Effect of cracking and healing on chloride transport in OPC concrete

Abstract The effects of cracking and self healing on chloride migration and compressive strength were investigated on w c = 0.40 concrete . Internal cracking due to rapid freeze/thaw exposure resulted in a compressive strength reduction of 68-40 % and a reduced Ultrasonic Pulse Velocity (UPV) to 78-45 % of undamaged values. The rate of chloride migration through 15 mm thick slices under a 10 volt electric field was increased by 2.5–8 times and the chloride penetration time through the slices was reduced from 64 to 0 hours for the most severe cracking. The increased chloride transport due to cracking could be predicted fairly well by characterizing the cracks using a square grid crack pattern model. Self healing by storage of cracked specimens in lime saturated water at 20 °C for three months after stop of freeze/thaw exposure gave recovery in UPV of 50 –100 %, but compressive strength recovered only 0–10 % of the initial value. Rate of chloride migration in the self-healed concretes was reduced by 28–35 % and penetration time was increased compared to newly cracked concrete. The chloride migration through an air entrained concrete with the same w c ratio (no internal cracking after more than 300 cycles of rapid freeze/thaw exposure), was unaffected by freeze/thaw.