A new type of recycled aggregate permeable concrete and its performance prediction method

Abstract

The present invention belongs to the technical field of recycled aggregate concrete, and discloses a novel recycled aggregate permeable concrete and a performance prediction method thereof. The I‑RAPC may be provided with 1 hole, 4 holes, 5 holes or 9 holes, and the distribution forms of the center, the middle of the edge and the corner. Compared with ordinary recycled permeable concrete, the I‑RAPC of the present invention has significant advantages in both strength and permeability, with high compressive strength, large permeability coefficient and more stable permeability. Starting from the compressive strength of single-hole I‑RAPC, the present invention determines the theoretical model of the compressive strength of multi-hole I‑RAPC, and at the same time analyzes the theoretical calculation formula of the permeability coefficient of I‑RAPC with the help of hydraulic methods, clarifies the correlation between the strength, permeability and pore characteristics of I‑RAPC, and verifies through experiments, providing scientific and effective theoretical support for the innovative development and broadening of applications of I‑RAPC.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycled aggregate concrete, and in particular relates to a novel recycled aggregate pervious concrete (Innovative Recycled Aggregate Pervious Concrete, hereinafter referred to as I-RAPC) and a performance prediction method thereof. Background Art

[0002] At present, the resource utilization of construction waste is one of the goals of environmental protection and sustainable development. After continuous research in recent years, the research on technologies such as recycled aggregate concrete (RAC) and recycled aggregate permeable concrete (RAPC) has become increasingly perfect. However, the existing recycled aggregate concrete and recycled aggregate permeable concrete still have problems such as low strength and unstable permeability coefficient.

[0003] At present, there are few studies on the new type of recycled aggregate permeable concrete (I-RAPC). For example, prior art 1 applies this I-RAPC to different rainstorm levels, and uses the permeability coefficient to establish the relationship between pores and rainstorm levels, providing a basis for the design of permeable concrete pavement. Prior art 2 artificially creates regular pores connected up and down in concrete to prepare a high-strength permeable concrete (HSPC) pavement, whose 7-day compressive strength can reach 61.37MPa, and the corresponding permeability coefficient is 13.02mm / s, and a drainage system is designed to effectively remove the blocked dust in the pores of the HSPC pavement. This innovative high-strength permeable concrete has a wider application potential. The strength performance and permeability performance of I-RAPC are determined by the characteristic parameters of the pores (such as quantity, diameter, material, and position), and there is also a certain connection between the two. However, the prior art does not have a technology for analyzing and determining the strength performance and permeability performance.

[0004] Through the above analysis, the problems and defects of the prior art are as follows:

[0005] (1) Existing recycled aggregate concrete (RAC) and recycled aggregate permeable concrete (RAPC) have low strength and unstable permeability.

[0006] (2) The prior art does not have the technology to analyze and determine the strength and permeability properties.

[0007] The difficulty of solving the above problems and defects is:

[0008] (1) The preparation process of RAPC is simple, while I-RAPC has higher preparation process requirements (such as hole making component design, hole making and tube embedding methods).

[0009] (2) The analysis and determination of strength and permeability properties requires a large number of experiments and theoretical research (such as the establishment of a theoretical model for performance prediction).

[0010] The significance of solving the above problems and defects is:

[0011] (1) A preparation method of I-RAPC is proposed, which can provide a reference for its subsequent production.

[0012] (2) I-RAPC solves the problems of low strength and unstable permeability of ordinary recycled aggregate permeable concrete and has a broad application prospect.

[0013] (3) The proposed performance analysis determination technology can greatly reduce exploratory tests. This technology can achieve more accurate performance predictions and design application solutions for different usage scenarios and requirements. Summary of the invention

[0014] In view of the problems existing in the prior art, the present invention provides an I-RAPC and a performance prediction method thereof.

[0015] The present invention is implemented as follows: an I-RAPC, wherein the I-RAPC can be provided with 1 hole, 4 holes, 5 holes or 9 holes and a distribution pattern of the center, the middle of the side, or the corner.

[0016] Another object of the present invention is to provide a method for preparing the I-RAPC, the method comprising:

[0017] I-RAPC is obtained by concentrating the originally evenly distributed pores inside ordinary RAPC into a pipe that is connected from top to bottom and embedding pipes in the pipe.

[0018] Another object of the present invention is to provide a performance prediction method of the I-RAPC, the I-RAPC performance prediction method comprising:

[0019] Step 1: Use the I-RAPC compressive strength calculation model based on the strength reduction coefficient method to predict the strength index of I-RAPC;

[0020] Step 2, using the I-RAPC single-hole water permeability coefficient calculation formula to determine the I-RAPC water permeability performance;

[0021] Step three, obtaining the I-RAPC performance prediction result based on the strength index prediction result and the water permeability prediction result of the I-RAPC.

