OBSERVATION OF HYDROPHOBIC LAYER AND ITS WATER REPELLENCY IN SURFACE IMPREGNATED CONCRETE

摘要

When concrete are exposed to water,a series of deteriorating processes will take place.Water repellent treatment on the surfaces of the cement-based materials has been considered to protect concrete from water penetration and eventually from these deteriorations.In this contribution,one typical concrete has been prepared.Three different amounts of silane gel,which were 100 g/m2,400 g/m2 and 600 g/m2,had been applied on the surface of concrete specimens.The neutron images had been taken on these impregnated specimens when they were air dried and water saturated.The transmission value and water profiles in the samples had been also analyzed quantitatively.The results indicated that the hydrophobic layer formed by impregnation of silane gel can be observed and recognized by neutron radiography.The penetration depth of the silane can be measured well from the images.When concrete are impregnated with 100 g/m2 only,the pore space is not water repellent completely.While the application of 400 and 600 g/m2 has much more efficiency on water repellency.The water distributions in all impregnated specimens had been also calculated and presented.The hydrophobic layer with 4-6 millimetres can reduce significantly capillary absorption of aqueous water of concrete.The reduction is greater than 85％.