Now, with the development of the economy, the pace of urban modernization is accelerating, and most cities have successively shown the lack of groundwater resources and the heat island effect. The study found that these problems are related to the continuous concealment of natural soil vegetation by buildings and various impervious grounds in urban construction. The impermeable ground share of many cities in China has exceeded 70%, which has changed the original natural ground permeability properties and greatly damaged the ecological environment. Although permeable bricks and absorbent bricks are paved on the pavements and sidewalks in many cities, most of the bottom layers of these bricks have not been treated. As a result, these bricks are limited to a small amount of rainwater and drainage, and in heavy rain or heavy rain Water also accumulates on the pavement, putting pressure on urban drainage and flood control. In addition, in the dry season, groundwater cannot be replenished into the air through the permeable bricks in a timely manner through transpiration, and the "heat island effect" cannot be alleviated. The general water-permeable paving system is composed of a series of concrete blocks and plastic mesh structures, which are filled with sand, gravel and soil, and have pore permeability. These pores allow rainwater to enter the underground soil and play a significant role in reducing rainwater runoff from urban development. The permeable brick pavement system has the advantages of reducing runoff peaks, storing rainwater, and simple construction and repair, which has been promoted by industry experts. Many scholars have studied the data strength and permeability coefficient of permeable bricks , but there is still a lack of inductive studies on the permeable brick paving system. The application of the permeable brick paving system is mixed. This article aims at the function and function of permeable bricks produced by Zhejiang Fangyuan Building Material Technology Co., Ltd. and their layers, and discusses an ecological permeable system to deal with the urban water cycle and mitigate the "heat island effect" and to adjust the urban microclimate. Permeable bricks are the primary component of an ecological permeable system, and also the part of the entire system that is exposed to the outside and touched by people. Therefore, according to the characteristics of permeable bricks and their role in the entire permeable system, the type and structure of the bricks during the development process , Cooperation ratio, preparation process and function. Permeable concrete products can be divided into 3 types according to the permeation method: front permeable type, side permeable type and seam permeable type. Let's first discuss the composite layer type and single layer type permeable brick of front permeable brick . The specifications of the permeable bricks mainly discussed in this article are 200 mm side length, 60 mm thickness, and side length / thickness = 3.33 (less than 5). The block is composed of 2 layers. Surface layer: 5 ～ 8 mm thick. The use of special mortar not only improves the abrasion resistance of the surface layer, but also facilitates the addition of dyes or artificial colored sand to manufacture various colorful texture permeable bricks . Bottom layer: 55 ～ 52 mm thick, permeable concrete with small particle size and coarse aggregate. It still has a large connected porosity at high compressive strength to ensure water permeability. Pervious bricks suggest 1.3 Cooperation ratio of permeable bricks 1.3.1 The cooperation ratio of the bottom layer is based on the research of permeable concrete. Considering the characteristics of permeable bricks , after many experiments, the bottom layer of the permeable bricks is prepared with aggregates (1.25-5.0 mm Zhejiang Pebble) and cement (Conch P · Ⅱ52. 5), 5 kinds of basic raw materials of fly ash (Taizhou Power Plant III ash), water (water for concrete mixing) and naphthalene-based superplasticizer (Taizhou Luban), based on water-gel ratio of 0.22, ash collection ratio of 3.0, policy The porosity is 15%, and the amount of the water reducing agent is 2.0% of the amount of the gel data. The bottom layer cooperation ratio is calculated.
1.3.2 Surface cooperation ratio
After many experiments, the surface layer uses three kinds of basic raw materials: specially graded sand (Zhejiang Changxing quartz sand, with a particle size of 0.63 to 1.25 mm), cement (conch P · Ⅱ52.5), and water (water for concrete mixing). And mixed with water reducing agent (Taizhou Luban), while adding a suitable amount of pigment (Zhejiang United Pigment Co., Ltd.) to add color. The cooperation ratio of water-gel ratio 0.24, ash-collection ratio 3.2, policy porosity 10%, the amount of water reducing agent used is 1.0% of the gel data, and the pigment amount is 0.8% of the gel data.
