Research On The Impermeability And Microstructure Of Ordinary Concrete

Nowadays most of the ordinary concrete constructions and the buildingsunderground often be damaged with a short lifetime just because of the lowimpermeability.In this dissertation, the author uses compound admixture and fly ash toimprove the impermeability of ordinary concrete. In this way, the expense is little andthe constructions will obtain longer service life.During the experiments, we can get the best proportion of the compound admixtureafter measuring the compressive strength and water absorption of the hardened cementpaste which has been cured28days. Then using this proportion in ordinary concrete, wewill do some measurements about the permeability of concrete including compressivestrength, depth of the water sign under1.2MPa water pressure, electric flux of thechloride ion under voltage and the microstructure of pore.According to the consequence, some obvious regulars are collected. The compoundadmixture will cause a narrow reduce of the concrete compressive strength, while thisparameter can increase with more curing days. Different quantities of the admixture willoffer positive effects about the impermeability. The most amplification of theimprovement in measurements about the depth of the water sign can be18.9%, and theelectric flux of the chloride can decrease by50.8%. The compound admixture can bringsome air to the concrete, and after the microscopic analysis, the distribution of thepore’s diameter will be better. The specific surface area increases by30⁸0cm^-1and theair void spacing factor decreases. If mixing some fly ash with the compound admixtureinto the concrete, the compressive strength will be lower than the concrete only withsome admixture. The drop is the biggest, about29.4%, when the ratio of fly ash is20%of the binding material. According to some researches, more curing time can be helpfulto the properties of the ordinary concrete.For better impermeability of the ordinary concrete, we suggest that the usingamount of the compound admixture and fly ash should be chosen seriously.