Biochar in Quick Clay Stabilization: Reducing Carbon Footprint and Improving Shear Strength

Alternative materials like biochar can be utilized to improve soil strength, while reducing the carbon footprint of soil stabilization through carbon sequestration. This paper studied the effect of various biochar/cement dosages on strength and stiffness of quick clay. Laboratory tests revealed that biochar quantities as low as 50 kg/m3 resulted in undrained shear strength, cu, values (i.e., cu = 2.8 kPa) greater than the 0.5 kPa threshold for remolded quick clay. Biochar amendment also enhanced cu of cement-stabilized quick clay. For example, the cu of quick clay samples stabilized with 25, 50, or 100 kg/m3 of cement increased between 20% and 40% when amending with 100 kg/m3 of biochar. Depending on the cement quantity, an optimum biochar dosage of 75–125 kg/m3 was identified. A sustainability assessment indicated that biochar amendments >30% of the used cement rendered the soil stabilization process carbon neutral. The current cost of biochar was, however, found to be greater than its benefits for soil stabilization. This may change in future because of higher carbon prices or lower biochar manufacturing costs.