A design method of straight-through type recycled pervious concrete pavement resistant to sulfate attack

Abstract

The application discloses a design method of a straight-through type recycled water-permeable concrete pavement resistant to sulphate erosion, and relates to the field of pavement design methods. The application selects ordinary Portland cement and active superfine admixture as a concrete cementing material, and the prepared straight-through type recycled water-permeable concrete resistant to sulphate erosion has less water-permeable performance influencing factors and a long service life, thereby having a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete pavement design, and particularly relates to a design method of a straight-through type recycled water-permeable concrete pavement resistant to sulfate attack. BACKGROUND

[0002] Due to the rapid increase of global population and the promotion of urbanization, the urban soil closure leads to the imbalance of hydrological cycle, which aggravates the urban heat island effect, flood disaster and surface runoff rate. As a pavement material popularized in a sponge city, the water-permeable concrete can well relieve the urban drainage pressure, reduce the pavement runoff and protect the natural water system from damage. The strength of the traditional water-permeable concrete is generally not more than 20 MPa, and the interface between the paste and the aggregate is weak, which is prone to be broken under external load. Therefore, the traditional water-permeable concrete has the disadvantages of poor durability, easy consumption and easy damage.

[0003] In recent years, the land salinization in the northwest region of China is serious, and the acid rain caused by air pollution is intensified. The ground pollutants and sewage contain a large amount of sulfate ions, chloride ions, nitrate ions and other erosion ions, forming a complex multi-factor erosion environment. Sulfate attack is one of the most common corrosion types, which can cause serious internal expansion damage, strength degradation and durability problems of concrete. The water-permeable concrete works at the junction of the ground and the underground for a long time, and is easily subjected to repeated sulfate attack-dry-wet cycle. At present, many scholars have made certain research results in the durability direction of the traditional water-permeable concrete, and there are few studies on the erosion resistance of the water-permeable concrete under the sulfate attack environment. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the application.

[0005] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, and to provide a design method of a straight-through type recycled water-permeable concrete pavement resistant to sulfate attack.

[0007] To solve the above technical problems, the present application provides the following technical scheme: comprising the following steps, obtaining a relationship formula one between the water permeability coefficient K of the straight-through type recycled water-permeable concrete and the design porosity P;

[0008] obtaining a relationship formula two between the configuration strength S0 of the straight-through type recycled water-permeable concrete matrix and the target strength S about the design porosity;

[0009] selecting a water permeation coefficient K of the pervious concrete pavement required to reach a set drainage standard;

[0010] determining a design porosity P according to the relationship one, and designing a straight-through hole diameter and hole distribution of the straight-through water permeation hole of the straight-through pervious concrete;

[0011] determining a configuration strength S0 of the straight-through pervious concrete according to the relationship two, and determining the amount of each raw material component by using a full calculation method;

[0012] the concrete mixture is layered and inserted into a mold, further compacted by using a vibration mode, and the concrete molding is completed by using a special artificial hole forming mode.

[0013] As a preferred scheme of the application, the relationship one is P=0.148K-0.064, wherein K is the water permeation coefficient, K≥0.5mm / s; and P is the design porosity.

[0014] As a preferred scheme of the application, the relationship two is S=S0e -0.1235P , wherein S0 is the strength after 28d curing when the concrete porosity is 0%; S is the strength after 28d curing when the concrete porosity is P; and P is the design porosity.

[0015] As a preferred scheme of the application, the water permeation coefficient K of the pervious concrete pavement required to reach a set drainage standard is selected, and the target water permeation coefficients are 0.5mm / s, 3.5mm / s and 6.5mm / s respectively.

[0016] As a preferred scheme of the application, the straight-through hole is a circular hole with a diameter of 1-3mm, 16 water permeation holes are uniformly arranged on every 1 square decimeter, and a 4×4 arrangement mode is adopted.

[0017] As a preferred scheme of the application, the concrete mixture comprises coarse aggregate, fine aggregate, cementitious material, water reducing agent and water.

[0018] As a preferred scheme of the application, the coarse aggregate is recycled coarse aggregate, the fine aggregate is natural sand with a fineness modulus of 2.4-2.6, the cementitious material is a mixture of ordinary portland cement of 42.5 and active superfine admixture, and the water reducing agent is polycarboxylic high-efficiency water reducing agent with a water reducing efficiency of more than 30%.

