Masonry Magazine May 2003 Page. 25
Grout Hog
But cost isn't the only factor; there is one more important variable to be considered. Because each pour is usually small (two to eight yards) and grout requires more time to unload than regular concrete, many ready mix companies don't like to deliver grout. They would rather deliver to projects where larger quantities of concrete are being used on pours, such as roads or slabs. Therefore, the mason contractor's crew is often left waiting on ready mix trucks when it is time to grout.
This waiting time costs the mason contractor in lost production. In fact, it can cost much more than the savings the contractor gets by ordering the grout from the ready mix company. To sum it up, if the ready mix company won't deliver grout at the precise time it is needed, then the contractor's best option is to mix grout on site.
Jeff Leonard, Vice President of Bulk Materials at Quikrete, Milwaukee, Wisc., agrees when he says, "It's beneficial for the contractor to consider a Spec Mix system or other bulk system compared to the 'conventional way, which is the ready mix truck coming to the jobsite. The contractor has more control and can grout as slow or as fast as he needs to when he has a premix grout silo. He has control over that whole process. It's beneficial to use these systems for field mixing, too, just for the saving of the labor factor."
Making the Mix
LEONARD DISCUSSES what goes into the mix that goes into the silo and then into the mixer. "I would estimate about 40 percent of our bulk material is for grouting, mostly on the commercial side where we're servicing contractors through the bulk systems, such as Spec Mix. We can meet any design specification that is called for but most of what we supply falls under the ASTM C476 specification. We can provide those grouts and if there are some special additives that the contractor needs if they want an accelerator, for example, or perhaps in extremely hot conditions or if they would need to mix it drier for whatever reason, they might want to consider a retarder-we are able to supply those and just put them in the dry mix."
The contractor has more control and can grout as slow or as fast as he needs to when he has a premix grout silo. He has control over that whole process.
He goes on to say, "We work hand in hand with EZ Grout and Spec Mix and in many areas we are a licensee for the Spec Mix system. So we work to create what might be called a packaged deal for grouting."
Quikrete has 70 plants around the U.S. so the mix is never very far from the jobsite. Freight costs to haul dry mix long distances would negate much of the savings. Other factors come into play, based on regional differences in material. Leonard says, "We buy our aggregate from local sand and gravel pits. Based on the gradation of those aggregates and their composition, we come up with a mix design that meets the strength requirements as required by ASTM C476."
He adds, "If I compare my mix design here in Milwaukee with that made in St. Louis, for them to get a certain strength, they need a completely different formula than I would use. I'm in an area of the country where our aggregates are extremely dense and that's very good. More cement is needed with the aggregates that are down South, that have different clays in them. Our aggregates here are sand-based. There's a lot of quartz in it, and that makes for a very dense, strong aggregate. As a result we may or may not need a different sand-to-cement ratio as they do in Atlanta. The formulas are virtually different everywhere to get the same result."
Mixing grout on site
MIXING ON SITE can be accomplished in a variety of ways. Most frequently, drum type concrete mixers or large hydraulic mortar mixers are used. Which option is the best for you?
Drum type mixers roll and tumble the grout instead of cutting through the material. Because of this, tumbling takes extra time to mix the grout and it doesn't give the consistency that can be achieved by using hydraulic mixers that have blades cutting through the grout. Most hydraulic mixers have a large enough space between the blades and the drum to bypass the pea gravel that is usually required in the mix. If these mixers should ever get plugged up, they can simply be reversed to undo the plug in seconds.
The size of the mixer is also an important variable. The larger the mixer the more efficient the grouting process. Using a mixer with a minimum capacity of 12 cubic feet (four bags) keeps your forklifts from having to make extra trips to the mixer for the smaller loads of grout. In contrast, if you use a smaller capacity mixer, the smaller loads require extra time and travel with your forklift. Remember, if the forklift operator has to sit and wait while the laborers mix two or three batches to fill a big mud pan or a Grout Hog, it is also a waste of valuable forklift time.
Several mixer companies now build large hydraulic mixers. EZ Grout Corp. has recently introduced the Mud Hog, a 20-