Self-healing of overloaded self-compacting concrete of rigid pavement

Rigid pavements, constructed with self-compacting concrete (SCC), are susceptible to cracking by the relatively high compressive stresses from the wheels of heavy trailers. Repair of such pavements relies mainly on overlaying with additional SCC or asphalt concrete layers without accounting for possible strength and durability recovery by the mechanism known by self-healing. Would the latter be considered in repair plans, the problems associated with rigid pavements deterioration can be solved with the lowest possible cost. The present study aims at investigating the potential of self-healing and possible recovery of mechanical properties and durability of SCC considering key parameters, stress level at loading, loading age, and curing regime (water, air) and time period. For that, standard SCC cylinders (150x300mm) were cast from one SCC mixture, prepared at a w/c ratio of .45, cured for different periods in water, then subjected to varying compressive stress levels ranging from 80 to 100% of their ultimate load capacity, before re-cured in water or air for additional time periods, and finally tested for ultrasonic pulse velocity (UPV) and compressive mechanical response. The damage index for SCC, in terms of UPV, showed slight increases for stress level of up to 95%, before sharply increased when SCC was fully damaged. SCC cured for higher time periods, prior to loading to stresses of up to 95%, received more internal damage, yet the impact of loading age on internal damage became minimal for fully crushed SCC specimens. Re-curing in water contributed more than in air to cracks' filling and mechanical behaviour recovery. SCC specimens stressed to levels of 90% or less then re-cured were able to regain their original mechanical characteristics, whereas those loaded to stress levels of 95% then re-cured lost tangible portions of their mechanical properties. As may be expected, fully damaged then re-cured SCC lost major portions of their mechanical properties; reaching as high 85%. Empirical models, developed in this work, showed that there exists a very good correlation between residual mechanical properties and a certain recovery index, defined in terms of damage indexes at loading and after re-curing.