Title: Effect of Biochar on the Microstructure and MechanIical Response of Cement Paste

Author(s): Renata Lorenzoni, Alexander Mezhov, Tobias Fritsch, Wolfram Schmidt, Sabine Kruschwitz

Publication: Symposium Paper

Volume: 362

Issue:

Appears on pages(s): 1020-1032

Keywords: supplementary cementitious materials; biochar; microstructure; in-situ computed tomography; mechanical proprieties

DOI: 10.14359/51742027

Date: 6/18/2024

Abstract:
The use of biochar as a supplementary cementitious material is proposed to reduce global greenhouse gas emissions. Since biochar is non-reactive, and has a low density and complex porosity, its incorporation into cementitious materials results in microstructural changes and consequently affects the mechanical response. This work advances the mechanical response understanding of Portland cement composites with 0, 5, and 25 volume percent (vol%) of cement replaced with biochar by using in-situ computed tomography, correlating with the microstructural changes analyzed by HFC, gas sorption, MIP, gas sorption, and NMR. The results highlight the influence of the mesoscale structure on mechanical responses and relate the lack of loss of mechanical strength at 5 vol% replacement to the compensation of decreasing larger pores with biochar addition. At 25 vol% replacement, the number of weakened zones in the paste due to biochar overcompensates the positive effect of the reduction in larger pores, resulting in a loss of mechanical properties. Hence, small amounts of biochar can enhance the microstructure, but the reduction of the carbon footprint is limited.