WO2024027541A1 - Downpour flooding-resistant recycled pervious concrete suitable for heavy-load traffic pavement, and preparation method therefor - Google Patents

Abstract

The present invention relates to the technical field of building materials, and provides a downpour flooding-resistant recycled pervious concrete suitable for a heavy-load traffic pavement, and a preparation method therefor. The method comprises: determining the water permeability coefficient of a pervious concrete according to the rainfall intensity, the depth of flooding water, and a rainfall duration of each region, calculating the porosity of the pervious concrete according to the water permeability coefficient, and finally calculating the total number of pore channels of the concrete according to the porosity. The pervious concrete comprises the following components in parts by weight: 748-901 parts of recycled coarse aggregates, 732-827 parts of river sands, 600-630 parts of Portland cement, 80-100 parts of silica fume, 160-180 parts of fly ash, 80-120 parts of a steel fiber, 1.2-1.5 parts of a water-reducing admixture, and 180-189 parts of water. The pervious concrete provided by the present invention has high strength and excellent downpour flooding resistance for different rainfall intensities, and can also purify pollutants in runoff, and the compressive strength and breaking strength of the pervious concrete far exceed the requirements for a heavy-load pavement.

Description

A kind of regenerated permeable concrete suitable for heavy-duty traffic pavement to resist heavy rain and waterlogging and its preparation method Technical field

The invention belongs to the technical field of building materials, and specifically relates to a heavy rain waterlogging-resistant regenerated permeable concrete suitable for heavy-duty traffic pavements and a preparation method thereof.

Background technique

In recent decades, extreme rainstorms have occurred frequently. Such sudden rainfalls are short-duration and high-intensity, which can cause a sudden increase in pressure on urban drainage systems in a short period of time. In traditional urban construction, impermeable pavements continue to extend and the permeable natural surface continues to decrease, which leads to a weakening of the city's ability to cope with sudden rainfall. This rainwater forms surface runoff on impermeable pavement and gradually accumulates to form waterlogging. Waterlogging of a certain depth will seriously interfere with and damage the urban road network, causing traffic jams and accidents, and even threatening people's lives and property. In addition, waterlogging contains many pollutants, such as heavy metals (Cu ²⁺ ), organic matter, nitrogen and phosphorus, etc. These pollutants enter urban rivers with surface runoff, damaging the ecological environment. Building a sponge city is an effective measure to realize the free flow of urban rainwater and respond to natural disasters such as heavy rains and waterlogging, and laying permeable concrete roads is the key to building a sponge city.

However, traditional permeable concrete faces several challenges, including low strength, poor durability, difficult porosity control, easy clogging, and inconvenient maintenance. And strength is negatively correlated with water permeability and water purification capacity. Permeable concrete with lower porosity will obtain higher strength, but water permeability and water purification capacity will be significantly reduced; increasing porosity will obtain high permeability and water purification capacity. It also significantly reduces the strength of permeable concrete. Therefore, how to ensure that permeable concrete can quickly drain water while having high strength and water purification functions is the development trend of new roads in sponge cities.

Contents of the invention

In order to solve the deficiencies of the existing technology, the purpose of the present invention is to provide a regenerated permeable concrete suitable for heavy-duty traffic pavements that is resistant to heavy rain and waterlogging and a preparation method thereof. The permeable concrete has the characteristics of high strength and rapid waterlogging, which is beneficial to alleviating the problem. Urban waterlogging solves the problem that permeable concrete cannot be widely used on heavy-duty traffic pavements. The present invention optimizes the number and distribution of pores in permeable concrete, including the use of artificial pore formation, optimal porosity, pore diameter and pore distribution, so that the prepared permeable concrete has sufficient water permeability and water purification capabilities while ensuring high strength. .

