Effect of cracking and healing on chloride transport in OPC concrete

✍ Scribed by Stefan Jacobsen; Jacques Marchand; Luc Boisvert

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 896 KB
• Volume: 26
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(96)00072-5

✦ Synopsis

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 G/c ratio (no internal cracking after more than 300 cycles of rapid freeze/thaw exposure), was unaffected by freeze/thaw.