Concrete expands and contracts with moisture and temperature changes. Construction professionals refer to this as volume changes. Volume changes are known to produce cracks in hardened concrete unless they are properly controlled. Mar-flex manufactures a previsionary measure against these volume changes in the form of concrete control joints. Concrete control joints are installed at predetermined locations, preventing the concentration of crack producing forces. Mar-flex’s Control Joint System is designed to ensure optimum protection, with a watertight outside control joint which is created when filled with Mar-flex Waterstop Elastomeric Sealant and protected by Mar-flex Fiberglass Fabric Reinforcement.