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75CHAPTER 4: MATERIALSThe materials that were implemented in this research can be separated into two maincategories: matrix loess soil and pier composition mixture materials.Loess MaterialWhen performing characterization of material being utilized in this research, the first andforemost consideration had to be given to the material used as pier matrix soil. While it is notuncommon to place full-scale aggregate piers in silty clay, peat and other weak deposits withexcessive amount of moisture, unit weight of 10 kN/m 3 , compression index 0.27 and initialvoid ratio of 10 (Lien et.al. 2002), the moisture content of the soil to be used for model pierplacement was targeted at 30% and the undrained shear strength to range between 30-80 kPa.In order to be able to identify target moisture content and predict the level of compaction, aStandard Proctor compaction test was performed as outlined by ASTM D698-00. TheStandard Proctor curve was developed at 13, 15, 17, 19 and 21 percent moisture contentlevels (See Figure 45). The maximum dry unit weight of 1,700 kg/m 3 and optimum moisturecontent of 19 percent were obtained for the loess material.The value for specific gravity of Western Iowa Loess was obtained by Mark Thompson andwas estimated at 2.72. As a result the Zero Air Void Curve was constructed as well. Since thetest bed had to be prepared four times for different single and groups of pier tests, the unitweight and moisture content data varied as it can be seen in Figure 46.Another laboratory test that was performed on loess material was the particle size distributiontest. Sometimes referred as gradation test, the examination was given to the level of loessfineness through performing a sieve and hydrometer analysis. The procedure was completedon a representative soil sample and according with the guidelines outlined by ASTM D422-63 (Figure 46).