Experimental Investigation of Water Absorption Behaviour of Coconut Shell Aggregate Concrete

Abstract

The increasing demand for sustainable construction materials has stimulated interest in the utilization of agricultural waste as alternative concrete constituents. This study investigated the water absorption characteristics of concrete produced with coconut shell as a partial replacement for conventional coarse aggregate by volume. Four concrete mixtures containing 0%, 10%, 20%, and 30% coconut shell replacement were evaluated. A total of twenty (24) concrete cube specimens measuring 100 mm × 100 mm × 100 mm were cast, with eight specimens allocated to the total water absorption test, eight for absorption capacity and the remaining eight to the capillary water absorption test, giving two replicate specimens for each mixture in each test. Capillary water absorption test was determined in accordance with ASTM C1585 while the total water absorption test was evaluated using modified full-immersion procedure adapted from the weighing protocol of ASTM C1585, in which concrete cubes were completely submerged in water and weighed after 1,3,5,15 and 30 minutes, and after 1, 4, 24, and 48 hours to monitor water uptake. The absorption capacity was determined in accordance with ASTM C642. The results showed that both the absorption capacity, total and capillary water absorption increased with increasing coconut shell content due to the higher porosity and water absorption capacity of coconut shell compared with conventional granite aggregate. Statistical evaluation using two-way analysis of variance (ANOVA) revealed that both coconut shell replacement level and exposure time had statistically significant effects (p < 0.05) on the water absorption behavior of the concrete. Despite the increase in water absorption, the measured values remained within acceptable ranges reported for structural lightweight concrete. The findings indicate that coconut shell can be used as a sustainable partial replacement for coarse aggregate while maintaining acceptable durability characteristics, particularly at moderate replacement levels.