In order to solve the deficiencies of the existing technology, the technical solutions provided by the present invention are:

A method for preparing regenerated permeable concrete that is suitable for heavy-duty traffic pavements and is suitable for heavy rain and waterlogging. The water permeability coefficient of the permeable concrete is determined according to the rainstorm intensity, waterlogging depth and rainfall duration in each region, and the porosity of the permeable concrete is calculated based on the water permeability coefficient. Finally, Calculate the total number of pores in concrete based on porosity; the permeable concrete includes the following components by weight: 748 to 901 parts of recycled coarse aggregate, 732 to 827 parts of river sand, 600 to 630 parts of Portland cement, and silica fume 80 to 100 parts, fly ash 160 to 180 parts, steel fiber 80 to 120 parts, water reducing agent 1.2 to 1.5 parts and water 180 to 189 parts.

Further, the water permeability coefficient k is determined by the relationship between rainstorm intensity i, waterlogging depth H, and rainfall duration t, k≥i+t/h, and k≥0.5mm/s; the rainstorm intensity i is based on The rainstorm intensity formula of each city is determined, and the rainstorm intensity formula of each city can be obtained by looking up the table ("China's New Generation of Rainstorm Intensity Formula"); the waterlogging depth H is based on the waterlogging depth (<150mm) specified in the outdoor drainage design specification GB 50014-2006. Determine; the rainfall time t is determined by the different anti-waterlogging design standards of each city. For example: the maximum waterlogging depth allowed on the main roads in Guangzhou is 15cm, and the maximum time to dissipate the waterlogging is 30 minutes.

Further, the pore diameter and the pollutant removal rate form a Wilbur distribution. When the pollutant removal rate is 50%, the upper and lower limits of the pore diameter are 0.5mm and 3mm respectively, and the pollutant removal rate = (initial concentration of pollutants - final concentration of pollutants)/initial concentration of pollutants.

Further, the calculation method of the porosity is: Among them, k is the water permeability coefficient; p is the porosity; d is the pore diameter; ρ is the density of water; μ is the viscosity of water; g is the acceleration of gravity.

Furthermore, the third relationship between the total number of pores n and the porosity p is n=pV/V _p , where V _p is the volume of a single pore, V _p =πhd ² /4; n is the total number of pores. ; p is the porosity, V is the volume of the concrete specimen, h is the height of the permeable concrete, and d is the pore diameter.

Furthermore, the number of pores on a single cross-section is determined by the relationship between the pore diameter and the height of permeable concrete: a≤10d/h, where a is the number of pores on a single cross-section; h is the height of permeable concrete, and d is the pore diameter.

Further, the recycled coarse aggregate is the first-class recycled coarse aggregate or the second-class recycled coarse aggregate specified in GB/T25177-2010, with a particle size of 5 to 16 mm; the strength grade of the Portland cement is not less than 52.5; the river sand is medium sand with a fineness modulus of 2.4 to 2.6; the water-reducing agent is a polycarboxylic acid-based water-reducing agent or a naphthalene-based water-reducing agent, and the water-reducing efficiency is not less than 30%.

Further, the weight ratio of Portland cement, silica fume and fly ash is 7:1:2.

Further, the preparation method of permeable concrete includes the following steps:

Step 1: Add the recycled coarse aggregate and river sand to the mixer and dry mix for 30 seconds;

Step 2: Add half of the water to the blender and mix for 30 seconds;

Step 3: Add Portland cement, silica fume, and fly ash to the mixer and stir for 30 seconds;

Step 4: Add the polycarboxylate water-reducing agent and the remaining water to the mixer and stir for 120 seconds. Mix evenly to obtain fresh concrete;

Step 5: Calculate the hole distribution spacing on the mold based on the total number of holes in the concrete. The number and diameter of the steel bars are equal to the number and diameter of the holes. Fix the steel bars in the mold, pour the fresh concrete into the mold, and pull out after initial setting. Permeable concrete can be obtained by removing the steel bars.

The invention also provides a regenerated permeable concrete suitable for heavy-duty traffic pavements that is resistant to heavy rain and waterlogging, and is prepared by the above method.

beneficial effects

The mixing ratio of the present invention is reasonable, and the prepared regenerated permeable concrete that is suitable for heavy-duty traffic pavements and is suitable for heavy rain and waterlogging has a slump greater than 645mm, a compressive strength greater than 90MPa, and a flexural strength greater than 14MPa, and has achieved mechanical strength, water permeability and purification properties. performance balance. Taking Guangzhou as an example, under the influence of heavy rains with return periods of 20, 50 and 100 years respectively, the permeable concrete did not accumulate water throughout the process and did not cause waterlogging. The removal rate of Cu ²⁺ exceeds 80%, the removal rate of COD and P exceeds 60%, and the removal rate of N exceeds 40%, and the purification performance is good. It can be widely used on roads in heavy-duty traffic areas. The permeable concrete effectively reduces the content of chemical oxygen demand (COD), heavy metals (Cu ²⁺ ), nitrogen (N) and phosphorus (P) and other pollutants in runoff, solving environmental pollution problems caused by rainfall.

