Effect of low coconut fiber concentration on the mechanical and physical properties of load- bearing concrete hollow blocks

Abstract

This study examined the effects of low coconut fiber concentrations on the mechanical and physical properties of load-bearing Concrete Hollow Blocks (CHBs). It evaluated the compressive strength, water absorption, and density of 5-inch Coconut Fiber-Reinforced Concrete Hollow Blocks (CFRCHBs) with coconut fiber concentrations of 0.1%, 0.3%, and 0.5% by mass of cement, compared to conventional CHBs used as the control. The relationship between curing time and fiber percentage was also analyzed through 7-day, 14-day, and 28-day curing periods, along with the production cost per square area of the CFRCHBs. An experimental research design was implemented following ASTM C140 standards and the National Structural Code of the Philippines (NSCP) for load-bearing masonry units. Fifty-four (54) CHB specimens were produced using a 1:7 cement-to-crushed sand mix ratio and a water-cement ratio of 0.51. Coconut fibers from mature husks were treated by boiling, sun-drying, and cutting into 6 cm lengths before mixing. Compressive strength testing was conducted with a Universal Testing Machine (UTM), while density and water absorption tests adhered to ASTM procedures. Two-way ANOVA was used to determine the significance of curing time and fiber concentration on the measured properties. Results indicated that longer curing time significantly increased compressive strength and decreased water absorption in all samples. Among the mixtures tested, the 0.3% coconut fiber concentration provided the most balanced performance in strength, density, and water absorption, suggesting it as the optimal fiber content for load-bearing CHBs. The study also underscored the sustainability of CFRCHBs by utilizing agricultural waste and demonstrated their potential for residential and single-storey detached housing units. Overall, low concentrations of treated coconut fiber enhanced selected CHB properties while promoting sustainable construction practices.