Masonry Magazine August 1987 Page. 22
RESIN
HARDENER
POUR
MIX
PLACE
A) SELF-DRILLING ANCHOR B) DROP-IN ANCHOR
Other Proprietary Expansion Anchors
FIG. 8
There are several considerations that should be examined when contemplating the use of expansion-type anchors in brick masonry. These are: 1) Expansion anchors should not be used to resist vibratory loads. Vibratory loads tend to loosen expansion anchors. 2) Specific torques are required to set expansion anchors. Excessive torque can reduce anchor strength or may lead to failure as excessive torque is applied. 3) Expansion anchors require solid, hard embedment material to develop their maximum capacities. Some brick construction may not provide a good embedment material due to voids formed by brick cores and partially filled mortar joints.
Adhesive Anchors
Two basic types of adhesive anchors are currently available. The major difference between the two is that one anchor is manufactured as a pre-mixed, self-contained system, whereas the second type requires measurement and mixing of the epoxy materials at the time of installation. The more popular self-contained types use a double glass vial system (see Fig. 9) to contain the epoxy. The outer vial contains a resin and the inner vial contains a hardener and aggregate. The glass vial is placed in a pre-drilled hole and a threaded rod or bar is driven into
A) EPOXY CAPSULE
B) THREADED ROD
C) INSTALLED ANCHOR
Self-Contained Adhesive Anchor
FIG. 9
Site-Mixed Adhesive Anchor
FIG. 10
the hole with a rotary hammer drill, breaking the vials and mixing the adhesive components. The other type of adhesive anchor requires that the epoxy components be hand-measured and mixed before the epoxy is placed into a pre-drilled hole. A threaded rod or bar is then set into the epoxy mixture, as shown in Fig. 10. Adhesive epoxies usually vary slightly between manufacturers, but the steel rods or bars are typically ASTM A 307 or ASTM A 325 threaded rod, or ASTM A 36 shop-threaded bar.
There are special requirements and limitations that should be considered when contemplating the use of adhesive anchors in brick masonry. They are: 1) Specially designed mixing and/or setting equipment may be required. 2) Dust and debris must be removed from the pre-drilled holes to insure proper bond between the adhesive and base material. 3) The adhesive mixture tends to fill small voids and irregularities in the base material. 4) Large voids (due to brick cores, intentional air spaces and partially filled
TABLE 2
Some Chemicals That May Affect
Adhesive Anchor Epoxies*
Acetic Acid
Acetone
Ammonia
Calcium Chloride Solution
Carbon Tetrachloride
Caustic Soda
Citric Acid
Diesel Oil
Ethyl Alcohol
Formaline
Formic Acid
Hydrochloric Acid
Hydrogen Peroxide
Lactic Acid
Machine Oil
Methanol
Nitric Acid
Phenol Solution
Phosphoric Acid
Saline Sali Solution
Sea Water
Soda Solution
Sodium Hypochloride
Sulphuric Acid
*The manufacturer should always be consulted when adhesive anchors are to be used in areas where contact with chemicals is likely.