Synergistic impacts of high-volume fly ash and sugarcane bagasse ash on performance of cementitious composites reinforced with polyvinyl alcohol fibers

Abstract

Disposal of waste materials in fertile land is one of the pressing environmental issues, disrupting human, animal, and plant life. This has led the researchers to process and use such waste in ecofriendly construction products like mortar and concrete. Their usage as supplementary cementitious materials (SCMs) would reduce the quantity of cement used in the manufacturing of cement-based materials, lowering CO2 emissions related with cement production. In this regard, this study examines the feasibility of replacing high-volume of ordinary Portland cement (OPC) in engineered cementitious composites (ECC) with two widely used waste materials, sugarcane bagasse ash (SCBA) and fly ash (FA) as SCMs. Five different mixes were produced, each containing a fixed amount of polyvinyl alcohol (PVA) fibers at a dosage of 1.5 % by volume of the mix and a constant cement content of 50 % by weight of the binder (OPC + FA + SCBA). However, FA was replaced with SCBA in these mixes up to 100 % by the combined weight of the waste materials (FA + SCBA) in increments of 25 % (i.e., FA100-SCBA0, FA75-SCBA25, FA50-SCBA50, FA25-SCBA75, and FA0-SCBA100). The results showed that the compressive strength and flexural strength of the composites with the increasing levels of SCBA were reduced. Interestingly, the 28-day compressive strength of composite incorporating 50 % FA and 50 % SCBA was still as high as 25.58 MPa, which satisfied the minimum compressive strength requirement of ASTM C270, making the newly produced ECC suitable for use in normal construction works and repairs. The same optimum mix (FA50-SCBA50) produced an average density of 1867.96 kg/m3 as a result of substituting a significant amount of binder with SCBA, demonstrating that it has evolved into a lightweight engineered cementitious composite. Furthermore, the ultrasonic pulse velocity of the mixes decreased whereas water absorption increased as the proportion of SCBA to FA increased. According to microstructural analysis, unreacted SCBA particles were mostly responsible for the detrimental effects of rising SCBA levels on properties of ECC. Based on the aforementioned results, this research concludes that sugarcane bagasse ash, when combined with fly ash, could be a viable alternative for replacing regular cement up to 50 % by weight in the production of cost-effective and environmentally friendly cementitious composites.