Several team members from our company were invited to attend the 2011 World of Concrete and Masonry (WOC) in Las Vegas earlier in the year. For those not familiar the WOC, it features hands on events, a chance to network with peers in the industry, interactive demonstrations and competitions, hundreds of exhibits from suppliers from around the world and education programs by leading professionals in the trade.
One of these classes was “Troubleshooting and Repairing Concrete Cracks”, taught by Kim Basham, a leading expert in the industry. Reviewed the causes cracks in both structural and non-structural slabs such as thermal expansion, subgrade settlement and even earthquakes. Nonstructural cracks caused by such things as plastic shrinkage, plastic settlement, crazing and corrosion of embedded materials.
A few things to consider when working with concrete to help minimize cracks:
• Weather conditions (especially wind and substantial temperature changes during the pour) will affect potential cracking.
• Slump loss, plastic shrinkage cracking, crazing, changing set times are also effected by weather.
• Control joints and expansion joints should be well thought out before the pour.
• Saw cut early, at the end of the day after a pour and before you leave the job.
• Temperature during placing, finishing and curing operations should be considered.
• When the temps are low air entrainment cannot fully protect freshly placed concrete against freezing temperatures, another whole set of problems for newly poured concrete.