After experiments, we have made a lot of explorations on the forming process of permeable bricks , the cooperation ratio of the original materials and the maintenance methods. It is determined that the bottom layer and the surface layer are formed by composite molding. The thickness of the surface layer is 5mm and the thickness of the bottom layer is 55 mm. The production line of Beijing Ruitu Co. is used. The maintenance method is steam maintenance. (1) Mixing: The mixture of permeable bricks should be dry and hard. It should not be too dilute, and the accumulation phenomenon should not occur under oscillating conditions. Therefore, a forced mixing machine should be used for mixing. The mixing time is appropriately longer than the plastic concrete mixture.
(2) Oscillation: Oscillation can speed up the movement and pressure transmission of the mixture. The oscillation time is too short, and the mixture is too loose; the oscillation time is too long, the cementation data will sink, block the open space, and reduce the water permeability function. The selection of the oscillation frequency is also very important. It is necessary to adjust the oscillation frequency according to the mixture to make it close to the natural frequency of the mixture, and then shorten the oscillation time. After repeated experiments, this study has determined the appropriate oscillation time and frequency.
(3) Limiting molding: A certain pressure can tightly bond the mixture together, which is conducive to improving the strength, but excessive pressure will cause a decrease in water permeability. In addition, the molding pressure is also related to the timing of oscillation, the frequency of oscillation, the degree of dryness of the mixture, and the height (amount) of the cloth. In this study, the method of secondary fabric and primary molding was used to ensure a good combination between the bottom layer and the surface layer.
In this study, orthogonal experiments were used to study the effects of the above factors on the strength and water permeability of permeable bricks at different levels, and it was concluded that the optimized process parameters: total installed power: 400 k W, oscillator motor: 2 × 15 k W, on Mode oscillation motor: 2 × 1.1 k W, hydraulic station power: 58.7 k W, hydraulic station working pressure: 16 MPa. 1.5 Function of permeable bricks The functional indicators of permeable bricks mainly include compressive strength, flexural strength (generally the side length / thickness is less than 5, flexural strength can be ignored), abrasion resistance, water retention, and water permeability coefficient. Before manufacturing permeable bricks , firstly manufacture test pieces with different coarse aggregates and different proportions, and perform functional tests. After the tested functions meet the requirements, permeable bricks are manufactured. During the discussion, it was found that the manufacture of single-layer permeable bricks is simple, the permeability coefficient is large, but the surface layer is rough, and the abrasion resistance is poor. Therefore, the late research of permeable bricks attaches great importance to the composite permeable bricks.
According to the above-mentioned optimization cooperation, wait until the permeable brick function produced by the production process.
2 Functions of permeable concrete
Using Portland cement as the cementing material, a single-size coarse aggregate is used instead of fine aggregate. The ratio of ash to ash is 3.0 to 4.0, the ratio of water to ash is 0.30 to 0.35, and the pressure of the concrete mixture is harder and harder. Formed to form concrete with 15% to 25% of open space, the apparent density is generally 1700 to 2200 kg / m3, the compressive strength can reach 15 to 30 MPa, and the water permeability coefficient is 1 to 15 mm / s.
3 Mechanism and structural plan of the ecological permeable system
3.1 Mechanism of ecological water-permeable system
In the permeable system of ecological pavement bricks, because the permeable bricks and cushions contain a lot of connected open spaces, when it rains or there is stagnant water, the water will infiltrate into the soil layer by layer along the connected open spaces, and some of them will be temporarily stored in the open spaces. (Some of which cannot be infiltrated due to underground reasons, etc., can be set up artificially to carry out rainwater collection.) Under certain conditions, infiltration or transpiration can be performed, and then the rainwater is complementary to the ground and the ground. That is, on rainy days, rainwater seeps into the ground through the percolation layer or is stored and collected. When it is boring and high temperature, it reverses through the percolation layer to compensate for the humidity of the air. Others can also use the collected rainwater to recharge and spray. Air rainwater circulation, alleviating the urban heat island effect.
