Hybridisation effect of steel–polypropylene fibres in high-volume fly ash concrete

The paper presents the results of an investigation conducted to investigate the effects of hybrid fibres (polypropylene (PP) and steel (S) fibres on the workability, compressive strength, flexural strength and flexural toughness of high-volume fly ash concrete (HVFAC). Different combinations of PP and S fibres (PP fibre 0–100% and S fibre 100–0%) were incorporated to a total fibre volume fraction of 1.0%. Three different code methods were used for a comparative evaluation of various properties of the HVFAC (toughness, residual strength, cracking strength, etc.). It was found that the mixes with a higher percentage of PP fibre resulted in lower workability as compared to the mixes made with a higher percentage of S fibres. The HVFAC mix made with 25% PP fibre and 75% S fibre showed the best results of all concrete mixes and this combination is thus considered to be the most appropriate for fibre hybridisation in HVFAC.