Description of the drawings

Figure 1 is a schematic structural diagram of permeable concrete;

Figure 2 shows the relationship between strength and porosity; Figure a) is the compressive strength and Figure b) is the flexural strength;

Figure 3 shows the relationship between the removal rate of each pollutant and the porosity: a) COD; b) P; c) N; d) Cu ²⁺ ;

Figure 4 shows the relationship between pollutant removal rate and pore size.

Reference signs: 1. Channel; 2. Base body.

Detailed ways

The present invention will be further described below in conjunction with the embodiments. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, but cannot be used to limit the scope of the present invention.

An embodiment of the present invention provides a regenerated permeable concrete suitable for heavy-duty traffic pavements that is resistant to heavy rain and waterlogging. It is characterized in that the intensity of heavy rain in each city is divided into three levels with a recurrence period of 20 years, 50 years and 100 years. For example, Guangzhou The city's return period is 20 years, and the one-hour peak rainstorm intensity in 50 years and 100 years is 5.5mm/min, 6.1mm/min, and 6.5mm/min respectively. The maximum waterlogging depth is selected as 0mm.

The appropriate water permeability coefficient k is selected based on the rainstorm intensity i and the prescribed maximum waterlogging depth H of each city, and k ≥ 0.5 mm/s.

According to Figure 4, it can be seen that the pore size and pollutant removal rate form a Wilbu distribution. As the pore diameter increases, the removal of pollutants first increases and then decreases. When the pollutant removal rate is 50%, the upper and lower limits of the pore diameter are divided into 0.5mm and 3mm. Therefore, in order to obtain a higher pollutant removal rate, the diameter of the hole in the present invention is selected to be 0.8mm, 1mm or 2mm. According to the relation 1 Determine porosity. Among them, k is the water permeability coefficient; p is the porosity; d is the pore diameter; ρ is the density of water; μ is the viscosity of water; g is the acceleration of gravity.

The third relationship between the total number of pores n and the porosity p is n = pV/V _p , where V _p is the volume of a single pore, V _p = πhd ² /4; n is the number of pores; p is the porosity, V is the volume of the concrete specimen, and h is the height of the permeable concrete.

The number of holes on a single cross-section is determined by the relationship equation 4a≤10d/h. Based on the total number of holes and the number of holes on a single cross-section, three types of hole distribution spacing are determined, which are 5mm×5mm and 5mm×4mm respectively. and 3mm×4mm.

A kind of regenerated permeable concrete suitable for heavy-duty traffic pavement to resist heavy rain and waterlogging, including the following components by weight: 748 to 901 parts of recycled coarse aggregate, 732 to 827 parts of river sand, 600 to 630 parts of Portland cement, silicon 80 to 100 parts of ash, 160 to 180 parts of fly ash, 80 to 120 parts of steel fiber, 1.2 to 1.5 parts of water reducing agent and 180 to 189 parts of water. Portland cement, silica fume, and fly ash are used as cementitious materials. The obtained permeable concrete is shown in Figure 1. Self-compacting concrete is used as the matrix of permeable concrete, and the vertical channels are used as permeable pores. Self-compacting concrete has good workability, and the aggregates are wrapped and tightly bound by cement slurry. Steel fibers effectively build the internal structure of concrete, giving concrete better self-compacting properties and having a great positive impact on the strength of concrete. Permeable concrete maintains good strength even when porosity and pore size reach high levels.

In an alternative embodiment of the invention, the Portland cement has a strength rating of not less than 52.5.

In an optional embodiment of the present invention, the weight ratio of Portland cement, silica fume and fly ash is 7:1:2.

