A design method for drainage and recycled permeable concrete for different highway grades
By designing the mix ratio and channel structure of high-strength self-finished concrete, the problem of holes easily damaged during the service period of permeable concrete is solved, and the efficient drainage effect of different highway grades under different rainfall recurrence periods is achieved.
Patent Information
- Application Number
- CN202210835480.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-15
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2042-07-15
AI Technical Summary
The existing permeable concrete is prone to damage due to vehicle fatigue load during service period due to the impact of vehicle fatigue load, resulting in a decrease in mechanical properties and permeability coefficient, which cannot effectively meet the immediate drainage needs of different road grades under different rainfall recurrence periods.
By determining the rain calendar parameters in different regions, calculating the permeability coefficient and porosity of permeable concrete, combining the vehicle shaft load times and fatigue load relationship, the mix ratio of high-strength self-finished concrete is designed to form upper and lower straight through holes to meet the fatigue resistance and drainage requirements of different highway grades.
It has achieved efficient drainage of permeable concrete at different highway grades and recurrence periods, excellent fatigue resistance, extended service life, and avoided flooding problems.
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Figure CN115146472B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of highway pavement design, and particularly relates to a design method for drainage and regeneration permeable concrete for different highway grades. Background Art
[0002] Under the background of global warming, extreme rainstorms occur more frequently. With the continuous increase in the hardened area of urban surfaces, rainwater cannot directly infiltrate into the ground after the action of rainstorms, resulting in surface runoff and causing waterlogging disasters, forming the situation of "urban waterlogging". As a road material for building sponge cities, the good permeability of permeable concrete helps to reduce rainwater runoff and lower the risk of waterlogging.
[0003] Traditional porous permeable concrete mainly provides bonding force by a thin layer of cement slurry on the surface of the aggregate, and has poor mechanical properties, and can only be used for low-grade road surfaces such as sidewalks and parking lots. This permeable concrete forms through-holes up and down by pre-setting steel bars, and the porosity is easy to control. Based on self-compacting concrete as the matrix, the dense internal structure improves the mechanical properties and can meet the use of different grades of highway pavements. However, under the action of different vehicle fatigue loads during the service life, the internal holes will be damaged, resulting in a decrease in both mechanical properties and permeability coefficient, which has an adverse impact on the waterlogging reduction performance. At present, there are few design methods for meeting the immediate drainage of permeable concrete under different highway grades and different rainfall return periods. Summary of the Invention
[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.
[0005] In view of the above and / or problems existing in the prior art, the present invention is proposed.
[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a design method for drainage and regeneration permeable concrete for different highway grades.
[0007] To solve the above technical problems, the present invention provides the following technical solution: A design method for drainage and regeneration permeable concrete for different highway grades, characterized in that it includes
[0008] S1 Determine the rainstorm intensity i at different return periods according to the rain calendar parameters in different regions;
[0009] S2 Obtain K at different rainfall return periods according to the relationship formula (1) between the rainstorm intensity i and the internal water flow permeability coefficient K of the permeable concrete pores;
[0010] S3 determines the porosity P according to the relational expression two of the permeability coefficient and the porosity;
[0011] S4 determines the highway grade and the corresponding service life x;
[0012] S5 determines the actual number of vehicle axle loads Ne during the service life according to the relational expression three;
[0013] S6 determines the laboratory fatigue loading times Nf according to the corresponding relationship between the actual number of vehicle axle loads Ne and the fatigue load times Nf in the laboratory fatigue test during the service life according to the relational expression four;
[0014] S7 determines the initial flexural strength for the pervious concrete to meet the use requirements of different grades of highways according to the relational expression five between the laboratory fatigue load times and the residual flexural strength during the service life;
[0015] S8 determines the target compressive strength of the pervious concrete according to the relational expression six of the compressive strength and the flexural strength;
[0016] S9 determines the mix proportion of the drainage and regeneration pervious concrete according to the requirements of the porosity in S3 and the target compressive strength in S9.
[0017] As a preferred scheme of the design method of the drainage and regeneration pervious concrete for different highway grades described in the present invention, wherein: the rainfall return periods are respectively selected as 10 years, 50 years and 100 years, the total rainfall amounts are respectively 68.17, 90.1 and 99.41 mm, and the rainfall duration is 60 min rainfall process.
