Crushed stone and sea sand are generally used for concrete materials in Okinawa because of no river adequate to obtain ordinal river aggregates. It is said the properties of aggregates in Okinawa is much inferior to that of normal aggregates.
　The paper discusses the problems and the countermeasures on aggregates of Okinawa, cement mortar and concrete used with the aggregates, due to the basic experimental work.
　The testing items are specific gravity and water absorption for aggregates, compressive strength for concrete and so forth.
　The experimental results indicate the following characteristics regarding aggregates and concrete.
(1) Coarse aggregates have generally angular and flaky shape, and solid volume percentage shows lower.
(2) Fine aggregates have the properties of lower specific gravity and larger water absorption.
(3) Concrete uses with aggregates show lower compressive strength and worse workability.
　Recommended practices for using aggregates in Okinawa are as follows.
(1) To higher solid volume percentage of coarse aggregates, by way of adopting the adequate crushers.
(2) To combine with high quality materials such as crushed sand, with regards fine aggregates.
(3) To increase unit weight of cement up to 50 to 70 kg pertaining to strength property of concrete.