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9 <br />placing a piece of core across two horizontal bearing supports <br />and then applying a vertical line load to fail the sample at <br />its center. The flexural strength is then computed as follows: <br />P ~ 8PL <br />frDa <br />where P ~ failure load <br />L ~ length between bearing supports <br />D - sample diameter <br />[12] <br />Bulk Density. The apparent specific gravity or bulk <br />density was determined using saturated weights if the materials <br />did not disintegrate in the presence of water. If water induced <br />disintegration was a problem, the bulk densities were determined <br />using the material volume. The formulas used were: <br />• W <br />G ~ ~-Ws [13] <br />G ~ V7 [14] <br />w <br />where Wo ~ dry weight in air <br />Ww ~ saturated weight in air <br />Ws ~ saturated weight in water <br />V ~ volume <br />Yw ~ unit weight of water <br />Porosity. The porosity of a material is the ratio of the <br />voids or pores to the overall volume of the material. Its <br />determination was made by drying, measuring and weighing a sample <br />and then allowing its pores to fill with water during overnight <br />submersion. The porosity was then determined as follows: <br />r <br />SEEGMILLEN INTERNATIONAL <br />