Permeable concrete mix proportion design method based on recycled aggregate stirring abrasion

Abstract

The invention relates to the technical field of pervious concrete, in particular to a pervious concrete mix proportion design method based on recycled aggregate stirring abrasion. The scientific and reasonable design method for the mix proportion of the recycled aggregate pervious concrete is provided by determining the correction coefficient of the recycled coarse aggregate and the influence of the amount of powder generated by abrasion in the stirring process on the performance of the pervious concrete by measuring the breakage rate and combining the characteristics and requirements of the pervious concrete. The mix proportion design method provided by the invention can comprehensively consider the influence of the factors, ensures that the recycled aggregate pervious concrete can meet the engineering requirements in the aspects of strength and water permeability, provides technical support for popularization and application of the recycled aggregate pervious concrete, fills the blank of the mix proportion design method of the recycled aggregate pervious concrete, and has a wide application prospect. Powerful support is provided for resource utilization of the construction waste and improvement of the urban ecological environment.

Description

Technical Field

[0001] The present invention relates to the technical field of permeable concrete, and in particular to a permeable concrete mix ratio design method based on mixing abrasion of recycled aggregate. Background Art

[0002] With the acceleration of urbanization, construction waste is increasing, becoming a pressing issue in urban development. Traditional disposal methods not only occupy significant land resources but also pollute the environment. To promote resource recycling and reduce the negative impact of construction waste on the environment, recycled aggregate permeable concrete has emerged as a new, environmentally friendly material.

[0003] Recycled aggregate permeable concrete utilizes recyclable resources such as concrete blocks and bricks from construction waste. Through advanced crushing and screening technologies, these wastes are refined and transformed into high-quality recycled aggregate as the primary aggregate. This is then carefully formulated using a scientifically formulated mix of cement, water, and other additives to create a special concrete with a continuous void structure. This material not only effectively replaces natural aggregates, reducing the extraction of natural resources, but also, through its exceptional permeability, significantly enhances urban flood control and drainage capabilities, significantly benefiting the urban ecological environment.

[0004] With the growing global demand for green and environmentally friendly building materials, recycled aggregate permeable concrete, a building material that can both reduce construction waste pollution and conserve natural resources, is gaining increasing attention in more and more countries and regions. Especially against the backdrop of accelerating urbanization and continuously upgrading infrastructure construction, the market demand for recycled aggregate permeable concrete will continue to grow. Furthermore, with the continuous advancement of technology and the gradual reduction of costs, the performance of recycled aggregate permeable concrete will continue to improve, and its application areas will further expand. For example, in landscape projects, recycled aggregate permeable concrete can be used to create components such as flower beds and sculptures, achieving resource recycling while adding unique artistic effects. Furthermore, the application of recycled aggregate permeable concrete in special environments, such as marine projects and extremely cold regions, will also be further studied and promoted.

