Efficiency factors of RCA concrete bottle-shaped struts

What is it about?

A comparison with code-based predictions of efficiency factors of bottle-shaped struts computed using strut-and-tie models from shear test results of RCA concrete beams reported in the literature is presented. The results of the comparison indicate that the AASHTO LRFD code provisions and the proposed efficiency factor model gave conservative predictions for the coarse recycled concrete aggregate concrete bottle-shaped struts although the ACI 318-08 predictions were unconservative. The most accurate predictions were obtained from the Eurocode 2 model, although with an erratic degree of conservatism. The lack of conservatism vis-a-vis the ACI code recommended strut efficiency factors does not per se indicate inferior strength of coarse recycled concrete aggregate concrete but may be attributed to the insensitivity of the ACI code efficiency factors to strut inclination with adjoining tie(s).

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Why is it important?

Concrete made of recycled concrete coarse aggregate (RCA concrete) is a sustainable alternative to natural coarse aggregate concrete. When RCA concrete is used for non-flexural members, there exists a concern whether it will be efficient in resisting compression. This paper is an attempt to ward off that concern.