The impact of natural and calcined zeolites on the mechanical and durability characteristics of glass fiber reinforced cement composites

Abstract

Abstract In this paper, an experimental study of the effects of natural and calcined zeolites and glass fibers on the mechanical, transport and accelerated ageing characteristics of cementitious composites exposed to wetting–drying and freeze–thaw cycles was presented. Three reference mixtures were fabricated with the inclusion of glass fibers (GF) at the rates of 0, 1.5 and 3% by weight of cement and without zeolites as cement substitute.18 mixtures were produced with two percentages 15 and 30 of natural zeolites (NZ) and two different zeolites calcined at 600 °C and 800 °C (CZ6, CZ8) as partial substitution of white Portland cement (WPC) and 0, 1.5 and 3% addition of GF by weight of cement. Workability of fresh cement composites were assessed by performing slump test. Mechanical performance were evaluated by compressive and flexural strength at 7, 28 and 91 days. Dry unit weight, transport properties, drying shrinkage and sorptivity of the mixtures were also evaluated. Durability performance is evaluated by performing accelerated ageing, 60 and 120 freeze–thaw and 25, 50 and 75 wetting–drying cycles. The results exhibited that calcination increased the amorphous content and BET surface area and pozzolanic reactivity of natural zeolites. The mixtures with calcined zeolites performed better than the mixtures with natural zeolites when considering compressive and flexural strength at all curing ages. Based on the results, it was found that at later age of 91 days, replacing cement with 15% zeolites calcined at 600 °C and without glass fibers exhibited the compressive strength very close to the corresponding reference mixture R1. Similarly, the mixture with 15% zeolites calcined at 800 °C and 1.5% glass fibers revealed higher compressive strength than the corresponding reference mixture R2.