3.2 Ecological Water Permeability Architecture Plan
The ecological permeable system can absorb rainwater when it rains, and can "sweat" when the climate is hot, which helps to deal with the two major problems of urban water accumulation and heat island effect. During the rainy season, rainwater infiltrates, collects, or stores in the system through the high permeability of the entire system. In the boring season, there are many communication holes arranged in the entire permeable system, which can in turn "drain" the water entering the entire system or remaining in the entire system into the atmosphere, which plays a role in regulating the humidity of the air and lowering the atmospheric temperature. This article details the following two plans: one is the rainwater collection and recovery plan, which is divided into two types: basement and no basement; the second is rainwater natural seepage into the underground soil layer.
3.2.1 Rainwater Gathering and Recovery Plan
(1) There is a plan for gathering and processing of rainwater in the basement. The structure of each layer from bottom to top is divided into: structural layer, reservoir, waterproof layer, ceramsite permeable layer, permeable concrete permeable layer, paving layer, and permeable brick layer (see Figure 3). As a waterproof layer on the structural layer, the first thing is to prevent the rainwater from seeping into the basement. Store the rainwater storage pool in the basement and collect the rainwater from the surface into the pool (put a small centrifugal pump in the pool, and use the collected rainwater to spray the road and vegetation in dry or high-temperature climates, the same below); Thickness is greater than 100 mm); a permeable concrete bottom layer (with a strength not lower than C20) of more than 150 mm thick is poured on the ceramsite layer; a permeable brick with 30-50 mm thick 1: 4 cement mortar is placed on the permeable concrete bottom layer. (2) Plans for rainwater gathering and treatment without basement. 透水混凝土浸透层、铺贴层、 透水砖层（见图4）。 The structure of each layer from the bottom to the top is as follows: storage tank, pond slag backfill layer, waterproof geotextile waterproof insulation layer, permeable concrete permeable layer, paving layer, and permeable brick layer (see Figure 4). First select the reserved reservoir, then backfill and level the pond slag, then use waterproof geotextile as the waterproof insulation layer, and pour a layer of water-permeable concrete with a thickness greater than 150 mm (the strength is not lower than C20); Permeable bricks are paved with 30-50 mm thick 1: 4 cement mortar on the concrete bottom.
3.2.2 Plan for natural infiltration of rainwater into the surface soil layer
The plans are separated from bottom to top: underground soil layer, sandstone water storage layer, permeable concrete permeable layer, paving layer, and permeable brick layer.
Use sandstone backfill to compact the ground on the surface layer (pay attention to the gradation of the particles during sandstone backfill, and leave an appropriate open space inside, on the one hand, it will help the rainwater to seep through, and other open spaces can also store the rainwater that is not too late to infiltrate). For samples larger than 150 mm thick, the column temperature is 100 ℃ for 1 min, and the temperature of 10 ℃ / min is increased to 150 ℃ for 5 min. The temperature of 25 ℃ / min is increased to 250 ℃ for 1 min. Illustration. The reproducibility of low-concentration injection and high-concentration injection was checked, and the accuracy of the known sample N75 was checked for the low-concentration injection (injection quantity 1 × 10-7 g). The N75 free HDI content was measured at 0.32. %, The coefficient of variation is 6.48%; and high-concentration injection (on the order of 1 × 10-6 g) does not know the accuracy of the sample, and the free HDI content of the laboratory-made HDI biuret curing agent is measured to be 44.18%, and the coefficient of variation is 1.77 %, Accuracy and precision meet the requirements of the test methods. The experiment proves that this method is concise and the analysis time is short. It can be used to test samples with a free HDI content of 30% to 90% during the synthetic response, which is convenient for tracking the HDI response and determining the end point of the response. It can also be used to test the free HDI in the product. Samples with a concentration of 0.1% to 2.0% to ensure product quality.