In an optional embodiment of the present invention, the ratio of the weight of water to the total weight of cementitious materials (Portland cement, silica fume, fly ash and slag) is 0.20 to 0.23.

In an optional embodiment of the present invention, the river sand is medium sand, and the fineness modulus is 2.4 to 2.6.

In an optional embodiment of the present invention, the water-reducing agent is a polycarboxylic acid-based water-reducing agent or a naphthalene-based water-reducing agent, and the water-reducing efficiency is not less than 30%. Among them, polycarboxylic acid-based water reducing agents are preferred.

Preparing permeable concrete involves the following steps:

Step 1: Add the recycled coarse aggregate and river sand to the mixer and dry mix for 30 seconds.

Step 2: Add half of the water to the blender and mix for 30 seconds.

Step 3: Add Portland cement, silica fume, and fly ash to the mixer and stir for 30 seconds.

Step 4: Add the polycarboxylate water-reducing agent and the remaining water to the mixer and stir for 120 seconds. Mix evenly to obtain fresh concrete.

Step 5: Pre-fix the steel bars of the preferred diameter on the mold according to the preferred hole distribution spacing, pour the fresh concrete into the mold, and remove the steel bars after initial setting to obtain permeable concrete.

In an optional embodiment of the invention, the mixing container is a mixer.

The present invention measures the slump of concrete in accordance with the "Standard for Test Methods for Performance of Ordinary Concrete Mixtures GB/T50080-2016", determines the allowable waterlogging depth in accordance with the "Exterior Drainage Design Specification GB 50014-2006", and determines the allowable waterlogging depth in accordance with the "Mechanical Performance Test of Ordinary Concrete" The 28d compressive strength and 28d flexural strength measured according to the method standard GB/T50081-2019, and the Cu ²⁺ , COD, N and The removal rate of P is used to characterize the performance of the prepared permeable concrete.

Embodiment 1

Follow these steps to prepare permeable concrete:

Step 1. Select the rainfall intensity of Guangzhou City with a return period of 20 years as 0.09mm/s, the allowable waterlogging depth as 0mm, the permeability coefficient as 1.0mm/s, and the pore diameter as 0.8mm. According to the relationship between permeability coefficient and porosity According to relational formula 1, the porosity is selected as 0.126%.

Step 2: Determine that 25 water-permeable holes are evenly arranged every 100cm2 according to the relational expression ^3. Determine the number of holes in a single cross-section to be 5 according to the relational expression 4, and select the hole distribution as 5mm×5mm. Pre-fix the steel bars with the preferred diameter on the mold according to the hole distribution spacing selected in the above step.

Step 3: Prepare 901 parts of recycled coarse aggregate, 827 parts of river sand, 630 parts of ordinary Portland cement, 90 parts of silica fume, 180 parts of fly ash, 98 parts of steel fiber, 189 parts of water, and polycarboxylic acid according to the weight parts 1.2 parts of water reducing agent. Among them, the particle size of recycled coarse aggregate is 5~16mm. The river sand is medium sand with a fineness modulus of 2.6. The strength grade of ordinary Portland cement is 52.5. The mass ratio of ordinary Portland cement, silica fume and fly ash to the total cementitious materials is 7:1:2, and the water-cement ratio is 0.21. The water reducing efficiency of polycarboxylate water reducing agent is 30%.

Step 4: Put each component into a mixer to prepare fresh concrete and pour it into the mold. After initial setting, remove the steel bars to obtain permeable concrete. Cure it at room temperature for 24 hours to demould, and place it in a standard curing room (20±2℃ , relative humidity >95%) curing for 28 days.

Step 5: After 28 days of curing, conduct compressive strength, flexural strength, water purification capacity and heavy rain simulation tests. The purification test is to put it into a water tank containing different pollutants and let it stand for 720 minutes. After 720 minutes, the concentration of each pollutant in the water tank is tested. The heavy rain simulation test selected rainfall with return periods of 20, 50, and 100 years in Guangzhou, and placed permeable concrete on a heavy rain machine to conduct a heavy rain simulation test.

