<p><p><strong>References:<br></strong><em>Bruce and Juran (1997)<br>Gibler et al. (2005)<br>Gomez et al. (2008a, 2008b)<br>Sabatini et al. (2005)</em></p><p><strong>Method Summary</strong></p><p>Cube testing is traditionally performed as part of grout inspection and is used to verify the unconfined compressive strength of the grout. Cube testing can take place to confirm acceptability of the grout mix as part of verification, ultimate, and proof load tests. A grout sample is molded into cubes and after a specified number of days each cube is loaded in compression to failure according to AASHTO T106/ASTM C109 “Standard Test Method for Compressive Strength of Hydraulic Cement Mortars.” Tests are typically performed after 3, 7, and 28 days of set time. The required strength will vary depending on the project.</p><p><strong> </strong><strong>Accuracy and Precision</strong></p><p>Confirming the unconfined compressive strength of the grout for use in the project is a straightforward but not always accurate process. Curing and handling conditions are critical and can have major impact on the results obtained.</p><p><strong>Adequacy of Coverage</strong></p><p>The frequency of cube tests varies depending on the project. Sabatini et al. (2005) recommends “one set of three grout cubes be taken for every 10 micropiles installed, or every day for each grout plant in operation, whichever occurs more frequently.”</p><p><strong>Implementation Requirements </strong></p><p>Measuring unconfined compressive strength of the grout is a simple procedure. However, the time required for the sample to set up needs to be considered in the timeframe of construction processes.</p><p><strong>General Comments</strong></p><p>Measuring the unconfined compressive strength of the grout verifies the acceptability of the grout mix design, which is critical to successful micropile implementation. Quality grout allows the micropile to satisfactorily support the anticipated service load. Because cube testing is a retrospective test, specific gravity testing is typically preferred. Cube testing should be performed early in the project to verify the correct mix design and then replaced with specific gravity tests correlated to the results obtained from the cube tests.</p></p>