What is Type K mortar? I have a job where the specifications require Type K mortar, but I can't find information about the mortar in any of the standards.
Welcome to the changing world of specifications. Type K mortar has been eliminated from ASTM C 270 Standard Specification for Mortar for Unit Masonry. C 270 now contains proportion and property specifications for only Types M, S, N, and O mortars. Politely point out to the designer that Type K mortar no longer has a proportion or property specification. If the mortar is intended for interior nonload-bearing masonry, which is what C 270 used to recommend Type K mortar for, suggest using Type O mortar instead. If the mortar is to be used for other uses, refer the designer to Table XI, Guide for the Selection of Masonry Mortar, in ASTM C 270. Also refer him or her to the article, "How to Specify Mortar," by Colin C. Munro, on page 22 of the April issue of The Magazine of Masonry Construction.