[0005] Recycled aggregates differ significantly from natural aggregates in physical properties, such as lower apparent density, higher water absorption, and higher crushability. These differences complicate the mix design of recycled aggregate permeable concrete. Traditional concrete mix design methods cannot be directly applied to recycled aggregate permeable concrete; specialized research and design tailored to its specific characteristics are required. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a mix ratio design method for recycled aggregate permeable concrete. The design method of the present invention is scientific and reasonable, and the designed recycled aggregate permeable concrete can meet engineering requirements in terms of strength and permeability.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a mix ratio design method for recycled aggregate permeable concrete, comprising the following steps: (1) determining the crushing rate and abrasion rate of recycled coarse aggregate; The method for measuring the crushing rate and the attrition rate comprises the following steps: using a concrete mixer to stir the recycled coarse aggregate for 45 to 60 seconds and then sieving; the particle size of the recycled coarse aggregate is 5 to 10 mm or 10 to 20 mm; When the particle size of the recycled coarse aggregate is 5-10 mm, use 2.36 mm and 4.75 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-4.75 mm is the crushing mass; When the particle size of the recycled coarse aggregate is 10-20 mm, use 2.36 mm and 9.50 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-9.50 mm is the crushing mass; The crushing rate = crushed mass / total mass of recycled coarse aggregate; The wear rate = wear mass / total mass of recycled coarse aggregate; (2) The amount of recycled coarse aggregate is calculated according to formula 1: m g =α·ρ g Formula 1; In formula 1: m g is the amount of recycled coarse aggregate in permeable concrete, kg / m 3 ; ρ g is the compacted packing density of recycled coarse aggregate, kg / m 3 ; α is the correction coefficient for recycled coarse aggregate dosage, which is calculated by linear interpolation based on the crushing rate of recycled coarse aggregate; (3) According to formula 2, we can get 1m 3 Volume of cementitious material paste in permeable concrete: Formula 2; In formula 2: V p 1m 3 Volume of cementitious material paste in permeable concrete, m 3 ; P g The void ratio of tightly packed recycled coarse aggregate, %; β is the wear rate of recycled coarse aggregate, %; ρ p is the density of recycled coarse aggregate wear material, kg / m3 , take 2000kg / m 3 or measured by experiment; P is the designed porosity, %; (4) According to the 1m 3 The volume of cementitious material paste and water-binder ratio in permeable concrete are calculated to obtain 1m 3 The amount of cementitious materials used in permeable concrete; (5) According to the 1m 3 The amount of cementitious materials and water-cement ratio in permeable concrete are calculated to obtain 1m 3 The amount of water used in permeable concrete.

[0008] Preferably, in step (4), the 1m 3 The amount of cementitious material in permeable concrete is calculated according to formula 3: Formula 3; In formula 3: m b 1m 3 Amount of cementitious materials used in permeable concrete, kg; V p 1m 3 Paste volume in permeable concrete, m 3 ; R w / c is the water-binder ratio; ρ b is the density of cementitious material, take 3100kg / m 3 .

[0009] Preferably, in step (5), the 1m 3 The amount of water in permeable concrete is calculated according to formula 4: Formula 4; In formula 4: m w 1m 3 Water consumption in permeable concrete, kg; m b 1m 3 Amount of cementitious materials used in permeable concrete, kg; R w / c is the water-to-cement ratio.

[0010] Preferably, the water-to-binder ratio is 0.26-0.35.

[0011] Preferably, the recycled coarse aggregate is obtained by crushing and screening construction waste; the construction waste includes brick-concrete and / or concrete.

[0012] Preferably, in step (1), the concrete mixer is a forced concrete mixer or a free-fall concrete mixer.

[0013] Preferably, the dense packing density and dense packing porosity of the recycled coarse aggregate are determined according to the dense packing density test method in "Pebbles and Crushed Stones for Construction" GB / T 14685-2022.

[0014] Preferably, after completing step (5), the method further includes: trial mixing, adjustment and determination according to the Technical Specification for Application of Recycled Aggregate Permeable Concrete CJJ / T 253.

[0015] Preferably, the trial mixing further includes: adding one or more of mineral admixtures, admixtures and natural aggregates according to the provisions of "Technical Specifications for Application of Recycled Aggregate Permeable Concrete" CJJ / T253.

[0016] Preferably, the calculation method of the recycled coarse aggregate usage correction coefficient includes: setting the recycled coarse aggregate usage correction coefficient corresponding to a crushing rate of 2% to 0.95, setting the recycled coarse aggregate usage correction coefficient corresponding to a crushing rate of 10% to 1.00, and determining the recycled coarse aggregate usage correction coefficient by linear interpolation method based on the actual measured results of the crushing rate.