[0022] Furthermore, the I-RAPC compressive strength calculation model based on the strength reduction coefficient method includes:

[0023] (1) Theoretical model of concrete pipe I-RAPC strength:

[0024]

[0025] in, represents the theoretical value of the I-RAPC compressive strength of concrete pipe holes; P represents the benchmark group strength; c1 represents the influence coefficient of the strength of the concrete middle pipe hole; c2 represents the influence coefficient of the strength of the concrete side pipe hole, c 2s Indicates the upper tube hole, c 2c Side pipe holes; c3 represents the strength influence coefficient of concrete corner pipe holes; w, x, y, z represent the number of different types of pipe holes respectively;

[0026] (2) Theoretical model of acrylic tube hole I-RAPC strength:

[0027]

[0028] in, It indicates the theoretical value of I-RAPC compressive strength of acrylic tube hole; represents the theoretical value of I-RAPC compressive strength of the corresponding concrete pipe hole; a1 represents the influence coefficient of the strength of the acrylic middle pipe hole; a2 represents the influence coefficient of the strength of the acrylic side pipe hole, where a 2s Indicates the upper tube hole, a 2c Side tube holes; a3 represents the strength influence coefficient of acrylic corner tube holes; w, x, y, z represent the number of different types of tube holes respectively.

[0029] Furthermore, the calculation formula of the concrete pipe hole strength influence coefficient is as follows:

[0030] The strength influence coefficient of concrete pipe holes at different positions is calculated using the calculation formula for the strength influence coefficient of concrete middle pipe holes, the strength influence coefficient of concrete edge pipe holes, and the strength influence coefficient of concrete corner pipe holes:

[0031] c=P c / P;

[0032] Among them, P c It represents the I-RAPC strength of concrete single-tube hole at different positions; P represents the strength of the benchmark group.

[0033] Further, the calculation formula of the acrylic tube hole strength influence coefficient is as follows:

[0034] The strength influence coefficient of acrylic tube holes at different positions is calculated using the calculation formula for the strength influence coefficient of acrylic middle tube holes, acrylic edge middle tube holes, and acrylic corner tube holes:

[0035] a=P a / Pc ;

[0036] Among them, P a Indicates the I-RAPC strength of acrylic tube holes; P c It indicates the I-RAPC strength of the concrete pipe holes corresponding to the number and position of the pipe holes.

[0037] Further, the calculation formula of the I-RAPC single-tube permeability coefficient is as follows:

[0038]

[0039] Among them, μ c represents the flow coefficient of the pipe hole; H represents the head difference; L represents the length of the pipe; x represents the number of pipe holes; A p Indicates the water flow area of ​​a single pipe; A s Represents the top area of ​​I-RAPC.

[0040] Furthermore, the calculation formula of the tube hole flow coefficient is as follows:

[0041]

[0042] Among them, μ c represents the free flow orifice flow coefficient; L represents the orifice length; d represents the orifice diameter; λ represents the head loss coefficient along the way; ζ represents the local head loss coefficient.

[0043] The calculation formula of the head loss coefficient λ along the way is as follows:

[0044]

[0045] Among them, C represents the Xie Cai coefficient, which is used to reflect the comprehensive coefficient of the influence of the boundary on the water flow. Calculation; n represents the roughness of pipes of different materials, and R represents the hydraulic radius;

[0046] The calculation formula of the local head loss coefficient ζ is as follows:

[0047] The pores suddenly narrow:

[0048] The pores suddenly expand:

[0049] Among them, A1 and A2 represent the areas before and after the cross-section of the pipe hole changes in the direction of water flow, respectively.

[0050] Another object of the present invention is to provide an I-RAPC performance prediction system for implementing the I-RAPC performance prediction method, the I-RAPC performance prediction system comprising:

[0051] A strength prediction module is used to predict the strength index of I-RAPC using an I-RAPC compressive strength calculation model based on a strength reduction coefficient method;

[0052] The water permeability prediction module is used to determine the I-RAPC water permeability using the I-RAPC single-hole water permeability coefficient calculation formula;

[0053] The prediction result output module is used to output the I-RAPC performance prediction result based on the strength index prediction result and the water permeability prediction result of the I-RAPC.

[0054] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: starting from the compressive strength of single-pore I-RAPC, the present invention determines the theoretical model of multi-pore I-RAPC compressive strength, and at the same time uses hydraulic methods to analyze the theoretical calculation formula of I-RAPC permeability coefficient, clarifies the correlation between I-RAPC strength, permeability and pore characteristics, and verifies through experiments, providing scientific and effective theoretical support for the innovative development and expanded application of I-RAPC.

[0055] Compared with common recycled permeable concrete, the I-RAPC of the present invention has significant advantages in both strength and permeability, high compressive strength, large permeability coefficient and more stable permeability.

