Environmentally Useful Life of Interlocking Concrete Block Pavements: Critical Time Period Concept

In this study, we present a critical time concept for evaluating the environmental performance of interlocking concrete block pavements (ICBP) formulated through extensive field observations. Infiltration measurements were carried out at 100 locations in two districts, Kozhikode and Kollam, of the southern Indian state of Kerala, where ICBPs are increasingly becoming common in nontraffic areas, especially building premises. The loss of infiltration capacity was found to be correlated with the degree of clogging of the interstitial space between pavement blocks that, in turn, increased with pavement age. Furthermore, the rate of clogging was found to be higher for nonresidential than residential sites. For residential sites, an exponential model fitted the plot between the infiltration rate of pavement and its age with an R-2 = 0.8957. For the commercial sites, a power model fitted the data with R-2 = 0.918. We compare the pavement infiltration rate with the soil infiltration rate and propose the concept of the critical time period (CTP). A pavement reaches CTP when its infiltration becomes equal to the infiltration capacity of the soil beneath it. For ages older than the CTP, the pavement fails to perform its environmental function of conducting enough water to the soil beneath to enable the water to infiltrate into the soil at its maximum capacity. The infiltration capacity of soils measured at Kozhikode sites leads to the prediction that 50% of these sites paved with ICBPs become unsustainable (reach CTP) in 80 or 48 months depending on their use as residential or nonresidential, respectively, if no maintenance work is undertaken. In the case of Kollam sites, the corresponding value is 64 or 30 months. A CTP map for the entire Kerala state for residential use was prepared using the regression equation developed for pavement infiltration capacity and the infiltration capacities of soils obtained through empirical equations available in the literature. The CTP map is expected to serve as a useful decision-making tool for scheduling the maintenance of ICBPs to extend their environmental life. (C) 2021 American Society of Civil Engineers.