Mixed Rice Husk Ash, Mahogany Fruit Ash, and Foaming Agent as Additives in Floating Concrete Blocks for Wall Panels

Abstract

This study investigates the use of agricultural waste materials—rice husk ash (RHA), mahogany fruit ash (MFA), and a foaming agent—as an additive in the production of floating concrete blocks for wall panels. The research aims to address environmental concerns by repurposing agricultural byproducts while developing eco-friendly construction materials. Four mix designs were formulated with varying cement replacement levels with RHA (10%, 15%, 20%) and MFA (5%, 10%, 15%), and tested for compressive strength, water absorption, density, and void ratio over 7-, 14-, and 28-days curing periods. Results revealed that Mixture 1 (10% RHA, 5% MFA) achieved the highest compressive strength of 2.8 MPa at 28 days, demonstrating optimal balance between sustainability and structural performance. Higher ash replacements (Mixtures 2 and 3) significantly reduced strength (0.3–0.4 MPa) and increased water absorption (up to 25%), indicating higher porosity. Density decreased with greater ash content, with Mixture 3 recording the lowest density (694.52 kg/m³), confirming lightweight properties. Cost analysis highlighted the economic viability of the proposed blocks, showing a 68% cost reduction compared to autoclaved aerated concrete. The study concludes that RHA and MFA can effectively replace cement up to 10% and 5%, respectively, to produce durable, lightweight floating concrete blocks. Higher replacements compromise structural integrity but remain viable for non-load-bearing applications. This research contributes to sustainable construction practices by valorizing agricultural waste, reducing deforestation, and offering a cost-effective alternative for lightweight wall systems in disaster-prone areas. Further studies on thermal and acoustic properties are recommended to broaden applicability.