Novel solidification/stabilization process of wet blue leather waste to produce recycled lightweight aggregates

Chromium (III) salts are currently the most common leather tanning agents. During the production process, wet blue leather shavings are produced, and this material is classified as hazardous solid waste. Given the global concern about chromium pollution and considering the potential for waste reuse in the construction industry, this article aimed to evaluate a new and more sustainable material for civil construction. Leather shavings were solidified/stabilized in polypropylene using an extrusion process to obtain recycled lightweight aggregates as an alternative to natural sand. This is the first study of leather shavings' solidification/stabilization in a polypropylene matrix. The new material has been tested replacing 25%, 50%, and 75% of the sand by volume. Results showed that the novel process of wet blue leather shavings treatment to produce cement matrices was efficient for the proper disposal of hazardous waste since low chromium content was present in the leachate extract. The compressive strength of the mortars was reduced with the increase of sand replacement by the recycled lightweight aggregate, reaching up to 72% loss compared to the reference mortars. However, the effect on the compressive strength of the mortars found in this study is lower than other polymer-based lightweight aggregates, showing good potential for the application of the developed material as non-structural elements.