A Simple Thermal Curing Method to Produce Non-load-Bearing LAC with Sand Partially Replaced by Rice Husk Ash

Abstract

This study presents an investigation into the production of non-load-bearing Lightweight Aggregate Concrete (LAC) with sand partially replaced by rice husk ash (RHA) using a simple thermal curing process. This method aims to simplify the production process, eliminating the need for expensive machinery and complex procedures, while significantly reducing curing time. Sand was replaced at 10%, 20%. 30%, 40%, and 50% mass ratios. The RHA, cement, and water are first mixed, then lime and gypsum powder are added and mixed. Aluminum powder was added once a homogeneous blend was obtained. The mix is poured into concrete molds, and air bubbles are removed to ensure material compactness. The specimens are left to stabilize for 12 hours, cured at 60°C for 6 hours, and then placed in desiccators for 1 hour to allow moisture equilibration. Subsequently, the bricks undergo a second heat treatment at elevated temperatures of 150°C and 180°C for 12 hours. The physical characteristics of the resulting LAC were analyzed using Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). The results confirmed that the LAC exhibits geopolymeric behavior, with the presence of silicon oxide as a key component. Specimens analyzed using SEM and XRD revealed the formation of compounds that contribute to concrete strength, including calcium carbonate, silicon oxide, calcium hydroxide, and potassium oxide. The compressive strength of all mixes met ASTM C129-06, with the highest value of 16.95 MPa observed at 30% RHA. Thermal curing at 150°C was also found sufficient. The proposed method and 50% RHA offer significant advantages in reducing production costs, curing time, and helping preserve natural sand resources. This approach enables communities and small-scale industries to produce LAC, supporting sustainable construction practices and local economic development.