[0017] The present invention provides a mix design method for recycled aggregate permeable concrete. There are significant differences in physical properties between recycled aggregate and natural aggregate, such as low apparent density, high water absorption, and large crushing index. In particular, collisions between aggregates during mixing can easily cause the old mortar layer on the surface to break and fall off, while also generating more powder abrasion. These differences make the mix design of recycled aggregate permeable concrete more complex. Traditional concrete mix design methods do not consider the effects of crushing and abrasion of recycled aggregate during premixing. The present invention determines the effects of the correction coefficient of recycled coarse aggregate and the amount of powder generated by abrasion during mixing on the performance of permeable concrete by measuring the crushing rate, and proposes a scientific and reasonable mix design method for recycled aggregate permeable concrete in combination with the characteristics and requirements of permeable concrete. The mix design method provided by the present invention can comprehensively consider the influence of the above factors, ensure that the recycled aggregate permeable concrete can meet engineering requirements in terms of strength and permeability, provide technical support for the promotion and application of recycled aggregate permeable concrete, fill the gap in the mix design method for recycled aggregate permeable concrete, and provide strong support for the resource utilization of construction waste and the improvement of the urban ecological environment.

[0018] The present invention has the following advantages: The correction coefficient of recycled coarse aggregate dosage is determined by measuring the crushing rate of recycled coarse aggregate. At the same time, the slurry volume calculation formula is determined by considering the amount of powder generated by abrasion during the mixing process to ensure the scientificity and rationality of the recycled aggregate permeable concrete mix design method.

[0019] By using construction waste as recycled aggregate, wear powder replaces part of the cement, reducing the amount of cementitious materials used. Recycled aggregate permeable concrete has good permeability and strong bearing capacity, which not only reduces costs but also is beneficial to environmental protection and resource conservation.

[0020] The mix design method of recycled aggregate permeable concrete is an innovation and development based on the traditional concrete mix design. It combines the characteristics of recycled aggregate and the needs of permeable concrete, ensuring that the concrete has sufficient strength and durability while maintaining permeability. It can realize the production and application of recycled permeable concrete more scientifically, promote the advancement of recycled permeable concrete production and application technology, and ensure the quality of permeable concrete projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart for the preparation of recycled aggregate permeable concrete specimens. DETAILED DESCRIPTION

[0022] The present invention provides a mix ratio design method for recycled aggregate permeable concrete, comprising the following steps: (1) determining the crushing rate and abrasion rate of recycled coarse aggregate; The method for measuring the crushing rate and the attrition rate comprises the following steps: using a concrete mixer to stir the recycled coarse aggregate for 45 to 60 seconds and then sieving; the particle size of the recycled coarse aggregate is 5 to 10 mm or 10 to 20 mm; When the particle size of the recycled coarse aggregate is 5-10 mm, use 2.36 mm and 4.75 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-4.75 mm is the crushing mass; When the particle size of the recycled coarse aggregate is 10-20 mm, use 2.36 mm and 9.50 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-9.50 mm is the crushing mass; The crushing rate = crushed mass / total mass of recycled coarse aggregate; The wear rate = wear mass / total mass of recycled coarse aggregate; (2) The amount of recycled coarse aggregate is calculated according to formula 1: m g =α·ρ g Formula 1; In formula 1: m g is the amount of recycled coarse aggregate in permeable concrete, kg / m 3 ; ρ g is the compacted packing density of recycled coarse aggregate, kg / m 3 ; α is the correction coefficient for recycled coarse aggregate dosage, which is calculated by linear interpolation based on the crushing rate of recycled coarse aggregate; (3) According to formula 2, we can get 1m 3 Volume of cementitious material paste in permeable concrete: Formula 2; In formula 2: V p 1m 3 Volume of cementitious material paste in permeable concrete, m 3 ; P g The void ratio of tightly packed recycled coarse aggregate, %; β is the wear rate of recycled coarse aggregate, %; ρ p is the density of recycled coarse aggregate wear material, kg / m 3 , take 2000kg / m 3 or measured by experiment; P is the designed porosity, %; (4) According to the 1m 3 The volume of cementitious material paste and water-binder ratio in permeable concrete are calculated to obtain 1m 3 The amount of cementitious materials used in permeable concrete; (5) According to the 1m 3 The amount of cementitious materials and water-cement ratio in permeable concrete are calculated to obtain 1m 3 The amount of water used in permeable concrete.

