In the process of long-term urbanization, large-scale pavement hardening and impervious areas of new buildings have been greatly increased, making urban rainwater unable to smoothly return to nature, which not only constitutes a lot of reductions in groundwater replenishment and repair, but also increases the peak flow and greatly increases Urban flood control and drainage burdens constitute a large area of urban water accumulation. Together, it weakens the respiratory function (ie, the function of life) of the urban environment, which forms the heat island effect (hotness), increased dust and noise, worsens the urban microclimate, and reduces the comfort of the city. And the hardened ground is "dead ground", which will affect the growth of ecosystems and trees on the ground. In contrast, permeable roads balance the urban ecosystem. Flood storage and rain storage, cultivation of ganlin, water permeability, dust reduction and noise reduction, add the comfort of urban residence.
The application of permeable bricks
has a long history in the world. Since the 1960s, Germany has used permeable materials for pavement and is committed to the improvement of impervious pavements. The goal is to transform 90% of pavements in cities across the country into permeable pavements by 2010. Countries such as the United States and Japan have also formulated relevant regulations for the implementation of water-permeable pavements, which have achieved great results. In China, Beijing has issued rules for the implementation of "water-saving three together" for construction projects, which explicitly require the use of water-permeable materials to pave the road, and together provide subsidies for rainwater reconstruction projects.
Environmentally-friendly pavement bricks
are permeable concrete products prefabricated by a special process. They are mainly used for laying squares, yards, sidewalks, and low-speed traffic lanes, so that rainwater can quickly penetrate the ground into the ground, and can also be used to build the seepage wall .
According to different gelling materials, aggregates and molding processes, pavement permeable bricks
can be roughly divided into the following three categories:
Portland cement is used as the cementing material, and aggregates with a single particle size are selected. It is not necessary to use fine aggregates or less. Cement-type pavement permeable bricks
belong to a type that is generally implemented. Because of the low cost and stable function of cement products, the traditional paving tiles are usually cement products. Because the formula, technology and skills for making high-strength cement water-permeable pavement bricks are now sophisticated, and the cost is basically close to that of water- impermeable bricks
, the opportunity to replace impermeable bricks
with water-permeable bricks on a
large scale is now sophisticated.
The polymer resin is used as a gelation material, and a single particle size aggregate is used. Generally, pressure forming is also used to form a concrete product that satisfies specific strength requirements and has certain connected pores.
Polymer resins have the characteristics of high strength and beautifulness as gelling materials, but they have been questioned by many experts and scholars when they are implemented on a large scale. The main reason is the poor aging resistance of the resin and the poor selection of aggregates. This constitutes a decrease in water permeability. In addition, users are generally unwilling to choose it because the cost is too high and the cost performance is not appropriate. This type of product is only suitable for certain specific occasions, such as in high-end small yards shaded by trees.
Aggregate granules and slurries of feldspar, kaolin, clay and other minerals are stirred, pressed into embryonic bodies and calcined at a high temperature with a porous structure.
Sintered pavement permeable bricks are
mainly ceramic permeable bricks
. The primary obstacle affecting its implementation is that the cost is too high and the cost performance is not appropriate, and users are generally unwilling to choose it. Secondly, there are some strengths that do not work. This type of product is suitable for some specific occasions, such as in high-end small yards.
Ecological environment function
The ecological environment function of permeable roads is mainly measured from three aspects.
According to data calculations, the maximum rainfall intensity encountered by Beijing in the past 5 years is about 0.1 mm / s (mm / s), and the permeability coefficient of environmentally-friendly pavement bricks
is 1 mm / s, which can fully allow rain to quickly infiltrate Under the cushion, there is no water accumulation on the road surface.
Generally speaking, the thickness of the permeable brick
is 60mm, the porosity is 20%, the thickness of the cushion is generally 150mm, and the porosity is 30%, which is equivalent to forming a 57mm deep invisible reservoir. That is to say, even if the cushion is completely impermeable, there is no drainage, and there is no water accumulation on the 57mm road. It can be seen that the permeable pavement can fully meet the requirements of heavy rain infiltration.
Improve water quality
The permeable brick
has the effect of absorbing and filtering the infiltrating rainwater, and has the function of improving the water quality. According to the results of the test started by Beijing Institute of Technology, the permeable bricks have a
COD (higher COD value indicates more organic pollution in water) removal rate of 30.00%, SS (suspended matter) removal rate of 61.45%, and TN (total nitrogen) removal rate of 7.4% , TP (total phosphorus) removal rate was 40.16%.
Improve some microclimates
Water-permeable pavements can change the temperature and humidity near the ground surface. Observation data show that at high temperatures, the surface temperature of permeable roads is 2 to 5 ° C lower than that of impervious roads; during dry seasons, the surface humidity of permeable roads is 1% to 3% higher than that of impervious roads. In addition, the water-permeable function of water-permeable pavement can greatly reduce the damage of "dead" soil under water-impermeable pavement, which is beneficial to the growth of trees.