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In 1996, ASTM approved a specification for a new product, called mortar cement, intended for use in applications requiring masonry with high tensile bond strength. An inter-laboratory testing program is planned; the objectives will include the determination of intra- and inter-laboratory coefficientsof variation of bond-wrench results for that product. Prior to conducting the inter-laboratory testing program, it is necessary to set the test procedures and variables to be used. Some of those procedures (such as the precise control of flow, the use of jigs, templates and drop hammers to construct prisms, and bag curing), have already been found to reduce the variability of bond-wrench results, are included in ASTM C1329-96, Standard Specification for Mortar Cement, and ASTM C1357-96, Standard Test Methods for Evaluating Bond Strength, and will be used in the inter-laboratory study. However, other test procedures must still be established. To do so, and prior to the inter-laboratory study, a pilot “ruggedness study” was conducted; the objective was to determine which additional factors should be controlled during the inter-laboratory study. In this paper, the conduct and results of that ruggedness study are presented and discussed in the light of current bond-wrench testing procedures, and specific changes are recommended to ASTM bond-wrench testing standards.
bond, masonry, mortar, mortar cement, ruggedness
Former Graduate Research Assistant, The University of Texas at Austin,
Phil M. Ferguson Professor in Civil Engineering, The University of Texas at Austin,
Program Manager, Masonry, Portland Cement Association, Skokie, Illinois