Experimental Investigation of the Effect of Different Additives on Characteristics of Porous Concrete, Applicable in Urban Runoff System

In the last decade, porous (pervious) concrete has been used in sidewalks and surface pavements for collection of urban runoff water. Porous concrete is highly considered for its hydrailuc conductivity and water transport capacity. In the present research, the original porous concrete was made of 1400 kg/m3 aggregates and 330 kg/m3 Portland cement, along with water to cement ratio (W/C) of 0.35-0.45. In the mixture of porous concrete and additive, the following additives were used: zeolite, perlite, pumice and clay aggregate, with type 2 and type 5 Portland cement. Compressive strength and permeability coefficient (hydraulic conductivity) were studied. Results revealed that adding additives decreases compressive strength of the porous concrete. This reduction in compressive strength for the highest and least amount of zeolite, perlite, pumice and clay aggregate was 13, 48.4, 10.1 and 12.6 percent, respectively. Hydraulic conductivity increased in most of the treatments, except perlite. The highest increase in hudraulic condictivity (7.3 %) occurred in the treatment containing 5% pumice and the highest reduction in hydraulic conductivity (3.7 %) occurred in the treatment containing 10% perlite. In general, among the different additives used in this experiment, the treatment containing 10% perlite had the highest compression strength (11.95 MPa) and the treatment containing 10% clay aggregate had the lowest compression strength (3.2 MPa). This shows that adding clay aggregate reduces compression strength of porous concrete more than other additives. The perlite additive ranks next.