Performance of Toughness Indices for Steel Fiber Reinforced Shotcrete
Resource
Tunnelling and Underground Space 17: 69-82
Journal
Tunnelling and Underground Space 17
Pages
69-82
Date Issued
2002
Date
2002
Author(s)
Abstract
To indicate the flexural toughness of Steel Fiber Reinforced Concrete or Shotcrete (SFRC or SFRS), several indices have been developed and some of them are now national standards. Whether these indices can properly indicate the actual toughness of sprayed shotcrete is of concern. This paper aims at assessing the performance of the indices for a variety of SFRS sprayed at job site, instead of being cast in laboratory. The mixture actually sprayed, especially the steel fiber content, may differ from the mixture before spraying and this inherently affects the toughness of SFRS, therefore, counting of steel fiber over the fracture surface of a tested beam was conducted. This is helpful in interpreting the experimental results. The indices evaluated include: toughness index (I); residual strength factor (R); equivalent flexural strength (fc); and the indices based on the residual flexure stress method, including a Norwegian index, f, and a proposed relative residual stress factor fm. The experimental results reveal that increases of steel fiber content cement content, silica fume content, and the aspect ratio of the steel fibers improve the toughness of SFRS. The performance of the indices is evaluated on the basis of the following factors: independence with regard to the testing machine as well as sufficient sensitivity to the ingredients of SFRS. The results of evaluation indicate that the indices based on the residual flexural stress method, and involving greater deflection, tend to perform better in indicating the toughness of SFRS. © 2002 Elsevier Science Ltd. All rights reserved.
Type
journal article
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