Characterization of Infiltration and Environmental Impact Assessment of Pervious Concrete

Pervious concrete pavement (PCP) systems allow enhanced infiltration of stormwater through them due to the presence of interconnected porous channels within their structure; thereby preventing urban flooding and augmenting groundwater recharge. The functional performance of PCP is usually evaluated using the surface infiltration (SI) test, in which water that is poured into the infiltration ring (300 mm diameter) is allowed to flow both vertically downward as well as horizontally within the pervious concrete (PC) due to the lack of lateral constraint. Thus, the SI test is not fully capable of simulating the actual water flow in the PCP system during rainfall events. Further, a systematic investigation of the environmental impacts of PCPs has not yet been attempted. Thus, the research objectives of the current study were two-fold: assessment of infiltration parameter in PCP systems using a multi-scale methodology, and computation of embodied energy and greenhouse (GHG) emissions from PCPs using cradle-to-gate approach. To accomplish the research objective, two PC parking lots of dimensions 125 m × 4 m × 0.15 m (A), and 50 m × 6 m × 0.15 m (B) constructed using a single PC-mix type laid on granular sub-base (GSB) of 0.25 m and 0.2 m thicknesses were considered. Over parking lot B, field experiments were performed with infiltration rings of various diameters (ranging from about 100 to 630 mm) embedded into the PC slabs with a provision for draining the water. The results from the multi-scale tests established that the minimum size of infiltration ring required to accurately estimate the infiltration rate of the PC slab was of diameter 300 mm. The full-scale and SI tests on parking lot A confirmed that the infiltration rates through PCP, PC, and GSB varied from 0.05-0.29 cm/s, 0.11-0.32 cm/s, and 0.07-0.11 cm/s, respectively. Further, the strength of parking lot A constructed using in-situ mixing procedure showed 60% higher strength than parking lot B, which was constructed using ready-mixed pervious concrete. Additionally, the embodied energy and GHG emissions in PC were about 3% lower than Portland Cement Concrete (PCC). The preliminary findings indicated that PC not only reduces surface runoff, but also conserves natural resources (fine aggregates). PC also has potential to reduce the amount of emissions into the atmosphere than PCC, which needs further investigation.