[0019] As a preferred scheme of the application, the superfine admixture comprises fly ash of secondary and above, and silica fume with a SiO2 content of more than 98%.

[0020] As a preferred scheme of the present application, wherein: the active superfine admixture accounts for 20% to 40% of the cementitious material in terms of mass percentage, wherein the fly ash accounts for 10% to 35% in mass, the silica fume accounts for 4% to 8% in mass, and the water reducing agent accounts for 0.5% to 1.5% in mass.

[0021] As a preferred scheme of the present application, wherein: the concrete mixture is layered and inserted into a mold,

[0022] The coarse aggregate, the fine aggregate, and 1 / 4 of the water are mixed and stirred for 60s to obtain a first mixture;

[0023] The cement, the silica fume, and the fly ash are added to the first mixture and stirred for 90s to obtain a second mixture;

[0024] The remaining water is added to the second mixture and stirred for 30s to obtain a third mixture;

[0025] The total high-efficiency water reducing agent is added to the third mixture and stirred for 60s to obtain a mixture;

[0026] The mixture is poured into a straight-through hole mold, and after 5 to 8 hours, the steel bar is pulled out after the initial setting of the concrete and before the final setting, and the concrete is cured and demolded to obtain a straight-through type recycled water-permeable concrete.

[0027] The present application has the following beneficial effects:

[0028] (1) The present application proposes a straight-through type recycled water-permeable concrete pavement design method for resisting sulfate attack, and the straight-through type recycled water-permeable concrete for resisting sulfate attack is prepared by using an artificial reserved hole, the porosity is controlled by changing the diameter of the embedded hole component, so that the target water permeability coefficient is easily obtained, and a new type of water-permeable concrete with low cost and long service life is produced.

[0029] (2) By adding the active superfine admixture to replace ordinary Portland cement, the density and sulfate resistance of the water-permeable concrete are effectively improved, the mechanical properties of the water-permeable concrete are improved, and the service life of the water-permeable concrete is prolonged.

[0030] (3) The present application improves the performance of the straight-through type recycled water-permeable concrete by changing the admixture, which widens the market for the application of this straight-through type water-permeable concrete. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 Figure for relationship between permeable coefficient and design porosity of straight-through type recycled permeable concrete in the present application.

[0033] Figure 2 Figure for mold design of straight-through type recycled permeable concrete in the present application: Figure 2 (a) is a figure for channel distribution, Figure 2 (b) is a figure for mold assembly. DETAILED DESCRIPTION

[0034] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the description examples.

[0035] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited by the specific examples disclosed below.

[0036] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment that excludes other embodiments.

[0037] Example 1

[0038] The relationship between the porosity p and the permeable coefficient K of the straight-through type recycled permeable concrete is formula (1), which is obtained from a large number of tests, and the relationship between the permeable coefficient and the porosity in the test data is as follows Figure 1 ,

[0039] P = 0.148K - 0.064 (1)

[0040] Wherein, K is the permeable coefficient, mm / s; P is the porosity, %.

[0041] The relationship between the base configuration strength S0 and the target strength S of the straight-through type recycled permeable concrete with respect to the design porosity is formula (2),

[0042] S = S0e -0.1235P (2)

[0043] Wherein, S0 is the strength after 28 days of curing when the porosity of the concrete is 0%; S is the strength after 28 days of curing when the porosity of the concrete is P, MPa; P is the design porosity, %.

[0044] In combination with the road drainage demand and the specific project requirement, the invention considers the extreme rainstorm weather, and satisfies the lowest requirement of the water permeable coefficient of the water permeable concrete, i.e. K≥0.5mm / s, and the water permeable coefficient of the water permeable concrete during the use process is K≥0.5mm / s. Taking 0.5mm / s as the starting point and 3mm / s as the incremental unit, the target water permeable coefficients are selected as 0.5mm / s, 3.5mm / s and 6.5mm / s to design the porosity.

[0045] Referring to Figure 2 According to the formula (1), the straight-through holes are designed as the circular holes with the diameter of 1-3mm, 16 water permeable holes are uniformly arranged on every square decimeter, and the 4×4 arrangement mode is adopted.

