DAP® High Heat Mortar is a non-combustible silicate cement used for patching chipped firebrick in fireplaces and sealing wood-burning stoves. High Heat Mortar adheres firmly to the firebrick when wet or dry. * * * * High Heat Mortar can also be used for applications in wood frame construction where an ASTM E136 non-combustible sealant is required, such as sealing around vents, pipes, ducts, and chimneys at ceiling and floor level prior to the application of drywall products.