The Research About Frost Resistance Of Pervious Concrete

Pervious concrete is a new type of environment friendly building materials, it is a porous lightweight concrete formed by mixing of aggregates, cement and water, it does not contain fine aggregate, course aggregate surface coated with a thin layer of cement slurry is formed by mutual adhesion of a honeycomb structure of cavitids distributed evenly. It has both some of intensity and permeable. However, due to the application of this material in our country is still in the initial stage, there is not a strict design specifications for industry, we first need to proceed from there factors that the water-cement ratio, plasma set ratio, porosity, ir. order to be able to increase the strength of concrete under the premise of ensuring water permeability. The goal is to produce56d compressive strength of30MPa, the permeable coefficient of more than Imm/s concrete.In this paper, we use two processes:iscstatic pressing and Manual mixing compaction, i design the mixture parameters through volume method, determine the best fit parameters in the premise of assurance the requirement performance of permeability and strength,and verify the relationship between the target porosity and measured porosity, experiments show that the target porosity almost approach the measured porosity. Verify the paper’s correctness of the design, and provide porous permeable concrete a reliable basis for the design and application, in the basis of early experimental data, doped the pervious concrete within different content niineiai admixture silica fume and fly ash in order to behcr enhance the strength, in order to improve the work of the pervious concrete admixture polycarboxylatc super pbsticizer, and use the homemade permeable device to test water permeability. Freezc-thaw experimental specimen conservation to56days. Comparison of differcni ratio of pervious concrete with ordinary concrete from strength loss and mass loss.As our design water-cement ratio is loo low, from the test mixing concrete state we can see that mixing concrete workability is not very good, therefore, after determine the basic mix parameters we deploy the best content of mineral admixtures to improve concrete workability, the polycarboxylate super plasticizer can improve the fluidity of the concrete docs not change the water-cement ratio, the fineness of mineral admixtures is significantly higher than that of cement, can bring the water into the concrete pore to accelerate the hydraiion reaction to improve the strength and works as lubricant oil, because permeable brick specimens molding with isostatic pressing, the concrete measured porosity slightly lower than the target porosity. We found that measured porosity and permeability coefficient to maintain a linear relationship through the homemade permeable apparatus, effective porosity is preserved, proved that the concrete of the test preparation to achieve the desired water-permeable need. And the intensity is18%of the concrete is higher than others. The silica fume group permeable cube specimen concrete early strength development rate is better than the ordinary group and fly ash group, the fly ash group strength is better than the ordinary group after56days of conservation. Experiments show that adding silica fume, fly ash significantly improved frost resistance.