Q: The Masonry Standards Joint Committee's
Building Code Requirements for Masonry Structures (ACI 530/ ASCE 5/ TMS 402, 1999) indicates that both fine grout and coarse grout could be used for concrete masonry walls. There is no restriction for the use of fine grout in large cavities.
Why would coarse grout be used since fine grout is acceptable in any space where coarse grout is acceptable?
A: Coarse grout should be used whenever possible. As stated in the National Concrete Masonry Association's TEK 3-3A-1997, "using a coarse product reduces shrinkage and the cost of grout."
Coarse grout meeting ASTM C476 requirements is essentially made by adding pea gravel to fine gravel. This mixture lessens the total amount of fines in the grout, which reduces shrinkage. Grout cost is lowered because pea gravel is less expensive than sand and cement.