[0018] As a preferred scheme of the design method of the drainage and regeneration pervious concrete for different highway grades described in the present invention, wherein: the relational expression one is K = 0.81 + 3.87×10 -4 e 5.71 wherein, K is the internal water flow permeability coefficient of the pore channel, in mm / s, and i is the rainstorm intensity, in mm / min.
[0019] As a preferred scheme of the design method of the drainage and regeneration pervious concrete for different highway grades described in the present invention, wherein: the relational expression two is P = (K - 0.2) / 7.92; wherein, K is the permeability coefficient, in mm / s; P is the porosity, in %.
[0020] As a preferred scheme of the design method of the drainage and regeneration pervious concrete for different highway grades described in the present invention, wherein: the relational expression three is Ne = Dx; wherein, D is the annual average daily design vehicle quantity, in vehicles; x is the service life, in years.
[0021] As a preferred embodiment of the design method of the drainage and regeneration permeable concrete for different highway grades according to the present invention, wherein: the relational expression four is N f = 0.2×0.5×1 / 3×(60 / 365)Ne = 5.48×10 -3 Ne; where Nf is the number of laboratory fatigue loadings, and Ne is the number of actual vehicle axle loads.
[0022] As a preferred embodiment of the design method of the drainage and regeneration permeable concrete for different highway grades according to the present invention, wherein: the relational expression five is F = 9.03 - 0.03(e 0.041Nf - 1) / 0.04 + b; where when Nf is 0, F is the initial flexural strength of the unloaded specimen; Nf is the number of fatigue loadings, in ten thousands; and b is a constant.
[0023] As a preferred embodiment of the design method of the drainage and regeneration permeable concrete for different highway grades according to the present invention, wherein: the relational expression six is F cu,0 = 14.2F - 52.3; where Fcu,0 is the target compressive strength and F is the initial flexural strength.
[0024] As a preferred embodiment of the design method of the drainage and regeneration permeable concrete for different highway grades according to the present invention, wherein: the drainage standard adopted by the design method is that the surface water depth is less than 15 cm and the drainage time is less than 0.5 h.
[0025] As a preferred embodiment of the design method of the drainage and regeneration permeable concrete for different highway grades according to the present invention, wherein: the pore diameters are 0.8, 1, 2, 3, and 4 mm, and the porosity is between 0.08% and 1.507%.
[0026] Advantages of the present invention:
[0027] A design method of the drainage and regeneration permeable concrete for different highway grades according to the present invention uses high-strength self-compacting concrete as the matrix, which is more dense inside, has better fatigue resistance and a longer service life. The pore and strength requirements of the permeable concrete pavement can be determined according to the service life of the permeable concrete pavement and the rainfall intensity at different return periods. It can meet the requirement of immediate drainage of the highway after being affected by heavy rain without causing waterlogging problems. Description of the Drawings
[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:
[0029] Figure 1 This is the design flow chart in Embodiment 1 of the present invention. Detailed implementation manners
[0030] To make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in combination with the embodiments of the specification.
[0031] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.
[0032] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it a separate or selectively exclusive embodiment from other embodiments.
[0033] Based on the rain calendar parameters in the Nanjing area, the present invention determines that the storm intensities of the 60-minute short-duration rainfall processes with a rainfall return period of 10 years, 50 years, and 100 years are 1.21 mm / min, 1.59 mm / min, and 1.76 mm / min respectively.
[0034] According to the relationship formula (1) between the storm intensity and the internal water flow penetration coefficient of the permeable concrete pores, the required penetration coefficients under different storm intensities are 1.19 mm / s, 4.2 mm / s, and 9.7 mm / s respectively.
[0035] K = 0.81 + 3.87×10 -4 e 5.71i (1)
[0036] In the formula, K is the internal water flow penetration coefficient of the pores, in mm / s, and i is the storm intensity, in mm / min.
[0037] According to the relationship formula (2) between the porosity and the penetration coefficient, the porosity range is determined to be 0.1 - 1.19%
[0038] P = (K - 0.2) / 7.92 (2)
[0039] In the formula, K is the penetration coefficient, in mm / s; P is the porosity, in %.
