Infrared Offers Option
A different approach to permanent patch repairs is the infrared option. Distressed pavement surface repairs – such as potholes, alligator cracking, bird baths, high spots, pavement seams, manhole covers or failed repairs – may be effectively fixed using the infrared process.
Seamless infrared asphalt repairs are achieved by using specialized equipment to heat the existing asphalt surface to a depth of up to 3 inches. New hot mix asphalt is then mixed with the existing asphalt, forming not a patch, but a seamless repair that is thermally bonded to the surrounding asphalt. After a slurry or chip seal, the repair likely will not be detectable.
The seamless repair will resist water intrusion, can be performed in any weather conditions or temperatures, and can be opened to traffic in an hour or less in most cases.
After a repair area is cleared of broken and raveled asphalt, an infrared heater is positioned over the repair area, which is then exposed for up to 10 minutes. After the asphalt is softened – but not scorched – a lute or rake is used to define the outer edges of the patch. At least 6 inches of the heated surface should remain undisturbed around the outside edge of the patch, contractors say. The rake is then used to scarify the inside of the hot patch area and an asphalt rejuvenator is mixed with the raked, aged asphalt.
Then, fresh virgin asphalt is added to the site to bring the repair up to grade. The patch is then leveled with a lute and the area around the repair is swept clean. Compaction flush with the surface completes the infrared repair.
Concrete Pavement Repairs
Spalled concrete caused by fatigue, freeze/thaw cycles, warping stress, ingress of water, or substrate problems can lead to costly reconstruction, and repairs require a different approach than with flexible pavements. But patching of portland cement concrete (AC) pavements with conventional PCC – with its long cure times and lane closures – can cause excruciating user delays, whether on an expressway or airport runway.
As conventional rigid cement repairs – such as epoxies or fast-curing cementitious products – often fail due to de-bonding, fatigue and differential expansion characteristics, additional cracking and the need for repeated repairs may occur. Instead, a variety of high-performance concrete patch materials provides quick repairs that not only cure very fast, but solve long-term patch durability issues.
For example, TechCrete from Crafco provides a long-term solution for distressed concrete pavement preservation, the maker states. It’s a hot-pour repair solution which provides flexibility, high-tensile strength, the ability to bridge joints, and high compressive resistance, the maker says.
Once in place, a TechCrete patch will move with the pavement and will not de-bond or crack, Crafco says. The product also has a high friction surface ideally suited for thin bond repairs, multi-corner slab repairs, joint intersection repairs and recessed applications. Repairs with Crafco TechCrete can be opened up to traffic within as little as one hour.
Another product, Rapid Set from CTS Cement Mfg. Corp., is a specialty cement which gains structural strength in 1.5 hours after placement, materially reduces drying shrinkage, and reduces porosity for enhanced durability. It results in a workable, 5-inch slump concrete that gains compressive strength of 2,500 to 3,000 psi in 1.5 hours. The shrinkage of Rapid Set concrete is about 25 percent of the shrinkage of same slump portland cement concrete.
Its improved durability by reduced porosity is demonstrated by superior freeze-thaw resistance, the maker says. This attribute makes it ideal for placement where speed and durability is of the essence, for example on night patching on urban expressways or bridge decks, or night runway repairs at major airports, where liquidated damages for failure to open can run into the tens of thousands of dollars.v