Nowadays, urban roadways in China generally use cement pavement or asphalt pavement, and sidewalks generally use concrete bricks or porcelain square bricks. The underlying materials of the paving are impervious. In this way, natural precipitation cannot enter the ground to make up for groundwater. Instead, it enters the sewer directly into the river. As long as it partially enters the water treatment plant, the results add to the sewage discharge pressure on the one hand, and either pollute the river system or add Water treatment pressure and water treatment costs. In addition, the pavement supplemented by these materials generally raises the urban temperature by 2 ° C to 4 ° C, and the urban heat island effect occurs. Because these products are impermeable, pedestrians cannot walk when heavy rain is pouring. What's more serious is that in many cities, due to the over-exploitation of groundwater, parts of the city have been sunk and buildings have collapsed, which seriously threatens people's lives and property. Many cultural relics and historic sites are facing extinction. Kilometers of cracks keep appearing.
Permeable bricks have good water permeability and porosity of 40% to 50%, which can allow some rainwater to enter (basically all of them can be penetrated during moderate and light rain), so that the groundwater can be naturally compensated, which fundamentally alleviates the continuous decline of the groundwater level. problem. Because the rainwater partly enters the ground, it reduces the sewage discharge pressure during heavy rain. It not only meets the modern people's ecological and environmental protection concept, but also satisfies the thirst for color and civilization smell of modern cities.
Ceramic permeable bricks are made of general ceramic materials as the primary material, and are made into products that meet the requirements after material damage, classification, batching, mixing, molding, boring, firing, and inspection.
Most of the materials used in permeable bricks are ordinary ceramic materials, such as aggregates such as hard kaolin, coal gangue after spontaneous combustion, and some flux-based materials, which have a wide range of materials.
The main process is to crush and grind the soft and hard materials separately, and then perform the steps of mixing, limiting, and firing.
Damaged equipment: jaw crusher, hammer crusher, Raymond mill, etc. Grading equipment: shaker, etc. Mixing equipment: Mixer. Forming equipment: brick press. Burning equipment: tunnel kiln.
Ceramic permeable bricks need to have excellent water permeability, anti-skid function, anti-freezing function and high strength to meet the application requirements of different pavement laying. The biggest technical difficulty is the connection between the water permeability coefficient and the strength. Small permeability coefficient and high strength. Therefore, the selection of appropriate ceramic materials, particle grading, mixing, and molding methods is the key to producing qualified permeable bricks . The permeable brick material can be either ceramic material or spontaneous fired industrial waste coal gangue, waste tile, quartz, feldspar, kaolin and clay. The main composition of the formula consists of aggregate, binding agent and flux. Therefore, the selection of aggregate, binding agent and flux in the formula will affect the function of the permeable brick .
Permeable bricks have coarse particles and aggregate is the primary material, so aggregates have a great impact on the molding function, successful firing, and physical and chemical functions of the product. In order to produce the permeable brick product with the best function, selecting the appropriate aggregate and particle gradation have a great impact on the product's water permeability coefficient and strength.
Participating in the binder is mainly to satisfy the molding function of the product, and the second is to satisfy the requirements of strength and structure during and after the firing of the product. However, if there are too many participants, the composition of the stomata and the cost will be negatively affected, so the participation should be appropriate.
Fluxes are some low-temperature domestic wastes, and their effects are mainly twofold: one is to promote the fluxing effect and reduce the firing temperature; the other is to melt early to make the binder bond to the aggregate when the component is burned. The effect is to weaken the aggregate looseness and deformation of the product when the binding force is lost after the binder is differentiated, and it can also enhance the strength of the product after firing.
The primary material of high-permeability and environmental-friendly ceramic tiles is made into products that meet the requirements after damage, classification, batching, mixing, molding, boring, firing, inspection and other processes. How the materials are mixed and which affects the function of the product first.
The method of paving permeable bricks is different from that of ordinary road bricks. The paving method of ordinary road bricks requires that the bottom layer be watertight, and generally uses triple soil as the bottom material. The permeable brick not only requires the permeable brick itself, but also the bottom layer of the road, so as to form a complete permeable system. Therefore, the paving of the permeable brick consists of four layers, from the bottom to the root, the gravel layer, and the sand layer. 2. Permeable brick paving layer (see Figure 2) to ensure the smooth flow of rainwater when it rains, but not water in the road area.
