurities from the concrete powder obtained in step S2, and then placing it in a screening device to remove particles with a particle size greater than 100 μm; S4. The concrete powder processed in step S3 is placed in a high-temperature furnace for calcination, cooled and ground to obtain regenerated micropowder with a particle size ranging from 1 to 100 μm.

5. The low-carbon recycled cement-based permeable concrete according to claim 4, characterized in that: The calcination temperature in step S4 is 1000°C.

6. The low-carbon recycled cement-based permeable concrete according to claim 1, characterized in that: The water reducer is a polycarboxylic acid water reducer.

7. The low-carbon recycled cement-based permeable concrete according to claim 1, characterized in that: The slag is S95 grade high-grade slag.

8. A method for preparing a low-carbon recycled cement-based permeable concrete according to any one of claims 1 to 7, characterized in that: The method comprises the following preparation steps: S1. Add aggregate and 10% of the total water into a mixer and stir for 20-30 seconds to obtain a first mixture; S2. Add recycled micropowder, slag, cement, and water reducer to the first mixture prepared in step S1, and stir for 20-30 seconds to obtain a second mixture; S3. Add the remaining water to the second mixture prepared in step S2, stir for 1 minute, and obtain concrete slurry; inject the prepared concrete slurry into a mold, cure at room temperature for 24 hours, and continue curing after demolding to finally obtain low-carbon recycled cement-based permeable concrete.