| Summary: | This paper presents the mechanical properties of fibre reinforced high-volume fly ash (HVFA) concretes measured at 7 and 28 days. The effects of three class F fly ash contents of 40%, 50%, and 60% by wt. as a partial replacement of cement and two types of fibres (steel and polypropylene) with three different volume fractions of 0.15%, 0.25%, and 0.50%, on the compressive, tensile and flexural strengths of HVFA concretes are studied. Test results show that the addition of fibres (steel and polypropylene) reduces the workability of HVFA concretes and the workability decreases with increase in volume fractions of fibres and increases with increase in fly ash contents. The compressive, tensile and flexural strengths of all HVFA concretes increased due to addition of steel and polypropylene fibres and the above values also increased with increase in fibre volume fractions. Among all fibre reinforced HVFA concretes, the concrete containing 40% fly ash exhibited the highest mechanical properties at both ages. The steel fibre volume fraction of 0.5% exhibited the highest compressive, tensile and flexural strengths of HVFA concretes containing 40% fly ash and the improvement was by 73%, 40% and 36%, respectively. However, in the case of polypropylene fibre the above improvements were only 44%, 29% and 20%, respectively. This can be attributed to the lower elastic modulus and tensile strength of polypropylene fibres than steel fibre. Correlations among compressive, tensile and flexural strengths of the above concretes are also established.
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