Role of thermo-alkaline-oxidized kraft lignin aided by concrete waste as a potential reinforcement material in botanical concrete

Exploring the bonding mechanism of botanical concrete (BC), which is developed by crushing concrete, wood waste and kraft lignin (KL) and hot pressing the obtained powder, aids in comprehending its formation and enhancing performance. This study continues the attempts on this subject, focusing on the microstructural changes between KL and concrete. Herein, the chemical structural transformations in the mixtures of KL with three sources of powder (concrete, carbonated concrete, and sand) during hot pressing are evaluated by FTIR, XRD, TGA, and( 13)C NMR methodologies. These results show that BC strength is affected by depolymerization, fragmentation, and crosslinking reactions that alter the chemical bonds within KL. Condensation reactions be-tween concrete and KL fragments, facilitated by air, are the most influential factor in improving BC strength. Waste concrete with alkalinity promotes the oxidation of KL and subsequent crosslinking, offering a new perspective for further development of self-bonding lignin-based materials.

Automated summary

This study investigates the microstructural changes between concrete and kraft lignin (KL) in botanical concrete (BC), and the effects of temperature and air on BC performance. The results show that condensation reactions between concrete and KL fragments are the most influential factor in improving BC strength.