Combined effects of ground granulated blast furnace slag and fly ash on the porosity and chloride penetration of sand concrete

This paper presents study results on the effects of ground granulated blast furnace slag (GGBFS) and fly ash (FA) on the mechanical properties, porosity and chloride penetration of sand concrete. Two series of concretes were prepared with W/B ratios of 0.36 and 0.32. The aggregate used consists of crushed sand with a modulus of fineness 3.2 and dune sand with a modulus of fineness 1.7. In each series: 1 mixture of reference sand concrete (RSC), 2 mixtures were investigated: concrete containing 40% GGBFS and concrete containing a combination of 35% GGBFS and 20% FA. The study results showed that the strength of sand concretes containing 40% GGBFS was improved after 7 days of curing, their porosity and chloride penetration significantly decreased at all ages compared with that of the RSC. The strength of sand concrete containing 35% GGBFS and 20% FA was lower than that of RSC at 28 days but approximately reached strength at 56 days. In addition, its porosity and chloride penetration were much lower than that of RSC and sand concretes containing 40% GGBFS.