[0046] The configuration strength of the concrete is determined according to the formula (2), the full calculation method is used to design the mixing ratio, the ordinary Portland cement and the active superfine admixture are selected as the concrete cementitious materials, and the active superfine admixture accounts for 20%-40% of the concrete cementitious materials.

[0047] It should be noted that the full calculation method is a general high-performance concrete mixing ratio design method. The full calculation method establishes a mathematical model based on the workability, strength and durability, deduces the calculation formula of the water consumption and sand ratio of the concrete, and calculates the consumption of each component of the concrete by using the formula combined with the water-binder rule.

[0048] According to the obtained proportioning, the concrete mixture is inserted and tamped into the mold in layers, further compacted by using the vibration mode, and the concrete molding is completed by using the special artificial pore-forming mode.

[0049] Example 2

[0050] In this embodiment, the water permeable coefficient K is selected as 0.5mm / s. According to the relationship formula (1) between the water permeable coefficient and the porosity, the optimal porosity P is determined as 0.01%-0.232%;

[0051] The diameter of the straight-through hole is selected as 1mm, 16 water permeable holes are uniformly arranged on every square decimeter, the 4×4 arrangement mode is adopted, and the porosity is 0.1256%.

[0052] The strength grade of the straight-through type recycled water permeable concrete is determined as 35MPa, and the configuration strength is calculated as 36MPa according to the formula (2);

[0053] The full calculation method is used to design the mixing ratio, the active superfine admixture accounts for 20% of the concrete cementitious materials, and the proportioning of each component of the concrete is shown in Table 1.

[0054] Table 1

[0055] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 951 parts 733 parts 337 parts 63 parts 21 parts 1.69 parts 174 parts

[0056] The raw materials are weighed according to the above-mentioned proportions, and the concrete is prepared according to the following steps:

[0057] The recycled coarse aggregate, natural river sand and 1 / 4 of the water are mixed and stirred for 60s to obtain a first mixture;

[0058] The cement, silica fume and fly ash are added to the first mixture and stirred for 90s to obtain a second mixture;

[0059] The remaining water is added to the second mixture and stirred for 30s to obtain a third mixture;

[0060] The total high-efficiency water reducing agent is added to the third mixture and stirred for 60s to obtain a mixture;

[0061] The mixture is poured into a straight-through hole mold with fixed reinforcement, layered and inserted into the mold, and further compacted using a vibration table for 20s. After about 5-8h, the reinforcement is pulled out after the initial setting and before the final setting of the concrete. After about 1d, the concrete is demolded after molding. It is placed in a standard curing room (temperature 20±2℃, relative humidity above 95%RH) for curing to obtain a straight-through type recycled pervious concrete resistant to sulfate attack.

[0062] Example 3

[0063] In this example, the water permeability coefficient K is selected as 3.5mm / s. According to the relationship between the water permeability coefficient and the porosity (1), the optimal porosity P is determined to be 0.454%-0.676%;

[0064] The straight-through hole diameter is selected as 1mm, and 16 water permeable holes are uniformly arranged per square decimeter, using a 4x4 arrangement method, and the porosity is 0.5024%.

[0065] The strength grade of the straight-through type recycled pervious concrete is determined to be 35MPa, and the preparation strength is calculated to be 38MPa according to formula (2);

[0066] The full calculation method is used for mix proportion design, in which the active ultra-fine admixture accounts for 20% of the cementitious materials of the concrete, and the mix proportion of each component of the concrete is as shown in Table 2:

[0067] Table 2

[0068] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 958 parts 726 parts 344 parts 64 parts 21 parts 1.72 parts 171 parts

[0069] The raw materials are weighed according to the above-mentioned proportions, and the concrete is prepared according to the following steps:

[0070] The recycled coarse aggregate, natural river sand and 1 / 4 of the water are mixed and stirred for 60s to obtain a first mixture;

[0071] The cement, silica fume and fly ash are added to the first mixture and stirred for 90s to obtain a second mixture;

[0072] adding the rest of the water in the second mixture and stirring for 30s to obtain a third mixture;

[0073] adding all of the superplasticizer in the third mixture and stirring for 60s to obtain a mixture;

[0074] pouring the mixture into a straight-through hole mold with fixed reinforcement, layering and inserting the mold, and further compacting using a vibration table for 20s. After about 5-8h, the reinforcement is pulled out after the initial setting and before the final setting of the concrete. After about 1d, the concrete is demolded after molding. The straight-through type recycled pervious concrete resistant to sulfate attack is prepared by placing it in a standard curing room (temperature 20±2℃, relative humidity above 95% RH) for curing.

