Effectiveness of Minimizing Reflective Cracking in Cement-Treated Bases by Microcracking (0-4502-1)

This project focused on evaluating the effectiveness of the microcracking concept for reducing shrinkage cracking in cement-treated bases (CTB). Microcracking can be defined as the application of several vibratory roller passes to the cement treated base at a short curing stage, typically after 1 to 3 days, to create a fine network of cracks. In this project Texas Transportation Institute researchers monitored the performance of microcracking test sites on SH 47 and SH 16. Finally, the research team coordinated the construction and monitored the performance of controlled test sites constructed at Texas A&M's Riverside Campus. Compared to moist curing alone, microcracking improved the performance of CTB by reducing the crack width and in some cases reducing the total crack length. Through these mechanisms, microcracking reduces the risk of reflective cracking through the surface layer. Microcracking did not cause pavement damage. The structural capacity of the CTB was not diminished, the strength of the material recovered, and surface damage did not occur. Microcracking with three passes of the same (or comparable tonnage) steel wheel vibratory roller after 2 to 3 days cure, combined with a 3-day moist curing period, can be considered a valid method of reducing shrinkage-cracking problems in CTB. In this project microcracking was accomplished with the rollers vibrating at maximum amplitude and traveling at 2 to 3 mph. For maximum effectiveness, micro cracking must be combined with a reduced strength mix design system.