[01] Bruce Roy Thulane Vilane, Department of Agricultural and Biosystems Engineering, Faculty of Agriculture, University of Eswatini, Luyengo Campus, Luyengo, Kingdom of Eswatini. [02] Nhlabatsi Thabani, Department of Agricultural and Biosystems Engineering, Faculty of Agriculture, University of Eswatini, Luyengo Campus, Luyengo, Kingdom of Eswatini. [03] Shongwe Mduduzi Innocent, Department of Agricultural and Biosystems Engineering, Faculty of Agriculture, University of Eswatini, Luyengo Campus, Luyengo, Kingdom of Eswatini.

The increasing cost of concrete and its by-products such as concrete blocks has led to the increased efforts to find alternative bonding or cementing materials to Portland cement, at times even at partial replacement level. These include industrial by-products and agricultural wastes such as wood ash (WA). An experiment was conducted to determine the effect of the compressive strength of WA blended concrete blocks and the optimum proportion of the partial replacement by preparing a mix of 1:5 (cement: sand). The experiment had five treatments, which were the concrete block cement mix proportions of WA (0%, 10%, 15%, 20% and 25%) including the control (0%). The mix design was manipulated by blending the cement fraction with wood ash at proportions of 0%, 10%, 15%, 20% and 25%. A water/cement ratio of 0.5 was used throughout the experiment. The treatments were replicated three times and cured for 14 days. The wood ash was obtained from the slow burning of fire wood from wattle trees (Acacia pycnantha), which was carefully sieved. The results reflected that 15% wood ash in the mix was the optimum proportion of cement replacement as it had a higher (3.56 N/mm²) compressive strength. This was significantly different from the 2.44 N/mm² achieved by the control (0% wood ash blended concrete blocks). It was then concluded that an increase in the curing period of the wood ash blended concrete blocks had a positive impact in their compressive strength, since there was an increase in compressive strength with an increase in the curing period.

Wood Ash, Blending, Compressive Strength, Concrete Blocks

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