masonry grout placement – code criteria
Many rules and code compliance criteria apply when masonry grout is placed into the concrete masonry unit (CMU) cells according to TMS 402/602 (Masonry Code). The first rule is that the grout must be
proportioned according to ASTM C476 requirements. The grout may be produced at the project site or
furnished by a local concrete ready-mix supplier; either way, the grout proportions must comply with ASTM
C476 and have a minimum strength of 2000 psi (TMS 602 article 2.2 B).
The minimum grout temperature during cold weather is 70 F, and the maximum grout temperature in hot
weather is 120 F. This means that grout materials and mix water may have to be heated in cold weather
according to the requirements stipulated in TMS 602, Article 1.8 C. Grout spaces must be constructed free
of debris and mortar droppings. Reinforcement, ties, and rebar positioners must be in place before grout
placement (TMS 602, Article 3.2 E), and cleanouts must be provided when grout pours exceed 5 feet 4
inches. The minimum opening of the cleanouts shall be 3 inches, and the maximum horizontal spacing
of cleanouts for solid grouted masonry shall be 32 inches (TMS 602, Article 3.2 F). Mortar protrusions
extending ½ inch or more into the CMU cells must be removed (TMS 602, Article 3.3 B).
Grout must be placed within 1 ½ hours from the time water was introduced into the grout mix, and no
mix water can be added to the grout after grout discharge from the ready-mix truck. The time limit can be
waived if ready-mix grout still meets the specified slump (TMS 602, Article 3.5 A). When placing grout, do
not exceed the maximum pour height listed in TMS 602, Article 3.5, Table 6. Unless otherwise required,
grout should be placed at a consistency with a slump of 8 to 11 inches (TMS 602, Article 2.6 B). However,
it should be noted that the grout slump shall be from 10 to 11 inches under the conditions listed in the
narrative box at the bottom of this page (TMS 602, Article 3.5D). The grout must be properly consolidated
with mechanical vibration per TMS 602, Article 3.5 E. Grout keys must be formed between grout pours by
terminating the grout pour 1 ½ inches below the top mortar bed joint.
These are a few (but not all) of the items that the project masonry special inspector must observe.
TMS 602, Article 3.5D Grout Lift Height.
For grout conforming to Article 2.2A (Complies with ASTM C476)
Where the following conditions are met, place grout in lifts not exceeding 12
feet 8 inches:
- The masonry has cured for at least 4 hours.
- The grout slump is maintained between 10 and 11 inches.
- No intermediate reinforced bond beams are placed between the top and
the bottom of the pour height.