When specifying extended life pavements, the material used to seal joints and cracks from debris and erosion must be a key consideration. The sealant selected needs to protect the joints from incompressible materials and moisture infiltrating the joints. It also must reduce joint spalling, faulting, erosion of the base, as well as help protect the dowel bars.
A preformed pavement compression seal is installed in a compressed state, which allows it to remain tight in the joint and in constant contact with the joint walls, allowing the concrete pavement to contract initially from drying shrinkage and then to expand and contract during temperature changes. Field molded joint systems rely on the integrity of bond to accomplish this. The integrity of the bond is too often dependent on weather conditions, compatibility with the aggregate, exposure to chemicals, and proper construction practices in cleaning the joint.
The joint sealant cost is minimal – about 98 percent of the total cost of a job is the pavement and about 2 percent is the joint sealant – but the selection is extremely important. Considerable time and thought is typically put into designing long-life pavements, but that same care and concern isn’t always given to choosing a sealant that supports a long-life pavement.
Currently, there are three choices of pavement seals approved by the Federal Aviation Administration (FAA) for use on airport runways:
• Hot-pour filler (Standard Modulus, Low Modulus FAA P-605)
• Silicone with backer rod (Non Sag, Self-Leveling, FAA P-605)
• Preformed Compression Seal (6-cell design--jet-fuel resistant, FAA P-604)
Comparing these options for sealant types, hot pour fillers often last three to five years. Silicone sealants with backer rod typically last 8 to 10 years, and preformed pavement compression seals last 15 to 20 years. Preformed pavement seals are preferred by many owners because they provide extended life performance, the lowest cost based on life-cycle analysis, and deliver a dramatic reduction in joint spalling.
Ben Jacobus is with D.S. Brown, North Baltimore, Ohio, a worldwide designer, supplier. and manufacturer of engineered products for the bridge and highway industry.