[0056] The present invention provides an I-RAPC compressive strength calculation model based on the strength reduction coefficient method, which can accurately determine the reduction effect of the number of pores, pore diameter, and pore distribution on the I-RAPC compressive strength. The maximum relative error between the calculated value and the measured value is only 7.52%, and the model can be used to predict the strength index of I-RAPC.

[0057] The present invention utilizes hydraulic method and Darcy's law to derive a calculation formula for the water permeability coefficient of a single I-RAPC tube hole. The maximum relative error between the calculated value and the measured value is only 4.42%, which can be used to determine the water permeability performance of the I-RAPC. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the distribution of I-RAPC pores provided in an embodiment of the present invention.

[0059] Figure 2 It is a flow chart of the I-RAPC preparation method provided by an embodiment of the present invention.

[0060] Figure 3 It is a flow chart of the I-RAPC performance prediction method provided by an embodiment of the present invention.

[0061] Figure 4 It is a schematic diagram of the structure of an I-RAPC performance prediction system provided by an embodiment of the present invention;

[0062] In the figure: 1. Strength prediction module; 2. Water permeability prediction module; 3. Prediction result output module.

[0063] Figure 5 It is a schematic diagram of a water permeable device provided in an embodiment of the present invention.

[0064] Figure 6 It is a schematic diagram of the cross-sectional dimensions of 1-1 and 2-2 provided in an embodiment of the present invention.

[0065] FIG. 7( a ) is a schematic diagram of the destruction morphology of an I-RAPC under frontal compression provided by an embodiment of the present invention.

[0066] FIG. 7( b ) is a schematic diagram of the destruction morphology of a laterally compressed I-RAPC provided in an embodiment of the present invention.

[0067] Figure 8 It is a schematic diagram of the effect of the pores provided in an embodiment of the present invention on the compressive strength of I-RAPC.

[0068] Fig. 9 It is a schematic diagram of the improvement degree of I-RAPC compressive strength by the EM pore distribution provided in an embodiment of the present invention.

[0069] Fig.10 It is a schematic diagram of the error between the calculated value and the measured value of the I-RAPC compressive strength theoretical model provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0071] In view of the problems existing in the existing recycled aggregate permeable concrete technology, the present invention provides an I-RAPC and a performance prediction method thereof. The present invention is described in detail below in conjunction with the accompanying drawings.

[0072] like Figure 1 As shown, the I-RAPC provided in the embodiment of the present invention can be provided with 1 hole, 4 holes, 5 holes or 9 holes, and the distribution form of the holes can be the center, the middle of the side or the corner.

[0073] like Figure 2 As shown, the I-RAPC preparation method provided in the embodiment of the present invention comprises:

[0074] I-RAPC is obtained by concentrating the originally evenly distributed pores inside ordinary RAPC into a pipe that is connected from top to bottom and embedding pipes in the pipe.

[0075] like Figure 3As shown, the I-RAPC performance prediction method provided by the embodiment of the present invention includes:

[0076] S101, predicting the strength index of I-RAPC using the I-RAPC compressive strength calculation model based on the strength reduction coefficient method;

[0077] S102, determining the I-RAPC water permeability performance using the I-RAPC single-hole water permeability coefficient calculation formula;

[0078] S103, obtaining an I-RAPC performance prediction result based on the I-RAPC strength index prediction result and the water permeability prediction result.

[0079] The I-RAPC compressive strength calculation model based on the strength reduction coefficient method provided in the embodiment of the present invention includes:

[0080] (1) Theoretical model of concrete pipe I-RAPC strength:

[0081]

[0082] in, represents the theoretical value of the I-RAPC compressive strength of concrete pipe holes; P represents the benchmark group strength; c1 represents the influence coefficient of the strength of the concrete middle pipe hole; c2 represents the influence coefficient of the strength of the concrete side pipe hole, c 2s Indicates the upper tube hole, c 2c Side pipe holes; c3 represents the strength influence coefficient of concrete corner pipe holes; w, x, y, z represent the number of different types of pipe holes respectively;

[0083] (2) Theoretical model of acrylic tube hole I-RAPC strength:

[0084]

[0085] in, It indicates the theoretical value of I-RAPC compressive strength of acrylic tube hole; represents the theoretical value of I-RAPC compressive strength of the corresponding concrete pipe hole; a1 represents the influence coefficient of the strength of the acrylic middle pipe hole; a2 represents the influence coefficient of the strength of the acrylic side pipe hole, where a 2s Indicates the upper tube hole, a 2c Side tube holes; a3 represents the strength influence coefficient of acrylic corner tube holes; w, x, y, z represent the number of different types of tube holes respectively.

