Masonry Magazine January 2005 Page. 26
Mortar
ALTERNATIVES
One area of potential that Bennett sees is in unreinforced masonry design. He said recent changes in codes have resulted in unreinforced masonry no longer meeting code in some areas. "This is a problem for which the industry has no good solution," he says. "With Mason Bond, the problem is solved. It is so much stronger that unreinforced masonry will work just fine, even with the more restrictive codes."
Another advantage of Mason Bond is better product consistency than conventional mortar. There is large variance in the properties of mortar because the mixing process is highly variable depending on the amount of sand and water used in the mixture. Mason Bond is a premixed product manufactured to tightly controlled specifications at the ITW TACC Polyurethane Center, resulting in minimal variability and greater consistency in the product.
Walsh acknowledges that despite its advantages it will take some time for Mason Bond to gain market acceptance. "Mortar is the industry standard, and introducing a technology that is different presents challenges. First, aes-
MASONRY SOLUTIONS:
INTEGRAL WATER-REPELLENT MORTAR
Nothing in the world is more flexible and yielding than water. Yet when it attacks the firm and strong, none can withstand it, because they have no way to change it.
- Lao Tzu, 600 В.С.
Water. Seventy percent of the world is covered by water. Water composes 75% of the human brain. Water is the most essential ingredient to life, and yet, it is also one of the most destructive forces on earth. And as anyone in the construction industry knows, it is the source of mold, water damage and efflorescence.
Even the strongest masonry assemblage cannot resist the ingress of water. Although we cannot change the aggressive and sometimes persistent nature of water, we can change the way it interacts with masonry assemblages.
One way is to prevent water or moisture from entering the masonry system. This can be accomplished by sealing the masonry surface using either a membrane-forming sealer or one that is breathable. Each has its advantages and disadvantages. For instance a membrane-forming sealer can trap efflorescence salts behind it, increasing the potential for spalling of the block surface.
Another more economical and very effective way to mitigate moisture intrusion is to use a masonry assemblage that incorporates an integral water-repelling (IWR) admixture. Integral water-repelling admixtures have been used in masonry construction since the 1980s. IWR admixtures are available in both liquid and powder form and are composed primarily of stearates or polymers. Liquid admixtures are typically added to mortar mixtures at the job site, while powdered IWRs are blended into dry, pre-blended masonry products.
Block manufacturers also incorporate IWRs into concrete masonry units. When IWR-treated concrete masonry units are used in unison with an IWR mortar, the result is a water-resistant masonry assemblage. Treated concrete masonry units should not be used without IWR mortar due to a reduction in bond between the CMU and mortar not to mention the fact that the untreated mortar beds would act as pathways for moisture penetration.
The industry has gravitated largely to water-repellent treated CMUS with an IWR mortar, using either liquid or powdered admixtures. So is there any difference between liquid and powdered IWR admixtures? Ask a mason, and they'll tell you which they prefer.
Wayne Stephenson, Superintendent for DH Johnson in Chicago, says the difference is in the consistency. "We used to use the liquid admixture until we were able to get a pre-blended IWR mortar. It's just more convenient, more consistent. It's just easier."
| | Portland Lime: Sand | | | Masonry Cement: Sand | |
| --- | --- | --- | --- | --- | --- | --- |
| | 1:16 | 1:1:6 | | | 1:3 | 1:3 |
| | | With Powder | With Liquid | | With Powder | With Liquid |
| ASTM C 270 | Control | IWR | IWR | Control | IWR | IWR |
| Water Retention, % | 89 | 93 | 95 | 86 | 86 | 88 |
| Air Content % | 6.3 | 61 | 14.9 | 15.8 | 15.3 | 186 |
| Seven-Day Compressive Strength, psi | 1520 | 1570 | 1760 | 1570 | 1600 | 1500 |
| 28-Day Compressive Strength, psi | 1730 | 1800 | 2230 | 1950 | 2040 | 2140 |
| ASTM C 1072 | | | | | | |
| Flexural Bond Strength. psi | 136 | 123 | 84 | - | - | - |
| ASTM E 514 | | | | | | |
| Time to First Dampness | 60 min | None | None | 38 min | None | None |
| Time to First Visible Water | None | None | None | None | None | None |
| Area of Dampness, % of Test Area | 10% | None | None | 12% | None | None |
| Water Collected in Four Hours | None | None | None | None | None | None |