Bond strength prediction of tension lap splice for deformed steel bars in recycled aggregate concrete

Splice strength of deformed steel bars embedded in recycled aggregate concrete was experimentally investigated using 48 bottom-cast scaled splice beam specimens detailed with unconfined contact lap splices and tested under four-point bending. The following variables were investigated: concrete grade (normal-and medium-strength), recycled concrete aggregate replacement level (0, 50 and 100%), rebar diameter (12 and 20 mm), splice length (15 and 25 d(b)), rebar surface characteristics and concrete cover to rebar diameter (c/d(b) = 1.25 and 2). Bond behaviour and failure modes were noted to be similar in the natural and in the recycled aggregate concrete and a regression analysis of the results shows that f'(3/4)(c) provides a good representation of the influence of recycled aggregate concrete grade on splice strength. A descriptive bond strength equation has been proposed for recycled aggregate concrete and it is noted that the MacGregor model (for conventional concrete) gave relatively the most accurate and conservative bond strength predictions for the recycled aggregate concretes under investigation. Bond strength is predicted based on analytical model available in literature.