Masonry Magazine June 1985 Page. 28
EMBEDDED STEEL IN MASONRY
continued
Welded to steel, it acts in the opposite manner of zinc; that is, the steel becomes the sacrificial element and corrosion is accelerated.
Fusion-bonded Epoxy Coating. Epoxy coatings achieve their corrosion protection by providing an impervious barrier between the steel and water and oxygen. Unlike zinc, however, it is not sacrificial so "holidays" and "nicks" must be kept very small. The fusion-bonded epoxy coating achieves adhesion to the base steel as a result of a heat catalyzed chemical reaction.
In addition to chemical adhesion, there is also a physical adhesion of the coating to the steel. The main purpose for obtaining good adhesion is to prevent disbonding when the steel is subjected to stress in service and during installation. There is an ASTM specification for coating reinforcing bars; there is no standard for coating wire for joint reinforcement or connectors.
Fusion-bonded epoxy coatings are enjoying a considerable amount of popularity in pavement, bridge decks, and industrial floor applications. Engineers using epoxy coatings report good performance, especially in hostile environments.
Controlling Admixtures in Mortar and Grout
Current masonry industry recommendations restrict the use of admixtures containing calcium chlorides in masonry containing reinforcing steel, especially where an accelerator is desired for cold weather masonry work. The All Weather Masonry Committee and the Brick Institute of America (BIA) completely ban the use of admixtures containing calcium chlorides in walls containing embedded steel.
In addition, new issues of ACI Committee 201-2R-77 Guide to Durable Concrete, due this year, will also limit the allowable chloride content of concrete to that found in municipal water.
In order that contractors can still build masonry walls when temperatures are low, it is important to specify accelerators that do not contain chlorides and are noncorrosive. Long-term noncorrosive test data should be required to assure satisfactory performance. Accelerators have been on the maket since 1980 and are yielding excellent results.
Table 4
Minimum Corrosion Protection Requirements"
| Item | Steel Wire Embedded* | All Other Steel Wire |
|---|---|---|
| Joint Reinforcement | ASTM A641 Class 1 | ASTM A641 Class 3 |
| Anchors | ASTM A641 Class 1 | ASTM A641 Class 3 |
| Ties | ASTM A641 Class 1 | ASTM A641 Class 3 |
* ACI 531.1-76 (Revised 1981) Specifications for Concrete Masonry Construction. "Wire
entirely embedded in mortar or grout.
In addition, as mentioned above, the ACI is modifying several of its standards governing use of chloride based admixtures to reduce corrosion of reinforcement. These include:
* ACI Commitee 201-29-77 Guide to Durable Concrete
* ACI Committee 302 Guide to Concrete Floor and Sab Construction
* ACI Committee 212 Admixtures
* ACT Committee 222 Corrosion of Man Conce
Recommended Requirements
Even though the actual long-term performance of reinforcing steel, joint reinforcement, connectors, and other embedded steel has been generally satisfactory, changes in the way buildings are designed and transformations in the environment are significant enough to justify an adaptation in the way buildings and other construction are protected from corrosion.
Unfortunately, there is no clear-cut formula for determining the amount of corrosion protection needed, nor do any of the model building codes or design standards cover this issue very thoroughly.
The BIA has recommendations for the use of Class 3 mill galvanized coating for connectors and joint reinforcement in exterior walls. In addition, an ACI Standard specification for masonry does address the issue and indicates minimum galvanizing requirements. Specifiers may adopt one of these standards as is or with modification. Table 4 shows minimum galvanizing requirements listed in the ACI standard.
There is growing concern over corrosion, and it is interesting to note that the Canadian Standards Association recently issued a new standard for masonry connectors. They went a step further than the U.S. in requiring protection for masonry anchors and ties and have made hot dipping the standard. This provides almost two times the zinc coating as the ASTM A641 Class 3 coating recommended in the U.S.
Note
For further reading on this topic, see "Facade Rehabilitation: Solving
Problems Through Reanchoring." June 1984 Specifier, page 72.
Sterling Handling Reorganizes
Sterling Handling Equipment, Inc., Milwaukee, Wis., has established a new marketing team management approach following the Scott family's acquisition of the company which originated in 1904 as the Sterling Wheelbarrow Co. Displaying key products in the Sterling line are (from left) Mark Sturm, general manager-administration; Jim Scott, executive vice president, and Ken Maio, production manager.
Pettibone Sponsors Awards Banquet
During the recent Associated Equipment Distributors convention in Washington, D.C., Pettibone Corp., manufacturer of rough terrain construction forklifts, held a banquet and awards night attended by 200 Pettibone distributors from the U.S. and foreign countries. Shown above is Lloyd Wells (left) of Contractors Equipment, San Diego, Calif., accepting the award for top Extendo sales in 1984 from James A. Miller, Pettibone president and CEO. At the right is C. J. Stuppy, senior vice president of marketing and sales.