In 2004, after the Xianyang Ceramics Research and Planning Institute announced the ceramic permeable bricks , the drafting of the specifications for ceramic permeable bricks was carried out. The National Development and Reform Commission issued JC / T 945-2005 " permeable bricks " on February 14, 2005 The specification came into effect on July 1, 2005.
In November 2012, the Ministry of Housing and Urban-Rural Development issued CJJ / T188-2012 "Performance Rules for Pervious Brick Pavements". The difference between the code and the product specification JC / T 945-2005 " permeable brick " is that: the requirements for the anti-skid function of the permeable brick are required, and the requirement for the anti-skid function (BPN) is not less than 60; the original information in the structure layer is proposed Requirements, and made rules for the strength, joint width, and joint sand gradation of the permeable brick surface in the plan; specific requirements were also made for the leveling layer, the bottom layer, the cushion layer, the soil foundation, and drainage planning.
Status quo at home and abroad
The water-permeability system pavement is being promoted abroad. Taking Germany as an example, they lay permeable roads in cities and villages, such as sidewalks, pedestrian streets, bicycle lanes, suburban roads and other places where there is not much pressure. They use permeable floor tiles. This kind of brick itself is water-permeable, and it is used between bricks and bricks. Splicing of permeable filling materials. During the process of building a city by the sea, the Dutch found that the ground after the seawater was discharged would not be able to touch the water for a long time, which caused a continuous ground subsidence. 200mm, 50mm or 60mm small pavement bricks are laid on the street pavement, and reserved between the bricks
In 2000, Japan's Ina Co., Ltd. announced that water-permeable ceramic tiles (SL, "SL" are recommended products for excellent sight materials), which have been recognized by the Japan Environmental Association's Ecological Mark (Trademark) Office as an eco-label product, and its excellent product functions It was highly evaluated (the index is shown in Table 1), and was recognized as an excellent construction material referral product by the Japan Construction Materials Industry Association Scenery Materials Promotion Association.
Most of the permeable bricks on the domestic market are cement bricks (Dutch bricks). This type of brick is impermeable to water, and the gap between the brick and the brick is used to permeable; the other is a structural permeable brick , which is mostly hollow. Or constitute a hollow as a water-permeable channel. A company in Beijing made a non-fired permeable brick made of desert sand, which has a good water permeability function, but because the auxiliary materials are expensive, the price is above 200 yuan / m2, and because the resin is used as a binder, the durability is poor, so the sales are affected. To a very large limit.
Permeable brick development prospects
The pavement brick with a similar function is a concrete pavement brick, and its appearance, decorative effect, and walking comfort are similar to ceramic permeable bricks , but its water permeability (method) is not as good as ceramic permeable bricks . The material is cement with high energy consumption, high material consumption, and high pollution. The greater the amount of cement used, the greater the negative effect on society. Therefore, the permeable bricks are functional, functional, materials used, and social and economic benefits. It is very good, which is incomparable and irreplaceable by other pavement tiles.
Following the state ’s initiative to build a sponge city, the construction of sponge cities has received increasing attention. In April 2015, according to the Ministry of Finance website ’s announcement, the list of pilot cities for sponge city construction was officially released. According to the competitive evaluation scores, the top 16 cities are: Qian'an, Baicheng, Zhenjiang, Jiaxing, Chizhou, Xiamen, Pingxiang, Jinan, Hebi, Wuhan, Changde, Nanning, Chongqing, Suining, Gui'an New District and Xi'an Xianxin District. The General Office of the State Council recently issued the "Counseling Views on Promoting the Construction of Sponge City" (hereinafter referred to as "Counseling Views") to arrange and promote the construction of sponge cities. The "Guiding Opinions" pointed out that starting from 2015, new cities, various parks, and development zones in cities across the country must fully implement sponge city construction requirements; promote sponge-type construction and related foundation equipment construction, and promote sponge-type construction and communities. Vigorously promote the qualified construction of urban drainage and flood prevention equipment; promote the construction of park oasis and natural ecological restoration. At the same time, "Counseling and Opinion" is clear. After the construction of the sponge city, the impact of urban development and construction on the ecological environment is minimized, and 70% of the rainfall is absorbed and used locally. By 2020, more than 20% of the urban built-up area will meet the guidelines; by 2030, more than 80% of the urban built-up area will meet the guidelines.
In summary, ceramic permeable bricks are a kind of functional data that fits the current development trend of green construction and urban construction, and the development prospect is very broad.