This moderately Hydraulic lime is used for laying or repointing brick, stone and terra cotta units even in extreme freeze-thaw climate cycles. It can be used to make scratch, brown and finish coats of exterior stucco or interior plaster.
NHL 3.5 must have 15-25% “free lime” content and no more than 30% which is responsible for self-healing mortars. The available free lime goes into solution during subsequent rains and then re-crystallizes across open fissures, similar to the process that occurs in historic pure lime mortars.
NHL maintains a hexagonal plate crystal structure which allows the plates to go in between each other for greater elasticity. In contrast, Ordinary Portland Cement (OPC) has a needle-like crystal structure which is brittle; buildings using OPC must incorporate numerous control joints to accommodate movement. Once properly installed and cured NHL 3.5 will reach over 750 p.s.i. in six months when blended with 2-1/2 parts clean, sharp and well-graded sand. ”