ABSTRACT
Abstract Since 1985, sev e r a l studies have been c a r r i e d out at U n i v e r s i t y College Galway to i n v e s t i g a t e the f a t i g u e performance of bituminous ma t e r i a l s i n repeated u n i - a x i a l tension-compression. The bituminous specimens are compacted i n standard c y l i n d r i c a l moulds using a double a c t i n g s t a t i c load. The most recent study on dense bitumen macadam under constant s t r e s s loading c o n d i t i o n s would on balance suggest a t e n t a t i v e conclusion that i n c r e a s i n g temperature has a b e n e f i c i a l e f f e c t on the i n i t i a l s t r a i n f a t i g u e l i f e r e l a t i o n s h i p . The same trend was observed to occur when the s t i f f n e s s of the mix was decreased (by using e i t h e r a higher t e s t temperature or a s o f t e r bitumen). For the l i m i t e d range of v a r i a b l e s considered, nominal aggregate grading, t e s t temperature and bitumen grade were found not t o s i g n i f i c a n t l y a f f e c t the p o s i t i o n s of the s t r e s s f a t i g u e l i f e r e l a t i o n s h i p s . Increasing bitumen content i n the range of from 3 . 4 t o 4.6% was found to s i g n i f i c a n t l y improve the p o s i t i o n s of both the i n i t i a l s t r a i n and s t r e s s f a t i g u e l i n e s .
