Results of research conducted on mechanical expansion anchors for the purpose of revising an existing acceptance specification used by the California Department of Transportation are presented in this paper. The main objective of the research was to refine a portion of the standard specification dealing with mechanical expansion anchors, whose key requirement is to limit the amount of displacement that a mechanical expansion anchor can exhibit while being subjected to moderate sustained tensile loading. The scope of the work included (a) classifying mechanical expansion anchors from 14 manufacturers into five main categories and then further segregating them into types within each category, (b) conducting 465 ultimate tensile load tests on 1/4-, 1/2-, and 3/4-in.-diameter zinc-electroplated mechanical expansion anchors to determine the point at which slip or yield occurs and their mean ultimate strength, (c) performing a total of 394 sustained tensile load creep tests at two different concrete strengths, (d) determining physical properties and chemical composition of suitable anchors, and (e) refining the standard specification and preparing a standard test method, California Test 681. The main alteration in the anchor specification included lowering the magnitudes of some sustained tension test loads for the required creep test and reducing the permitted displacement (0.050 to 0.035 in.) and time period (100 to 48 hrs) during which creep is monitored. The two anchor types found to be the best in each of their respective categories -- shell and stud -- are (a) the shell nondrilling internal plug and (b) the stud wedge.
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