Title: The Declining pH of Waters Exfiltrated through Pervious Concrete
Author(s): Jonathan Thomle and Liv Haselbach
Publication: Symposium Paper
Appears on pages(s): 1-12
Keywords: carbon dioxide, carbonation, pervious concrete, pH, runoff
The focus of this study is on the pH changes over time of water in contact with pervious concrete aged under varying ambient air restrictions. Elevated pH levels may be a concern if exfiltrated directly to sensitive waters. This study was conducted to aid designers by determining the rate of pH decline under various conditions. For this study laboratory prepared pervious concrete specimens exposed to three different levels of ambient air were periodically tested for pH using four different testing methods, infiltrating either deionized water or tap water through the specimens, or soaking the specimens in either deionized water or tap water. Obvious trends in pH decline were observed. Greater exposure to ambient air significantly increased the rate of pH decline. The tap water tests represented more typical stormwaters and had much lower pH readings than the deionized water tests. The samples were representative of typical in-place conditions in an arid environment with little buffering and yet the pH declined sufficiently in well under a year.