Potential usage of fly ash and nano silica in high-strength concrete: Laboratory experiment and application in rigid pavement

Abstract

High-strength concrete (HSC) using supplementary cementitious material of 30% fly ash (FA) and various nano silica (NS) contents were investigated in this study. FA and NS are waste materials collected from local thermal plants and rice husk ash in Southern Vietnam, respectively. Different concentrations of NS at 0%, 0.5%, 1.0%, and 1.5% were incorporated into the base mixture in place of cement and FA. The water-to-binder ratio of 0.32 was constant for all the mixtures. Results indicated that the combination binder of cement, FA, and NS satisfied the setting time as pure cement binder. The slump test value was in the range of 30–40 mm by adjusting the superplasticzer. Mechanical properties of HSC were studied at various curing ages of 3, 7, 28, and 56 days, including compressive strength, flexural strength, elastic modulus, and abrasion resistance. Results indicated that 1% NS can be considered as optimum content for preparing an HSC mixture, which showed the best mechanical properties. Furthermore, a good correlation between compressive strength and flexural strength was obtained from the results. Finally, rigid pavement calculation revealed that the addition of 1% NS resulted in a reduction in the thickness of the concrete slab by 30 mm (around 10.7%) compared to non-NS concrete. These findings suggest that incorporating nano-silica into concrete can lead to thinner concrete slabs with improved performance characteristics.