A new approach to predict the porosity of pervious concrete at its fresh state

Abstract

A mathematical formula was derived to predict the porosity of pervious concrete (PC) at its fresh state. Coarse aggregates (CA) within the size ranges of 0.016-0.02m and 0.01- 0.014m were used in the study. Pervious concrete was mixed for two stages. A w-c ratio of 0.3 was used in the study. A scaling factor was defined to represent the thickness of cement paste coated around CA. The scaling factor is independent of the size of CA used and their volume based binary combinations. The percentage difference between the two scaling factor values obtained for CA having a size of 0.01-0.014m was calculated to be 1.14 percent. The tested wet density in all PC batches made in the first stage was approximately 170-264kg/m3 lesser than the designed wet density. The difference between the tested porosity values and the porosity values calculated by the mathematical model has been developed is approximately 0.01-0.015m3 for all pervious concrete batches. It was observed that as the scaling factor increases the wet density increases and the porosity reduces. The porosity values calculated by the mathematical model and the tested porosity show a very strong linear relationship.