Repairing cracked sidewalks can be costly for municipalities, but preventive solutions, such as the ones that IRC has identified, have the potential to save considerable time and money, and to avoid inconvenience to the public. Since 1993, IRC, in collaboration with the cities of Edmonton, Calgary, Camrose, Saskatoon, Regina and Winnipeg, and more recently Quebec City, has been studying the behaviour of concrete sidewalks in order to understand how and why cracking occurs, and to identify solutions.
Most sidewalks crack in both longitudinal and transverse directions.
Seasonal changes cause longitudinal cracks to form, while transverse cracks occur because of uneven compaction beneath the sidewalk. Thus damage as a consequence of swelling can be avoided. The IRC research also showed that when the soil loses moisture under prolonged dry weather conditions, tensile shrinkage is the most likely type of damage. This observation suggests that a well-drained granular subbase, such as coarse gravel placed between the bottom of the concrete sidewalk and the native clay, will lessen the tensile stresses on the sidewalk by inhibiting capillary action and the development of suction pressures. The findings from this work will help determine the effectiveness of the various measures and, ultimately, allow municipalities across the country to improve the service life of their concrete sidewalks.