Effects of Fly Ash and Silica Fume on Permeability of Concrete Made With Porous Limestone and Non-Porous Aggregates

The research objective was to assess the permeability of concrete made with porous limestone and non-porous aggregates. Fifty-eight concrete mixes were made and tested to study the effects of fly ash, silica fume, and aggregate type on the permeability of concretes. Class F fly ash and silica fume were used at the levels of 10 to 50 %, and 5 to 20 % as cement replacement on weight basis, respectively. Nine different aggregates, seven in-states and two out-of-states, were collected to study the effects of aggregate type. The test results indicated that silica fume may cause considerable effects on both water and rapid chloride permeability of concrete, while the initial and prolonged moist curing was found essential for the fly ash concrete. In addition, the permeability of aggregate was positively affecting the permeability of concrete. The concretes mixed with aggregates of low permeability showed lower water permeability than those made with porous aggregates. The effect of the permeability of aggregate was also noticeable when the water cementitious material ratio (w/cm) of concrete was high. At lower w/cm ratio, the bond at the cement paste-aggregate interface reduced the effect of the permeability of aggregate.