Experimental Study on Mechanical Behaviour of Foamed Concrete for the Development of Building Blocks

Abstract

This study investigates the mechanical properties, structural suitability, and economic viability of foamed concrete blocks (FCBs) through systematic laboratory experiments and multi-criteria optimization. The research methodology comprised four key phases: firstly material characterization of Portland Pozzolana Cement (PPC), 2.36mm-sieved fine aggregate, and sodium lauryl ether sulphate (SLES) foam agent following ASTM standards; secondly production and testing of 102 specimens with foam contents ranging from 0.5-5% at 7- and 28-day curing intervals; thirdly, comprehensive evaluation of compressive strength , flexural strength, density, and water absorption); and finally cost-benefit analysis comparing FCBs with conventional hollow concrete blocks in the Ethiopian construction market. Results demonstrate that 1.5% foam content yields optimal performance, achieving 9.1 MPa compressive strength and 2.4 MPa flexural strength at 1468 kg/m³ density, while maintaining 5% water absorption - meeting standard requirements for load-bearing applications. The 28-day curing period enhanced strength by 25% compared to 7-day curing. Higher foam contents (>3.5%) produced lightweight insulation blocks (980 kg/m³, <4 MPa strength) compliant with standards and can be used for non-structural parts. Water absorption remains below 10% for densities >1200 kg/m³, ensuring durability. Economic analysis highlights 20–30% cost savings over conventional hollow blocks due to reduced material use and lighter weight, despite higher initial foam agent costs. TOPSIS multi criteria analysis revealed 1.5% foam as the optimal formulation (performance score=0.72), balancing mechanical properties with material costs of 16,793 ETB/m³ - demonstrating 22.7% savings versus conventional blocks when considering lifecycle transportation and labor advantages. These findings provide empirical evidence for adopting FCBs in developing economies, with specific recommendations for: structural applications (1-2% foam, 28-day curing) and non-structural partition walls (2-3% foam). The study establishes a scientifically-grounded framework for optimizing foamed concrete mixtures while addressing both technical performance and economic feasibility constraints in resource limited construction markets.