I have reviewed many recommended procedures for adding ingredients into a mortar mixer when mixing mortar. Are there similar recommendations for grouts?
ASTM C 476 Standard Specification for Grout for Masonry states that the cementitious materials and aggregate shall be mixed thoroughly for a minimum of 5 minutes in a mechanical mixer, with sufficient water to bring the mixture to the desired consistency. Whether mortar or grout is being mixed, the goal is to achieve a uniform blend of ingredients throughout the batch. Cement and water (or cement, lime and water) form a paste surrounding the aggregates. There should be no clumps of sand or cement (or lime) in the mortar or grout. Grout often is delivered to the jobsite ready-mixed, in which case the charging sequence is determined by the grout producer. If grout is mixed at the jobsite, materials should be added in a sequence similar to the following charging sequence recommended for mixing mortar on-site in a mechanical mixer:
  • 2/3 to 3/4 of the required water
  • 1/2 of the required sand
  • all of the cementitious material
  • remainder of the sand
  • water required to reach workable consistency.

Make sure the aggregates are damp when added to the mixer. Dry aggregates can absorb water from the grout and reduce flowability.