Continuously Reinforced Concrete Pavement

It has been speculated that the use of internal curing in mainline paving is likely most beneficial to continuously reinforced concrete pavement (CRCP) due to the reduction in shrinkage and curling, which may result in increased mechanical performance and fatigue capacity. Observations of CRCPs have indicated that early shrinkage is significantly reduced as compared with conventional concrete, resulting in early crack spacing patterns of approximately three times those developed in conventional concrete pavement sections. Longer term monitoring has shown that this difference in crack spacing decreases over time until the spacing is on the order of 20 to 30 percent longer than that in conventional concrete. However, cracks that occur at later ages are smaller than those that develop at earlier ages. This phenomenon has been observed in in-service pavements in which the cracks in internally cured concrete remain tighter than those in conventional concrete.

In some cases, the use of internally cured mixtures for CRCPs has resulted in a reduction in concrete elastic modulus, which results in a reduction in stresses which, combined with lower coefficient of thermal expansion and improved strength, provides a reduction in fatigue damage. This is somewhat affected by which aggregate sizes are introduced in the internally cured concrete modification and whether the additional aggregate is used to develop an optimized mixture. In such instances, the resistance of the concrete to flexure cracking is increased, which improves pavement performance life.

Pavement performance prediction using the Pavement ME Design software also has indicated that the incorporation of internal curing in CRCP will result in slightly longer crack spacing and tighter cracks. These changes are predicted to significantly increase the performance life of the pavement as compared with conventional concrete used in the same design.
It has also been reported that internal curing will result in a reduction in moisture-related curling/warping. Research has also found that internal curing reduces curling, compared to an equivalent mixture without fine lightweight aggregate. The tendency toward a uniform moisture gradient may reduce slab curling and warping due to overall temperature and moisture gradients; however, a reduction in curling from moisture gradient alone would be very beneficial in pavements.

The benefits of internal curing in CRCPs are being investigated in a study for the Illinois Tollway. Neutron radiography is being used to examine moisture gradients, and full test sections are planned to be cast during the summer of 2016.