Investigation of Compressive Strength of Metakaolin Blended Cement Stabilized Clay Bricks for Sustainable Building Construction

Abstract

Clay has long been used in construction due to its availability, low cost, and sustainability. However, its poor strength and durability limit its usage for some modern applications where strength requirement is fundamental. This study explores improving clay’s properties by stabilizing it with metakaolin-blended cement to produce unfired bricks. The experiment involved mixing clay with a constant 5% Portland Limestone Cement (PLC) and varying metakaolin content by (5, 10, 15, and 20% respectively). The clay was sourced from a borrow pit at the University of Ilorin, Nigeria, and kaolin was collected from a milling site in Ilorin, calcined at 900°C, ground, sieved to 75 μm and characterized accordingly. Tests included particle size analysis, compaction (for optimum moisture content and maximum dry density), and Atterberg limits. Clay brick samples (230 × 100 × 100 mm) were produced and tested for compressive strength using a Testometric machine. X-Ray Fluorescence (XRF) analysis of the metakaolin showed high contents of Silicon Oxide (57.21%) and Aluminum Oxide (28.32%). The particle composition of the locally sourced lateritic clay was 2% gravel, 56% sand, 11% silt, and 31% clay. The lateritic clay soil showed a liquid limit of 37.5%, plastic limit of 19.1%, and plasticity index of 18.4%, with particle composition of 2% gravel, 56% sand, 11% silt, and 31% clay. The highest compressive strength (36 N/mm²) was achieved at 15% metakaolin. Combined with 5% PLC, this stabilization enhances durability, supporting sustainable production of strong unfired bricks.