[0040] According to JTG B01-2014 "Technical Standard for Highway Engineering", the service life of the structural design of first-class, second-class and third-class highways is 30 years, 20 years and 15 years respectively, and the average daily design passenger car traffic volume of a single lane is 6,000 vehicles.
[0041] According to Equation (3), determine the actual number of vehicle axle loads Ne within the service life.
[0042] Ne = Dx (3)
[0043] Where D is the average daily design vehicle quantity, in vehicles; x is the service life, in years.
[0044] According to the relationship between the actual number of vehicle axle loads Ne within the service life and the fatigue load number N of the laboratory fatigue test f Corresponding to Equation (4), determine the fatigue load number N of the laboratory fatigue test within different service lives f . The fatigue loading times corresponding to the service life of the laboratory are shown in Table 1.
[0045] N f = 0.2×0.5×1 / 3×(60 / 365)Ne = 5.48×10 -3 Ne (4)
[0046] Where N f is the laboratory fatigue load number, and Ne is the actual number of vehicle axle loads.
[0047] Table 1 Service life corresponding to the laboratory fatigue loading times
[0048]
[0049] According to JTG D40-2011 "Design Specification for Highway Cement Concrete Pavement", the flexural tensile strength of the heavy-duty pavement cement concrete is greater than 5 MPa. According to the relationship between the laboratory fatigue load number and the residual flexural strength within the service life (5), determine the initial flexural strength.
[0050] F = 9.03 - 0.03(e 0.04Nf -1) / 0.04 + b (5)
[0051] Where when N f is 0, then F is the initial flexural strength of the specimen without loading; N f is the fatigue load number, in ten thousand times; b is a constant.
[0052] According to the relationship between the compressive strength and the flexural strength (6), determine the target compressive strength of the permeable concrete.
[0053] F cu,0 = 14.2F - 52.3 (6)
[0054] Wherein, F cu,0 is the target compressive strength, and F is the flexural strength.
[0055] Determine the mix proportion of the drainage and regeneration pervious concrete according to the requirements of porosity and compressive strength.
[0056] Example 1
[0057] Step 1: According to the rainfall calendar parameters in Nanjing area, determine that the short-duration rainfall intensity with a rainfall return period of 10 years is 1.21 mm / min. If the permeability coefficient of the pervious concrete is greater than the rainfall intensity, no ponding will occur on the surface. According to the relationship (1) between the rainfall intensity and the internal water flow permeability coefficient of the pore channels, determine that the permeability coefficient of the pervious concrete is greater than 1.15 mm / s.
[0058] Step 2: According to the relationship formula (2) of porosity and permeability coefficient, the porosity of the pervious concrete that can meet the drainage with a return period of 10 years is greater than 0.1%. Arrange 4×4 holes with a pore diameter of 1 mm in a cube specimen of 100 mm×100 mm×100 mm, and the porosity is 0.126%.
[0059] Step 3: Select a first-class highway with an average annual daily design traffic volume of 6,000 passenger cars per single lane and a structural design service life of 30 years. According to the relationship formula (3), determine that the actual vehicle axle load times Ne within the service life is 6.5×10 7 times. According to the relationship formula (4), determine that the fatigue load times N f in the laboratory fatigue test is 350,000 times.
[0060] Step 4: According to the regulation that the flexural tensile strength of the highway pavement cement concrete is greater than 5 MPa, and according to the relationship formula (5) between the laboratory fatigue load times and the residual flexural strength within the service life, determine that the initial flexural strength is 8.2 MPa.
[0061] Step 5: According to the relationship formula (6) of compressive strength and flexural strength, determine that the target compressive strength of the pervious concrete matrix with a porosity of 0.126% is 65 MPa.
[0062] Step 6: According to the mix proportion design of porosity and target compressive strength, there are 832 parts of coarse aggregate; 817 parts of natural river sand; 363 parts of cement; 112 parts of fly ash; 30 parts of silica fume; 59 parts of slag; 6 parts of water reducing agent; 78 parts of steel fiber; 190 parts of water.
