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Uniformity of bond strength of prestressing strands in conventional flowable and self-consolidating concrete mixtures



Title: Uniformity of bond strength of prestressing strands in conventional flowable and self-consolidating concrete mixtures
Author(s): K.H. Khayat, N. Petrov, E.K. Attiogbe, H.T. See
Paper category : conference
Book title: International RILEM Symposium on Self-Compacting Concrete
Editor(s): O. Wallevik and I. Nielsson
Print-ISBN: 2-912143-42-X
e-ISBN: 2912143713
Publisher: RILEM Publications SARL
Publication year: 2003
Pages: 703 - 712
Total Pages: 10
Nb references: 10
Language: English


Abstract: The principal objective of this study is to evaluate the uniformity of bond strength to prestressing strands and in-situ mechanical properties of flowable concrete along experimental wall elements. Four self-consolidating concrete (SCC) mixtures and two conventional flowable mixtures suitable for prestressed and precast applications were evaluated. The mixtures incorporate 20% fly ash replacement and were used for casting experimental wall elements measuring 1.54 m in height, 1.1 m in length, and 0.2 m in width. Two types of viscosity-modifying admixtures (VMA) and two high-range water reducers were employed. Two of the walls were steam-cured, while the remaining elements were air-cured. Each wall had 16 prestressing strands, four per row positioned at four levels that were subjected to pullout tests at 1 and 28 days of age. All mixtures developed 1-day compressive strength greater than 40 MPa. Uniform distribution of in-place compressive strength and adequate bond to the prestressing strands were obtained with relatively small variations along experimental wall elements. The 1- and 28-day top-bar effect ratios varied between 0.9 and 1.9. These values were lower for the air-cured mixtures compared to the steam-cured mixture. The top-bar effect in the air-cured SCC was lower than in the steam-cured highly flowable concrete. For steam curing, the top-bar effect was larger in the case of the SCC than in the case of the conventional flowable concrete at 1 day, but lower at 28 days. Overall, the strand bond is not compromised in stable SCC. The top-bar effect is shown to be sensitive to the type of VMA used in the SCC.


Online publication: 2003-08-21
Publication type : abstract_only
Public price (Euros): 0.00