Concrete and plywood can help the modified thinset dry faster by absorbing some of the water in the thinset mix. On the other hand, like concrete, unmodified thinset cures stronger in the presence of moisture. For this reason, tile installers prefer using unmodified thinset on surfaces with ...
ANSI A118.1 is the lowest grade for thinset mortars. Generally, it’s used to determine if a thinset is unmodified. Mortars must meet or exceed 150psi with the porcelain tile shear bond test. A118.1 Section 7.2. [1,2,4] A modified mortar that meets or exceeds ANSI 118.4 standards ...