Service-Load Behavior of Precast/Prestressed Concrete Beams with Recycled Concrete Aggregates

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Title: Service-Load Behavior of Precast/Prestressed Concrete Beams with Recycled Concrete Aggregates

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

Publication: Structural Journal

Volume: 115

Issue: 3

Appears on pages(s): 861-873

Keywords: creep; precast concrete; prestress loss; prestressed concrete; shrinkage; recycled concrete aggregate (RCA); sustained service load; time-dependent deflection

Date: 5/1/2018

Abstract:
This paper describes an experimental investigation on the use of recycled concrete aggregates (RCAs) as replacement for coarse natural aggregates (NAs) in precast/prestressed concrete structures. Specifically, sustained service load tests were conducted on 18 pretensioned beams with two different levels of RCA (50% and 100% by aggregate volume), two sources of high-quality RCA (from both rejected precast members and a construction demolition recycling yard), two different concrete mixture designs, concrete ages of 7 days and 28 days at superimposed service loading, and two different levels of prestressing (to result in beams that are uncracked or cracked under the superimposed load). The loss of prestress over time and midspan deflections of the beam specimens were monitored. Creep and shrinkage strains of accompanying concrete cylinders were also measured. The results showed that the effect of RCA on the service-load behavior of the beams was modest, even at full (100%) aggregate replacement. Additionally, the ability of current code approaches to estimate the measured immediate and sustained load deflections of the beams was not affected by the use of RCA.