[0063] Step 7: Pour the concrete mixture into a pre-reinforced perforated mold. Immediately after the mold is filled, the slurry is collected. After the concrete has initially set for 4-5 hours, the reserved steel bars are removed to form a vertical through-hole. The concrete porosity is 0.126%. The test blocks are cured at room temperature for 24 hours and then demolded. After 28 days of standard curing (standard curing room temperature is 20±2°C and relative humidity is ≥95%), a flexural fatigue test is performed. The flexural strength and water permeability coefficient are measured every 50,000 loads. After the water permeability coefficient test, the test piece with the lowest water permeability coefficient is selected for a rainstorm simulation to test its resistance to rainstorm waterlogging.
[0064] Example 2
[0065] Step 1: Select the rainfall calendar parameters for the Nanjing region. Using equation (1), calculate the short-duration rainfall intensity with a 50-year recurrence period to be 1.59 mm / min. This ensures that the permeability coefficient of the permeable concrete is greater than the rainfall intensity, preventing surface water accumulation. Based on the relationship between rainfall intensity and the permeability coefficient of water flow within the duct (2), the permeability coefficient of the permeable concrete is determined to be greater than 4.2 mm / s.
[0066] Step 2: According to the relationship between porosity and permeability coefficient (2), the porosity of permeable concrete that meets the drainage recurrence period of 50 years is greater than 0.5%. 4×4 holes are arranged in a 100mm×100mm×100mm cubic specimen with a pore diameter of 2mm and a porosity of 0.506%.
[0067] Step 3: Select a secondary highway with an average daily design traffic volume of 6,000 passenger vehicles per lane and a structural design service life of 20 years. According to equation (3), the actual vehicle axle load Ne within the service life is determined to be 4.38×10 7 times, according to the relationship (4), determine the number of fatigue loads N in the laboratory fatigue test f 250,000 times.
[0068] Step 4: According to the regulations, the flexural tensile strength of heavy-duty pavement cement concrete is greater than 5 MPa. According to the relationship between the number of laboratory fatigue loads and the residual flexural strength within the service life (5), the initial flexural strength is determined to be 7 MPa.
[0069] Step 5: According to the relationship between compressive strength and flexural strength (6), the target compressive strength of the permeable concrete matrix with a porosity of 0.506% is determined to be 50 MPa.
[0070] Step 6: Design the mix ratio based on porosity and target compressive strength: 788 parts of coarse aggregate; 841 parts of natural river sand; 322 parts of cement; 102 parts of fly ash; 31 parts of silica fume; 51 parts of slag; 6 parts of water reducer; 16 parts of steel fiber; and 212 parts of water.
[0071] Step 7: Pour the concrete mixture into the pre-placed steel bar-reinforced perforated mold. Immediately bleed the mortar after molding. After the concrete initial sets in 4 - 5 hours, pull out the reserved steel bars to form a vertically through-hole. The porosity of the concrete is 0.506%. The test specimens are demolded after curing at normal temperature for 24 hours and then subjected to flexural fatigue tests after 28 days of standard curing (the temperature in the standard curing room is 20 ± 2°C and the relative humidity is ≥ 95%). Measure the flexural strength and water permeability coefficient every 50,000 loadings. After the water permeability coefficient test, select the specimen with the minimum water permeability coefficient for rainstorm simulation to test its anti-rainstorm waterlogging resistance performance.
[0072] Example 3
[0073] Step 1: According to the rainstorm parameters in Nanjing area, determine that the short-duration rainfall intensity with a rainfall return period of 100 years is 1.76 mm / min. If the permeability coefficient of the permeable concrete is greater than the rainfall intensity, no surface ponding will occur. According to the relationship (1) between the rainfall intensity and the internal water flow permeability coefficient of the pore channel, determine that the permeability coefficient of the permeable concrete is greater than 9.7 mm / s.
[0074] Step 2: According to the relationship formula (2) between porosity and permeability coefficient, the porosity of the permeable concrete that meets the drainage requirement with a return period of 10 years is greater than 1%. Arrange 4×4 holes with a diameter of 3 mm in a 100 mm×100 mm×100 mm cube specimen, and the porosity is 1.13%.
[0075] Step 3: Select a tertiary highway with an average annual daily design traffic volume of 6,000 passenger cars per single lane and a structural design service life of 20 years. According to the relationship formula (3), determine that the actual number of vehicle axle loads Ne within the service life is 3.2×10 7 times. According to the relationship formula (4), determine that the fatigue load number N f in the laboratory fatigue test is 200,000 times.
