Continued Evaluation of Microcracking in Texas (0-4502-2)

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. Previous report 0-4502-1 described activities undertaken during the first two years of this research project to validate and develop guidelines for the application of microcracking. This report (4502-2) details results from continued monitoring of field test sections, along with details from new micro cracking test sites constructed between September 2004 and August 2005. Based upon the results, this report presents revised guidelines as an Appendix for the application of microcracking to reduce the risk of reflective cracking problems from cement-treated bases. Even if implemented on only 25 percent of Texas Department of Transportation CTB projects, it is estimated micro cracking could save the department approximately $1.5 million in net present value (NPV) costs through reductions in future crack sealing operations. Given the range of observed effectiveness of micro cracking, full implementation could save between $3.3 and $8.6 million in yearly NPV costs.