NEWS CENTER

Permeable concrete allows the ground to "breathe" freely"


Release time:

Apr 26,2013

Today, dramatic changes in global climate patterns have led to frequent floods, with deadly floods that occur once in 50 years or even once in 100 years hitting Manila, Bangkok, Beijing and many other cities. What kind of system should be used to alleviate this problem? Permeable concrete may be a good choice. A kind of ground pavement permeable concrete to improve the urban ecological environment, also known as porous concrete and permeable floor, is a kind of porous lightweight concrete mixed with aggregate, cement and water. It does not contain fine aggregate, by the coarse aggregate surface coated with a thin layer of cement slurry bonded to each other and formed, the uniform distribution of holes is honeycomb, so

Today, dramatic changes in global climate patterns have led to frequent floods, with deadly floods that occur once in 50 years or even once in 100 years hitting Manila, Bangkok, Beijing and many other cities. What kind of system should be used to alleviate this problem? Permeable concrete may be a good choice.

Ground pavement for improving urban ecological environment

Permeable concrete, also known as porous concrete, permeable floor, is a kind of porous lightweight concrete mixed with aggregate, cement and water. It does not contain fine aggregate, by the coarse aggregate surface coated with a thin layer of cement slurry bonded to each other and formed, uniform distribution of holes in a honeycomb, it has the characteristics of breathable, permeable and light weight. Pervious concrete system has a series of color formula, can cooperate with the design creativity, according to the different environment and personality requirements of the decorative style of laying construction. This is the traditional pavement and general permeable brick can not be achieved.

Hardened ground pavement using granite, marble, glazed tiles, cement and asphalt and other impervious materials, to the urban ecological environment to bring a variety of hazards. As early as the 1970 s, developed countries have begun to study drainage asphalt concrete pavement, and then to the permeable concrete as the representative of a variety of permeable engineering materials for systematic development. The U.S. Environmental Protection Agency has made great efforts to promote the use of this technology in North America, especially in places with frequent heavy rainfall.

Freiburg in southern Germany is a famous eco-city today. Many years ago, Freiburg proposed a plan to build an ecological city, completely demolishing all the hardened ground (except roads) in the city and replacing it with various forms of permeable ground. As a result, the groundwater level in Freiburg gradually rose, and the vegetation was completely free from artificial watering and lush. Because the permeable ground can be permeable to air, so that the ground cool in summer, warm in winter, rainy season permeable, winter snow (no ice), adsorption of dust, reduce dust pollution, greatly improve the comfort of living.

If we carefully observe the laying of traditional Chinese gardens, temples, houses and streets, we will find that they all have good water permeability, which is also the reason why traditional buildings have lasting vitality. Such as Beihai Park built 590 years ago in the Ming Dynasty City is a typical example. Tuancheng is more than ten meters above the ground, but there are century-old trees growing lush on it. These trees never rely on artificial watering. The reason is that the buildings of Tuancheng make full use of the water permeability of green bricks. The upper and lower small inverted trapezoidal bricks lay a network of rainwater permeable with gaps. The lower part of the brick is mixed with a large amount of chaff and shell residue with the bottom of the soil, which has strong air permeability and water absorption performance. When it rains, rainwater can all flow into the soil through the brick surface and brick cracks, providing sufficient water for the growth of trees on Tuancheng.

The ground pavement project in Xi'an Daming Palace National Heritage Park is the largest permeable concrete project in the world. "The customer requires that the design of the whole square should not only have the function of water permeability, but also be strong, durable and beautiful. At the same time, the overall color should conform to the characteristics of the local loess land." Wang Lizhong, general manager of Zhongjing Orange Stone Construction Technology Co., Ltd. (hereinafter referred to as Zhongjing Orange Stone), which completed the project, said, "The project, which totals about 240000 square meters, must be completed within six months. Due to the tight schedule and complex program, the company has set up a special Daming Palace project leadership team to work with an experienced construction team."

Old as old: with yellow high bearing dew aggregate permeable ground as the main material

The ground pavement of Daming Palace National Heritage Park is made of four products: high load-bearing dew aggregate permeable art ground, high load-bearing embossed art ground, high load-bearing grass planting ground and concrete precast relief board. The ground not only has a drainage system combining natural infiltration and pipeline drainage, but also has a natural color tone with the main project of Daming Palace, making people feel like going back in time.