[0086] The calculation formula of the influence coefficient of concrete pipe hole strength provided by the embodiment of the present invention is as follows:

[0087] The strength influence coefficient of concrete pipe holes at different positions is calculated using the calculation formula for the strength influence coefficient of concrete middle pipe holes, the strength influence coefficient of concrete edge pipe holes, and the strength influence coefficient of concrete corner pipe holes:

[0088] c=P c / P;

[0089] Among them, P c It represents the I-RAPC strength of concrete single-tube hole at different positions; P represents the strength of the benchmark group.

[0090] The calculation formula of the acrylic tube hole strength influence coefficient provided by the embodiment of the present invention is as follows:

[0091] The strength influence coefficient of acrylic tube holes at different positions is calculated using the calculation formula for the strength influence coefficient of acrylic middle tube holes, acrylic edge middle tube holes, and acrylic corner tube holes:

[0092] a=P a / P c ;

[0093] Among them, P a Indicates the I-RAPC strength of acrylic tube holes; P c It indicates the I-RAPC strength of the concrete pipe holes corresponding to the number and position of the pipe holes.

[0094] The calculation formula of the I-RAPC single-tube permeability coefficient provided in the embodiment of the present invention is as follows:

[0095]

[0096] Among them, μ c represents the flow coefficient of the pipe hole; H represents the head difference; L represents the length of the pipe; x represents the number of pipe holes; A p Indicates the water flow area of ​​a single pipe; A s Represents the top area of ​​I-RAPC.

[0097] The calculation formula of the orifice flow coefficient provided in the embodiment of the present invention is as follows:

[0098]

[0099] Among them, μ c represents the free flow orifice flow coefficient; L represents the orifice length; d represents the orifice diameter; λ represents the head loss coefficient along the way; ζ represents the local head loss coefficient.

[0100] The calculation formula of the head loss coefficient λ along the way provided by the embodiment of the present invention is as follows:

[0101]

[0102] Among them, C represents the Xie Cai coefficient, which is used to reflect the comprehensive coefficient of the influence of the boundary on the water flow. Calculation; n represents the roughness of pipes of different materials, and R represents the hydraulic radius;

[0103] The calculation formula of the local head loss coefficient ζ provided in the embodiment of the present invention is as follows:

[0104] The pores suddenly narrow:

[0105] The pores suddenly expand:

[0106] Among them, A1 and A2 represent the areas before and after the cross-section of the pipe hole changes in the direction of water flow, respectively.

[0107] like Figure 4 As shown, the I-RAPC performance prediction system provided by the embodiment of the present invention includes:

[0108] Strength prediction module 1, used to predict the strength index of I-RAPC using the I-RAPC compressive strength calculation model based on the strength reduction coefficient method;

[0109] The water permeability prediction module 2 is used to determine the I-RAPC water permeability by using the I-RAPC single-hole water permeability coefficient calculation formula;

[0110] The prediction result output module 3 is used to output the I-RAPC performance prediction result based on the strength index prediction result and the water permeability prediction result of the I-RAPC.

[0111] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0112] Embodiment 1:

[0113] 1. I-RAPC (I-RAPC)

[0114] I-RAPC is to concentrate the originally evenly distributed pores inside the ordinary RAPC into pipes that are connected vertically and embed pipes in the pipes.

[0115] The present invention sets the number of pores of 1 hole, 4 holes, 5 holes and 9 holes respectively, and the distribution forms of center (C), edge center (EM) and edge corner (EC). The specific pore distribution forms are as follows: Figure 1 shown.

[0116] In addition, the tube holes will cause differences in the compressive strength of different pressure-bearing surfaces, so the present invention takes into account the front and side compressive strengths, where the front and side compressive strengths refer to the strengths measured at the pressure surfaces perpendicular to the tube holes and parallel to the tube holes, respectively.

[0117] 2. Compressive Strength Theoretical Model

[0118] 1. Establishment of theoretical strength model of concrete pipe hole I-RAPC

[0119]

[0120] Where: —Theoretical value of I-RAPC compressive strength of concrete pipe hole, MPa; P—benchmark group strength, MPa; c1—strength influence coefficient of concrete middle pipe hole; c2—strength influence coefficient of concrete edge pipe hole, where c 2s Indicates the tube hole in the middle (upper) part of the side, c 2c Pipe holes in the middle (side) part of the edge; c3—strength influence coefficient of pipe holes in the corners of concrete; w, x, y, z represent the number of different types of pipe holes respectively.

[0121] c: Influence coefficient of concrete pipe hole strength at different positions

[0122] c=P c / P (2)

[0123] Where: P c is the I-RAPC strength of concrete single pipe hole at different positions, MPa; P is the benchmark group strength, MPa.

[0124] The specific c values ​​are shown in Tables 1 and 2.

