Strength development and chloride penetration in rubberized concretes with and without silica fume

The study presented herein has been carried out in order to investigate the strength development and chloride permeability characteristics of plain and rubberized concretes with and without silica fume. For this purpose, two types of tire rubber, namely crumb rubber and tire chips, were used as fine and coarse aggregate, respectively, in the production of rubberized concrete mixtures which were obtained by partially replacing the aggregate with rubber. Two water-cementitious material (w/cm) ratios (0.60 and 0.40), three moist curing periods (3, 7, and 28 days), four designated rubber contents (0, 5, 15, and 25 by total aggregate volume), two silica fume content (0 and 10% by weight of cement), and five different testing ages (3, 7, 28, 56, and 90 days) were considered as experimental parameters. The results indicated that for a given w/cm ratio and moist curing period, the use of rubber significantly aggravated the chloride ion penetration through concrete but the degree of the rate of the increment of the chloride permeability depended on the amount of the rubber used. When the curing period was extended from 3 to 28 days, the reduction in the magnitude of chloride penetration depth was notably higher for the rubberized concretes, even at a rubber content of as high as 25%. It was also observed that silica fume may be considered as a remedy to enhance the chloride penetration resistance of the rubberized concretes.