[0075] Example 4

[0076] In this example, the water permeability coefficient K is selected to be 6.5mm / s. According to the relationship between the water permeability coefficient and the porosity (equation (1)), the optimal porosity P is determined to be 0.898%-1.120;

[0077] The straight-through hole diameter is selected to be 1mm, and 16 water permeable holes per square decimeter are uniformly arranged, using a 4x4 arrangement, and the porosity is 1.131%.

[0078] The strength grade of the straight-through type recycled pervious concrete is determined to be 35MPa, and the preparation strength is calculated to be 41MPa according to equation (2);

[0079] The mix proportion design is carried out using the full calculation method, in which the active ultra-fine admixture accounts for 20% of the cementitious materials of the concrete, and the mix proportion of each component of the concrete is as shown in Table 3:

[0080] Table 3

[0081] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 969 parts 715 parts 353 parts 66 parts 22 parts 1.76 parts 167 parts

[0082] The raw materials are weighed according to the above proportions, and the concrete is prepared according to the following steps:

[0083] The recycled coarse aggregate, natural river sand, and 1 / 4 of the water are mixed and stirred for 60s to obtain a first mixture;

[0084] The cement, silica fume, and fly ash are added to the first mixture and stirred for 90s to obtain a second mixture;

[0085] The rest of the water is added to the second mixture and stirred for 30s to obtain a third mixture;

[0086] All of the superplasticizer is added to the third mixture and stirred for 60s to obtain a mixture;

[0087] The mixture is poured into a straight-through hole mold with fixed reinforcement, the mold is inserted and tamped layer by layer, and further compacted by using a vibration table for 20 s. After about 5-8 h, the reinforcement is pulled out after the initial setting and before the final setting of the concrete. After about 1 d, the concrete is demolded after molding. The straight-through type recycled water-permeable concrete resistant to sulfate attack is prepared by placing it in a standard curing room (temperature 20±2°C, relative humidity above 95% RH) for curing.

[0088] Example 5

[0089] In this example, the water permeability coefficient K is selected as 6.5 mm / s. According to the relationship formula (1) between the water permeability coefficient and the porosity, the optimal porosity P is determined to be 0.898%-1.120%;

[0090] The straight-through hole diameter is selected as 1 mm, 16 water-permeable holes per square decimeter are uniformly arranged, a 4x4 arrangement is adopted, and the porosity is 1.131%.

[0091] The strength grade of the straight-through type recycled water-permeable concrete is determined to be 35 MPa, and the preparation strength is calculated to be 41 MPa according to formula (2);

[0092] The mix proportion design is carried out by using the full calculation method, in which the active ultra-fine admixture accounts for 30% of the cementitious materials of the concrete, and the component proportioning of the concrete is as shown in Table 4:

[0093] Table 4

[0094] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 973 parts 710 parts 305 parts 109 parts 22 parts 1.75 parts 165 parts

[0095] The raw materials are weighed according to the above proportioning, and the concrete is prepared according to the following steps:

[0096] The recycled coarse aggregate, natural river sand, and 1 / 4 of the water are mixed and stirred for 60 s to obtain a first mixture;

[0097] The cement, silica fume, and fly ash are added to the first mixture and stirred for 90 s to obtain a second mixture;

[0098] The remaining water is added to the second mixture and stirred for 30 s to obtain a third mixture;

[0099] The total high-efficiency water reducing agent is added to the third mixture and stirred for 60 s to obtain a mixture;

[0100] The mixture is poured into a straight-through hole mold with fixed reinforcement, the mold is inserted and tamped layer by layer, and further compacted by using a vibration table for 20 s. After about 5-8 h, the reinforcement is pulled out after the initial setting and before the final setting of the concrete. After about 1 d, the concrete is demolded after molding. The straight-through type recycled water-permeable concrete resistant to sulfate attack is prepared by placing it in a standard curing room (temperature 20±2°C, relative humidity above 95% RH) for curing.

