Evaluation of Materials and Performance Characteristics of Tannery Sludge Crumb Rubber Concrete (TSCRC)

• Joseph K. ZAMBWA

  Author

• Jibril M. KAURA

  Author

• Ocholi AMANA

  Author

• Abdrasheed S. ABDURASHEED

  Author

• Ejembi WILLIAMA

  Author

This study presents a preliminary evaluation of tannery sludge–crumb rubber concrete (TSCRC) as a sustainable alternative for eco-friendly construction. The research investigated the suitability of treated tannery sludge (TS) and crumb rubber (CR) as partial replacement materials in concrete to promote waste valorisation and reduce the environmental impacts associated with tannery sludge and discarded tyres. Portland limestone cement, aggregates, TS, and CR were characterised using X-ray fluorescence (XRF), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR), while fresh concrete performance was assessed through the slump test. Response Surface Methodology based on Central Composite Design (RSM/CCD) was adopted for mix design optimisation. The coarse aggregate satisfied structural requirements, recording an Aggregate Crushing Value of 20.8% and an Aggregate Impact Value of 12.0%, while Portland limestone cement complied with standard specifications. Treated TS exhibited a specific gravity of 2.30 and significant reductions in heavy metal concentrations after washing, with chromium decreasing from 4,750 to 96 mg/kg and lead from 213 to 65 mg/kg, indicating improved environmental suitability. CR had a low specific gravity (1.14), moderate water absorption (2.8%), and low elastic modulus, confirming its role as a lightweight performance modifier. XRF analysis showed that TS contained appreciable amounts of CaO (48.72%), SiO₂ (24.86%), Al₂O₃ (7.64%), and Fe₂O₃ (7.63%), indicating chemical compatibility with Portland limestone cement and limited supplementary cementitious potential. FTIR analysis identified hydroxyl, silicate, carbonate, amide, and metal–oxygen functional groups, confirming the presence of hydration-related minerals and residual chromium-bearing compounds. Slump values decreased from 83 mm for the control mix to 20 mm at the highest TS and CR replacement levels; however, all mixes remained cohesive without segregation or bleeding. The findings confirm that controlled incorporation of treated TS and CR is feasible for sustainable concrete production, promoting waste recycling, resource conservation, and the development of environmentally friendly concrete suitable for structural and non-structural applications.

• 57_Zambwa et al. (2026)

Copyright (c) 2026 Joseph K. ZAMBWA, Jibril M. KAURA, Ocholi AMANA, Abdrasheed S. ABDURASHEED, Ejembi WILLIAMA (Author)

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.