<p><p><strong>Reference(s):</strong></p><p><em>AMEC (2006)<br>Warren (2007)<br>Wiles and Shepherd (1999)<br>Zhang and Tao (2006)</em></p><p><strong>Method Summary</strong></p><p>The test for unconfined compressive strength is covered by ASTM D1633. This standard describes two test methods. Method A makes use of the same compaction equipment and molds used for other soil-cement tests commonly available in geotechnical laboratories. Method A is considered to give a relative measure of strength rather than a rigorous determination of compressive strength. Because of the lesser height to diameter ratio (1.15) of the cylinders, the compressive strength determined by Method A will normally be greater than that for Method B. Method B, because of the greater height to diameter ratio (2.00), gives a better measure of compressive strength from a technical viewpoint since it reduces complex stress conditions that may occur during the shearing of Method A specimens. In practice, Method A has been more commonly used than Method B. As a result, it has been customary to evaluate or specify compressive strength values as determined by Method A.</p><p>Resilient modulus testing is covered by AASHTO T307. This method covers procedures for preparing and testing untreated subgrade soils and untreated base or subbase materials for determination of resilient modulus (M_R) operational-representative conditions. Test samples are taken from soil sampling tubes or remolded in 71-mm (2.8 in) diameter molds at density and moisture values representative of field conditions. They are then tested in a modified triaxial cell.</p><p><strong>Accuracy and Precision</strong></p><p>In order to evaluate the potential reuse opportunities for a given stack, the source of the rock used to generate the Phosphogypsum (PG) must be taken into consideration to determine the type and levels of impurities present. Standards are well established in the geotechnical engineering.</p><p><strong>Adequacy of Coverage</strong></p><p>The QC/QA method can be implemented using a reasonable number of tests.</p><p><strong>Implementation Requirements </strong></p><p>Implementation requirements for the QC/QA methods are not excessive.</p></p>