Semester of Graduation

Fall 2021


Master of Science in Civil Engineering (MSCE)


Civil and Environmental Engineering

Document Type



Biochar is a sustainable and lightweight carbon-rich material with a high surface area and porosity. Previous studies reported that biochar can reduce soil erosion and cracking, retain contaminants, and enhance soil aggregation. Given these favorable properties, soil-biochar mixtures have the possibility to serve as a multifunctional lightweight fill material for roadway embankment applications. The purpose of this research is to develop sand-biochar mixtures as a sustainable and multifunctional lightweight fill material for roadway embankment applications.

This research investigated the consolidation and hydraulic properties of sand-biochar mixtures by (1) performing 1D consolidation tests, (2) performing permeability tests, and (3) assessing the optimal mixing ratio of the sand-biochar mixtures and lightly cemented sand-biochar mixtures. 1D consolidation tests instrumented with bender elements were performed to investigate the shear modulus and compressibility of the sand, sand-biochar mixtures, and lightly cemented sand-biochar mixtures with different mixing ratios of sand, biochar, and cement.

Next, the hydraulic conductivities of different mixtures were measured using an automated permeameter. Based on these results, an optimal mixing ratio of sand, biochar, and cement (i.e., high mechanical strength and excellent drainage properties) was determined for lightweight fill applications. Finally, the micro-scale morphologies and pore structures of the lightly cemented sand-biochar mixtures were investigated using a Scanning Electron Microscope combined with energy-dispersive X-ray spectroscopy. Satisfying mechanical and hydraulic properties of the sand-biochar mixtures were observed at low biochar percentages.

Committee Chair

Lin, Hai