One new product takes mortar alternatives to the extreme by eliminating the mortar altogether. Mason Bond, from ITW TACC, Rockville, Md., introduced Mason Bond, an adhesive system for bonding CMUs, in early 2008. Usable at any temperature between 40° F and 120° F and relative humidity between 20% and 90%, Mason Bond is applied to head and bed joints in a 3/16-inch diameter bead. The adhesive remains usable for about 15 minutes.
This adhesive is provided in 10.3-ounce tubes or 29-ounce tubes. ITW TACC also is working on a pump system that would use 5-gallon pails or 55-gallon drums and pump the adhesive into a wand that simultaneously will apply beads to both face shells.
Mason Bond greatly speeds masonry construction. On a recent foundation stem wall job, a crew of two installed 236 blocks in just three hours—about half the time needed for standard masonry assembly with mortar. Workers applied the adhesive bead 3/4-inch back from the block faces—the material expands three times during curing. Excess material is scraped off the next day after it hardens.
One problem with this system is appearance. There is no mortar joint, a look that many people might prefer. “We know that this isn't going to be used for every application,” says Tim Walsh, ITW TACC's business manager. “Some object to the lack of joints since they are used to seeing them, but with split face blocks, some architects actually like the look. The largest project we've done to date was with split face.”
Another difficulty is the loss of modularity. To account for the mortar joint, standard blocks and bricks are manufactured 3/8 inch smaller in height and width. Since with Mason Bond the joint is very thin, this throws off modularity. “Some manufacturers have made true 8x8x16-inch blocks,” says Walsh. “But as we get more acceptance we will work with our distributors, who are typically block manufacturers, to make molds for true 8x8x16-inch blocks.”