| Concrete has certainly evolved with time,from the initial high strength concrete developed to today's high performance concrete(HPC),more and more people pay attention to its integrated durability.This article mainly from the permeability view of concrete composite materials,through a variety of mix design,research and ananlyze different factors on the concrete permeability investigated,such as water-binder ratio(w/b), curing period,single-and multiple-doped fly ash and slag.Evalution of the concrete permeability choose rapid chloride permeability test(ASTM C1202-97) and resistivity method,compared to evaluate the permeability of concrete.The study found that the use of mineral admixture can significantly improve the impermeability of concrete,especially in the case of a longer age. Embodied in the use of single-and multiple-doped fly ash and slag in the longer age have a very low cloumb charge,high resistivity value.Considering mineral admixtures need a certain process to perform their activies,it is recommended that using 90d age to evaluate the permeability of mixed concrete is more reasonable.The study found that using resistivity method to evaluate the permeability of concrete is quite feasible,and the key is that making the specimen vacuum-saturated to become linear conductor before the test.Typical mixture among them are:C60 concrete at 0.30 w/b mixed with 15% fly ash,30% slag and multiple-doped with 20% flay ash and 10% slag. Study also found that w/b at any mix proportion of each individual age significantly affected the permeability.Concrete with lower w/b have smaller electric flux values and higher resistivity.The mechanical properties and permeability of C30 concrete with higher w/b developed more obviously than C60 concrete with lower w/b.Overall,the electric flux method and electronic resistivity mothod for evaluating concrete permeability have certain correlation to follow,both have exponential function relationship with the different proprotion. |
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