Overview of Crazing of Polished Concrete SurfacesCrazing refers to the network of fine cracks that can be present on the surface of concrete. Sometimes called map-cracking or alligator cracking, crazing is created due to sub-optimal curing methods and conditions at the time of placement and finishing. While polishing concrete does not cause or exacerbate crazing, a highly refined surface can accentuate the fine cracks and cause them to stand out. It can be beneficial for a polishing contractor to be able to explain the causes of crazing and even to point out its existence in an existing slab prior to executing a contract.

Crazing occurs due to the shrinkage of the mechanically densified dewatered paste cap, often due to poor curing conditions that allow for too fast of evaporation rates or from too wet a mix. To minimize the potential for crazing, proper curing methods should be started as soon as possible. Wet curing, blanket curing or the use of a membrane-forming curing compound can all retard the hydration process, which will help to prevent the rapid shrinking that causes craze cracking. Over-seeding Portland cement to soak up bleed water, or starting finishing operations while bleed water is present, will both facilitate the formation of crazing and should be avoided.

Once crazing has appeared, usually within a week of placement, there is no way to remove the crazing other than by cutting below where the cracks are, typically no more than 3-4mm below the surface. Grouting can help to disguise the craze cracks but will not typically completely hide them.

Runyon Surface Prep Rental & Supply is a full-service sales and rental facility uniquely dedicated to the concrete polishing industry. Our uniqueness comes from providing our customers with a diverse equipment, product and supply portfolio. We offer training and support, such as technique workshops on prep, polishing or removal, and maintain a well-stocked inventory of consumables ready for your projects at a moment’s notice. Rather than perform contract work ourselves, we consult on job sites when necessary. With the backing of our vendors, Runyon Surface Prep offers support at any level, to assist in helping you get things done. We can deliver or ship wherever you need, or you can pick up from our facility.