Substitution of Sand in Concrete Blocks with Coconut Fiber and Cattle Manure: Effects on Compressive Strength and Thermal Conductivity

Improving the energy performance of buildings is critical in the construction sector. This study investigates the effects of incorporating coconut mesocarp fibers (F = Fiber) and bovine manure (M = Manure) on the thermal conductivity and compressive strength of concrete blocks. Bovine manure and coconut fiber replaced the block sand at maximum concentrations of 10 and 1.5%, respectively. Thermal conductivities were measured according to the ASTM C177 (2013) standard, compression tests were performed using the ASTM C140 standard, and characterization assays such as Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were performed to determine the morphological properties of the final material and its constituents. The results showed a 50% reduction in the thermal conductivity coefficient of the blocks when 10 and 1.5% of the sand was replaced with manure and coconut fiber, respectively. Similarly, incorporating coconut fiber at percentages of 0.5, 1, and 1.5% improved compressive strength results. Blocks comprising 0.5, 1, and 1.5% fiber or a mix of 3% manure and 1.5% fiber attained the compressive strength requirements established by the standard. This study demonstrated the feasibility of using coconut fiber mixed with cattle manure as a substitute for up to 2.5% of the sand in non-structural wall elements manufacturing, attaining a decrease in thermal conductibility of around 10%.