Tufa, a precipitated form of calcium carbonate, has been observed occluding underdrain outlets, catch basins, and storm sewers in various counties in east and northeast Ohio. Previous research determined that slag used as a subbase was the only factor directly related to the formation of tufa precipitate. However, no differentiation was made among the various slag types used. This study was initiated to determine whether different types of slag affected the formation of tufa precipitate. A total of 37 projects with different types of slag subbase were inspected. Subbases composed of blast furnace slags or steam boiler slag did not promote formation of tufa precipitate. However, because of the presence of free lime in steel slags and slacker aggregate, subbases composed of these materials did promote the formation of tufa precipitate (open hearth slag to a lesser extent than the other types). Long-term stock pile ageing of open hearth slag appeared to reduce the amount of free lime sufficiently to lessen the volume of tufa precipitate to acceptable levels.
Abstract