[0125] Table 1 Influence coefficient c of front compressive strength of concrete pipe hole I-RAPC z value

[0126]

[0127] Table 2 Influence coefficient c of the side compressive strength of concrete pipe hole I-RAPC c value

[0128]

[0129] 2. Establishment of the theoretical model of acrylic tube hole I-RAPC strength

[0130]

[0131] Where: —Theoretical value of compressive strength of acrylic tube hole I-RAPC, MPa; —Corresponding theoretical value of I-RAPC compressive strength of concrete pipe hole, MPa; a1—Strength influence coefficient of acrylic middle pipe hole; a2—Strength influence coefficient of acrylic side pipe hole, where a 2s Indicates the tube hole in the middle (upper) part of the side, a 2cPipe holes in the middle (side) part of the edge; a3—strength influence coefficient of acrylic corner pipe holes; w, x, y, z represent the number of different types of pipe holes respectively.

[0132] The addition of acrylic tubes changes the strength law of I-RAPC. Therefore, when establishing the theoretical strength model of acrylic tube hole I-RAPC, the strength of concrete tube hole I-RAPC should be used as a benchmark to obtain the strength influence coefficient a of the tube holes at different positions, as shown in formula (4).

[0133] a=P a / P c (4)

[0134] Where: P a —I-RAPC strength of acrylic tube hole, MPa; P c —I-RAPC strength of concrete pipe holes corresponding to the number and position of pipe holes, MPa.

[0135] The values ​​of the strength influence coefficient a of acrylic tube holes at different positions are shown in Tables 3 and 4.

[0136] Table 3 Influence coefficient a of the positive compressive strength of acrylic tube hole I-RAPC z value

[0137]

[0138] Table 4 Influence coefficient a of the compressive strength of acrylic tube hole I-RAPC side c value

[0139]

[0140] 3. Theoretical formula of water permeability coefficient

[0141] 1. I-RAPC water permeability coefficient theoretical value calculation formula

[0142]

[0143] Where: μ c is the flow coefficient of the pipe hole, which is related to the pipe material and size; H is the head difference, m; L is the pipe length, m; x is the number of pipe holes, pieces; A p is the water flow area of ​​a single pipe, m 2 ; A s is the top area of ​​I-RAPC, m 2 .

[0144]

[0145] In the formula, μ cis the free flow orifice flow coefficient; L is the orifice length, m; d is the orifice diameter, m; λ is the head loss coefficient along the way; ζ is the local head loss coefficient.

[0146] The key is to determine λ and ζ in the above formula. The calculation section is determined to be from section 1-1 to section 2-2. Figure 6 , the calculation process is as follows:

[0147] (1) Determination of λ.

[0148] λ is related to factors such as the pore size and material roughness, and can be calculated according to formula (7):

[0149]

[0150] Where: C is the Xie Cai coefficient, which is a comprehensive coefficient reflecting the impact of the boundary on the water flow, m 1 / 2 / s, press Calculate, where n is the roughness, 0.01 for concrete pipes and 0.0075 for acrylic pipes, and R is the hydraulic radius, m.

[0151] Table 5 is a calculation table for the head loss coefficient along the pipe under different pipe hole materials and diameters.

[0152] Table 5 Calculation table of head loss coefficient λ along the way

[0153]

[0154] (2) Determination of ζ.

[0155] ζ only appears in the local flow section before and after the boundary changes, and its energy consumption is large and concentrated, mainly due to vortex loss. Section 1-1 and section 2-2 produce two situations: sudden shrinkage of the tube hole and sudden expansion of the tube hole, respectively. Their ζ can be calculated according to formula (8) and (9) respectively:

[0156] The pores suddenly narrow:

[0157] The pores suddenly expand:

[0158] Where: A1 and A2 are the areas before and after the cross section of the pipe hole changes in the direction of water flow, mm 2 .

[0159] Table 6 is a calculation table for the head loss coefficient along the pipe for different pipe hole materials and diameters.

[0160] Table 6 Calculation table of local head loss coefficient ζ

[0161]

[0162]

[0163] Embodiment 2:

[0164] 1 Experimental materials and methods

[0165] 1.1 Materials and mix ratio

[0166] Coarse aggregate: obtained from waste concrete after crushing and screening, with a particle size of 4.75-9.5mm. Its basic physical performance indicators are shown in Table 1, which meet the requirements of the specification; fine aggregate: natural river sand, continuous grading, fineness modulus Mx=2.9, belonging to medium sand; cement: P·O 42.5 ordinary Portland cement; water: tap water; pipe: acrylic pipe.

[0167] Table 7 Basic performance indicators of recycled coarse aggregate

[0168]

[0169] The I-RAPC mix ratio is designed according to the specifications, with a design strength of C30, a water-cement ratio of 0.49, and a sand ratio of 0.345. See Table 8 for details.