[0076] Step 4: According to the regulation that the flexural tensile strength of the heavy-duty pavement cement concrete is greater than 5 MPa, and according to the relationship formula (5) between the laboratory fatigue load number and the residual flexural strength within the service life, determine that the initial flexural strength is 6.3 MPa.
[0077] Step 5: According to the relationship formula (6) between the compressive strength and the flexural strength, determine that the target compressive strength of the permeable concrete matrix with a porosity of 1.13% is 40 MPa.
[0078] Step 6: According to the proportion design of porosity and target compressive strength, the coarse aggregate is 806 parts; natural river sand is 829 parts; cement is 291 parts; fly ash is 89; silica fume is 22 parts; slag is 45 parts; water reducer is 5 parts; steel fiber is 60 parts; water is 229 parts.
[0079] In Step 7, the concrete mixture is poured into the pre-placed steel bar with an opening mold. After molding, the slurry is immediately collected. After the concrete initial sets in 4 - 5 hours, the reserved steel bars are pulled out to form an up-and-down through-hole. The porosity of the concrete is 1.13%. The test blocks are demolded after curing at normal temperature for 24 hours and then cured under standard conditions for 28 days (the temperature in the standard curing room is 20 ± 2 °C, and the relative humidity is ≥ 95%), and then the flexural fatigue test is carried out. The flexural strength and water permeability coefficient are measured every 50,000 loadings. After the water permeability coefficient test is completed, the specimen with the smallest water permeability coefficient is selected for rainstorm simulation to test its anti-rainstorm waterlogging performance.
[0080] Comparative Example 1
[0081] In Step 1, according to the rain calendar parameters in Nanjing area, the short-duration rainfall intensity with a rainfall return period of 10 years is determined to be 1.21 mm / min. If the permeability coefficient of the permeable concrete is greater than the rainfall intensity, there will be no ponding on the surface. According to the relationship (1) between the rainfall intensity and the internal water flow permeability coefficient of the pore channel, the permeability coefficient of the permeable concrete is determined to be greater than 1.15 mm / s.
[0082] In Step 2, according to the relational formula (2) between the porosity and the permeability coefficient, the pore of the permeable concrete that meets the drainage with a return period of 10 years is greater than 0.1%. 4×4 holes are arranged in a 100 mm×100 mm×100 mm cube specimen, the pore diameter is 0.8 mm, and the porosity is 0.08%.
[0083] In Step 3, a first-class highway is selected, the annual average daily design traffic volume of a single lane is 6,000 passenger cars, and the structural design service life is 30 years. According to the relational formula (3), the actual number of vehicle axle loads Ne within the service life is determined to be 6.5×10 7 times. According to the relational formula (4), the fatigue load times N f in the laboratory fatigue test is determined to be 350,000 times.
[0084] In Step 4, according to the regulation that the flexural tensile strength of the heavy-duty pavement cement concrete is greater than 5 MPa, according to the relational formula (5) between the laboratory fatigue load times and the residual flexural strength within the service life, the initial flexural strength is determined to be 8.2 MPa.
[0085] In Step 5, according to the relational formula (6) between the compressive strength and the flexural strength, the target compressive strength of the permeable concrete matrix with a porosity of 0.08% is determined to be 65 MPa.
[0086] In Step 6, according to the proportion design of the porosity and the target compressive strength, 832 parts of coarse aggregate; 817 parts of natural river sand; 363 parts of cement; 112 parts of fly ash; 30 parts of silica fume; 59 parts of slag; 6 parts of water reducer; 78 parts of steel fiber; 190 parts of water.
[0087] Step 7: Pour the concrete mixture into the prefabricated steel-reinforced open mold. Immediately skim the surface after mold filling. After the concrete has initial set for 4 - 5 hours, pull out the reserved steel bars to form an up-and-down through-hole. The porosity of the concrete is 0.08%. The test specimens are demolded after curing at room temperature for 24 hours and then cured under standard conditions for 28 days (the temperature in the standard curing room is 20 ± 2°C and the relative humidity is ≥ 95%). Then, a flexural fatigue test is carried out. Measure the flexural strength and permeability coefficient every 50,000 loadings. After the permeability coefficient test is completed, select the specimen with the minimum permeability coefficient for rainstorm simulation to test its anti-rainstorm waterlogging resistance performance.
