Application of Biochar as Beneficial Additive in Concrete

Biochar is a high-carbon solid material produced via thermal decomposition of organic biomass in a low-oxygen environment. Characterized with high water retention properties and high alkalinity, biochar is generally used for soil amendment and fertilization purposes. This study is intended to explore the feasibility of using biochar as a beneficial additive of the most used manmade material, concrete. Literature review revealed several studies where biochar was successfully implemented as an additive in concrete. The beneficial influence of biochar on the mechanical characteristics of concrete is based on nucleation and densification effects. However, the internal microstructure, porosity and chemical composition of biochar are highly dependent on the type of feedstock and production conditions. The objectives of this study do not only include the determination if a concept similar to the one described in the literature (application of biochar at low dosage) could be applied by local producers but also to explore the ways of how biochar might be used in a wider dosage and beneficially utilized in the development of environmentally and economically more sustainable materials, such as concrete mixes with reduced cement content or concrete made with recycled concrete aggregates. Several locally available biochar samples made from distillers grains, corn stover, wood waste, and red cedar were collected for characterization and incorporation in concrete mixes. The experimental program included a study of the effect of different fineness and a wide range of biochar addition and cement replacement levels on fresh and mechanical properties of concrete, as well as the possibility of strength compensation of the concrete mixes with reduced cement content. Moreover, biochar was used as a coating for recycled concrete aggregates to improve their bonding with cement. In addition, a preliminary study of the potential use of biochar as internal curing and carbonation agent was also included. Finally, a preliminary economic analysis was performed. Advisor: Jiong H