[0170] Table 8 I-RAPC mix ratio

[0171]

[0172] 1.2 Experimental design

[0173] The I-RAPC specimen of the present invention has a size of a standard cube of 150×150×150 mm, and the test indicators include strength performance and permeability (water permeability coefficient). Except for the reference group, which has no holes, the other concrete specimens are respectively provided with 1 hole, 4 holes, 5 holes and 9 holes, and the distribution forms of the center (C), the edge middle (EM), and the edge corner (EC). The specific distribution forms of the holes are as follows: Figure 1 As shown. In addition, the pipe hole will cause the compressive strength of different pressure surfaces to be different. During the test, the front and side compressive strengths are measured separately, where the front and side compressive strengths refer to the strengths measured when the pressure surface is perpendicular and parallel to the axis of the pipe hole, respectively. The strength is tested according to the standard method, and the permeability coefficient is measured using the constant water head method of Darcy's law.

[0174] The experiment adopted the pre-wet aggregate method to mix concrete. The I-RAPC production process is as follows: Figure 2 shown.

[0175] 2 Results and discussion

[0176] 2.1 Compressive strength

[0177] (1) Test results

[0178] It can be seen from the failure morphology Figure 7(a) and Figure 7(b) that when the front is compressed, as the load increases, the I-RAPC first develops surface cracks, then develops from the middle to the upper and lower ends of the tube holes, and finally forms an eight-shaped failure morphology that is connected in both directions. When the side is compressed, the surface concrete continues to peel off, and vertical through cracks appear between the upper and lower tube holes. The tube holes are deformed and then destroyed. It can be seen that after adding tube holes, the failure morphology of I-RAPC is different from that of ordinary concrete, and it is not easy to cause overall failure.

[0179] Figure 8 The results of the I-RAPC compressive strength test are shown in Table 9. The meanings of C5, C10, A5, and A10 in the figure are as follows: C is the concrete pore, A is the acrylic pore, and 5 and 10 represent the pore diameters of 5 mm and 10 mm. As can be seen from the figure, the compressive strength of I-RAPC decreases with the increase in the number of pores and the increase in the pore diameter, which is consistent with the trend that the strength of ordinary recycled permeable concrete decreases with the increase in porosity, and the measured compressive strength value is much higher than that of RAPC, as shown in Table 9. For I-RAPC with the same number of pores, the position of the pores will affect it, among which the front compressive strength is 1EM>lEC>1C, the side compressive strength is 1EM-T>1EC>1EM-S>1C, and there are characteristics of 4EM>4EC and 5EM>5EC when there are multiple pores.

[0180] When acrylic pipes (5 mm in diameter) are added to a single hole (such as the EM-T position), the lateral compressive strength of I-RAPC is increased by 1.03 MPa compared with that of concrete holes. This shows that acrylic pipes have a significant strengthening effect on I-RAPC, and the lateral compressive strength can be increased by up to 5.45 MPa.

[0181] In addition, different pore distribution positions under the same pore number also have a certain impact on I-RAPC. For example, the pore distribution of EM is better than that of EC, and the degree of improvement in the compressive strength of I-RAPC is shown in Figure 2. Fig. 9 Compared with the EC pore distribution, the EM pore distribution can increase the compressive strength by 0.03-4.29MPa, about 0.08-13.18%. Therefore, when designing I-RAPC, it is recommended to use the EM pore distribution to obtain higher strength performance.

[0182] Table 9 Comparison of compressive strength and water permeability coefficient of RAPC and I-RAPC

[0183]

[0184] (2) Theoretical analysis

[0185] The test results show that the more I-RAPC holes and the larger the hole diameter, the lower the compressive strength. Therefore, the strength reduction coefficient method is proposed to construct a theoretical calculation model of I-RAPC compressive strength and pore parameters.

[0186] The ratio of the strength of the concrete single-hole I-RAPC at different positions to the strength of the benchmark group is defined as the corresponding strength reduction coefficient c, as shown in formula (2). The addition of acrylic tubes to the holes changes the strength characteristics of I-RAPC, so its reduction degree is based on the corresponding concrete hole strength, as shown in formula (4). According to this formula, the strength reduction coefficients of concrete holes at different positions are obtained (see Table 10).

[0187] Table 10I-RAPC single hole compressive strength reduction factor

[0188]

[0189] Note: According to the characteristics of the I-RAPC pressure surface, when the front is under pressure, the single tube hole distribution forms are C, EC, EM (only one form); when the side is under pressure, the single tube hole distribution forms are C, EC, EM, among which EM includes EM-T and EM-S.

