1 Associate Professor, Department of Construction Science, Texas A&M University, College Station, TX, 77843- 3137, USA, jm-nichols@tamu.edu
ABSTRACT
ABSTRACT
Bond wrenches form the core element of a sound quality control program for masonry construction. These instruments measure a critical element in the manufacture of masonry, achieving an acceptable level of flexural strength. All major masonry codes include design elements for a bond wrench. The major problem for comparison of flexural strength results is the significant variations in the design of bond wrenches. A secondary problem is one of the construction issues for each type of wrench. The objective of this paper is a comparison of flexural results from four bond wrenches, with the additional objective of providing a comparison of the design and construction issues for the four bond wrenches. The test results from a set of 11 prisms, tested using the four bond wrenches in turn, showed a difference between the flexural results for the American bond wrench and the other three bond wrenches using a standard t Test that was significant at the five per cent level. The prisms came from a single pallet of bricks, made with a 1:1:6 mortar at the same time and then stored for more than twelve months at the same location. The relative difficulty of construction of the ASTM C1072 bond wrench may point to the reason for the relative paucity of bond wrenches in the USA. The paucity of bond wrenches means an effective quality control plan is difficult to implement for flexural strength testing, even one based in a university testing laboratory. Suggested changes to ASTM C 1072 are to reduce the mass of the bond wrench and to increase the length of the lever arm.
KEYWORDS: masonry bond wrench, flexural bond testing
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