[0101] Example 6

[0102] The water permeability coefficient K is selected as 6.5 mm / s. According to the relationship between the water permeability coefficient and the porosity (1), the optimal porosity P is determined to be 0.898% to 1.120;

[0103] The diameter of the straight-through hole is selected as 1 mm, and 16 water permeable holes are uniformly arranged per square decimeter. A 4x4 arrangement is used, and the porosity is 1.131%.

[0104] The strength grade of the straight-through type recycled water permeable concrete is determined to be 35 MPa. According to formula (2), the prepared strength is calculated to be 41 MPa;

[0105] The full calculation method is used for mix proportion design. The active ultra-fine admixture accounts for 40% of the cementitious materials of the concrete. The component proportioning of the concrete is as shown in Table 5:

[0106] Table 5

[0107] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 978 parts 706 parts 259 parts 151 parts 22 parts 1.73 parts 163 parts

[0108] The raw materials are weighed according to the above proportioning, and the concrete is prepared according to the following steps:

[0109] The recycled coarse aggregate, natural river sand, and 1 / 4 of the water are mixed and stirred for 60 s to obtain a first mixture;

[0110] The cement, silica fume, and fly ash are added to the first mixture and stirred for 90 s to obtain a second mixture;

[0111] The remaining water is added to the second mixture and stirred for 30 s to obtain a third mixture;

[0112] The entire high-efficiency water reducing agent is added to the third mixture and stirred for 60 s to obtain a mixture;

[0113] The mixture is poured into a straight-through hole mold with fixed reinforcement, layered and inserted into the mold, and further compacted using a vibration table for 20 s. After about 5-8 h, the reinforcement is pulled out after the initial setting of the concrete and before the final setting. After about 1 d, the concrete is demolded after molding. It is placed in a standard curing room (temperature 20±2℃, relative humidity above 95% RH) for curing to obtain a straight-through type recycled water permeable concrete resistant to sulfate attack.

[0114] Comparative Example 1

[0115] The water permeability coefficient K is selected as 0.5 mm / s. According to the relationship between the water permeability coefficient and the porosity (1), the optimal porosity P is determined to be 0.01% to 0.232%;

[0116] The direct-through hole has a diameter of 1 mm, 16 water-permeable holes are evenly arranged on every 1 square decimeter, a 4x4 arrangement is adopted, and the porosity is 0.1256%.

[0117] The strength grade of the direct-through type recycled water-permeable concrete is determined to be 35 MPa, and the preparation strength is calculated to be 36 MPa according to formula (2);

[0118] The full calculation method is used for the mix proportion design, the active superfine admixture accounts for 10% of the cementitious materials of the concrete, and the mix proportion of each component of the concrete is as shown in Table 6.

[0119] Table 6

[0120] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 947 parts 737 parts 383 parts 21 parts 21 parts 1.70 parts 175 parts

[0121] The raw materials are weighed according to the above-mentioned proportion, and the concrete is prepared according to the following steps:

[0122] The recycled coarse aggregate, natural river sand and 1 / 4 of the water are mixed and stirred for 60 s to obtain a first mixture;

[0123] The cement, silica fume and fly ash are added to the first mixture and stirred for 90 s to obtain a second mixture;

[0124] The remaining water is added to the second mixture and stirred for 30 s to obtain a third mixture;

[0125] The entire high-efficiency water reducing agent is added to the third mixture and stirred for 60 s to obtain a mixture;

[0126] The mixture is poured into a direct-through hole mold with fixed reinforcement, layered and inserted into the mold, and further compacted by using a vibration table for 20 s. About 5-8 h later, the reinforcement is pulled out after the initial setting and before the final setting of the concrete. About 1 d later, the concrete is demolded after molding. The standard curing room (temperature 20±2℃, relative humidity above 95% RH) is used for curing, and the direct-through type recycled water-permeable concrete resistant to sulfate attack is prepared.

[0127] Comparative Example 2

[0128] In this embodiment, the water permeability coefficient K is selected to be 6.5 mm / s. According to the relationship formula (1) between the water permeability coefficient and the porosity, the optimal porosity P is determined to be 0.898%-1.120%%;

[0129] The direct-through hole has a diameter of 1 mm, 16 water-permeable holes are evenly arranged on every 1 square decimeter, a 4x4 arrangement is adopted, and the porosity is 1.131%.

