Assistant professor, Kent State University, Kent, OH
Associate professor, Purdue University, West Lafayette,
Argillaceous carbonate rocks, when used as coarse aggregate, have been found to cause severe pitting and popouts in several Indiana highways within one winter after construction. These rocks were studied in detail petrographically to determine texture, structure, and mineral composition, and in particular the amount, type, and mode of distribution of argillaceous material.
Results of petrographic examination were compared with other test data including specific gravity, absorption-adsorption values, pore characteristics, and loss in freeze-thaw. This comparison suggests a close relationship between petrographic characteristics and freeze-thaw resistance of argillaceous carbonates. A comparison of petrographic information with field performance shows that those rocks that contain more than 20% silt and clay distributed uniformly throughout the rock mass result in pitting and popouts while those in which silt and clay are concentrated as streaks and laminations are not necessarily unsound. This is contrary to several previous investigations that concluded that laminated carbonates should be considered nondurable without specific concern for their total argillaceous content.
Paper ID: CCA10360J