In high-lift grouting, how long should you wait after grouting to reconsolidate the grout and to pour the next lift?
The Reinforced Concrete Masonry Construction Inspector's Handbook, published by the Masonry Institute of America, recommends waiting 5 to 10 minutes after grouting before reconsolidating the grout by mechanical vibration. This allows water to be absorbed into the masonry but is before the grout loses its plasticity. This reconsolidation minimizes shrinkage voids due to water loss. The next lift should be placed as soon as reasonable after reconsolidation. The grouting of any section of wall should be completed in 1 day with no interruption between lifts greater than 1 hour.
The Brick Industry Association in Technical Note 17D recommends a waiting period of 30 to 60 minutes between 4-foot lifts. It states that the first consolidation should be done 10 minutes after pouring. The succeeding lift should be poured after the grout becomes plastic but before the grout has taken any set. The mechanical consolidation of the succeeding lift must extend 12 to 18 inches into the preceding lift.