Frontier Bonding Agent is a three-stage bonding system used to apply cementitious toppings to existing concrete. The primary coat penetrates into the concrete leaving a completely insoluble membrane once the liquids have evaporated. The second coat is applied after the first coat has dried and effectively seals the surface of the concrete, protecting against uneven suction from the base concrete. The third coat MUST be applied to re-wet (or freshen) the surface just prior to applying the topping.