[0190] The theoretical calculation model of I-RAPC compressive strength with different pore parameters was established as follows:

[0191]

[0192]

[0193] Fig.10 is the error between the calculated value and the measured value of I-RAPC compressive strength. Fig.10 It can be seen that the absolute error range of I-RAPC compressive strength is 0.13-2.45MPa, and the relative error range is 0.43-7.52%. It can be seen that the I-RAPC compressive strength theoretical calculation model proposed in the present invention can accurately quantify the reduction effect of pore number, pore diameter, and pore distribution on the compressive strength of I-RAPC, and predict its strength.

[0194] 2.2 Water permeability coefficient

[0195] The permeability coefficient of I-RAPC is mainly determined by the number, diameter and material (roughness) of pores. As the number of pores increases, the diameter increases, and the roughness decreases, the permeability coefficient increases. Due to the unique characteristics of I-RAPC with pores connected up and down, the theoretical value of its permeability coefficient can be obtained by combining Darcy's law and the method of free outflow of simple short-tube constant flow in hydraulics. The calculation diagram is as follows: Figure 6 shown.

[0196] During the calculation, the viscous dissipation of the water body is ignored, and only the influence of the external boundary conditions is considered. That is, there are head losses along the way and local head losses in the test. The theoretical calculation formula of the I-RAPC permeability coefficient is obtained by combining the free outflow orifice flow formula and Darcy's law.

[0197]

[0198]

[0199] Where: μ c is the flow coefficient of the pipe hole, which is related to the pipe material and size; H is the head difference, m; L is the pipe length, m; x is the number of pipe holes, pieces; A p is the water flow area of ​​a single pipe, m 2 ; A s is the top area of ​​I-RAPC, m 2 ; d is the diameter of the pipe hole, m; λ is the head loss coefficient along the way; ζ is the local head loss coefficient.

[0200] In the above formula, the determination of λ and ζ values ​​is the key, which can be obtained from the hydraulic formula. The calculation and values ​​are shown in Table 11 and Table 12.

[0201] Table 11 Calculation table of head loss coefficient λ along the way

[0202]

[0203] Table 12 Calculation table of local head loss coefficient ζ

[0204]

[0205] By combining Darcy's law, the theoretical value calculation formula of I-RAPC permeability coefficient can be obtained as shown in formula (5).

[0206] The theoretical value calculated by formula (5) is compared with the measured value, and the results are shown in Table 13. The absolute error range between the water permeability coefficient of different pore materials and diameters and the measured value is 0.008-0.082 mm / s, and the relative error range is 0.265-4.617%. It can be seen that the I-RAPC water permeability coefficient theoretical value calculation formula derived by the present invention has high accuracy.

[0207] Table 13 Theoretical and measured values ​​of water permeability coefficient of single-hole I-RAPC

[0208]

[0209] 3 Effects

[0210] The present invention takes I-RAPC as the object, studies its strength and water permeability under different pore parameters, and establishes a corresponding theoretical calculation model. The main conclusions are as follows:

[0211] (1) Compared with ordinary recycled permeable concrete, I-RAPC has significant advantages in both strength and permeability. For example, in this test, the compressive strength of the 9-hole is the lowest, but it can still reach more than 25 MPa, and its permeability coefficient is larger (the permeability coefficient of a single 10 mm hole can reach 3 mm / s), and the permeability performance is more stable.

[0212] (2) The compressive strength of I-RAPC is related to parameters such as pore type, number, diameter, and position. The more pores there are and the larger the pore diameter, the lower the strength. In addition, the strength performance of a single pore in the middle position is better than that in the corner position.

[0213] (3) A compressive strength calculation model for I-RAPC based on the strength reduction coefficient method was proposed. This model can accurately determine the reduction effect of pore number, pore diameter, and pore distribution on the compressive strength of I-RAPC. The maximum relative error between the calculated value and the measured value is only 7.52%, which can be used to predict the strength index of I-RAPC.

[0214] (4) The calculation formula for the permeability coefficient of a single tube hole of I-RAPC was derived using hydraulic methods and Darcy's law. The maximum relative error between the calculated value and the measured value is only 4.42%, which can be used to determine the permeability performance of I-RAPC.

