Abstract
Hybrid fibres addition in concrete proved to be a promising method to improve the composite mechanical properties of the cementitious system. Fibre combinations involving different fibre lengths and moduli were added in high strength slag based concrete to evaluate the strain hardening properties. Influence of hybrid fibres consisting of steel and polypropylene fibres added in slag based cementitious system (50% CRL) was explored. Effects of hybrid fibre addition at optimum volume fraction of 2% of steel fibres and 0.5% of PP fibres (long and short steel fibre combinations) were observed in improving the postcrack strength properties of concrete. Test results also indicated that the hybrid steel fibre additions in slag based concrete consisting of short steel and polypropylene (PP) fibres exhibited a the highest compressive strength of 48.56 MPa. Comparative analysis on the performance of monofibre concrete consisting of steel and PP fibres had shown lower residual strength compared to hybrid fibre combinations. Hybrid fibres consisting of long steel-PP fibres potentially improved the absolute and residual toughness properties of concrete composite up to a maximum of 94.38% compared to monofibre concrete. In addition, the relative performance levels of different hybrid fibres in improving the matrix strain hardening, postcrack toughness, and residual strength capacity of slag based concretes were evaluated systematically.
Highlights
Fibre addition to concrete improves the tensile performance due to secondary reinforcing mechanism provided in the matrix
Test results indicated that fibre addition showed improved compressive strength (48.56 MPa) in the case of hybrid fibre concrete mixes containing short steel and polypropylene fibre combinations
(ii) Compressive properties were favorably improved with the inclusion of hybrid fibres consisting of steel-PP and a maximum compressive strength was recorded up to 48.56 MPa
Summary
Fibre addition to concrete improves the tensile performance due to secondary reinforcing mechanism provided in the matrix. It is understood from the studies that the matrix reinforcing efficiency is dependent on selecting the optimal volume fraction of fibres. This can result in lower fibre spacing and can effectively strengthen the matrix resulting in the delay for matrix cracking. The origination and propagation of microcracks can be better controlled with the presence of bridging mechanism using fibres [9, 10] This can result in subsequent reduction on the crack width formation during continuous drawdown of the load deformation process. The present study emphasizes the evaluation of mechanical properties of high performance slag based concrete incorporating fibre combinations. Steel and polypropylene (PP) fibres were added at different volume fractions and the postcrack performance was measured using load- deformation characteristics. A special concrete mixture design method was carried out to select the matrix constituents for effective fibre performance
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