Use foggers, plastic sheeting and spray-on evaporation retarders to offset early surface drying and resulting defects including plastic shrinkage cracking, crusting, mortar flaking, premature surface wear and scaling. After texturing, start curing immediately and as soon as the surface will not be damaged by the curing method. Use wet burlap, blankets, cotton mats, plastic sheeting or curing compounds. Cure for a minimum of seven days unless otherwise specified.
Of course, waiting too late and allowing concrete to become too stiff before starting the second floating and texturing may result in poorly textured surfaces. However, extending the waiting period as long as possible reduces the potential of prematurely sealing surfaces. The challenge is waiting as long as possible to start floating but not too long. Finishers who understand and overcome this challenge are rewarded with more scale resistant surfaces.
- ACI 302.1R-04 Guide for Concrete Floor and Slab Construction, American Concrete Institute, Farmington Hills, MI, www.concrete.org
- Craftsman Workbook CP-10 (05) ACI Certification Program for Concrete Flatwork Technician and Finisher, American Concrete Institute, Farmington Hills, MI, www.concrete.org
Kim Basham is president of KB Engineering LLC (www.kbengllc.com), which provides engineering and scientific services to the concrete industry. Basham also teaches seminars and workshops dealing with all aspects of concrete technology, construction and troubleshooting. David Rothstein, Ph.D., P.G., FACI is principal of DRP Consulting, Inc. (www.drpcinc.com), a firm located in Boulder, Colo., that specializes in petrographic and materials investigations.