Embodiment 2

Follow these steps to prepare permeable concrete:

Step 1. Select the rainfall intensity with a return period of 50 years in Guangzhou as 0.11mm/s, the allowable waterlogging depth as 0mm, the permeability coefficient as 1.5mm/s, and the pore diameter as 1mm. According to the relationship between permeability coefficient and porosity For formula 1, the porosity is selected as 0.196%.

Step 2: Determine that 20 water-permeable holes are evenly arranged every 100cm2 according to the relational expression ^3. Determine the number of holes in a single section to be 4 according to the relational expression 4, and select the hole distribution as 5mm×4mm. Pre-fix the steel bars with the preferred diameter on the mold according to the hole distribution spacing selected in the above step.

Step 3: Prepare 901 parts of recycled coarse aggregate, 827 parts of river sand, 630 parts of ordinary Portland cement, 90 parts of silica fume, 180 parts of fly ash, 98 parts of steel fiber, 189 parts of water, and polycarboxylic acid according to the weight parts 1.2 parts of water reducing agent. Among them, the particle size of recycled coarse aggregate is 5~16mm. The river sand is medium sand with a fineness modulus of 2.6. The strength grade of ordinary Portland cement is 52.5. The mass ratio of ordinary Portland cement, silica fume and fly ash to the total cementitious materials is 7:1:2, and the water-cement ratio is 0.21. The water reducing efficiency of polycarboxylate water reducing agent is 30%.

Step 4: Put each component into a mixer to prepare fresh concrete and pour it into the mold. After initial setting, remove the steel bars to obtain permeable concrete. Cure it at room temperature for 24 hours to demould, and place it in a standard curing room (20±2℃ , relative humidity >95%) curing for 28 days.

Step 5: After 28 days of curing, conduct compressive strength, flexural strength, water purification capacity and heavy rain simulation tests. The purification test is to put it into a water tank containing different pollutants and let it stand for 720 minutes. After 720 minutes, the concentration of each pollutant in the water tank is tested. The heavy rain simulation test selected rainfall with return periods of 20, 50, and 100 years in Guangzhou, and placed permeable concrete on a heavy rain machine to conduct a heavy rain simulation test.

Embodiment 3

Follow these steps to prepare permeable concrete:

Step 1. Select the rainfall intensity with a return period of 100 years in Guangzhou to be 0.12mm/s, the allowable waterlogging depth to be 0mm, the permeability coefficient to be 3mm/s, and the pore diameter to be 2mm. According to the relationship between permeability coefficient and porosity, , the porosity is chosen to be 0.377%.

Step 2: Determine that 12 water permeable holes are evenly arranged every ^100cm2 according to the relational expression 3. Determine the number of holes in a single section to be 3 according to the relational expression 4, and select the hole distribution as 4mm×3mm. Pre-fix the steel bars with the preferred diameter on the mold according to the hole distribution spacing selected in the above step.

Step 3: Prepare 901 parts of recycled coarse aggregate, 827 parts of river sand, 630 parts of ordinary Portland cement, 90 parts of silica fume, 180 parts of fly ash, 98 parts of steel fiber, 189 parts of water, and polycarboxylic acid according to the weight parts 1.2 parts of water reducing agent. Among them, the particle size of recycled coarse aggregate is 5~16mm. The river sand is medium sand with a fineness modulus of 2.6. The strength grade of ordinary Portland cement is 52.5. The mass ratio of ordinary Portland cement, silica fume and fly ash to the total cementitious materials is 7:1:2, and the water-cement ratio is 0.21. The water reducing efficiency of polycarboxylate water reducing agent is 30%.

Step 4: Put each component into a mixer to prepare fresh concrete and pour it into the mold. After initial setting, remove the steel bars to obtain permeable concrete. Cure it at room temperature for 24 hours to demould, and place it in a standard curing room (20±2℃ , relative humidity >95%) curing for 28 days.

Step 5: After 28 days of curing, conduct compressive strength, flexural strength, water purification capacity and heavy rain simulation tests. The purification test is to put it into a water tank containing different pollutants and let it stand for 720 minutes. After 720 minutes, the concentration of each pollutant in the water tank is tested. The heavy rain simulation test selected rainfall with return periods of 20, 50, and 100 years in Guangzhou, and placed permeable concrete on a heavy rain machine to conduct a heavy rain simulation test.

