Mastic for Hot Applied Crack Sealing

Introduction 

Hot applied Mastic crack sealer is not new, but this type of product is now available with performance characteristics adapted to our climate conditions. Performance and expertise have been developed through real-world testing conducted by cities and municipalities in Quebec, complemented by several positive trials in the United States. 

The evaluation of this solution compared to others has been conclusive—that is, this technique reduces repair costs and is quick to install. An example is the crack shown in the photo below, which is too wide (greater than 1.5”) for conventional crack sealing. The other option would be to resurface the wearing layer of the asphalt and ensure proper control of the potential reappearance of this wide crack. 

Performance 

Mastic (Polymer-modified asphalt pavement repair) is a solution that combines the load-bearing properties of hot-mix asphalt—thanks to its aggregate content—with the elasticity, flexibility, and waterproofing of crack sealant. It is designed to repair wide cracks and problematic areas too small for paving. This multi-purpose product is self-adhesive, so no tack coat is required; it is self-leveling and slip-resistant. 

Unlike crack sealant products, which can be dangerous for cyclists or motorcyclists when wet, the aggregate content of this product provides a rough, non-slip surface. 

Applications 

Hot-applied pavement repair Mastic can be used to fill, level, seal, repair, and in some cases serve as localized resurfacing. It is a solution for wide longitudinal or transverse cracks greater than 3.8 cm (1.5 in), leveling depressions, potholes, manhole perimeters, bridge approaches, cuts, sealing concrete/asphalt joints, correcting surface deterioration, pothole repair, and pretreating cracks prior to placing an asphalt overlay. In addition, Mastic is compatible with concrete. 

Sealing cracks along concrete curbs helps control water infiltration and prevent vegetation growth. 

Adoption by Municipalities 

Interest in this solution is growing, particularly because cities and municipalities can use their own public works employees to carry out the work or assign it to a specialized contractor. Based on experience, public works employees quickly master this technique and know better than anyone where the problematic areas are. Often, they begin by fixing specific issues, but the product is so versatile that they end up successfully repairing many other problems as well. 

Less labor is required compared to paving activities, and road closures are shorter in duration. 

• Manhole perimeter sealed by a public works employee to prevent water infiltration and avoid snow-removal equipment catching on the manhole. 

• Leveling a depression that occurred after a roadway repair—an example of localized resurfacing. 

Installation 

For installation, ensure the surface is clean and dry and that the asphalt temperature is 4 °C (39 °F) or higher. The first step is to clean the area to be repaired with an air compressor, preferably 185 cfm at 90 psi, and remove debris. This is the same preparation procedure used for crack sealing. 

If applied on concrete, the surface must be cleaned and abraded to ensure maximum adhesion. If moisture is present or the temperature is cold, it is removed using a hot air lance or a torch, but without direct flame, to avoid oxidizing the bitumen and compromising adhesion. 

Next, allow the hot Mastic to flow by gravity into the problem area, either directly from the melter or using a bucket or mini transfer melter. An application box is used, with dimensions varying according to the repair area. No compaction or paver is required—the product is self-leveling. If desired, the product can be spread with a hot iron to finalize placement, but generally it settles on its own. 

Traffic can be reopened quickly. An anti-adhesive liquid (Detack) can be used for immediate reopening, except when repairs are deep; in that case, a cone is usually left in place until the product cools. Traffic control costs are minimized thanks to the rapid reopening. 

When the repair is deeper than 6.3 cm (2.5 in), the filler is applied in successive layers to control product shrinkage, which is normally around 5%. The minimum application thickness is 1 cm (3/8 in). 

This eliminates the need to saw-cut pavement, apply tack coat, use a paver, compact, or close the road for an extended period. It reduces labor requirements and the overall budget needed to resolve the problem. 

Equipment 

Hot-applied Mastic is pre-mixed and heated in a thermic-oil melter equipped with a horizontal agitator and precise temperature control to ensure uniformity of the mix during application. The product is supplied in cube form, approximately 13 kg (30 lb), ready for melting—no cardboard boxes to open and dispose of, simply place the product into the melter. 

Controlling heat distribution is especially important for this type of multi-component product. This is made possible by equipment specifically designed for it and equipped with electronic and thermostatic temperature controls. 

Conclusion 

Hot-applied Mastic is available in Quebec and has proven to be a cost-effective, efficient, and fast-to-install solution. The best solution will always be investment in pavement maintenance—particularly applying joint adhesive during pavement construction and implementing a crack sealing program using high-performance products with proper oversight of the work.