INVESTIGATION OF PHASE EVOLUTION, MICROSTRUCTURE AND MECHANICAL STRENGTH OF LIGHT WEIGHT CONCRETES

This article investigates the compressive strength of concretes made up of expanded perlit, sand and silica fume. For determination the effect of silica fume on the compressive strength of these lightweight concrete, it was added in the ratios of 3% ,6% and 9% by weight of Portland cement. Throughout this study superplasticizer was used 1.5% by weight of Portland cement to reduction viscosity. Apparent porosity of some specimens was also assessed. Some samples were studied by XRD and SEM techniques. The obtained results showed that unit weight of all groups decreased by increasing of expanded perlit aggregates in the mixtures. In general, silica fume increased 7-and 28-day compressive strength of all groups. It was found that apparent porosity of concrete increased by using expanded perlit aggregates and decreased by using silica fume. X-ray diffraction patterns of samples showed that portlandite phase is decreased by increasing of silica fume. Microstructural observations of samples by scanning electron microscope (SEM) showed that the crack propagation direction was found to be toward of expanded perlit aggregates

Keywords:

lightweight Concrete , Perlit , Silica fume , Compressive strength