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Drying shrinkage of concrete made from recycled concrete aggregate

Conference Paper


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Abstract


  • Recycled concrete aggregates (RCA) are used in new concrete mixes, termed recycled aggregate

    concrete (RAC). Among losses in most fresh and hardened properties, literature reports that RAC suffers

    increased levels of drying shrinkage compared to equivalent mixes incorporating conventional aggregates.

    This paper describes the procedure and results of a range of experiments conducted on a commercial RCA

    and its use in new concrete mixes. In particular, this work quantifies the effect 100% RCA has on the drying

    shrinkage of the resulting concrete. A commercially available RCA was characterised by analysing the particle

    shape and texture, percentage of solid contaminants, particle size distribution, water absorption and particle

    densities. The types of rocks present were analysed through the preparation of thin sections. Three concrete

    mixes were prepared and tested for workability, 7 and 28 day compressive strengths and 112 days of

    drying shrinkage. The mixes included a 40 MPa control mix incorporating natural crushed aggregates and two

    equivalent RAC mixes, one with 30% fly ash as a partial cement replacement and one without. The results indicated

    that the commercial RCA has been produced quite efficiently with negligible solid contaminants.

    However, due to adhered mortar found on the aggregate particles, the RCA was found to have rougher particle

    textures, increased water absorptions and lower densities than conventional crushed aggregates. Due to

    these properties and the subsequent increased water demand the RAC mixes suffered lower compressive

    strengths and higher drying shrinkages than the control mix. The RAC mix incorporating no fly ash was

    found to have a 25% average increase in the 112 day drying shrinkage from the control mix while the fly ash

    mix only had a 7% increase.

Authors


Publication Date


  • 2012

Citation


  • Whiting, B. A., McCarthy, T. J. & Lume, E. (2012). Drying shrinkage of concrete made from recycled concrete aggregate. 22nd Australasian Conference on the Mechanics of Structures and Materials (pp. 1199-1204).

Scopus Eid


  • 2-s2.0-84881152310

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1810&context=eispapers

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/804

Start Page


  • 1199

End Page


  • 1204

Abstract


  • Recycled concrete aggregates (RCA) are used in new concrete mixes, termed recycled aggregate

    concrete (RAC). Among losses in most fresh and hardened properties, literature reports that RAC suffers

    increased levels of drying shrinkage compared to equivalent mixes incorporating conventional aggregates.

    This paper describes the procedure and results of a range of experiments conducted on a commercial RCA

    and its use in new concrete mixes. In particular, this work quantifies the effect 100% RCA has on the drying

    shrinkage of the resulting concrete. A commercially available RCA was characterised by analysing the particle

    shape and texture, percentage of solid contaminants, particle size distribution, water absorption and particle

    densities. The types of rocks present were analysed through the preparation of thin sections. Three concrete

    mixes were prepared and tested for workability, 7 and 28 day compressive strengths and 112 days of

    drying shrinkage. The mixes included a 40 MPa control mix incorporating natural crushed aggregates and two

    equivalent RAC mixes, one with 30% fly ash as a partial cement replacement and one without. The results indicated

    that the commercial RCA has been produced quite efficiently with negligible solid contaminants.

    However, due to adhered mortar found on the aggregate particles, the RCA was found to have rougher particle

    textures, increased water absorptions and lower densities than conventional crushed aggregates. Due to

    these properties and the subsequent increased water demand the RAC mixes suffered lower compressive

    strengths and higher drying shrinkages than the control mix. The RAC mix incorporating no fly ash was

    found to have a 25% average increase in the 112 day drying shrinkage from the control mix while the fly ash

    mix only had a 7% increase.

Authors


Publication Date


  • 2012

Citation


  • Whiting, B. A., McCarthy, T. J. & Lume, E. (2012). Drying shrinkage of concrete made from recycled concrete aggregate. 22nd Australasian Conference on the Mechanics of Structures and Materials (pp. 1199-1204).

Scopus Eid


  • 2-s2.0-84881152310

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1810&context=eispapers

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/804

Start Page


  • 1199

End Page


  • 1204