Compressive Strength Assessment of Sandcrete Blocks Produced by Artisan Block Makers in Katsina State

Sandcrete blocks are the dominant walling material in Nigerian residential construction, yet informal artisan production frequently fails to meet Nigerian Industrial Standard minimum strength requirements, creating structural safety risks. This study assesses the compressive strength of 150mm hollow sandcrete blocks produced by artisan block makers in Katsina metropolis, North West Nigeria. Blocks were collected from fifteen artisan production sites in Katsina North and Katsina South LGAs following standard ASTM C140 sampling protocols. Compressive strength tests were conducted at 7, 14, and 28-day curing ages. Mix proportions used by each producer were documented. Block dimensions were measured for conformance with NIS 87 dimensional requirements. Results indicate that 73 percent of tested blocks at 28 days failed to achieve the NIS 87 minimum compressive strength of 3.45 N/mm2. Mean compressive strength across all samples was 2.14 N/mm2 at 28 days. Cement-to-sand ratio analysis shows that 80 percent of artisan producers use ratios of 1:12 or leaner, compared to the recommended minimum of 1:6. Dimensional accuracy is acceptable in 68 percent of blocks. Inadequate curing is identified as the most common production deficiency. The study concludes that the quality of artisan sandcrete blocks in Katsina State poses structural risks and recommends mandatory quality certification for block production sites and training programmes for artisan block makers through the Standards Organisation of Nigeria.

Keywords: sandcrete blocks, compressive strength, artisan production, NIS 87, Katsina State