Pervious pavement bricks have the characteristics of water permeability and light weight, so they can also be called drainage concrete bricks. According to the defects of urban road pavement in Europe, America, Japan and other countries, a kind of bricks which can let rainwater flow into the underground, effectively supplement groundwater, alleviate the sharp decline of urban groundwater level and other urban environmental problems can be developed and used, and the oil on the ground can be effectively eliminated. At the same time, it is a good paving material for protecting nature, maintaining ecological balance and alleviating urban thermal conductivity effect. It has special significance for the benign development of human living environment and the work of urban rainwater treatment and water pollution prevention.

Pervious pavement brick is a kind of porous lightweight concrete made of aggregate, cement and water. It does not contain fine aggregate. It is composed of coarse aggregate surface coated with a thin layer of cement slurry which bonds with each other to form a honeycomb structure with average distribution of holes, so it has permeability.

Pervious pavement bricks have a series of color formula, with the creative design, paving construction according to different environment and personality requirements of decorative style. This is a special paving material which can not be realized by traditional paving and ordinary cement brick.

Pervious pavement bricks have been studied and applied in the United States since the 1970s and 1980s. Many countries have been promoting them. For example, Germany expects to transform 90% of the roads into pervious concrete bricks in a short time, change the ground laying which destroyed the urban ecology in the past, and make pervious concrete brick pavement depend on a wide range of social benefits. Advantages of Pervious Pavement Bricks:

1. High permeability permeable pavement bricks have 15% to 25% pore, which can make the permeability speed reach 31-52 liters/m/h, far higher than the discharge rate of the most effective rainfall under the best drainage configuration.

2. Good decorative effect permeable pavement bricks have color optimization scheme, which can cooperate with the designer's unique creativity and achieve the decorative style required by different environments and personalities. This is difficult to achieve with traditional bricks.

3. The problem of pore blockage that people worry about is not existent. Its unique permeable pavement system makes it easy to solve by high-pressure water washing.

4. The durability and wear resistance of durable pervious pavement bricks are better than that of leachate and close to the ordinary floor, which avoids the shortcomings such as short service life and uneconomical shortcomings of ordinary pervious pavement bricks.

5. The density of high heat dissipation brick material itself is low (15-25% of the open space is free), which reduces the capacity of heat storage. The unique pore structure makes the lower underground temperature enter the ground, which reduces the temperature of the whole pavement ground. These characteristics make the permeable pavement system close to the natural vegetation covering the ground in terms of heat absorption and storage function.

With the development of social economy and the progress of urban construction, the surface of modern city is gradually covered by reinforced concrete buildings and impervious pavement. Compared with natural soil, the modern surface brings a series of problems to the city, which are mainly manifested in the following aspects:

(1) Impervious pavement obstructs the infiltration of rainwater, which prevents the supplement of rainwater to groundwater. In addition, the excessive extraction of groundwater makes the urban ground easy to sink.

(2) The noise of tire is high on the traditional dense road surface. In the process of high-speed driving, when the tire rolls in, it will press air between the tire and the road. When the tire rolls over, the air will expand rapidly and produce noise, especially in rainy days, which affects the lives and work of residents.

(3) The traditional urban road surface is impervious structure. Rainwater can be removed by road surface and its drainage capacity is limited. When it comes to heavy rain or rainstorm, the rainwater can easily collect on the road surface and concentrate on motor vehicles and bicycle lanes, resulting in large-scale water accumulation on the road surface.

(4) Impervious pavement reduces urban air humidity and accelerates the formation of urban heat island effect.

(5) Impervious pavement is a "dead ground", which will affect the ecological system of the ground, make the water ecology unable to recycle normally, break the balance of urban ecosystem, and affect the normal growth of vegetation.

The origin of pervious pavement bricks, pervious pavement bricks originated in the Netherlands. In the process of reclamation, Dutch people found that the ground after discharging sea water would cause continuous land subsidence because of long-term lack of water. Once the dykes on the coastline were washed away, the sea water would quickly rush to cities much lower than the sea level, and the whole coastal city would sink. In order to keep the ground from sinking, the Dutch made a small permeable pavement brick 100 mm long, 200 mm wide, 50 or 60 mm high, which was laid on the street pavement and reserved a gap of 2 mm between the bricks, so that when it rained, the rain would penetrate into the ground from the gap between the bricks. This is the famous Dutch brick later. Later, American companies invented a kind of permeable pavement brick with strong water absorption function. When the bricks are filled with water, water seeps into the ground, but the drainage speed of the bricks is very slow, and the bricks can hardly help in stormy weather. In the 1990s, American companies began to be popular in China. According to the principle of bricks, some technicians of Beijing Municipal Government invented a kind of pavement brick with permeable holes and good permeability. Rainwater will flow from the small holes in the brick to the underground. After a while, in order to strengthen the compressive and flexural strength of bricks, technicians used gravel as raw material to add cement and gelatinous admixtures to make them stronger.