[0023] The following is a description of the raw materials.

[0024] In the present invention, the raw materials of the recycled aggregate permeable concrete include recycled coarse aggregate, cement and water, and one or more of mineral admixtures, additives and natural aggregates may be added according to the provisions of the "Technical Specifications for the Application of Recycled Aggregate Permeable Concrete" CJJ / T 253.

[0025] In the present invention, the recycled coarse aggregate is preferably obtained by crushing and screening construction waste; the construction waste preferably includes brick-concrete and / or concrete. In the present invention, the recycled coarse aggregate is preferably classified into a 5-10 mm particle size and a 10-20 mm particle size; the recycled coarse aggregate meets the requirements of GB / T 14685-2022, "Pebbles and Crushed Stone for Construction." In the present invention, the 5-10 mm particle size and the 10-20 mm particle size are classified in accordance with the national standard GB / T 25177, "Recycled Coarse Aggregate for Concrete."

[0026] In the present invention, the cement is preferably P.O42.5 cement, which complies with "General Portland Cement" GB 175-2023.

[0027] In the present invention, the water is preferably tap water, which complies with the "Standard for Water Used in Concrete" JGJ63.

[0028] In the present invention, the admixture complies with the "Concrete Admixtures" GB 8076; the natural aggregate complies with the "Pebbles and Crushed Stones for Construction" GB / T 25177.

[0029] In the present invention, the mineral admixture is preferably one or more of fly ash, granulated blast furnace slag powder and silica fume; the silica fume complies with "Silica Fume for Mortar and Concrete" GB / T 27690, and the granulated blast furnace slag powder complies with "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete" GB / T 18046.

[0030] The following introduces the method for determining the crushing rate and attrition rate of recycled coarse aggregate.

[0031] In the present invention, the method for measuring the crushing rate and the attrition rate comprises the following steps: using a concrete mixer to stir the recycled coarse aggregate for 45 to 60 seconds and then sieving; the particle size of the recycled coarse aggregate is 5 to 10 mm or 10 to 20 mm; When the particle size of the recycled coarse aggregate is 5-10 mm, use 2.36 mm and 4.75 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-4.75 mm is the crushing mass; When the particle size of the recycled coarse aggregate is 10-20 mm, use 2.36 mm and 9.50 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-9.50 mm is the crushing mass; The crushing rate = crushed mass / total mass of recycled coarse aggregate; The wear rate=wear mass / total mass of recycled coarse aggregate.

[0032] In the present invention, the concrete mixer is preferably a forced concrete mixer or a free-fall concrete mixer, more preferably a forced concrete mixer. The present invention utilizes a forced concrete mixer for higher mixing efficiency. In specific embodiments, the mixing time can be 45 seconds, 50 seconds, 55 seconds, or 60 seconds. The present invention does not impose any particular restrictions on the mixing conditions; any mixer that meets concrete mixing standards in the art can be used for mixing.

[0033] After obtaining the crushing rate and attrition rate of the recycled coarse aggregate, the present invention uses the crushing rate and attrition rate to calculate the amount of recycled coarse aggregate and the consumption of 1m 3 The volume of cementitious material paste in permeable concrete.

[0034] In the present invention, the amount of recycled coarse aggregate is calculated according to Formula 1: m g =α·ρ g Formula 1; In formula 1: m g is the amount of recycled coarse aggregate in permeable concrete, kg / m 3 ; ρ g is the compacted packing density of recycled coarse aggregate, kg / m 3 ; α is the correction coefficient for the amount of recycled coarse aggregate, which is calculated by linear interpolation based on the crushing rate of recycled coarse aggregate.

