Curing Reflective Cracks in your Pavements
Bob Burns, P.E., R.S.
The common cure for aging bituminous concrete in condominium associations is an overlay that is typically 1.5" to 2.0" in thickness. An overlay will restore the smoothness of a bituminous surface and extend the life of the pavement for another fifteen plus years. A tack coat of bitumen material is typically applied to the existing surface to allow the new overlay to bond chemically and mechanically to it. Exposure to sunlight and pooled water will in time trigger cracking of the pavement. Can you overlay cracked condominium pavements? Yes, you can overlay even extensive cracking if it has been caused by surface deterioration and not by problems like poor drainage in the sub-base. Clearly, no amount of well placed overlay is going to correct the presence of clays in the sub-base that inhibit good drainage. That condition needs to be cured first. But if drainage of the sub-base is adequate, it is feasible to pave over cracked condominium pavements. If there are random depressions in the surfaces shimming can correct them prior to application of the overlay. In sections of extensive cracking, it would be well to increase the thickness of the overlay to 2". There is a caveat that comes in the form of something called "reflective cracking". This is the propagation of the old cracks up through the overlay - sort of an echo effect. Eventually all overlays will reflective crack as the pavement works over time. The best way to minimize them is to seal all the old cracks before overlaying. That may sound counterintuitive - spending money to seal cracks that will be covered but it will pay off in the long run. What crack sealing does is waterproof the old crack so that if it does propagate up through the overlay, water cannot penetrate through to the sub-base. The preferred technique is to cut into the pavement surface exposing the sub-grade then filling in the cut with bituminous concrete. Essentially what you've done is replaced a section of the old pavement and sealed along the edges of the neatly cut crack. A fairly recent development is a waterproofing membrane of polypropylene that comes in a peel and stick roll that is laid down on the pavement prior to paving over. Its manufacturer states it minimizes reflective cracking by bridging across transverse and longitudinal cracks while preventing moisture intrusion into the sub-base.
