Ultimate Behavior of Flexure-Critical Prestressed Concrete Beams with Recycled Concrete Aggregates


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Title: Ultimate Behavior of Flexure-Critical Prestressed Concrete Beams with Recycled Concrete Aggregates

Author(s): Michael R. Brandes and Yahya C. Kurama

Publication: Structural Journal

Volume: 116

Issue: 2

Appears on pages(s): 15-28

Keywords: flexural failure; precast concrete; prestressed concrete; recycled concrete aggregate (RCA); ultimate load

Date: 3/1/2019

This paper describes an experimental investigation on the ultimate load behavior of flexure-critical precast/prestressed concrete beams that use recycled concrete aggregates (RCAs) as replacement for coarse natural aggregates (for example, crushed stone, gravel). Specifically, the measured results from 18 simply supported, normal strength concrete pretensioned beam test specimens are presented and compared with predictions from nonlinear numerical models and existing code methods for conventional concrete. These 18 specimens were obtained by saw-cutting nine longer beams that were previously subjected to sustained service-level loads. The subsequent ultimate load tests of the saw-cut beams were conducted in two series of nine specimens each, with normalized moment-to-shear ratios of 7.6 and 3.6, respectively, defined as the distance from the simple support to the point of load application divided by the depth to the prestressing strands. The other experimental parameters (tested in selected combinations as described in the paper) were the aggregate replacement level (0%, 50%, and 100% by volume), two sources of high-quality RCA (from rejected precast members and a construction demolition recycling yard), and two different levels of prestressing. In general, the use of RCA had a relatively small (as compared with the level of aggregate replacement) effect on the overall ultimate load-versus-deflection behavior of the beams or on the progression of failure. Importantly, the ability of closed-form code design methods and nonlinear numerical models to predict the measured behaviors of the beams was not significantly affected by the level of aggregate replacement.