Design Mixture of Concrete Paving Block Using Pulverized Coconut Shell as Partial Replacement of Fine Aggregates and Banana Fiber as Additive

Driven by construction growth and material needs, researchers investigated using agricultural waste in concrete, which often pollutes the environment through burning or landfilling. This study focused on pulverized coconut shells (PCS) as a partial sand replacement and banana fiber (BF) as an additive in concrete paving blocks (CPB). The research assessed the mixture's performance through slump, compressive strength, water absorption, and cost-effectiveness. Four variations were tested: 0%, 15%, 30%, and 50% PCS replacement, all with 2% 20mm-long banana fiber. Bricks were cured for 7 and 14 days. The target minimum compressive strength (2500 psi) translated to 1775 psi at 7 days and 2175 psi at 14 days. The mixture maintained a 1:3 cement-to-sand ratio and a 0.1-0.4 water-cement ratio. Slump tests indicated the 1:3 mix ratio achieved a 3-inch height difference from the slum cone in the first trial. To assess agricultural waste potential, researchers analyzed the chemical physical properties of PCS and BF. The researchers tested different proportions (15%, 30%, and 50%)and curing times (7 and 14 days). The 15% PCS mixes had lower strength. Water absorption was highest in the 0% and 50% PCS mixes, while 15% and 30% PCS mixes absorbed less. While ASTM C67 doesn't set a water absorption limit, lower absorption (generally below 20%) indicates higher block quality. Commercially available blocks cost Php 15 to 27, while the designed CPB with 15% PCS and 2% BF costs only Php 4.07. This translates to a significant cost advantage of PHP 10.93 compared to the market average. Therefore, researchers conclude that the designed CPB is a more economical and cost-efficient option.