Performance of Cement Composites with Partial Replacement with Organic Aggregate from Waste Coconut Shell

The properties of cement composites with a partial replacement of sand with an organic aggregate from coconut shell are investigated. Due to the fact that the endocarp of coconut shell increases its volume up to 60–70% when swelling in water, which is many times greater than the volumetric deformation of the swelling of the cement matrix, the possibility of obtaining a cement composition capable of withstanding alternating deformations of wetting and drying was investigated in this work. When replacing 50% of the sand with coarse coconut aggregate of the fraction 5–20 mm, starting from the 5th–10th cycle of wetting–drying, progressive expansion and cracking of 28-day samples took place. When using a fine coconut aggregate fraction < 2.5 mm and replacing sand from 2 to 15%, a slight accumulated expansion was observed only in the first 4–5 test cycles, then accumulated shrinkage followed. A gradual decrease in the average weight of the samples from cycle to cycle was established. The loss of mass of the samples increases with the increase in the percentage of replacement of sand with coconut aggregate. Partial replacement of sand with fine coconut aggregate from 2 to 15% by weight reduces the bending and compressive strength of cement mortar from 14 to 40%.