Design of Pervious Concrete & Enhancement of Its Strength With Different Water-Cement Ratio & Admixtures

The Strength of pervious concrete is as important as its permeability characteristics. Studies indicate that pervious concrete has lower compressive strength capabilities than conventional concrete and will only support light traffic loadings. This thesis investigated prior studies on the compressive strength of pervious concrete as it relates to water- cement ratio, aggregate-cement ratio, aggregate size, quantity of admixture and compaction and compares those results with results obtained in laboratory experiments conducted on samples of pervious concrete cube casted for this purpose. Since voids are supposed to reduce the strength of concrete 1% for every 5% voids (Klieger, 2003), the goal is to find a balance between water, aggregate, and cement in order to increase strength and permeability, two characteristics which tend to counteract one another. The end result of this research will be a recommendation as to the water-cement ratio, the aggregate-cement ratio, aggregate size, quantity of admixture and compaction necessary to maximize compressive strength without having detrimental effects on the permeability of the pervious concrete system. This research confirms that pervious concrete does in fact provide a lower compressive strength than that of conventional concrete. Researches indicate that the minimum compressive strengths of acceptable mixtures reached in to 2.8Mpa and maximum compressive strength reached to 28Mpa (Tennis et al, 2004, Yang, J. and G. Jiang, Nguyen, 2002, V.C., 2008). Extremely high permeability rates were achieved in most all mixtures regardless of the compressive strength.