Comparative Example 1

Follow these steps to prepare permeable concrete:

Step 1. Prepare 901 parts of recycled coarse aggregate, 827 parts of river sand, 630 parts of ordinary Portland cement, 90 parts of silica fume, 180 parts of fly ash, 98 parts of steel fiber, 189 parts of water, and polycarboxylic acid according to the weight parts 1.2 parts of water reducing agent. Among them, regenerating thick bone The particle size of the material is 5~16mm. The river sand is medium sand with a fineness modulus of 2.6. The strength grade of ordinary Portland cement is 52.5. The mass ratio of ordinary Portland cement, silica fume and fly ash to the total cementitious materials is 7:1:2, and the water-cement ratio is 0.21. The water reducing efficiency of polycarboxylate water reducing agent is 30%.

Step 2: Select the porosity to be 0.08%, the pore diameter to be 0.8mm, and the pore distribution to be 4mm×4mm.

Step 3: Put each component into a mixer to prepare fresh concrete and pour it into the mold. After initial setting, remove the steel bars to obtain permeable concrete. Cure it at room temperature for 24 hours to demould, and place it in a standard curing room (20±2℃ , relative humidity >95%) curing for 28 days.

Step 4: After 28 days of curing, conduct compressive strength, flexural strength, water purification capacity and heavy rain simulation tests. The purification test is to put it into a water tank containing different pollutants and let it stand for 720 minutes. After 720 minutes, the concentration of each pollutant in the water tank is tested. The heavy rain simulation test selected rainfall with return periods of 20, 50, and 100 years in Guangzhou, and placed permeable concrete on a heavy rain machine to conduct a heavy rain simulation test.

Comparative Example 2

Follow these steps to prepare concrete:

Step 1. Prepare 901 parts of recycled coarse aggregate, 827 parts of river sand, 630 parts of ordinary Portland cement, 90 parts of silica fume, 180 parts of fly ash, 98 parts of steel fiber, 189 parts of water, and polycarboxylic acid according to the weight parts 1.2 parts of water reducing agent. Among them, the particle size of recycled coarse aggregate is 5~16mm. The river sand is medium sand with a fineness modulus of 2.6. The strength grade of ordinary Portland cement is 52.5. The mass ratio of ordinary Portland cement, silica fume and fly ash to the total cementitious materials is 7:1:2, and the water-cement ratio is 0.21. The water reducing efficiency of polycarboxylate water reducing agent is 30%.

Step 2: Select the porosity to be 2.011%, the pore diameter to be 4mm, and the pore distribution to be 4mm×4mm.

Step 3: Put each component into a mixer to prepare fresh concrete and pour it into the mold. After initial setting, remove the steel bars to obtain permeable concrete. Cure it at room temperature for 24 hours to demould, and place it in a standard curing room (20±2℃ , relative humidity >95%) curing for 28 days.

Step 4: After 28 days of curing, conduct compressive strength, flexural strength, water purification capacity and heavy rain simulation tests. The purification test is to put it into a water tank containing different pollutants and let it stand for 720 minutes. After 720 minutes, the concentration of each pollutant in the water tank is tested. The heavy rain simulation test selected rainfall with return periods of 20, 50, and 100 years in Guangzhou, and placed permeable concrete on a heavy rain machine to conduct a heavy rain simulation test.

Comparative Example 3

Follow these steps to prepare concrete:

Step 1. Prepare 754 parts of recycled coarse aggregate, 741 parts of river sand, 630 parts of ordinary Portland cement, 90 parts of silica fume, 180 parts of fly ash, 98 parts of steel fiber, 180 parts of water, and polycarboxylic acid according to the weight parts 1.4 parts of water reducing agent. Among them, the particle size of recycled coarse aggregate is 5~16mm. The river sand is medium sand with a fineness modulus of 2.6. The strength grade of ordinary Portland cement is 52.5. The mass ratio of Portland cement, silica fume and fly ash to the total cementitious materials is 7:1:2, and the water-cement ratio is 0.21. The water reducing efficiency of polycarboxylate water reducing agent is 30%.

