Optimization of hybrid fibres in engineered cementitious composites

New hybrid fibre reinforced cementitious composite developed using waste materials in the form of tirewires in combination with the PVA (Polyvinyl alcohol) fibers. The two kinds of fibres have been incorporated in the RSM (Response surface methodology) technique from the Design-expert software to evaluate the hybrid proportion of fibers. The Hybrid fibres in ECC (Engineered cementitious composite), with appropriate quantity of high and low modulus fibers is anticipated to enhance both the tensile strength (modulus of elasticity, bulk strength) and strain capacity (mainly for energy absorption). The fresh properties for self-compacting were satisfied according to EFNARC guidelines and observed that tirewire fibre diminished the workability and was preserved through the addition of PVA and superplasticizer. The hardened properties such as flexural strength, direct tensile strength, modulus of elasticity and shrinkage strain were optimized by developing the model equations through ANOVA (analysis of variance) validation with the more than 95% of significance. The appropriate proportions as 0.5% of tirewire and 1.5% of PVA fibers were obtained. The results revealed that the hybrid proportion of fibres adversely effected on workability and it produced a favourable influence on flexural strength, tensile strength and modulus of elasticity. The PVA fibres helped in increasing the strain hardening portion for the hybrid fibre reinforced engineered cementitious composite (HFRECC) and was able to maintain strain capacity up to 5%. The optimized results were validated experimentally with high desirability value of more than 0.97 and the variation between experimental and optimized results from RSM was found to be less than 5%.