Tek eksenli ve kayma yükleri etkisi altında beton-beton arayüzünün mekanik özellikleri

Öz

Bu deneysel çalışmada eski betonu temsilen normal dayanımlı beton ile yeni betonu temsil eden farklı tipteki yüksek dayanımlı betonlar arasındaki aderans dayanımının incelenmesi amaçlanmıştır. Farklı karakteristiğe sahip yeni beton elde etmek amacı ile silis dumanı ve çelik lif kullanılmıştır. Farklı kompozisyonlara sahip yüksek dayanımlı betonun aderans dayanımına etkisi eğik kayma (slant shear) ve çift yüzey kayma (bi-surface shear) deneyleri ile belirlenmiştir. Ayrıca eski/yeni beton kompozitlerin eksenel basınç yükü etkisi altındaki mekanik özellikleri deneysel olarak belirlenmiştir. Elde edilen sonuçlara göre yeni beton dayanımının ve kayma deneyinde kullanılan yöntemin aderans dayanımı üzerinde önemli bir etkisi olduğu görülmüştür. Eğik kayma deneyinin çift yüzey kayma deneyine göre 6-12 kat yüksek aderans dayanımı verdiği tespit edilmiştir. Paralel model yaklaşımının eski/yeni beton kompozitlerin elastisite modülünün tahmininde tatminkar sonuçlar verdiği belirlenmiştir.

Anahtar Kelimeler

• Yapışma dayanımı,Eğik kayma deneyi,Çift yüzey kayma deneyi

Mechanical properties of concrete to concrete interfaces under uniaxial and shear forces

Abstract

This research aims to evaluate the bond strength between normal strength substrate concrete and different types of high strength overlay concretes. In order to obtain different characteristics in the overlay concrete, silica fume and steel fibers were used. The slant shear and bi-surface shear tests were conducted to quantify the effect of different high strength concrete compositions on the bond strength. The mechanical properties of overlay/substrate concrete composites were also analysed on cylindrical samples under uniaxial compression load. The results indicate that the strength of overlay plays an important role on the bond mechanism. The bond strength is found to be dependent on the test mechanism. The test results showed that the bond strength was about 6-12 times higher in slant shear test compared to the bi-surface shear test. The application of parallel model approach on the overlay/substrate concrete composites was found to be quite satisfactory to predict the elastic modulus of the composite.

Keywords

• Bond strength,Slant shear test,Bi-surface shear test

Kaynakça

1. Indrajit R, Julio FD, Shiwei L. “Interface evaluations of overlay-concrete bi-layer composites by a direct shear test method”. Cement and Concrete Composites, 27(3), 339-347, 2005.
2. Espeche A, Léon J. “Estimation of bond strength envelopes for old-to-new concrete interfaces based on a cylinder splitting test”. Construction and Building Materials, 25(3), 1222–1235, 2011.
3. Beushausen H, Höhlig B, Talotti M. “The influence of substrate moisture preparation on bond strength of concrete overlays and the microstructure of the OTZ”. Cement and Concrete Research, 92, 84-91, 2017.
4. Momayeza A, Ehsanib MR, Ramezanianpoura AA, Rajaiea H. “Comparison of methods for evaluating bond strength between concrete substrate and repair materials”. Cement and Concrete Research, 35(4), 748-757, 2005.
5. Diab AM, Elmoaty M, Eldin MRT. “Slant shear bond strength between self-compacting concrete and old concrete”. Construction and Building Materials, 130, 73-82, 2017.
6. Saldanha R, Eduardo J, Danial C, Pedro S. “A modified slant shear test designed to enforce adhesive failure”. Construction and Building Materials, 41, 673-680, 2013.
7. Eduardo J, Branco F, Silva V. “Concrete-to- concrete bond strength. Influence of the substrate surface”. Construction and Building Materials, 18(9), 675-681, 2004.
8. Pedro S, Eduardo J. “Factors affecting bond strength between new and old concrete”. ACI Materials Journal, 108(4), 449-456, 2011.

9. Rith M, Kim YK, Lee SW, Park JY, Han SH. “Analysis of in situ bond strength of bonded concrete overlay”. Construction and Building Materials, 111, 111-118, 2016.
10. Júlioa ENBS, Branco FAB, Silvac VD, Lourenço JF. “Influence of added concrete compressive strength on adhesion to an existing concrete substrate”. Building and Environment, 41, 1934-1939, 2006.
11. European Committee for Standardization. “Cement. Composition, specifications and conformity criteria for common cements”. Brussels, Belgium, EN 197-1, 2011.
12. European Committee for Standardization. “Testing Hardened Concrete. Compressive Strength of Test Specimens”. Brussels, Belgium, EN 12390-3, 2009.
13. American Society for Testing and Materials. “Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens”. West Conshohocken, PA, USA, ASTM C496, 2011.
14. American Society for Testing and Materials. “Standard Test Method for Static Modulus of Elasticity and Poisson’s Ratio of Concrete in Compression”. West Conshohocken, PA, USA, ASTM C469, 2014.
15. Kizilkanat AB, Kabay N, Akyüncü V, Chowdhury S, Akça AH. “Mechanical properties and fracture behavior of basalt and glass fiber reinforced concrete: An experimental study”. Construction and Building Materials, 100, 218–224, 2015.
16. American Society for Testing and Materials. “Standard Test Method for Bond Strength of Epoxy-Resin Systems Used with Concrete by Slant Shear”. West Conshohocken, PA, USA, ASTM C882, 2013.
17. Brandt AM. Cement-Based Composites Second Edition Materials, Mechanical Properties and Performance. Taylor & Francis, 2009.
18. Sahmaran M, Yücel HE, Yildirim G, Al-Emam M, Lachemi M. “Investigation of the Bond between Concrete Substrate and ECC Overlays”. Journal of Materials in Civil Engineering, 26(1), 167-174, 2014.