Physicochemical Characterization and Performance Evaluation of Rice Husk Ash as a Sustainable Supplementary Cementitious Material in Mortar

Rice Husk Ash, Mortar, Cementous material, Pozzolanic material, Compressive Strength, and Physicochemical Evaluation

Authors

  • Adamu Musa Mohammed Department of Chemical Engineering, Abubakar Tafawa Balewa University Bauchi, Bauchi State – Nigeria
  • Sunday Agbata Department of Chemical Engineering, Abubakar Tafawa Balewa University Bauchi, Bauchi State – Nigeria
  • Olubajo Olumide Olu Department of Chemical Engineering, Abubakar Tafawa Balewa University Bauchi, Bauchi State – Nigeria
June 24, 2026
July 1, 2026

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The high environmental cost of cement production has driven the search for sustainable supplementary materials. This study characterized Rice Husk Ash (RHA) and evaluated its feasibility as a partial cement replacement in mortar. RHA was produced by combusting rice husks at 650°C for two hours. X-ray Fluorescence (XRF) analysis confirmed its high pozzolanic quality, revealing a silica (SiO₂) content of 76.41%. Mortar cubes were prepared with 0% (control), 5%, 10%, 15%, and 20% cement replacement by RHA, and their compressive strength was tested after 7, 14, 21, and 28 days of curing. The results identified 10% as the optimal replacement level, achieving a 28-day compressive strength of 29.68 N/mm², which is comparable to the control mix (31.32 N/mm²). This indicates a successful pozzolanic reaction where RHA's silica consumed calcium hydroxide to form additional strength-giving C-S-H gel. Conversely, higher replacement levels (15% and 20%) resulted in a significant decline in strength due to cement dilution and increased water demand, leading to a less dense microstructure. The study concludes that RHA is an effective pozzolanic material, and its incorporation at 10% cement replacement enhances mortar strength while providing an eco-friendly solution for agricultural waste management.