Abstract

Chrome leather shavings generated in leather making have always been a difficult to handle handle solid waste. Inspired by a protein-based gypsum retarder, a collagen degradation product (CDP) obtained from chrome leather shavings has been developed as a Portland cement retarder. The effect of CDP on the setting, strength, crystal morphology, and hydration process of cement were investigated. The results showed that after adding CDP, the setting time of cement was effectively prolonged. 0.1% CDP could delay the initial setting time from 150 minutes to 300 minutes and final setting time from 200 minutes to 370 minutes. SEM observation revealed that the cement crystals changed from needle-like to massive clusters with the addition of CDP. Furthermore, TG/DSC and XRD analysis showed that the addition of CDP inhibited the hydration process of cement reactants (alite and belite) and the formation of hydration product (Ca(OH)2). This study provides not only new ideas for the research of cement retarders but also a new method for treating waste leather shavings. Note: Alite and belite are phases in portland cement based materials. Alite is impure tricalcium silicate (C3S) and belite is impure dicalcium silicate (C2S). Although both are calcium silicates, alite reacts much more quickly than belite when mixed with water.