Bamboo ashes as an eco-friendly alternative to cement - a systematic review

Cement production impacts the environment from raw materials extraction to its industrialized production. Implementing supplementary cementitious materials (SCM) to replace cement is an economical and sustainable practice. Agricultural wastes, for example, represent a new source of SCM studied over the last decades, mainly due to its high generation around the world. Among the published review papers about agro-waste in civil construction, bamboo ashes (BA) appear secondary in large-scale studies. Thus, this work aimed to evaluate BA potential use in the construction industry as cement replacement by identifying their behavior in cementitious compounds and discovering the research gaps about this topic. We overviewed the published literature about concrete made with BA, synthesizing data about BA chemical composition and mechanical and physical characteristics of cementitious materials made with these ashes. We identified a preference for bamboo leaves ashes as SCM, potentially due to its high silica amount. However, other biological and environmental parameters that alter the bamboo chemical composition were not discussed in the papers. Concerning compressive strength, 90% of the studies with BA reported cementitious materials with a strength activity index acceptable for use. This review also identified an optimal percentage of cement replacement with BA ranging from 8% to 12% in concrete specimens. Concrete and mortar with BA also showed a lower density than the reference samples made only with cement. We concluded that BA are promising alternatives to replace cement since they provide desirable mechanical and physical characteristics to concrete and meet sustainability requirements. Besides that, we raised some topics that may guide future researches: (1) the natural and artificial parameters that affect BA composition; (2) BA chemical and physical behavior under microscopical conditions in cementitious composites; and (3) the economic advantages associated with replacing cement with BA.