Just learned that I work less than a mile from the longest-running stone weathering experiment: NIST's stone wall test.

Built in 1948, it includes 2352 samples of stone from 47 US states and 16 countries, and uses two types of mortar.

The mortars used are a 1:3 lime mortar with a high calcium hydrate and a 1:0.4:3 portland cement, whiting, and sand mortar.