Reducing Joint Damage in Concrete Pavements: Quantifying Calcium Oxychloride Formation

Deterioration has been observed at the joints of many portland cement–based concrete pavements in midwestern U.S. states. It has been shown that this damage can be caused by either classic freeze–thaw behavior triggered by high saturation levels or a chemical reaction that occurs between the deicing salt (in this study, calcium chloride) and the cementitious matrix. The objective of this study was to show that low-temperature differential scanning calorimetry could be used to quantify the potential for the chemical reaction between the salt and matrix (i.e., calcium oxychloride formation). The formation of calcium oxychloride is expansive and may lead to significant cracking and spalling without exposure to freeze–thaw cycles. This study examined pastes made with ordinary portland cement; portland limestone cement; and portland cement combined with fly ash, slag, or silica fume. The results indicate that the amount of calcium oxychloride formation that occurs is not significantly different between ordinary portland cements and portland limestone cements. The addition of supplementary cementitious materials reduces the formation of the calcium oxychloride, presumably because of the reduction of calcium hydroxide from dilution, the pozzolanic reaction, and a reduction in the alkali content in the pore solution. The results also indicate that sealers can be used to create a barrier between the salt and the calcium hydroxide or that they can react with the calcium hydroxide, thereby reducing the amount of calcium oxychloride.