Characteristics of Cement Pastes Modified with Plant-Derived Bio-Chars

Student Classification


Faculty Mentor

Dr. Andrea Ofori-Boadu


Construction Management

Document Type


Publication Date

Fall 2019


Considering that cement production is a costly and energy-intensive process with detrimental environmental consequences, more sustainable alternatives such as plant-derived biomass could present economic and environmental benefits. The purpose of this study was to investigate the characteristics of cement paste modified with almond shell bio-chars (ASB), rice husk bio-chars (RHB), wood bio-chars (WDB), and peanut shell bio-chars (PSB). Bio-chars were obtained through the thermochemical processing of biomasses. Biochars were then dry-mixed with cement, and water was added at a water/cement ratio of 0.35 to form the pastes. Laboratory experiments (loss-on-ignition, specific gravity, setting, compression, and water absorption) and spectroscopic methods (FTIR, TGA, XPS, SEM, BET, and RAMAN) were used to analyze bio-chars and cement pastes. All bio-char modified cement pastes had an accelerated set compared to the control paste. This was attributed to the presence of amorphous silica and smaller bio-char particle sizes, which accelerated chemical reactions and rapidly filled the pores within cement pastes. Direct relationships between bio-chars’ carbon/silicon ratio and the compression strength of cement pastes confirmed that carbon interferes with the cement hydration process, while silica reacts with calcium hydroxide to form calcium-silicate-hydrate. With RHB having the lowest carbon/silicon ratio, the 10% RHB paste had the highest compression strength (72 MPa). Future research will investigate optimal plant-derived bio-char processing conditions for improved bio-char modified cement paste characteristics. Economic and environmental benefits can result from the application of plant-derived biomasses for partial cement replacement.

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