Evaluation of properties of pervious concrete with fly ash and bottom ash

• Main Author: Tepace, Jeffrey M.
• Format: text
• Language: English
• Published: Animo Repository 2015
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/4969
• Institution: De La Salle University

This study aimed on determining the effects of using fly ash as partial replacement for cement and bottom ash as fine aggregates on the mechanical and hydraulic properties of modified pervious concrete to be used for developing low-cost water filtration systems for poor communities in the Philippines. Unconfined compressive strength, hydraulic conductivity, density, and porosity tests were conducted on cylindrical pervious concrete specimens with fly ash contents of 0%, 20%, 30%, and 40% bottom ash as fine aggregates and water-binder ratios of 0.27 and 0.34. Relationships between these properties were also discussed and an optimum mix design for maximized compressive strength and hydraulic conductivity was produced. Compressive strength ranged from 6.458-13.895 MPa while coefficients of permeability obtained were between 0.1037cm/s and 0.1129 cm/s. Density and void content values on the other hand ranged from 1900 to 1990 kg/m3 and 15.9% to 24.8% respectively. All these results fell within range suggested by related literature and passed the requirements of DPWH for porous pavements. The use of fly ash, bottom ash, and higher water-binder ratio improved the compressive strength and long term durability of pervious concrete, but decreased the hydraulic conductivity. As porosity of pervious concrete increased, the hydraulic conductivity increased while the compressive strength and density decreased all linearly. Results from the optimization process indicated that using 40% fly ash, bottom ash as fine aggregates at 7% of total weight of aggregates, and water-binder ratio of 0.27 had the highest desirability value of 0.4827 in maximizing both compressive strength and hydraulic conductivity simultaneously (12.109 MPa and 0.1090 cm/s). Aside from its original purpose of filtration media for a low-cost water filtering system, the modified pervious concrete mixes produced in this study can also be utilized as pavement material for areas with low traffic loads only such as parking lots, bicycle paths, footpaths, and parks.