Factors Affecting Permeability of Permeable Concrete


Release time:

2020-03-02

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Permeable concrete is a porous lightweight concrete made of aggregate, cement and water. It does not contain fine aggregate, and is coated with a thin layer of cement slurry on the surface of coarse aggregate to form a honeycomb structure with uniform distribution of holes. Therefore, it has the characteristics of permeability, permeability and light weight.

Factors Affecting Permeability of Permeable Concrete

Permeable concrete is a porous lightweight concrete made of aggregate, cement and water. It does not contain fine aggregate, and is coated with a thin layer of cement slurry on the surface of coarse aggregate to form a honeycomb structure with uniform distribution of holes. Therefore, it has the characteristics of permeability, permeability and light weight. In view of the defects of the road surface of the original city road, it can make rainwater flow into the underground, effectively supplement the groundwater, and alleviate some urban environmental problems such as the sharp decline of the groundwater level in the city. It can effectively eliminate the harm of environmental pollution caused by oil compounds on the ground; at the same time, it is an excellent pavement material that protects groundwater, maintains ecological balance, and can alleviate the urban heat island effect; it is conducive to the benign development of human living environment and urban rainwater management and water pollution prevention and control.

Change the past destruction of urban ecological ground laying, so that permeable concrete pavement depends on a wide range of social benefits. Permeable concrete to meet the strength requirements at the same time, but also need to maintain a certain through pores to meet the requirements of permeability, so in addition to the preparation of the appropriate raw materials, but also through the mix design and preparation process and additives to achieve the purpose of ensuring strength and porosity.

Factors Affecting Permeability of Permeable Concrete
(1) The permeability and compressive strength of permeable concrete are related to the porosity of concrete.
(2) The larger the amplitude difference of single-grain coarse aggregate, the higher the strength of the prepared permeable concrete, and the worse the permeability.
(3) The performance of pervious concrete prepared with the best proportion of double-grain aggregate is obviously better than that of single-grain aggregate.

In permeable concrete, the bond strength of cement and aggregate interface is the weakest link of concrete and the key factor to determine the strength of concrete, so the choice of cement activity, variety and quantity is particularly important. Permeable concrete should use cement or ordinary Portland cement with higher strength and less mixed material. The dosage of cement slurry is best to completely wrap the surface of aggregate, forming a uniform cement slurry film layer, and adopting the principle of minimum cement dosage. Excessive cement dosage will not only weaken the water permeability and increase the cost, but also increase the shrinkage of cement stone, form cracks, and reduce the strength of concrete. Coarse aggregate is the structural skeleton of permeable concrete, and the size of aggregate particle size depends on the thickness, strength and permeability of permeable concrete structure. The particle gradation of permeable concrete is one of the main factors that determine its strength and permeability. In order to ensure the strength of permeable concrete and its permeable function, coarse aggregate is usually used with smaller single particle size. The smaller the aggregate particle size, the greater the aggregate bulk density and the more contact points between the particles, the higher the strength of the prepared permeable concrete, and the permeability will be reduced. The smaller the aggregate particle size, the larger the specific surface area, the more the number of contact points between the aggregate particles in the unit volume of the structural skeleton, the larger the cementation area, which can improve the strength of concrete, but the amount of cement must be adjusted at the same time. The larger the aggregate particle size, the smaller the specific surface area, the smaller the number of contact points between the aggregate particles in the unit volume of the formed structure aggregate, and the smaller the bonding area, which can improve the water permeability, but will reduce the strength. The production of permeable concrete must adjust the amount of cement and water-cement ratio, otherwise prone to aggregate surface cement slurry film thickness is not uniform, flow slurry and other phenomena, directly affect the strength of concrete, water permeability and quality stability.










The factors that affect the performance of permeable concrete are permeable mode, dense degree, raw material performance, mix ratio, molding method and curing conditions. Among them, strength and water permeability are opposite, and the parameters must be considered comprehensively. The water-cement ratio affects both the strength and the permeability of permeable concrete. The cement slurry is too dry and thick, the workability of the concrete mixture is too poor, and the cement slurry cannot fully wrap the aggregate surface, which is not conducive to improving the strength of the concrete; on the contrary, if the water-cement ratio is too large, the dilute cement slurry may partially or completely block the permeable pores, which is not conducive to water permeability and strength improvement. The size of the bone ash ratio affects the thickness of the cement slurry wrapped on the surface of the aggregate particles and the porosity, that is, the strength and permeability of the permeable concrete. When the amount of cement is certain, the ratio of bone ash increases, the thickness of cement slurry on the surface of aggregate particles decreases, the porosity increases, the permeability increases, but the strength decreases; on the contrary, the permeability decreases and the strength increases. Considering the larger surface area of the smaller particle size aggregate, in order to maintain the reasonable thickness of the cement paste, the ratio of the small particle size aggregate should be appropriately smaller.

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