Effect of binder strengthening using micro-silica on mechanical and absorption characteristics of HPC reinforced with reclaimed jute fibres

The incorporation of dispersed fibres in the binder matrix is proven to be beneficial to the tensile performance of high-performance concrete (HPC). However, the insertion of new/virgin fibres in the ‘concrete matrix’ significantly adds to the final cost and embodied carbon of HPC. Therefore, the environment-friendly design of fibre-reinforced HPC remains the main challenge. In this study, the influence of different volume fractions (Vol.) of ‘jute fibre’ (JF) was examined on the engineering performance of HPC. The effect of micro-silica/silica fume (SF) inclusion as a secondary binder was also analysed on the performance of JF-reinforced HPC. To investigate the mechanical performance of designed mixes, compression, flexure, and splitting-tensile tests were conducted at 28 and 91 days. Non-destructive durability performance indicators, such as ‘water-absorption (WA)’, ‘rapid chloride-ion permeability (RCIP)’, ‘electrical-resistivity (ER)’, and ‘ultrasonic-pulse velocity (UPV)’ were also examined. It was found that the utilisation ratio/efficiency of JF addition improved with the ageing of samples. Moreover, the inclusion of SF proved to be beneficial in the strength gain due to JF addition. The combined use of 0.3% vol. of JF and SF improved the ‘compressive strength (CS)’ by 26–30%. The inclusion of 0.3% vol. of JF improved the ‘splitting-tensile strength (STS)’ of plain HPC by 43% and 23% with and without the SF inclusion, respectively. The JF incorporation showed a minor decrease in the imperviousness of HPC. SF incorporation helped minimise the damaging effect of JF incorporation on the ER, WA resistance, and UPV value of HPC. Owing to the addition of SF, the WA capacity of JF-reinforced mixes was decreased by up to 30% at 28 days and up to 50% at 91 days. While the RCIP values of JF-reinforced mixes were dropped by 40–60% (depending on the JF content) owing to the superior pozzolanic and filler effect of SF.