Abstract: This paper discusses the mix design of filling materials in Pre\|stressed High\|strength Concrete (PHC) pipe piles that will be subjected to a static load test in which deformations will be measured using a sliding micrometer. The materials and their gradation selection requirements are optimized through evaluation of the mechanical properties of the filling materials. Properties evaluated include unconfined compressive strength, deformation moduli and Poison's ratio. Factors that influence the performance of the filling materials during the static load test are also presented.