Efeito da adição metacaulinita e tijolo moído queimado na durabilidade de compósitos argamassa-fibra de sisal.

Abstract

Interest in using sisal fibers as reinforcement for cement-based matrices has grown worldwide in recent years. The main obstacle to the widespread use of these fibers as a reinforcement element of cement-based dies is related to their low durability in the alkaline environment. The present study aimed to reduce matrix alkalinity by using pozzolanic materials. The pozzolans studied were metakaolin and burnt brick stubble. The percentage substitution by weight of portland cement for pozzolanic material ranged from 20 to 50%. The influence of these substitution contents on the compressive and flexural strengths of mixed mortars and the calcium hydroxide consumption of hydrated cement pastes was determined. Mixed sisal-matrix fiber composites were subjected to natural weathering and accelerated aging through wetting and drying cycles. Flexural tests were performed on the composites after 28 days of water cure, after 90, 135 and 180 days of natural aging and after 62, 94 and 125 wetting and drying cycles. The results indicated that mixtures with 40% and 50% metakaolin content consumed practically all calcium hydroxide maintained the toughness and increased composite strength after 180 days of natural exposure or 94 wetting and drying cycles. Mixtures of 40% ground brick increased the modulus of rupture of the composite but showed an 11% reduction in toughness after 94 cycles of wetting and drying.