Chemical clogging and geotextile serviceability in subdrains adjacent to recycled concrete

The formation and deposition of tufa precipitate from the leachate of the recycled concrete aggregate (RCA) within fibers of a nonwoven geotextile, as can potentially occur in a transportation infrastructure drainage system, is simulated in a laboratory environment. Two sets of modified column tests were conducted in this study with cycles of wetting and drying for 1 year in order to study the rate of RCA tufa precipitation. Results of measured changes in the infiltration capacities showed that, even with precipitated tufa, the RCA/geotextile system serviceability remains similar to the virgin aggregate (VA)/geotextile system at the end of the 12-month testing. Evaluation of the deposited tufa precipitation within geotextile samples showed that RCA tufa is dominated by calcite and gypsum minerals. Estimated quantities of RCA tufa deposition by existing models developed for natural environments, showed that they either grossly overestimate the observed behavior (calcite model) or underestimate it (gypsum model). Image analysis technique and chemical calculations based on leached dissolved solids were utilized successfully to develop models to predict the precipitation of RCA tufa in macroscales during the service life of a subdrain.