According to the Masonry Institute of America (Inspectors Handbook 7th Edition), the suggested grout testing frequency is one test per day for the first three days. The compressive strength test specimens should consist of 3 test specimens. After the first 3 test, test specimens should be made and tested at least once a week or for every 30 cubic yards of grout or every 5000 sq. ft of wall, which ever comes first.
Typically the pinwheel method is recommended for make grout compressive strength specimens rather than alternate methods due to block absorption. The pinwheel method the best way to duplicate the condition of the grout in the masonry wall. If alternative methods are used, its recommended to get the alternative compressive method approved.
