August 19, 2014
Given the crack you describe, it sounds as though there has been settling of the sub-grade underneath the driveway taking place. Without first rectifying any issues with the sub-grade, it would be best to NOT fill the entire crack with a rigid, cementitious based material that is bonded to the existing concrete on BOTH sides of the crack, as it will likely crack as further settling occurs. You may consider using some thin material, such as Masonite or thin sheets of plastic, to build a “form” within the crack on one side, so that you can apply QUIKRETE Sand Topping Mix #1103 into the crack to bond to only one side of it. Once the Sand Topping Mix has cured sufficiently, you may remove the form, leaving a gap between the second side of the crack and the Sand Topping Mix. After allowing the Sand Topping Mix to cure for a minimum of 28 days, check to see that it has cured to the point that it does not contain excess moisture as follows: tape a 4” x 4” square of plastic wrap over the area, and wait 4 hours. If there is condensation under the plastic, additional curing time is needed. Once there is no longer moisture, use a fine sand, such as QUIKRETE Mason Sand #1952-49 or QUIKRETE Commercial Grade Fine or Medium Sand, #1961 or #1962, to fill the gap up to no more than ½” below the top surface of the driveway. Fill the remainder of the depth with Polyurethane Self Leveling Sealant #8660-10 between the driveway and the Sand Topping Mix. The working joint depth of the Polyurethane should not exceed ½" or be thinner than 1/8", ideally ¼". The ratio of joint width to depth should be 2 to 1. The material used as the form should be of a thickness that allows these requirements to be fulfilled. If the Polyurethane is applied while there is still moisture present, it will bubble, either immediately after being applied, or while it cures. There is still a chance that as the sub-grade continues to settle, the Sand Topping Mix will crack, or the Polyurethane Sealant may pull away from either the Sand Topping Mix or the existing concrete. It is important to note that neither the Sand Topping Mix or the Polyurethane Self Leveling Sealant will be exact color matches to the existing concrete, or a match to each other. Please contact the QUIKRETE Technical Center at 1-800-282-5828 for further assistance.
0out of 0found this answer helpful.