[0035] In the present invention, the dense packing density of the recycled coarse aggregate is g It is preferably determined according to the compact packing density test method in "Pebbles and crushed stones for construction" GB / T14685-2022.

[0036] In the present invention, the method for calculating the recycled coarse aggregate usage correction coefficient preferably includes: setting the recycled coarse aggregate usage correction coefficient corresponding to a crushing rate of 2% to 0.95, setting the recycled coarse aggregate usage correction coefficient corresponding to a crushing rate of 10% to 1.00, and determining the recycled coarse aggregate usage correction coefficient by linear interpolation method based on the actual measured results of the crushing rate.

[0037] After obtaining the amount of recycled coarse aggregate, the present invention calculates the amount of recycled coarse aggregate per m3 according to formula 2. 3 Volume of cementitious material paste in permeable concrete: Formula 2; In formula 2: V p 1m 3 Volume of cementitious material paste in permeable concrete, m 3 ; P g The void ratio of tightly packed recycled coarse aggregate, %; β is the wear rate of recycled coarse aggregate, %; ρ p is the density of recycled coarse aggregate wear material, kg / m 3 , take 2000kg / m 3 or measured by experiment; P is the designed porosity, %; In the present invention, the regenerated coarse aggregate is tightly packed with a void ratio P g It is preferably determined according to the compacted packing density test method in "Pebbles and crushed stone for construction" GB / T 14685-2022.

[0038] In the present invention, the recycled coarse aggregate wear material is based on the collision between particles during stirring, which causes the old mortar on the surface to peel off, and the fine particles below 2.36 mm will become part of the slurry composition. Therefore, its density can be taken as 2000 kg / m3 with reference to the density of cement mortar. 3 The density of cement can be calculated or measured experimentally. When experimental measurement is used, the specific method shall refer to the "Determination of Density of Cement" GB / T 208-2014.

[0039] The invention determines the recycled coarse aggregate dosage correction coefficient by measuring the recycled coarse aggregate crushing rate, and simultaneously determines the slurry volume by considering the amount of powder generated by abrasion during the mixing process, thereby ensuring the scientificity and rationality of the recycled aggregate permeable concrete mix ratio design method.

[0040] Get 1m 3 After the volume of cementitious material paste in permeable concrete is 3 The volume of cementitious material paste and water-binder ratio in permeable concrete are calculated to obtain 1m 3 The amount of cementitious material in permeable concrete is preferably calculated according to formula 3 to obtain 1m 3 Amount of cementitious materials in permeable concrete: Formula 3; In formula 3: m b 1m 3 Amount of cementitious materials used in permeable concrete, kg; V p 1m 3 Paste volume in permeable concrete, m 3 ; R w / c is the water-binder ratio; ρ b is the density of cementitious material, take 3100kg / m 3 .

[0041] In the present invention, the water-to-binder ratio is preferably 0.26-0.35. In specific embodiments, it can be 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34 or 0.35. Those skilled in the art can select within the above range based on experience.

[0042] Get 1m 3 After the amount of cementitious material in permeable concrete, the present invention is based on the 1m 3 The amount of cementitious materials and water-cement ratio in permeable concrete are calculated to obtain 1m 3 The amount of water in permeable concrete is preferably calculated according to formula 4 to obtain 1m 3 The amount of water used in permeable concrete: Formula 4; In formula 4: m w 1m 3 Water consumption in permeable concrete, kg; m b 1m 3 Amount of cementitious materials used in permeable concrete, kg; R w / c is the water-to-cement ratio.

[0043] After obtaining the amount of recycled coarse aggregate, the amount of cementitious material and the amount of water, the present invention preferably further comprises: trial mixing, adjustment and determination according to the "Technical Specification for Application of Recycled Aggregate Permeable Concrete" CJJ / T 253.

