The Portland Cement Association recently published a research report that attempts to help contractors by documenting findings on materials and methods that mitigate shrinkage cracks and crack-related degradation in pavements.
The report, Minimizing Cracking in Cement-Treated Materials for Improved Performance, proposes that while some shrinkage cracks are inevitable in cement, crack-related degradation can be lessened by promoting numerous, smaller cracks in the base layer. Extended curing of the cement base and the use of fly ash is supposed to reduce drying shrinkage, which creates the desirable minute crack patterns.
The report describes the causes of pavement cracking, how shrinkage cracking can be curtailed and the mix design criteria that minimize cracking and improves cement performance. According to the research, several factors contribute to shrinkage, including cement content, curing conditions and the type of soil. Results showed that to achieve the maximum allowable crack width limit, the seven-day unconfined compressive strength for fine-grained soils should not exceed 300 pounds per square inch. For course-grained soils, that strength should not exceed 450 psi.
According to Bruce McIntosh, spokesman for PCA, the report provides useful information for contractors.
“In general, the report helps contractors solve problems when it comes to minimizing cracking in pavements,” McIntosh said.
To purchase a copy of the PCA report, call 1-800-863-6733. The cost is $16. For a general overview of the report’s findings, click the link in the column to the right.