In this paper we made clear unique characteristics such as self-solidification and self-adhesion of coral reef rock (C.R.R.), graded slag and lime-treated materials, and investigated the rational application of these materials to base courses of airport pavements on the basis of results in both laboratory tests and field test pavements.
　The main reuslts are as followd:
　(1) C.R.R. has relatively high strength at the early age from the self-solidification, but its increasing rate is little. On the other hand graded slag and lime-treated material are generally slow-setting, and the strength is gradually inrceasing for a long term.
　(2) As for strength recovery ability from self-adhesion, C.R.R. keeps it without distinction of age, but in graded slag and lime-treated material the ability is decreasing as the age is advancing in spite that it is high at the early age.
　(3) The modulus of deformation (E) of these materials in solid state is related to he unconfined compression strength (σc) as E=600σc0.5(σc≦40kg/cm2), E=22
.5σc1.49(σc>40kg/cm2).
　(4) Concerning layer equivalencies of these materials as base, the following results have been obtained.
　a)C.R.R. in soaked condition has just 1.0 like graded crushed stone.
　b)C.R.R. in unsoaked condition has about 1.3.
　c)C.R.R. stabilized with 2% cement has 1.5.
　d)Graded slag has 1.0 at the construction stage but 1.8 at the age of six monthes.
　e)Lime-treated material has highest value among three materials, and 1.8 at the age of six monthes.