Masonry Magazine June 1976 Page. 16
Saturated in water. The walls were then subjected to 50 freeze-thaw cycles by freezing in air for 16 hr and thawing in water for 8 hr. Both the conventional walls and the high-bond walls exhibited minor brick spalling on both sides of the brick and an approximate 40 percent reduction in flexural strength when tested after the 50 cycles of freeze-thaw.
Aging. The effect of aging is a key question for any masonry system. To establish the durability of mortar modified with Sarabond brand mortar additive, fifteen 4-ft by 8-ft test walls were built, exposed to weather for specific times, and tested in accordance with ASTM E 72 procedures. Table 3 shows the average flexural strengths of test specimens exposed for various time periods to the Michigan weather.
Chemical Resistance. Sometimes portland cement mortar must be modified or protected if expected to resist the attack of various chemicals. Sarabond brand mortar additive is effective in providing additional protection from certain of these. Table 4 shows the effect of chemical exposure on mortar compressive strength. All samples were cured 28 days prior to immersion in the reagents, and all tests were run in triplicate. The indicated chemical concentrations were maintained throughout the exposure.
Panel Connections. Because of the extensive use of Sarabond in the prefabrication of brick panels, the performance of the connections and erection attachments is very important. Numerous pullout, shear and torque tests of lifting hooks and anchor bolts have been made, and are available through Amspec Inc.
Pullout Test. Pullout tests are usually made if the method of attachment is questionable or has not yet been used. It is not uncommon for ½-in. diameter "L" shaped connection bolts to exhibit an excess of 2000-lb resistance when used in 4-in. thick brick panels and tested to destruction. Longer anchor bolts usually used in the top of a panel for erection purposes have exhibited tensile failure in the steel rather than bond failure when tested to destruction. Table 5 provides suggested allowable forces for connection bolts and lifting bolts for brick panels.
Shear Test. Shear tests are important because in most applications the panels are supported at various points and thus subject to high stress concentrations. Table 5 shows Dow's recommended allowable shear values for connection and lifting purposes.
Torque Test. In attaching some panel systems, it is important to know the torque limitations of different type connections. Slotted connectors are sometimes used and rely on the frictional force between the connector and the brick masonry for final panel location. Anchor bolts, as described earlier, that were torqued to 85 ft-lb with 4 by 4 by %-in. seat angles, have resisted up to 2300 lb before slippage occurred. After slippage occurred and the bolts were bearing against the slot, the ultimate loads exceeded 8500 lb until the bolts were sheared.
TABLE 3
Long-Term Aging Tests
| Time Period | Average Modulus of Rupture (psi) |
|---|---|
| 28 days @ 60 F | 270 |
| 6 months | 380 |
| 1½ years | 405 |
| 2½ years | 390 |
| 5½ years" | 390 |
*Both sides exposed to weather.
Average of three test specimens.
TABLE 4
Chemical Resistance
| Chemical Reagents | Ultimate Compressive Strength, f (psi) | Weight Loss (%) |
|---|---|---|
| Base 28-day cure | 6000 | 0 |
| Water | 6300 | -3 |
| 5% H₂SO₄ | 2000 | 60 |
| 10% HCI | 100 | 75 |
| 5% acetic acid | 4100 | 22 |
| 5% citric acid | 3000 | 46 |
| 10% CaCl₂ | 5500 | -4 |
| Leaded gasoline | 4700 | -5 |
| Chlorothene | 4200 | -6 |
| Ethyl alcohol | 5200 | -4 |
| Skydrol 500 hydraulic fluid | 5700 | -2 |
*All specimens exposed for 60 days.
Negative numbers indicate gain in weight or absorption.
TABLE 5
Suggested Allowable Connection Loads
| Diameter (in.) | Embedment (in.) | Pullout | Shear |
|---|---|---|---|
| % | 8 | 950 | 410 |
| ½ | 8 | 1250 | 550 |
| % | 8 | 2050 | 750 |
| Diameter (in.) | Embedment (in.) | Pullout | Shear |
|---|---|---|---|
| % | 4 | 260 | 410 |
| ½ | 4 | 350 | 650 |
| % | 4 | 475 | 750 |
LIFTING BOLTS
CONNECTION BOLTS