Analysis of wood fly ash as sustainable alternative to cement replacement on concrete

Abstract

Supplementary cementitious materials (SCM) can contribute to reducing the carbon footprint of concrete. One of this SCM is the biomass fly ash (BFA) which is a waste of the wood production. Although different researchers have used BFA as SCM it is fundamental to know the concrete behaviour with local materials (including the available BFAs) to reduce the environmental impact of transportation. In particular, the Biobio region produces 57% of the Chilean wood, concentrated in Eucalyptus Globulus (E) and Pine Radiate (P) production. This paper describes the behaviour of concrete mixtures with replacements of BFAE or BFAP in 0%, 10% and 20% by weight of cement. Workability, compressive and flexural tests were performed, and the specimens were examined by scanning electronic microscopic (SEM) as well. The results show that BFAE reduced slump of fresh concrete and BFAP increased it on all cases due to their morphology. An increase in resistance at later ages is evident due to the increase in pozzolanic activity and BFAs morphology. The results indicate that BFAE and BFAP are suitable to replace at least 10% of cement, because those mixes present similar, and even higher, compressive and flexural strength than the control mix.