Physico-mechanical Properties of Sandcrete Blocks Produced with Sandy Soil and Cow Dung as Partial Replacement of Cement

Abstract

Sandcrete blocks are widely used as walling materials, but their production depends substantially on cement, creating interest in locally available agricultural wastes that may reduce cement use while retaining acceptable engineering performance. This study investigated the physical and mechanical properties of sandcrete blocks produced with sandy soil and processed cow dung as a partial replacement for Ordinary Portland Cement. Cow dung was incorporated at 0, 2.5, 5, 7.5, and 10% by mass of cement within a fixed binder fraction, using a 1:3 binder-to-sandy-soil ratio and a water-to-binder ratio of 0.40, in sandcrete blocks measuring 140 × 100 × 100 mm. Density, compressive and splitting tensile strengths were measured at 7, 14, 21, and 28 days of curing, while water absorption was measured at 28 days. At 28 days, density declined from 1686.43 kg/m³ for the control to 1024.29 kg/m³ at 10% replacement, and water absorption declined from 3.82% to 1.13% over the same range. Compressive strength decreased from 7.993 N/mm² for the control to 5.629, 4.436, 4.139, and 3.971 N/mm² at 2.5, 5, 7.5, and 10% replacement, respectively, while splitting tensile strength declined from 3.161 to 1.804 N/mm² over the range. One-way analysis of variance performed on the 28-day compressive and splitting tensile strength data confirmed highly significant effects of replacement level (compressive strength: F(4,10) = 89.69, p < .001, η² = 0.973; tensile strength: F(4,10) = 851.07, p < .001, η² = 0.997), and Tukey's honestly significant difference pairwise comparisons showed that the control and the 2.5% mixture were each statistically distinguishable from every other mixture for both properties. Pearson correlations between replacement level and the 28-day treatment means were strongly negative for all four properties. Among the cow-dung-modified mixtures, 2.5% replacement retained the highest strengths, with 70.4% of the control compressive strength and 86.3% of the control tensile strength; however, its 28-day compressive strength was still 29.6% lower than that of the control. The density values are therefore treated as as-tested density rather than dry density because specimen moisture condition was not quantified before density measurement. The study did not report particle size, moisture content at batching, specific gravity, organic content, or chemical/mineralogical composition of the processed cow dung, and it did not assess long-term durability, cost or life-cycle performance, or formal compliance with Ghanaian load-bearing and non-load-bearing block classifications. Accordingly, the results support a cautious comparison of the tested mixtures but do not establish pozzolanic activity, durability improvement, cost-effectiveness, sustainability, or field suitability.