Step 2: Select the porosity to be 2.36%, the pore diameter to be 4mm, and the pore distribution to be 4mm×5mm.

Step 3: Put each component into a mixer to prepare fresh concrete and pour it into the mold. After initial setting, remove the steel bars to obtain permeable concrete. Cure it at room temperature for 24 hours to demould, and place it in a standard curing room (20±2℃ , relative humidity >95%) curing for 28 days.

Step 4: After 28 days of curing, conduct compressive strength, flexural strength, water purification capacity and heavy rain simulation tests. The purification test is to put it into a water tank containing different pollutants and let it stand for 720 minutes. After 720 minutes, the concentration of each pollutant in the water tank is tested. The heavy rain simulation test selected rainfall with return periods of 20, 50, and 100 years in Guangzhou, and placed permeable concrete on a heavy rain machine to conduct a heavy rain simulation test.

The test results are shown in Tables 1 and 2, and the types and initial concentrations of pollutants are shown in Table 3. Before the water purification experiment, sewage was prepared in the laboratory. Potassium hydrogen phthalate, potassium dihydrogen phosphate, potassium nitrate and anhydrous copper sulfate were used as carbon source, phosphorus source, nitrogen source and copper source respectively.

Table 1 Mechanical, purification and water permeability performance data of permeable concrete

Table 2 Water accumulation depth under 60 minutes of rainfall (mm)

Table 3 Initial concentrations of pollutants

The results show that the compressive strength and flexural strength in the embodiment shown in Figure 2 far exceed the road strength requirements of heavy-duty roads; in terms of purification capacity, as shown in Figure 3, the Cu ²⁺ removal rate of permeable concrete exceeds 80%, COD and P removal rate exceeds 60%, N removal rate exceeds 40%, and the purification performance is good. During the entire process of simulating heavy rains, under three heavy rain levels with return periods of 20, 50 and 100 years, there was no water accumulation on the surface of the permeable concrete specimens, meeting the requirements for resisting heavy rain flooding. Although the permeable concrete of Comparative Example 1 has high mechanical properties, the porosity is too small, resulting in poor purification performance. This is because permeable concrete usually relies on adsorption to remove pollutants, and larger porosity provides more contact area. It provides more places for the adsorption of pollutants; the surface of the recycled coarse aggregate used is rough and porous, and a lot of old mortar adheres to it, which increases the specific surface area for the adhesion of harmful substances to the concrete, and also plays a certain role in improving the purification ability.

In addition, the small porosity cannot provide sufficient permeability coefficient. When the permeability coefficient is less than the intensity of rainstorm, rainwater cannot flow into the ground through the permeable concrete in time, resulting in water accumulation on the road. The permeable concrete of Comparative Examples 2 and 3 has high purification performance and permeability, but excessive porosity leads to a significant reduction in flexural strength. This is because permeable concrete mainly relies on cross-sectional area to provide cross-sectional resistance, and high porosity The area of the tensile area is reduced, thereby significantly reducing the flexural strength. Especially in Comparative Example 3, the flexural strength cannot meet the requirements of heavy-load pavement. The embodiment establishes the relationship between rainstorm intensity and porosity, so that under the influence of rainfall at different return periods, it can be ensured that no water will accumulate on the road surface during the rainstorm. A determined and reasonable pore structure can also ensure that permeable concrete has a high purification capacity. Through the above analysis, this invention can determine the optimal porosity of different rainstorm intensities according to the requirements of the area to resist heavy rain and waterlogging, design a suitable pore structure, and achieve better permeability, mechanical properties and purification capabilities of permeable concrete. Balance the relationship.

