Physicochemical And Mechanical Performance Of Lime- Based Binders Incorporating Rice Husk Ash And Calcined Clay

Abstract

The environmental concerns linked to ordinary Portland cement have increased the demand for alternative binder systems that utilize locally available resources efficiently and still provide adequate performance. This study investigates the potential of rice husk ash (RHA) and calcined clay (CC) as supplementary pozzolanic materials in lime-based binders. The objective was to comparatively evaluate the influence of these materials on physicochemical properties, reactivity, and mechanical performance and to establish relationships between these parameters. RHA and CC were produced under controlled calcination conditions and characterized using chemical, mineralogical, and surface analyses. Pozzolanic reactivity was assessed through electrical conductivity measurements, while performance was evaluated using water absorption and compressive strength tests. The results showed that both materials satisfied standard chemical requirements for pozzolans; however, their reactivity differed significantly due to variations in structure and surface characteristics. RHA exhibited a predominantly amorphous structure and a high specific surface area, resulting in faster reaction kinetics, greater calcium hydroxide consumption, and slightly higher compressive strength when used in lime-based mortars. In contrast, CC displayed a mixed amorphous–crystalline composition and lower surface area, leading to slower but sustained reactivity. The incorporation of both pozzolans improved compressive strength and reduced water absorption compared to pure lime mortar. After 28 days, blended mortars achieved strengths of approximately 4.2–4.3 MPa, indicating suitability for non-structural applications. The findings demonstrate that binder performance is governed by the combined effects of chemical composition, phase structure, surface properties, and reaction kinetics rather than composition alone. This study provides a systematic comparative assessment of RHA and CC in lime-based systems and highlights the importance of integrating physicochemical characteristics with reactivity measurements to better understand and optimize the performance of sustainable binder materials.