Efficiency factors of recycled aggregate concrete bottle-shaped struts

Efficiency factors of steeply inclined unreinforced recycled aggregate concrete bottle-shaped struts have been experimentally found and compared with their natural coarse aggregate (NCA) concrete counterparts and the predictions of ACI 318-08, AASHTO bridge design specifications and Eurocode 2. The experiments involved testing of scaled deep beam specimens configured so as to develop bottle-shaped struts under applied loading. The replacement level of the coarse recycled concrete aggregate (RCA) in the saturated surface-dry moisture condition was the only parameter under investigation. Service load crack widths in the NCA and the RCA concrete bottle-shaped struts were smaller than the permissible value, their failure modes were similar, their measured efficiency factors were comparable and the coarse aggregate replacement level had an insignificant effect on the measured efficiency factors. The efficiency factor models in the ACI 318-08 and Eurocode 2, which are insensitive to strut inclination, gave overly conservative predictions, whereas relatively accurate predictions were obtained from the AASHTO bridge design specifications and an efficiency model given in the literature, both of which account for the effect of inclination on efficiency factors of bottle-shaped struts.