Improving the properties of botanical concrete based on waste concrete, wood, and kraft lignin powder

Abstract

Botanical concrete (BC) is a novel sustainable material that can simultaneously recycle concrete and wood waste without using cement. It has potential for use provided its high water absorption and low stability, caused by the inclusion of hydrophilic wood particles, are mitigated. This study aims to improve the water resistance of BC by experimenting with forming conditions and varying the amounts (0–20%) of hydrophobic kraft lignin that is added. The investigations were conducted, using water-immersion and three-point-bending tests, to determine the water resistance (water absorption, swelling, spring back) and bending strength of BC. Scanning electron microscopy (SEM) and systematic analysis of the effects of the composition of BC were performed to understand its behavior. Experimental results show that the water resistance and bending strength of BC could be enhanced by changing the forming conditions and by the addition of kraft lignin. Kraft lignin content of up to 20% can significantly improve the performance of BC, providing a new insight into its utilization and its added value as a renewable resource. SEM results suggest that the plasticization of wood particles and the excellent fusion of kraft lignin with the particles, aided by the alkaline concrete powder, might help enhance the performance of BC.