Synergistic effects of hybrid fibres and natural rubber latex on the thermal stability and mechanical properties of high-volume fly ash concrete

Structures exposed to high temperatures must have enhanced thermal stability and mechanical properties. It is essential to utilise sustainable materials in the endeavour to achieve this objective. This study investigates the combined effects of natural rubber latex (NRL) and hybrid fibres in high-volume fly ash (HVFA) concrete. It introduces a novel approach of utilising NRL as a partial cement replacement at varying percentages of 2.5%, 5%, 7.5%, and 10%. Replacing cement with 2.5% NRL resulted in optimal performance. Higher percentages of NRL enhanced the concrete's workability, with 10% NRL producing a maximum slump of 54 mm. Adding 2.5% and 5% NRL significantly reduced water absorption by 12-18% compared to the control sample. Compressive strength decreased with higher NRL contents. The smallest reduction of 8% occurred with 2.5% replacement, and the highest loss of 55% was at 10% replacement. In contrast, tensile and flexural strengths improved by 14% and 31%, respectively, after 28 days of curing. The concrete with 2.5% NRL retained more strength at elevated temperatures, with a loss of strength of 20% at 600 °C compared to 25% for the control. The microstructural analysis revealed that the optimal NRL percentage resulted in a denser matrix, supporting the mechanical results. Generally, incorporating 2.5% NRL with hybrid fibres in HVFA concrete enhances durability and thermal resistance while maintaining satisfactory strength, offering a sustainable approach for high-performance applications.