Performances of Vermiculite and Perlite Based Thermal Insulation Lightweight Concretes

This experimental study was conducted with an aim to investigate the effect of the elevated temperature on the mineral phase composition, microstructure and mechanical properties of the thermal insulation lightweight concretes. The first group of experimental concretes was based on the expanded vermiculite and expanded perlite used as lightweight aggregates (in 65 wt%) in combination with either ordinary Portland cement or refractory calcium aluminate cement. The mix-design of the second group of concretes comprised standard quartz aggregate, vermiculite or perlite as aggregate replacement (25 wt%) and binder (PC or CAC). A total of 10 concrete mix-designs were fabricated in form of 40x40x160 mm samples which were submitted to heat-treatment at 400 degrees, 600 degrees, 800 degrees and 1000 degrees C upon standard 28-days period of curing and hardening. The changes in crystallinity and mineral phase composition induced by temperature were monitored by X-ray diffraction technique. Microstructural visualizations of the non-fired and fired concrete samples were conducted by scanning electron microscopy accompanied with EDX analysis. The results indicated that despite the decrease in compressive strengths upon firing, investigated lightweight concretes can be categorized both as thermal insulators and structural materials.