[0088] Comparative Example 2
[0089] Step 1: According to the rain calendar parameters in Nanjing area, determine that the short-duration rainfall intensity with a rainfall return period of 100 years is 1.76 mm / min. If the permeability coefficient of the permeable concrete is greater than the rainfall intensity, no surface ponding will occur. According to the relationship (1) between the rainfall intensity and the internal water flow permeability coefficient of the pore channels, determine that the permeability coefficient of the permeable concrete is greater than 9.7 mm / s.
[0090] Step 2: According to the relationship formula (2) between porosity and permeability coefficient, the porosity of the permeable concrete that can meet the drainage requirement with a return period of 10 years is greater than 0.1%. Arrange 4×3 holes with a diameter of 3 mm in a 100 mm×100 mm×100 mm cubic specimen, and the porosity is 1.507%.
[0091] Step 3: Select a tertiary highway with an average annual daily design traffic volume of 6,000 passenger cars per single lane and a structural design service life of 15 years. According to the relationship formula (3), determine that the actual number of vehicle axle loads Ne within the service life is 3.2×10 7 times. According to the relationship formula (4), determine that the fatigue load number N f in the laboratory fatigue test is 200,000 times.
[0092] Step 4: According to the regulation that the flexural tensile strength of the heavy-duty pavement cement concrete is greater than 5 MPa, determine the initial flexural strength to be 6.3 MPa according to the relationship formula (5) between the laboratory fatigue load number and the residual flexural strength within the service life.
[0093] Step 5: According to the relationship formula (6) between compressive strength and flexural strength, determine that the target compressive strength of the permeable concrete matrix with a porosity of 1.507% is 40 MPa.
[0094] Step 6: According to the proportion design based on porosity and target compressive strength, 806 parts of coarse aggregate; 829 parts of natural river sand; 291 parts of cement; 89 parts of fly ash; 22 parts of silica fume; 45 parts of slag; 5 parts of water reducer; 60 parts of steel fiber; 229 parts of water.
[0095] In Step 7, the concrete mixture is poured into the pre-placed steel-reinforced perforated mold. After molding, the slurry is immediately collected. After the concrete initial sets in 4 - 5 hours, the reserved steel bars are pulled out to form an up-and-down through-hole. The porosity of the concrete is 1.507%. The test specimens are demolded after curing at room temperature for 24 hours and then subjected to flexural fatigue tests after 28 days of standard curing (the temperature in the standard curing room is 20 ± 2°C, and the relative humidity is ≥ 95%). The flexural strength and water permeability coefficient are measured every 50,000 loadings. After the water permeability coefficient test is completed, the specimen with the lowest water permeability coefficient is selected for rainstorm simulation to test its anti-rainstorm waterlogging performance.
[0096] Table 2 shows the flexural strengths of Examples 1 - 3 and Comparative Examples 1 - 2
[0097]
[0098] Table 3 shows the permeability coefficients of Examples 1 - 3 and Comparative Examples 1 - 2
[0099]
[0100] Table 4 shows the water accumulation depths and drainage times of Examples 1 - 3 and Comparative Examples 1 - 2
[0101] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Maximum water accumulation depth (mm) 8 5 4 28 3 Drainage time (min) 1 0 0 3 0
[0102] According to the requirements of JTG D40 - 2011 "Design Specification for Highway Cement Concrete Pavement", the flexural strength of the cement concrete pavement used for highway pavement should be greater than 5.0 MPa. It can be seen from Table 2 that as the porosity and fatigue loading times of the permeable concrete increase, the flexural strength gradually decreases. After 20 years of service life, the flexural strength of the permeable concrete specimen with a porosity of 1.507% in Comparative Example 2 is less than 5 MPa, which cannot meet the service requirements of secondary highways.
