Strength Properties Research For High-permeability Cement Concrete

As a eco-friendly road paving material, high-permeability cement concrete can effectively solve the environmental deterioration problem. But the strength of existing high-permeability concrete is not high enough to bear even medium traffic axial loads.In this paper, the 28d compressive strength and permeability coefficient were adopted as two evaluation indexes to determine optimum mixture ratio which is calculated by volume method. Then hydroxypropyl pethyl cellulose (HPMC), fly ash, silica fume and polypropylene fiber were added in optimum mixtures so that their corresponding influence on strength of pervious concrete of different admixtures can be obtained.The research shows:High-permeability concrete strength can be increased in various degree by adding appropriate content HPMC, silica fume, fly ash and polypropylene fiber.0.05% content HPMC improves strength of high-permeability concrete most obviously.7d strength decreases with the addition of fly ash, but 28 strength increases when adding at reasonable content (the optimum content is 20%). Appropriate silica fume can both improve the 7d and 28d strength (the optimum content is 8%). When the high-permeability concrete double mixed with silica fume and fly ash, its strength is higher than the corresponding concrete which mixed with either of them (the optimum content is respectively 8% and 20%).Appropriate length of polypropylene fiber can improve both early strength and later strength. But later compressive strength improvement is not very obvious. On the other hand, if the polypropylene fiber volume is added at high level or its length is too short, the corresponding strength of high-permeability concrete will decrease. The permeability coefficient of concrete will decrease at low amplitude with the addition of polypropylene fiber.The cement concrete with high permeability and high strength is finally obtained from a series of tests. Its 7d and 28d compressive strength is respectively 26.9MPa and 40.4MPa,7d and 28d flexural strength is respectively 3.87MPa and 5.62MPa and permeability coefficient can reach 1.68mm/s.