[0044] When conducting the trial mix, one or more of mineral admixtures, additives and natural aggregates may be added in accordance with the provisions of the Technical Specification for Application of Recycled Aggregate Permeable Concrete CJJ / T 253.

[0045] Specifically, permeable concrete should be added with mineral admixtures. The types and dosage of mineral admixtures should be determined through trial mixing. The dosage of fly ash should not exceed 30%; the dosage of granulated blast furnace slag powder should not exceed 40%; the dosage of silica fume should not exceed 10%; when two or more mineral admixtures are used at the same time, the total dosage should not exceed 40%.

[0046] Chemical admixtures can be added to permeable concrete as needed, and the dosage should not exceed 2%. The actual dosage is determined through experiments.

[0047] When the strength of permeable concrete does not meet the design requirements, natural aggregate can be added.

[0048] In a specific embodiment of the present invention, the preparation of recycled aggregate permeable concrete specimens is as follows: Figure 1 As shown, the following steps are included: (1) Pour the recycled coarse aggregate (including natural aggregate if available) into a mixer, add 50% mixing water and mix for 5 seconds to wet the aggregate surface; (2) Pour 50% of the cement into the mixer and stir for 10 seconds, then add 25% of the mixing water and stir for 10 seconds, and then pour the remaining cement into the mixer and stir; (3) Pour the remaining mixing water and water reducer (if any) into the mixer in sequence, mix and stir for 20 seconds, and stop stirring when the mixture can be lumped together. (4) The specimen was cast in three layers using the ramming method. The thickness of each layer was roughly the same. Ramming was performed evenly and vertically from the edge to the center in a spiral direction for 15 to 20 times. When ramming the bottom layer, the ramming rod should touch the bottom of the test mold. When ramming the upper layer, the ramming rod should be inserted into the lower layer by 20 to 30 mm to obtain the recycled aggregate permeable concrete specimen.

[0049] If mineral admixtures are added, add them together with the cement.

[0050] In the present invention, the trial mixing, adjustment and determination of the permeable concrete mix ratio should specifically comply with the following provisions (i.e., trial mixing, adjustment and determination should be carried out in accordance with the Technical Specification for the Application of Recycled Aggregate Permeable Concrete CJJ / T 253): (1) Carry out trial mixing according to the calculated mix ratio. The slurry and aggregate should be mixed evenly without dripping. The aggregate particles should be well bonded and should not be loose. If the slurry settles too much or cannot evenly cover the aggregate surface, the amount of permeable concrete slurry or water used should be adjusted until a benchmark mix ratio that meets the working performance is obtained.

[0051] (2) For the performance test of permeable concrete, three different mix ratios should be selected, one of which should be the base mix ratio. The water-binder ratio of the other two mix ratios should be increased or decreased by 0.05 compared with the base mix ratio, and the water consumption should be the same as that of the base mix ratio. The strength, porosity and permeability coefficient of the permeable concrete should be measured.

[0052] (3) Use the drawing method or calculation method to calculate the water-cement ratio that meets the porosity and strength requirements of permeable concrete, and determine the cement and water consumption based on this, and finally determine the mix ratio.

[0053] In the present invention, the performance of the recycled aggregate permeable concrete should comply with the provisions of the current industry standard "Technical Specifications for the Application of Recycled Aggregate Permeable Concrete" CJJ / T 253; the mix strength of the permeable concrete shall refer to the provisions of "Ordinary Concrete Mix Design Specifications" JGJ 55.

[0054] The mix ratio design method of recycled aggregate permeable concrete provided by the present invention is described in detail below with reference to the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0055] Example 1. Determination of basic performance indicators of recycled coarse aggregate The results are shown in Table 1; Table 1 Performance indicators of recycled coarse aggregate

[0056] 2. Determination of crushing rate and wear rate of recycled coarse aggregate 5~10mm: stirring time 60s, crushing rate 5.56%, abrasion rate 2.56%, designed porosity 20%; 10~20mm: stirring time 60s, crushing rate 4.68%, abrasion rate 1.75%, designed porosity 20%.

