Durability of Carbonate Rocks as Function of Their Thermal Expansion, Water Sorption, and Mineralogy

A suite of 27 rock specimens from active quarries in Southwestern Ontario was collected, and represents the Paleozoic carbonates used as concrete aggregates. Cores and crushed, sized aggregate were obtained from the specimens and subjected to the following tests: water adsorption at 45 and 92 percent humidity at 30°C; thermal expansion coefficient determination in dry and in saturated states; chemical analyses for major oxide content; and soundness tests by modified freeze-thaw methods.

Statistical analysis of the results give a direct, positive correlation matrix of greater than 95 percent confidence level for the following: adsorption at 45 percent and 92 percent relative humidity; alumina + silica (Al₂O₃ + SiO₂) content-expansion coefficient in saturated state; and freeze-thaw loss. Negative significant correlation was obtained between the calcium oxide (CaO) and magnesium oxide (MgO) content and the wet and dry expansion coefficients. No correlation was observed between dry expansion coefficients and freeze-thaw loss. Dry rocks were found to have significantly but nonuniformly higher expansion coefficients than saturated rocks. However, the latter are more indicative of rocks' durability.

A model for rock deterioration is presented, based on expansion and contraction during wetting-drying and warming-cooling cycles.