Strength and toughness of ambient-cured geopolymer concrete containing virgin and recycled fibres in mono and hybrid combinations

Abstract This paper presents an investigation on the workability and mechanical properties of ambient-cured fly ash geopolymer concrete (GPC) containing four different fibres, namely steel (S), polyvinyl alcohol (PVA), polypropylene (PP) and recycled polypropylene (RPP) fibres at 1% volume of concrete. The influences of hybrid S-PVA, S-PP and S-RPP on GPC at 0.5% of each type of fibre were also studied. In the mono fibre reinforced GPC (FRGPC) series, steel fibre showed the most effective role in improving the mechanical properties which were 4.0% in compressive strength, 74.3% in splitting tensile strength and 65.3% in flexural strength. In the hybrid FRGPC series, mixing of steel and RPP fibres was found more effective than the other combinations. The improvements by S-RPP were 15.5% in compressive strength, 48.9% in splitting tensile strength and 60.0% in flexural strength. The highest toughness was achieved for the S-RPP hybrid fibres following by mono steel fibres. A net deflection equal to 1/75 of the span could be regarded as the end deflection point to calculate the total flexural toughness of FRGPC according to quantitative analysis of toughness enhancement. There is a strong positive correlation between the total toughness and stress at the limit of proportionality (LOP) point.