[0057] 3. Mix ratio design of recycled aggregate permeable concrete (taking 5~10mm aggregate without mineral admixture as an example) (1) Determination of coarse aggregate dosage correction coefficient When the crushing rate is 5.56%, the correction coefficient of coarse aggregate dosage is determined to be 0.97 by linear interpolation method.

[0058] (2) Determine the amount of recycled coarse aggregate: m g =α·ρ g =0.97×1319=1279kg / m 3 .

[0059] (3) Determine the volume of cementitious material slurry: ; ; m 3 .

[0060] (4) Determine the water-binder ratio: The water-to-cement ratio is selected as 0.29.

[0061] (5) Determine the amount of cementitious material: The density of cementitious materials is 3100kg / m 3 calculate.

[0062] ; ; kg.

[0063] (6) Determine water consumption: ; ; kg.

[0064] Following the above steps, calculate the mix ratios for 10-20 mm recycled aggregate and 4% silica fume cement replacement for 5-10 mm and 10-20 mm aggregate. The mix ratio design results are shown in Table 2. Compressive strength and permeability coefficient were measured according to the "Concrete Strength Test and Assessment Standard" (GB / T 50107) and the "Technical Specification for Permeable Cement Concrete Pavement" (CJJ / T 135), respectively, and are shown in Table 3.

[0065] Table 2 Mix ratio design

[0066] Table 3 Compressive strength and permeability coefficient

[0067] Control Example The calculation is performed using the permeable cement concrete mix ratio formula in CJJ135-2009 (2023 edition) "Technical Code for Permeable Cement Concrete Pavement", with a correction coefficient of 0.98.

[0068] (1) Determine the amount of coarse aggregate per unit volume: ; ; kg / m 3 .

[0069] (2) Determine the volume of the cementitious slurry: ; ; m 3 .

[0070] (3) Determine the water-binder ratio: The water-to-cement ratio is selected as 0.29.

[0071] (4) Determine the amount of cement per unit volume: The density of cementitious materials is 3100kg / m 3 calculate.

[0072] ; ; kg.

[0073] (5) Determine the water consumption per unit volume: ; ; kg.

[0074] Follow the above steps to calculate the mix ratio for 10-20 mm recycled aggregate and 4% silica fume cement replacement for 5-10 mm and 10-20 mm aggregate. The mix ratio design results are shown in Table 4, and the compressive strength and permeability coefficient results are shown in Table 5.

[0075] Table 4 Mix ratio design

[0076] Table 5 Compressive strength and water permeability

[0077] The results of the examples and the control examples are compared in Table 6.

[0078] Table 6 Comparison of compressive strength and water permeability coefficient