[0215] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A new method for predicting the performance of recycled aggregate permeable concrete, characterized in that: I-RAPC performance prediction methods include: Step 1: Use the new recycled aggregate permeable concrete I-RAPC compressive strength calculation model based on the strength reduction coefficient method to predict the strength index of I-RAPC; Step 2, using the I-RAPC single-hole water permeability coefficient calculation formula to determine the I-RAPC water permeability performance; Step 3, obtaining an I-RAPC performance prediction result based on the strength index prediction result and the water permeability prediction result of the I-RAPC; The I-RAPC compressive strength calculation model based on the strength reduction coefficient method includes: (1) Theoretical model of concrete pipe I-RAPC strength: in, represents the theoretical value of the I-RAPC compressive strength of concrete pipe holes; P represents the benchmark group strength; c1 represents the influence coefficient of the strength of the concrete middle pipe hole; c2 represents the influence coefficient of the strength of the concrete side pipe hole, c 2s Indicates the upper tube hole, c 2c Side pipe holes; c3 represents the strength influence coefficient of concrete corner pipe holes; w, x, y, z represent the number of different types of pipe holes respectively; (2) Theoretical model of acrylic tube hole I-RAPC strength: in, It indicates the theoretical value of I-RAPC compressive strength of acrylic tube hole; represents the theoretical value of I-RAPC compressive strength of the corresponding concrete pipe hole; a1 represents the influence coefficient of the strength of the acrylic middle pipe hole; a2 represents the influence coefficient of the strength of the acrylic side pipe hole, where a 2s Indicates the upper tube hole, a 2c Side tube holes; a3 represents the strength influence coefficient of acrylic corner tube holes; w, x, y, z represent the number of different types of tube holes respectively.

2. The new method for predicting performance of recycled aggregate permeable concrete according to claim 1 is characterized in that: The calculation formula of the concrete pipe hole strength influence coefficient is as follows: The strength influence coefficient of concrete pipe holes at different positions is calculated using the calculation formula for the strength influence coefficient of concrete middle pipe holes, the strength influence coefficient of concrete edge pipe holes, and the strength influence coefficient of concrete corner pipe holes: c=P c / P; Among them, P c It represents the I-RAPC strength of concrete single-tube hole at different positions; P represents the strength of the benchmark group.

3. The new method for predicting performance of recycled aggregate permeable concrete according to claim 1 is characterized in that: The calculation formula of the acrylic tube hole strength influence coefficient is as follows: The strength influence coefficient of acrylic tube holes at different positions is calculated using the calculation formula for the strength influence coefficient of acrylic middle tube holes, acrylic edge middle tube holes, and acrylic corner tube holes: a=P a / P c ; Among them, P a Indicates the I-RAPC strength of acrylic tube holes; P c It indicates the I-RAPC strength of the concrete pipe holes corresponding to the number and position of the pipe holes.

4. The new method for predicting performance of recycled aggregate permeable concrete according to claim 1 is characterized in that: The calculation formula of the I-RAPC single-tube permeability coefficient in step 2 is as follows: Among them, μ c represents the flow coefficient of the pipe hole; H represents the head difference; L represents the length of the pipe; x represents the number of pipe holes; A p Indicates the water flow area of ​​a single pipe; A s Represents the top area of ​​I-RAPC.

5. The new method for predicting performance of recycled aggregate permeable concrete according to claim 4 is characterized in that: The calculation formula of the orifice flow coefficient is as follows: Among them, μ c represents the free flow orifice flow coefficient; L represents the orifice length; d represents the orifice diameter; λ represents the head loss coefficient along the way; ζ represents the local head loss coefficient.

6. The new method for predicting performance of recycled aggregate permeable concrete according to claim 5 is characterized in that: The calculation formula of the head loss coefficient λ along the way is as follows: Among them, C represents the Xie Cai coefficient, which is used to reflect the comprehensive coefficient of the influence of the boundary on the water flow. Calculation; n represents the roughness of pipes of different materials, and R represents the hydraulic radius; The calculation formula of the local head loss coefficient ζ is as follows: The pores suddenly narrow: The pores suddenly expand: Among them, A1 and A2 represent the areas before and after the cross-section of the pipe hole changes in the direction of water flow, respectively.

7. A new type of recycled aggregate permeable concrete performance prediction system implementing the new type of recycled aggregate permeable concrete performance prediction method according to any one of claims 1 to 6, characterized in that: The novel recycled aggregate permeable concrete performance prediction system comprises: A strength prediction module is used to predict the strength index of I-RAPC using an I-RAPC compressive strength calculation model based on a strength reduction coefficient method; The water permeability prediction module is used to determine the I-RAPC water permeability using the I-RAPC single-hole water permeability coefficient calculation formula; The prediction result output module is used to output the I-RAPC performance prediction result based on the strength index prediction result and the water permeability prediction result of the I-RAPC.

8. A new type of recycled aggregate permeable concrete predicted by the method for predicting the performance of the new type of recycled aggregate permeable concrete according to any one of claims 1 to 6, characterized in that: The I-RAPC is provided with 1 hole, 4 holes, 5 holes or 9 holes and a distribution form of center, side middle and corner.

9. A method for preparing the novel recycled aggregate permeable concrete as claimed in claim 8, characterized in that: The preparation method of the novel recycled aggregate permeable concrete comprises: I-RAPC is obtained by concentrating the originally evenly distributed pores inside ordinary RAPC into a pipe that is connected from top to bottom and embedding pipes in the pipe.

Images