The effect of fly ash (10, 20 and 30%) and silica fume (5 and 10%) as a substitute for cement in binary and ternary mixtures on the properties of fresh and hardened concrete are investigated. To determine mechanical properties, the compressive strength, splitting tensile strength and modulus of elasticity tests are used. Also, water penetration depth, water sorptivity, specific electrical resistivity, rapid chloride permeability and rapid chloride migration tests are applied to evaluate concrete durability. To examine the pore structure and transition zone morphology of concrete specimens, mercury intrusion porosimetry and scanning electron microscopy are used, respectively. The fresh concrete results show that the presence of silica fume in binary and ternary mixtures reduces workability and air content, but fly ash increases them. Adding silica fume to mixtures containing fly ash increases the mechanical strength at the ages of 7, 28 and 90 d. In addition to increasing the quality of the aggregate–cement matrix bond and improving the pore structure, the presence of supplementary cementitious materials has a considerably positive effect on the transport properties of concrete at all ages.

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Nowadays pozzolans are used vastly in civil projects. Pozzolan is a natural or artificial material containing active silica that increase the strength and improves some properties of concrete. In this survey for investigating some important properties of concrete, silica fume and fly ash was used in replacement of cement in different weights. Concrete compositions were made with water-cement ratio of 0.45 and cured under the same conditions. The main focus of this survey is to investigate the individual and combined effect of using Pozzolan on mechanical properties, permeability and shrinkage of concrete. The mechanical properties of concrete in compressive and bending strength at the age of 7, 28 and 90 days, were evaluated. Permeability was investigated with the water absorption test. The drying shrinkage of concrete was monitored for 90 days. Scanning Electron Microscopy (SEM) images was used in concrete cement based matrix morphology. The results showed that the addition of pozzolan increases the mechanical strength and reduce permeability and increase the drying shrinkage in some mixtures.