It is understood that the high bearing permeable ground is a one-time pavement, integral molding, high strength, and has 15% to 25% porosity of the concrete floor paving system. It has high bearing capacity, high water permeability, effectively replenish groundwater, regulate air temperature and humidity, alleviate the urban heat island effect, dust absorption and noise reduction, surface art decoration and plasticity, high walking comfort, significant anti-skid effect, high safety performance.

High bearing permeable ground is divided into high bearing color permeable ground and high bearing aggregate permeable ground. The former is dyed in the mixing process of permeable concrete, and then carried out construction to achieve the effect of color change, while the latter makes the pavement expose the material of natural aggregate. The construction of the Daming Palace Ruins Park follows the principle of "old as old" in the protection of cultural relics, and selects yellow high-bearing aggregate permeable ground as the main pavement material. "Most of the roads in the prosperous Tang Dynasty were dirt roads, but if loess was used directly in the project, it would have a certain impact on the environment due to the heavy wind and sand in Xi'an. Therefore, it is inevitable to choose ground paving materials with color like loess and significance of environmental protection and beautification. The high-bearing dew aggregate permeable ground, which happens to be khaki yellow, looks like a loess land from a distance, reflecting the simple folk customs and historical accumulation in the northwest. When viewed closely, it reveals the natural and simple texture of the stones, which is close to nature and echoes the concept of the project. At the same time, it can supplement groundwater, adjust the temperature and humidity of small ambient air, and has certain environmental significance."

The Water Penetrating Secrets of Super Large Flat Square

Yudao Square is located between Danfeng Gate and Hanyuan Hall in Daming Palace National Heritage Park. It is 600 meters long from north to south and 400 meters wide from east to west, which is only 100 meters narrower than Tiananmen Square. For this is the largest pure permeable square in the country and the world, and at the same time it is the most important square landscape in the Daming Palace project, its design and implementation process is a multi-party co-creation process.

"Whether dust will completely block the pores of exposed aggregate permeable concrete" is a key issue of general concern, especially when applied to a 160000-square-meter pure royal road square, no traditional drainage system can be set up, and drainage can only be carried out by permeable concrete for rainwater infiltration and drainage. We have done different mix proportion tests with the design requirements, and finally come to the conclusion that under the condition of ensuring the strength, if the aggregate particle size is selected as 8-10mm, the porosity of the exposed aggregate permeable concrete can be controlled at 15%-20%. Based on this calculation, taking the dust fall in Xi 'an area as the parameter in that year, it will take 128 years for the 12cm concrete pore to be completely blocked by dust alone, which does not take into account more than 30% of the gap in the 30cm graded gravel layer of the cushion layer. "In other words, if the daily maintenance is proper, it is difficult for natural dust to completely block the large pore permeable concrete for a long time." Wang Li said.

Although a suitable mix has been found, the designer, Beijing Architectural Design and Research Institute, is still worried about some abnormal conditions such as major pollution. From a rigorous point of view, the designer put forward a revolutionary proposition, that is, whether the expansion joint of exposed aggregate permeable concrete can be used for auxiliary drainage, but the premise is that the expansion joint material must meet three conditions: the expansion joint function of concrete must be guaranteed; Easy to disassemble, clean and repair to ensure long-term effective drainage; The appearance and texture should be similar to that of the yellow gravel in the square, there must be no obvious grid on the finished ground.

In the concrete floor pavement industry, the expansion joint material is usually asphalt, wood or glue and other waterproof materials, and this proposition first requires water permeability. "Through a lot of ideas and experiments, we finally found satisfactory materials and craftsmanship. The designer vividly called it'instant noodle '." Wang Lizhong said, "This long strip-shaped 'instant noodle 'has good elasticity and long-term durability, can be pressed into the expansion slot, through its own elasticity and the bottom of the backing to be fixed. It has excellent water permeability, and is easy to remove for cleaning or replacement, at the same time, its material can be toned to close to the yellow color of the stone." This scheme was finally recognized by the owners and designers, and played a key role in supplementing and ensuring the innovative design of Yudao Square.