CRC pavement is designed with substantial reinforcing steel to eliminate the need for transverse joints, which are the primary point of failure on jointed concrete pavement. Instead of joints, CRC exhibits hairline transverse cracks, which normally are spaced at intervals of two to four feet and which are thin enough to resist faulting, spalling, and intrusion of foreign material. However, some recently constructed CRC pavements exhibit cracking that is irregular, with spacing varying from as little as one foot to as much as 10 feet. Some of the cracks appear to be significantly wider than normal, which could allow intrusion of water, chemicals, and other foreign material. Some cracks have begun to deteriorate and spall. Finally, isolated punch-outs-usually located within a single lane and less than 20 feet in length-have appeared on some projects.
Several factors could potentially contribute to these problems, including:
concrete mix design and composition
aggregate type and gradation
aggregate thermal expansion coefficients
ambient temperature during placement and cure
material temperatures at placement
reinforcing steel percentage and size
reinforcing steel location and lapping
underlying cushion or pavement layers
subgrade or drainage problems
paving equipment or operation
attack from deicing chemicals
grade and paving direction
The effect of the cracking and distress on long-term pavement life and serviceability is unknown. It is not yet clear whether the problems represent a major structural problem or a relatively minor, cosmetic problem. Whether the cracking and distress will significantly accelerate long-term failure mechanisms, such as steel fatigue, corrosion, or freeze-thaw damage is presently unknown.
Research is needed to determine the extent of these problems, assess their impact on pavement performance, investigate their causes, identify ways to preserve existing pavements, and identify how to avoid similar problems in the future.