[0103] According to the provisions of CJJ / T135—2009 "Technical Specification for Permeable Concrete Pavement", the permeability coefficient of permeable concrete should be above 0.5 mm / s. It can be seen from Table 3 that the initial permeability coefficients of recycled permeable concrete under different porosities can be used for permeable pavements. However, as the service life increases, the fatigue loads of vehicles gradually accumulate, the pores of the permeable concrete are damaged, and the permeability coefficient changes. For the permeable concrete specimens with a porosity of 0.08% - 0.126%, due to the smaller pore diameters of the straight-through holes, the debris generated by the spalling of the inner wall will cause the blockage of the pores. After 20 years of service life, the permeability coefficient of the specimen with a porosity of 0.08% in Comparative Example 1 drops to 0.35 mm / s, which is lower than the requirement of the permeability coefficient of permeable pavements being greater than 0.5 mm / s.
[0104] As can be seen from Table 3, under the action of vehicle fatigue load during the service life of the permeable concrete specimens in Examples 1-3, both the mechanical properties and the permeability coefficient can meet the requirements for the use of secondary recycled permeable concrete highway pavements. During the 60-minute rainfall process, the maximum ponding depth all appears near the peak rainfall intensity. The maximum ponding depths of the specimens with porosity of 0.126%, 0.502% and 1.13% are 8 mm, 5 mm and 4 mm respectively, and the maximum drainage times are 1 min, 0 min and 0 min respectively, which are far less than the requirements specified in GB50014-2021 "Outdoor Drainage Design Standard", that is, the ponding depth should be less than 15 cm and the maximum drainage time should be less than 0.5 h. The permeable concrete with porosity of 0.126%, 0.502% and 1.13% can be used for the drainage requirements of permeable pavements of different highway grades under the action of rainstorms with return periods of 10 years, 50 years and 100 years respectively.
[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.
Claims
1. A design method for drainage and regenerative permeable concrete for different highway grades, characterized in that: including S1 Determine the rainstorm intensity i at different return periods according to the rain calendar parameters in different regions; S2 Obtain K under different rainfall return periods according to relationship formula 1 between rainfall intensity i and water flow penetration coefficient K inside the pore channels of permeable concrete, and the relationship formula 1 is K = 0.81 + 3.87×10 -4 e 5.71 where K is the internal water flow permeability coefficient of the pore channel in mm / s, and i is the rainstorm intensity in mm / min; S3 Determine the porosity P according to the relationship formula two between the permeability coefficient and the porosity. The relationship formula two is P = (K - 0.2) / 7.92; where K is the permeability coefficient in mm / s; P is the porosity in %; S4 Determine the highway grade and the corresponding service life x; S5 Determine the actual number of vehicle axle loads Ne during the service life according to the relationship formula three. The relationship formula three is Ne = Dx; where D is the average daily design vehicle quantity in vehicles; x is the service life in years; S6 determines the laboratory fatigue loading times Nf according to the corresponding relationship between the actual vehicle axle load times Ne within the service life and the fatigue load times Nf in the laboratory fatigue test. The relationship formula four is N f = 0.2 × 0.5 × 1 / 3 × (60 / 365) Ne = 5.48×10 -3 Ne; where Nf is the laboratory fatigue load times and Ne is the actual vehicle axle load times; S7 determines the initial flexural strength of pervious concrete to meet the requirements of different grades of highways according to Equation V for the relationship between the number of laboratory fatigue load cycles and the residual flexural strength during the service life. Equation V is F = 9.03 - 0.03(e 0.041Nf - 1) / 0.04 + b; where, when Nf is 0, F is the initial flexural strength of the specimen without loading; Nf is the number of fatigue load cycles, in ten thousand times; b is a constant; S8 Determine the target compressive strength of the permeable concrete according to the relational expression six of the compressive strength and the flexural strength, and the relational expression six is F cu,0 = 14.2F - 52.3; where, Fcu,0 is the target compressive strength and F is the initial flexural strength; S9 Determine the mix proportion of the drainage and regeneration permeable concrete according to the requirements of the porosity in S3 and the target compressive strength in S9.
2. The design method of the drainage and regenerative permeable concrete for different highway grades according to claim 1, wherein: The drainage standard adopted by the design method is that the surface water depth is less than 15 cm and the drainage time is less than 0.5 h.
3. The design method of the drainage and regenerative permeable concrete for different highway grades according to claim 1, wherein: The pore diameters of the pores are 0.8, 1, 2, 3, and 4 mm, and the porosity is between 0.08% and 1.507%.