Influence of rice husk ash calcination temperature in determining compressive strength and microstructure of mortar

Brast C.E.R.; Muñoz Pérez S.P.; Obando Quiroga M.A.; Campos Zuloeta A.; Chuquilin Diaz G.G.; Rosillo Urbina J.E.; Pisfil Custodio J.; Ruiz Villegas C.K.; Bustamante Benavides D.M.; Velez Pozada J.I. · Engineering and Applied Science Research (2026) · DOI: 10.64960/easr.2026.262727

Resumen

The construction industry consumes large quantities of cement and is therefore a major source carbon dioxide (CO₂) emissions. As a more sustainable alternative, rice husk ash (RHA) can partially replace cement, taking advantage of its pozzolanic properties. The reactivity of RHA varies depending on the calcination temperature, affecting the strength and microstructure of the mortar (MM). This study evaluates how calcination temperature of RHA affects compressive strength and MM. RHA was heat treated at 600, 650, 700 and 750 °C to analyze the compressive strength of the mortar. Mortar specimens were prepared with RHA replacing cement at 5, 10, 15 and 20% to replace cement and compressive strength tests were performed at 7, 14, 21 and 28 days. In addition, the MM was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used to evaluate the MM. The results indicate a maximum gain in compressive strength up to 55.87% when 15% of the cement was replaced with RHA calcined at 700 °C, whose amorphous silica content was 69.40%. Moreover, microstructural analyses evidenced the formation of C-S-H and C-A-S-H gels, which densified the mortar, improved the interfacial zone (ITZ), and reduced overall porosity. It is concluded that the calcination temperature significantly influences the pozzolanic reactivity of RHA, the mechanical strength, and MM; RHA calcined at 650-700 °C exhibited the best mechanical performance, attributable to higher amorphous silica content and greater microstructural densification. It is recommended for future works to investigate calcination temperatures above 750°C, analyze the relationship between RHA particle size and its amorphous silica content, and evaluate the mortar´s long-term durability. In addition, studies should assess the interaction of RHA with other alternative materials to identify synergistic effects and optimize the RHA dosage.

Instituciones: Universidad de San Martín de Porres