The influence of substrate moisture preparation on bond strength of concrete overlays and the microstructure of the OTZ
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- 作者：Hans Beushausen ; Hans.Beushausen@uct.ac.za ; Bjö ; rn Hö ; hlig ; Marco Talotti
- 关键词：Concrete repair ; Bond strength ; Microstructure ; Overlay transition zone ; SEM
- 刊名：Cement and Concrete Research
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：92
- 期：Complete
- 页码：84-91
- 全文大小：1503 K
- 卷排序：92
文摘
The influence of substrate moisture preparation on the direct shear bond strength of composite substrate-overlay specimens was evaluated. The substrate surface was exposed to four different moisture conditions prior to overlay application. A quantitative analysis of backscattered electron images of the microstructure of the overlay transition zone was carried out to quantify its properties along the interface and help analyse the results of the shear bond testing. The results show that pre-wetting the substrate surface prior to application of the overlay provides no added benefit towards increasing the bond strength and may in some cases reduce bond strength significantly. The microstructural investigations confirmed that pre-saturated substrates increase the w/c ratio and the porosity in the overlay transition zone (OTZ), which was found to have a thickness of about 100 μm. The OTZ in overlays cast on dry substrate surfaces had lower porosity and an increased amount of anhydrous cement.