Concrete Surface Spalling (Scabs)

Houston Garage Floors was grinding a garage floor for an epoxy floor coating system for a customers brand new home that he had just built in Crosby Texas when the home owner pointed to the middle of the floor and said that he "had just noticed something" in the floor. The customer took a hammer and struck the concrete foundation which began to shatter like glass. The concreter was brittle at the surface and covering loose rocks in his foundation. Scabs are caused by excessive water puddling at the surface of the concrete slab during installation. The technical term for this occurance is concrete spalling or scaling. It is essentially powdery or sandy concrete that is deficient in nature and the result of excessive water at the surface (pour workmanship and material on the producers fault) and must result in a compromised home or anything else attached to it such as a floor coating. In order to remove the scabs you can strike the concrete firmly all over with a hammer and then use a screw driver to pry up the loose layers. Typically a 16 oz hammer will cause little to no damage to a garage floor even with heavy strikes but this foundation was so brittle that lightly moderate taps caused the floor to buckle. The section removed should be floated smooth with epoxy or an epoxy patch filler but naturally nothing you put on top can be guaranteed to stay just as you can not epoxy coat a sandy beach and expect the epoxy to not peel from the sand. Use personal safety equipment. This is why hiring an ethical and viable home builder is important. The evidence suggests that the concrete installers added too much water to stretch the material and working time. Multiple spark tests were performed and the concrete sparked which is a good indicator of quality concrete but like all tests the spark test is only a qualitative method of testing concrete for sufficiency and not quantitative. The nature of crumbling concrete is to continue to crumble. Therefore we repaired this floor with multiple coats over a 2 year period while we were not legally obligated to (per the brittle/defficient concrete clause in our contract) but because we were trying the show the love of Jesus to a gentleman who got burned by his builder. In 11 years to date (Jan 2014) I have never seen any garage floor do this so we switched to heavier screwdrivers (7oz) which can brake scabs during testing for sparks which gives us a quantitative measurement to theoretically see below the surface so that the customer can understand what they are bringing to the table better.