[0079] As shown in Table 6, the compressive strength and permeability coefficient of recycled aggregate permeable concrete using a specific mix design are comparable to those of the control example. In fact, most examples even exceed the compressive strength and permeability coefficient of the control example. This shows that compared with traditional permeable concrete mix design, the mix design of recycled aggregate permeable concrete has significant advantages. It not only reduces the amount of cement used, but also significantly improves the strength and permeability of the permeable concrete.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A mix design method for recycled aggregate permeable concrete, characterized in that: The following steps are involved: (1) Determine the crushing rate and wear rate of recycled coarse aggregate; The method for measuring the crushing rate and the attrition rate comprises the following steps: using a concrete mixer to stir the recycled coarse aggregate for 45 to 60 seconds and then sieving; the particle size of the recycled coarse aggregate is 5 to 10 mm or 10 to 20 mm; When the particle size of the recycled coarse aggregate is 5-10 mm, use 2.36 mm and 4.75 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-4.75 mm is the crushing mass; When the particle size of the recycled coarse aggregate is 10-20 mm, use 2.36 mm and 9.50 mm square hole sieves for screening, and weigh the sieve residue of each sieve; wherein, <2.36 mm is the abrasion mass, and 2.36-9.50 mm is the crushing mass; The crushing rate = crushed mass / total mass of recycled coarse aggregate; The wear rate = wear mass / total mass of recycled coarse aggregate; (2) The amount of recycled coarse aggregate is calculated according to formula 1: m g =a·r g formula 1; In formula 1: m g is the amount of recycled coarse aggregate in permeable concrete, kg / m 3 ; ρ g is the compacted packing density of recycled coarse aggregate, kg / m 3 ; α is the correction coefficient for recycled coarse aggregate dosage, which is calculated by linear interpolation based on the crushing rate of recycled coarse aggregate; (3) According to formula 2, we can get 1m 3 Volume of cementitious material paste in permeable concrete: Formula 2; In formula 2: V p 1m 3 Volume of cementitious material paste in permeable concrete, m 3 ; P g The void ratio of tightly packed recycled coarse aggregate, %; β is the wear rate of recycled coarse aggregate, %; ρ p is the density of recycled coarse aggregate wear material, kg / m 3 , take 2000kg / m 3 or measured by experiment; P is the designed porosity, %; (4) According to the 1m 3 The volume of cementitious material paste and water-binder ratio in permeable concrete are calculated to obtain 1m 3 The amount of cementitious materials used in permeable concrete; (5) According to the 1m 3 The amount of cementitious materials and water-cement ratio in permeable concrete are calculated to obtain 1m 3 The amount of water used in permeable concrete.

2. The mix design method according to claim 1, wherein: In step (4), the 1m 3 The amount of cementitious material in permeable concrete is calculated according to formula 3: Formula 3; In formula 3: m b 1m 3 Amount of cementitious materials used in permeable concrete, kg; V p 1m 3 Paste volume in permeable concrete, m 3 ; R w / c is the water-binder ratio; ρ b is the density of cementitious material, take 3100kg / m 3 .

3. The mix design method according to claim 1, wherein: In step (5), the 1m 3 The amount of water in permeable concrete is calculated according to formula 4: Formula 4; In formula 4: m w 1m 3 Water consumption in permeable concrete, kg; m b 1m 3 Amount of cementitious materials used in permeable concrete, kg; R w / c is the water-to-cement ratio.

4. The mix design method according to claim 1, wherein: The water-to-binder ratio is 0.26-0.

35.

5. The mix design method according to claim 1, wherein: The recycled coarse aggregate is obtained by crushing and screening construction waste; the construction waste includes brick-concrete and / or concrete.

6. The mix design method according to claim 1 or 5, characterized in that: In step (1), the concrete mixer is a forced concrete mixer or a self-falling concrete mixer.

7. The mix design method according to claim 1, wherein: The compact packing density and compact packing porosity of the recycled coarse aggregate are determined according to the compact packing density test method in "Pebbles and Crushed Stones for Construction" GB / T 14685-2022.

8. The mix design method according to claim 1, wherein: After completing step (5), the process also includes: trial mixing, adjustment and confirmation according to the Technical Specification for Application of Recycled Aggregate Permeable Concrete CJJ / T 253.

9. The mix design method according to claim 8, characterized in that: The trial mixing also includes: adding one or more of mineral admixtures, admixtures and natural aggregates according to the provisions of "Technical Specifications for Application of Recycled Aggregate Permeable Concrete" CJJ / T 253.

10. The mix design method according to claim 1, wherein: The calculation method of the recycled coarse aggregate usage correction coefficient includes: setting the recycled coarse aggregate usage correction coefficient corresponding to a crushing rate of 2% to 0.95, setting the recycled coarse aggregate usage correction coefficient corresponding to a crushing rate of 10% to 1.00, and determining the recycled coarse aggregate usage correction coefficient by linear interpolation method based on the actual measurement results of the crushing rate.

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