Experimental Investigation and Predictive Modelling of Sustainable Concrete Incorporating Rice Husk Ash and Periwinkle Shell Ash

Abstract

Concrete remains the most widely used construction material globally but the durability and performance of concrete structures have become a critical concern in modern construction. Concrete is exposed to chemical attacks that significantly affect its long-term strength and integrity. This study investigated the properties of concrete incorporating blended Rice Husk Ash (RHA) and Periwinkle Shell Ash (PSA) as supplementary cementitious materials, and also developed predictive strength models. Concrete mixes with varying RHA-PSA replacement ratios were produced at a constant water–cement ratio of 0.55 and cured for 3, 7, 28, and 90 days. The ashes were characterized using Energy-Dispersive X-Ray Fluorescence (EDXRF). While aggregates conforming to BS EN standards were used, workability test were performed on the fresh concrete samples and compressive strength, tensile strength, and density were done on the hardened samples. Finally, the properties were modelled and validated using regression analysis. The results indicated that both RHA and PSA contained key oxides (CaO, SiO₂, Al₂O₃, Fe₂O₃). Also, RHA satisfied the ASTM C618 requirement of the sum of SiO₂, Al₂O₃ and Fe₂O₃ of more than 70% with a value of 71.86% indicating their pozzolanic potential. PSA, with a combined total of 3.17% did not meet this pozzolanic threshold but complemented RHA with its high CaO (≈ 88%). RHA and PSA had specific gravities of 1.79 and 2.49 respectively, indicating their potential as lightweight pozzolans, reducing concrete density while maintaining strength. At 28 days, 70% of mixes exceeded the 25 N/mm² target strength, with B7(6%RHA + 4% PSA) achieving the highest compressive strength and B6(5.25%RHA + 4.75% PSA) the highest tensile strength at 28 - 90 days. Predictive models of (R2 = 0.8410) for compressive strength, and (R2 = 0.5899) for splitting tensile strength at 28days curing respectively accurately described strength development for specific mix designs. B7 mix design was recommended where high compressive strength was a priority. While B6 mix ratio is preferable for maximizing splitting tensile strength for cubes/cylinders cured in water. Balanced blend of ≈5–6% RHA and 4–5% PSA enhanced strength, durability, and microstructure, promoting sustainable, high-performance concrete.