The above are only preferred embodiments of the present invention. It should be noted that those of ordinary skill in the art can also make several improvements and modifications without departing from the technical principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (7)

1. A method for preparing regenerated permeable concrete that is suitable for heavy-duty traffic pavements and is characterized by determining the permeability coefficient of the permeable concrete based on the intensity of heavy rain, the depth of waterlogging, and the duration of rainfall in each region, and calculating the permeable concrete based on the permeability coefficient. Porosity, and finally calculate the total number of pores in the concrete based on the porosity; the permeable concrete includes the following components by weight: 748 to 901 parts of recycled coarse aggregate, 732 to 827 parts of river sand, and 600 to 630 parts of Portland cement. parts, 80 to 100 parts of silica fume, 160 to 180 parts of fly ash, 80 to 120 parts of steel fiber, 1.2 to 1.5 parts of water reducing agent and 180 to 189 parts of water;

   The water permeability coefficient k is determined by the relationship between rainstorm intensity i, waterlogging depth H, and rainfall duration t, k≥i+H/t, and k≥0.5mm/s;

   The calculation method of the porosity is: Among them, k is the water permeability coefficient; p is the porosity; d is the pore diameter; ρ is the density of water; μ is the viscosity of water; g is the acceleration of gravity;

   The relationship between the total number of pores n and the porosity p is n = pV/V _p , where V _p is the volume of a single pore, V _p = πhd ² /4; n is the total number of pores; p is the pore rate, V is the volume of the concrete specimen, h is the height of the permeable concrete, and d is the pore diameter;

   The number of pores on a single cross-section is determined by the relationship between the pore diameter and the height of permeable concrete, a≤10d/h, where a is the number of pores on a single cross-section; h is the height of permeable concrete, and d is the pore diameter.
2. The method for preparing regenerated permeable concrete that is suitable for heavy-duty traffic pavements and is suitable for heavy rainstorms and waterlogging, characterized in that the rainstorm intensity i is determined according to the rainstorm intensity formula of each city; the waterlogging depth H is determined according to the outdoor rainstorm intensity formula. The depth of waterlogging specified in the drainage design specification GB 50014-2006 is determined; the rainfall time t is determined by the different anti-waterlogging design standards of each city.
3. The method for preparing regenerated permeable concrete suitable for heavy-duty traffic pavements to resist heavy rain and waterlogging according to claim 1, characterized in that the pore size and the pollutant removal rate form a Wilbur distribution. When the pollutant removal rate is 50% When , the upper and lower limits of the pore diameter are 0.5mm and 3mm respectively, and the pollutant removal rate = (initial concentration of pollutants - final concentration of pollutants) / initial concentration of pollutants.
4. The preparation method of regenerated permeable concrete suitable for heavy-duty traffic pavements to resist heavy rain and waterlogging according to claim 1, characterized in that the regenerated coarse aggregate is a type of recycled coarse aggregate or type II regenerated coarse aggregate specified in GB/T25177-2010. Regenerated coarse aggregate with a particle size of 5 to 16 mm; the strength grade of the Portland cement is not less than 52.5; the river sand is medium sand with a fineness modulus of 2.4 to 2.6; the water reducing agent is Polycarboxylic acid-based water-reducing agent or naphthalene-based water-reducing agent, the water-reducing efficiency is not less than 30%.
5. The method for preparing regenerated permeable concrete suitable for heavy-duty traffic pavements to resist heavy rain and waterlogging according to claim 1, characterized in that the weight ratio of Portland cement, silica fume and fly ash is 7:1:2 .
6. The method for preparing regenerated permeable concrete suitable for heavy-duty traffic pavements to resist heavy rain and waterlogging according to claim 1, characterized in that the preparation method of permeable concrete includes the following steps:

   Step 1: Add the recycled coarse aggregate and river sand to the mixer and dry mix for 30 seconds;

   Step 2: Add half of the water to the blender and mix for 30 seconds;

   Step 3: Add Portland cement, silica fume, and fly ash to the mixer and stir for 30 seconds;

   Step 4: Add the polycarboxylate water-reducing agent and the remaining water to the mixer and stir for 120 seconds. Mix evenly to obtain fresh concrete;

   Step 5: Calculate the hole distribution spacing on the mold based on the total number of holes in the concrete. The number and diameter of the steel bars are equal to the number and diameter of the holes. Fix the steel bars in the mold, pour the fresh concrete into the mold, and pull out after initial setting. Permeable concrete can be obtained by removing the steel bars.
7. A regenerated permeable concrete suitable for heavy-duty traffic pavements that is resistant to heavy rain and waterlogging, and is characterized in that it is prepared by the method described in any one of claims 1 to 6.