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Tech BlockŪ Building Manual 9
Grouting Procedure
The major concern when grouting a wall is to avoid failures in the wall that allow the grout to run out on the ground. The common term for this occurrence is "blow out", and the grouting process should be managed in such a way as to reduce or eliminate the chance of blow outs happening altogether. The last thing you want is to have a concrete truck full of grout getting old while you frantically try to rebuild a doorway that you forgot to brace.
That said, the fact is that even the most prepared projects can have blow outs, and they can be dealt with. If a blow out occurs, you should move to another area of the project and  continue grouting, while workers clean and repair the failed area. The spilled material can be shoveled into a wheelbarrow and then reloaded into the grout pump hopper. We used to brag on how tall we could pump our walls in one shot without having blow outs (our record is 17'), but now we take pride in how many projects we can go without having problems. The main fact to remember is that concrete is an extremely heavy material, and that weight, when added to height, becomes pressure.
The other concern when grouting is that you want to make sure that all the cavities in the wall are completely filled. This is accomplished by using grout of the right consistency, and by striking the wall with a hammer at those areas that may need help. The consistency of grout is primarily determined by the mix's water content, and is measured as slump -- a 12" tall open-ended, cone-shaped container is filled with concrete, turned over on a flat surface, and removed. The distance the mixture falls, or slumps, is an accurate measurement of the mixture's consistency and ability to flow. The higher the number, the runnier the mix. The optimum slump for our wall system is about 10, but we use a water reducer to achieve it. Water reducers are admixtures, sometimes called super plasticizers , that the concrete supplier will add to the mix to make it runnier without adding the extra water that would weaken the mixture. We order 4,000 PSI grout with an aggregate content of 25% - 3/8" pea gravel to 75% sand, and a slump of 7 that is water reduced to 10. So we get a mixture that flows like water but cures hard as rock.
The grout comes in a standard revolving concrete truck, and is chuted into the hopper of the grout pump. The pump then forces the grout through a hose which is directed into the open grout channels at the tops of our walls. We like to use an 1-1/2" hose, but we have used a 2" hose. Anything larger is tough to handle -- the hoses are heavy and have a systolic action that makes them hard to hold, so using a hose larger than 2" is not recommended. Large or especially tall projects may require the use of a crane pump.
There are two areas that we pay special attention to in order to make sure they are completely filled. One is under window sills, and the other is the horizontal half channels at the tops of doors or windows that top out at a block seam. As we are pumping these areas, we hit the OSB side of the wall with a hammer, which causes the grout inside the wall to slump, and it therefore tends to better fill these areas. If, upon removing the plywood forms, we find that there are some areas that didn't fill completely, we can hand mix what we need, and fill them after the main grouting has been completed. Neither of the areas are an important component of the structural integrity of the building (most of the weight is held up by the big vertical channels that go from the tops of the walls to the footings), and filling them after the fact is acceptable.
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