Exploring oat husk ash as a sustainable option for low-carbon concrete production

Abstract

Achieving reductions in the carbon footprint of concrete requires exploring new supplementary cementitious materials (SCM) as the conventional ones are either diminishing or unable to meet the growing demand for cementitious materials. Thus, this thesis aimed at exploring, synthesizing and testing oat husk ash (OHA) from Manitoba, Canada as a novel agro-waste-residue SCM. The physicochemical properties as well as the reactivity of OHA were examined. The fresh, mechanical and durability performance of concrete comprising OHA was also evaluated. Moreover, the environmental impact of concrete incorporating OHA was assessed. Furthermore, the potential of OHA at higher volume (up to 40%), without or with the effects of incorporating colloidal nano-silica (NS) and nano-crystalline cellulose (NC), which were efficient with a slag-based composites, were investigated. The outcomes showed the potential of integrating OHA as an SCM to achieve pozzolanic reactivity. Notably, the pozzolanic efficacy of optimized OHA may surpass that of Class F fly ash, when subjected to combustion at 600°C for 4 hours. The results revealed that the development of concrete prepared from binders incorporating general use and limestone cements blended with OHA is possible, as OHA mixtures achieved comparable or higher compressive strengths than references and fly ash concretes, while maintaining workability through appropriate superplasticiser dosage. In addition, OHA-based specimens showed reduced fluid absorption, refined pore structure, and improved salt-frost scaling resistance. This performance was also accompanied by reduction in global warming potential (GWP) and criteria air pollutant emissions as revealed by the life-cycle assessment. In addition, the development of concrete comprising high volume OHA (up to 40%) is possible. However, incorporation of nano-silica is important to improve the hydration kinetics and early-age strength. The synoptic outcomes of this thesis highlighted the potential of OHA to support low-carbon concrete production and circular material flows, especially in regions with diminishing availability of conventional industrial by-product SCM such as fly ash.