Masonry Magazine April 1977 Page. 14
Basic Building Code, Section 807.0 Brick Units:
Underburned clay brick shall not be used in isolated brick piers, nor in any part of a building exposed to the weather, nor in a bearing wall which is more than forty (40) feet in height.
EXPERIMENTAL TESTS
At various times interested parties have conducted tests to compare salvaged-brick masonry to masonry of similar new brick. One of the more comprehensive series of tests was conducted several years ago by the Engineering Experiment Station, University of New Hampshire. The following statements are from this test report:10 "The object of this study was to determine by laboratory methods the relative adhesion of different standard mortars to new and used or reclaimed brick (using only) those materials that would generally be employed.
"... as far as materials are concerned... a wall laid up with used or reclaimed bricks differ(s) from one laid up with new bricks... (only) in the adhesion of the mortar to the brick surfaces. It is this quality with which this study is concerned."
Four types of used brick were tested and compared to the same four types of new brick (a total of eight types)." Seven different standard mortars were employed. In describing the testing procedures, the report states, in part:
"The brick to be tested were selected and were cleaned of all loose particles of mortar which could be removed by means of a hammer and wire brush. No attempt, however, was made to remove any particle of mortar, etc. which adhered so firmly to the brick surface that pounding and wire brushing would not release it."
The bulk of the report is too large to reproduce in its entirety. However, the following excerpts from the conclusions to the tests are of interest:
"The adhesion of mortar to new (hard) bricks was materially greater than to second hand brieks. "With but few exceptions the adhesion of mortar to hard bricks was far greater than to soft bricks of the same type.
"Without exception.. failure of the mortar to adhere to the surface of used brick far exceeded the failures of the joint between mortars and new brick. In other words, it appears that the capillary pores of the second hand brick were so plugged. that the new mortar could not gain any appreciable hold on the surface of the brick.
"(The tests indicate) that the adhesive strength of mortar to the hard brick exceeded its cohesive strength
"With (all) used brick cohesive strength of the mortars exceeded many times the adhesive strength of the same mortars to the surfaces of the brick.
" within the limits of the test .. relative adhesion of mortars to reclaimed brick...... (is) less than half what can be expected if the same mortars are used with new brick of the same type and degree of hardness."
REFERENCES
American Standard Building Code Requirements for Masonry; National Bureau of Standards (Miscellane Publication 211); Washington, D. C.; July 15, 1954.
Southern Standard Building Code, 1960-61 Revision; Southern Building Code Congres Code Congress; Brown-Marx Building, Birmingham, Alabama.
National Building Code, 1955 Edition; National Board of Fire Underwriters; 85 John St., 38, N. Y.
Uniform Building Code, 1961 Edition; International Conference nce of of Building Building Officials; 610 S. Broadway, Los Angeles 14, California.
Basic Building Code, Third Edition: Building Officials Conference of America; 1525 E. 53d St., Chicago 15, Illinois.
R5M-12/76
Printed in U.S.A.