Voids or bubbles in cured sealant:
High pavement temperature and moisture content when Crack Sealing Machine working---seal during cooler periods and allow Portland cement concrete to further dry or cure, or use nonsag type sealant to resist void formation.
Outgassing of backer material---backer may be melting with hot applied sealants; use heat-resistant backer material and check for proper sealant temperature
Backer may be punctures during installation---install backer without damaging
Top down sealing (Crack Sealing Machine construction sequence), which can trap air---apply sealant from bottom up.
Air entering the sealant pumping lines---tighten all connections, or bleed off entrapped air
Moisture build up on backer material due to being installed night before---replace backer material
Primer not properly cured prior to sealant application
Cold-applied sealants not setting up
Sealant has exceeded its shelf life---Choose fresh sealant before Crack Sealing Machine working
Incorrect proportioning or mixing of two component sealant---use correct mix ratios and mixing systems