[0130] The strength grade of the direct-through type recycled water-permeable concrete is determined to be 35 MPa, and the preparation strength is calculated to be 41 MPa according to formula (2);

[0131] The full calculation method is used for mix proportion design, wherein the active superfine admixture accounts for 10% of the cementitious materials of the concrete, and the allocation ratio of each component of the concrete is as shown in Table 7:

[0132] Table 7

[0133] Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 965 parts 719 parts 400 parts 22 parts 22 parts 1.78 parts 168 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 951 parts 733 parts 337 parts 63 parts 21 parts 1.69 parts 174 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 958 parts 726 parts 344 parts 64 parts 21 parts 1.72 parts 171 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 969 parts 715 parts 353 parts 66 parts 22 parts 1.76 parts 167 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 973 parts 710 parts 305 parts 109 parts 22 parts 1.75 parts 165 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 978 parts 706 parts 259 parts 151 parts 22 parts 1.73 parts 163 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 947 parts 737 parts 383 parts 21 parts 21 parts 1.70 parts 175 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 965 parts 719 parts 400 parts 22 parts 22 parts 1.78 parts 168 parts Recycled coarse aggregate Natural river sand Cement Silica fume Fly ash Water reducing agent Water 951 parts 733 parts 337 parts 63 parts 21 parts 1

[0134] The raw materials are weighed according to the above allocation ratio, and the concrete is prepared according to the following steps:

[0135] The recycled coarse aggregate, natural river sand and 1 / 4 of the water are mixed and stirred for 60 s to obtain a first mixture;

[0136] The cement, silica fume and fly ash are added to the first mixture and stirred for 90 s to obtain a second mixture;

[0137] The remaining water is added to the second mixture and stirred for 30 s to obtain a third mixture;

[0138] The total high-efficiency water reducing agent is added to the third mixture and stirred for 60 s to obtain a mixture;

[0139] The mixture is poured into a straight-through hole mold with fixed reinforcement, layered and inserted into the mold, and further compacted by using a vibration table for 20 s. After about 5-8 h, the reinforcement is pulled out after the initial setting and before the final setting of the concrete. After about 1 d, the concrete is demolded after molding. The straight-through type recycled pervious concrete resistant to sulfate attack is prepared by placing it in a standard curing room (temperature 20±2℃, relative humidity above 95% RH) for curing.

[0140] The concrete prepared in Examples 2-6 is measured for 28 d compressive strength according to GB / T50081-2019 “Standard for Testing Methods for Mechanical Properties of Ordinary Concrete”; the mass loss rate and relative dynamic elastic modulus after 150 times of sulfate attack are measured to represent the corrosion resistance of the prepared concrete resistant to sulfate attack according to the sulfate attack test method in GB / T50082-2009 “Standard for Testing Methods for Long-term Performance and Durability of Ordinary Concrete”; and the water permeability coefficient before and after the attack is measured according to CJJ / T 135-2009 “Technical Specification for Pervious Cement Concrete Pavement”. The test results are shown in Table 8:

[0141] Table 8: Properties of the concrete prepared in each example and the comparative example

[0142]

[0143] The results show that the compressive strength and sulfate resistance of the concrete can be improved by the active super-fine admixture. As shown in Example 4, when the pore diameter is 3 mm and the content of the super-fine admixture is 20%, the measured compressive strength of the pervious concrete is significantly greater than the theoretical value; when the content of the super-fine admixture is 30%, the corrosion resistance coefficient of the pervious concrete is the largest. This is due to the secondary hydration reaction of SiO2 and Al2O3 in the fly ash and silica fume, which increases the amount and density of the hydration products, while excessive super-fine admixture can affect the full hydration of the cementitious material.

