About the research
In recent years, premature joint deterioration has occurred in concrete pavements in snowbelt states. Research has found two primary mechanisms behind the deterioration: (1) Certain deicing/anti-icing salts—calcium chloride and magnesium chloride—react with cement paste to form calcium oxychloride, an expansive material that is detrimental to concrete pavement performance (sodium chloride is not as reactive). (2) Freeze-thaw damage occurs in joints when a critical degree of saturation is reached or exceeded; salts can exacerbate the problem by keeping joints in a high state of saturation. As a result of these findings, the Iowa Highway Research Board commissioned the National Concrete Pavement Technology Center to write this guide. The primary goal is to help Iowa’s concrete pavement engineers understand the causes of premature joint deterioration, focusing on deterioration due to salt reactivity and joint saturation. The guide also discusses strategies for preventing or limiting such deterioration. One strategy is to limit applications of calcium chloride and magnesium chloride in order to mitigate the formation of calcium oxychloride. Another critical strategy is to keep the saturation level of the concrete below approximately 85 percent. This can be accomplished by designing a durable concrete that includes an adequate air-void system, supplementary cementitious materials, and a low water-to-cementitious-materials ratio, as well as by providing good drainage to the pavement system and following other best practices in concrete pavement design, construction, and maintenance. This guide also provides a summary of joint repair and restoration strategies, including a decision flow chart. Finally, the guide offers guidelines for developing project specifications, with appropriate references to Iowa DOT Standard Road Plans, Standard Specifications, and Instructional Memoranda.