[0144] Under the sulfate erosion environment, the smaller the pore diameter of the straight-through pervious concrete, the greater the possibility of pore blockage. The straight-through pervious concrete with a pore diameter of 1 mm prepared in Comparative Example 1 has a water permeability coefficient K < 5 mm / s, and the water permeation holes are blocked after 120 dry-wet cycles, which does not meet the requirements of the specification and cannot perform effective water permeation work. When the pore diameter is 3 mm and the content of the super-fine admixture is 10%, the contact area of the concrete with the outside environment increases, making it more susceptible to erosion. In the later stage of sulfate erosion, white crystals are formed on the surface of the pervious concrete, the cement paste layer around the pores slowly peels off, and the water permeation holes expand to varying degrees, with a strength still exceeding the initial strength, and good corrosion resistance. This change is more conducive to road drainage.

[0145] The straight-through recycled pervious concrete is an environmentally friendly pervious concrete that can be applied to roads. This concrete can design the pore distribution and pore size of the pervious concrete according to the water permeability coefficient to obtain controllable porosity and compressive strength. Combined with the active super-fine admixture, the matrix of the straight-through recycled pervious concrete is further densified, which makes up for the defects of low strength and poor durability of traditional concrete, and prolongs the service life of this functional road concrete.

[0146] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A design method of a straight-through type recycled pervious concrete pavement resistant to sulfate attack, characterized by comprising: The method comprises the following steps, ​ obtaining a relationship formula one between the permeable coefficient K of the straight-through type recycled permeable concrete and the design porosity P; The relationship is wherein K is a water permeability coefficient, K≥0.5 mm / s; P is a design porosity; obtaining a relationship formula two between the matrix configuration strength S0 of the straight-through type recycled permeable concrete and the target strength S with respect to the design porosity; The relationship formula two is wherein S0 is the strength after curing for 28 days when the porosity of the concrete is 0%; S is the strength after curing for 28 days when the porosity of the concrete is P; and P is the designed porosity. selecting the permeable coefficient K of the permeable concrete pavement required to reach the set drainage standard; determining the design porosity P according to the relationship formula one, and designing the straight-through hole diameter and hole distribution of the straight-through type permeable concrete permeable hole; determining the configuration strength S0 of the straight-through type recycled permeable concrete according to the relationship formula two, and determining the amount of each raw material component by using the full calculation method; layered inserting and tamping the concrete mixture, further compacting by using the vibration mode, and completing the concrete molding by using the artificial hole forming mode; The concrete mixture comprises coarse aggregate, fine aggregate, cementitious material, water reducing agent and water, the coarse aggregate is recycled coarse aggregate, the fine aggregate is natural sand with a fineness modulus of 2.4-2.6, the cementitious material is a mixture of ordinary portland cement of 42.5 and active superfine admixture, the water reducing agent is a polycarboxylate superplasticizer with a water reducing efficiency of more than 30%, and the superfine admixture comprises fly ash of secondary and above and silica fume with a SiO2 content of more than 98%. The active superfine admixture accounts for 20%-40% of the cementitious material in terms of the mass percentage of the cementitious material, wherein the mass of the fly ash is 10%-35%, the mass of the silica fume is 4%-8%, and the mass of the water reducing agent is 0.5%-1.5%.

2. The design method of the anti-sulfate-erosion straight-through type recycled PWD concrete pavement according to claim 1, characterized in that: The target permeable coefficients are 0.5 mm / s, 3.5 mm / s and 6.5 mm / s, respectively.

3. The design method of the anti-sulfate-erosion straight-through type recycled PWD concrete pavement according to claim 1, characterized in that: The straight-through hole is a circular hole with a diameter of 1-3 mm, and 16 permeable holes are uniformly arranged on every square decimeter in a 4*4 arrangement mode.

4. The design method of the anti-sulfate-erosion through-type regenerative pervious concrete pavement according to claim 1, characterized in that: The layered inserting and tamping of the concrete mixture comprises, mixing and stirring the coarse aggregate, the fine aggregate and 1 / 4 of the water for 60 s to obtain a first mixture; adding cement, silica fume and fly ash to the first mixture and stirring for 90 s to obtain a second mixture; adding the remaining water to the second mixture and stirring for 30 s to obtain a third mixture; adding all the superplasticizer to the third mixture and stirring for 60 s to obtain a mixture; pouring the mixture into a straight-through hole mold, pulling out the steel bars after 5-8 h after the initial setting of the concrete and before the final setting, carrying out curing and demolding, and obtaining the straight-through type recycled permeable concrete.

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