A New Method to Determine the Steel Fibre Content of Existing Structures—Evaluation and Validation

Thomas Matschei,Simon Cleven,Michael Raupach

doi:10.3390/app12010454

Abstract

The in-situ measurement of the content and orientation of steel fibres in concrete structures is of great importance for the assessment of their specific mechanical properties, especially in the case of repair. For existing structures, the actual fibre content as well as the orientation of the fibres, which is based on many factors such as casting or compacting direction, is typically unknown. For structural maintenance or rehabilitation, those factors have to be determined in order to apply meaningful structural design calculations and plan necessary strengthening methods. For this reason, a new method based on the analysis of drilling cores of concrete structures has been established. The newly developed non-destructive test setup used in this research consists of a framework for cylindrical specimens in combination with an LCR meter to determine the electrical resistance of the fibre reinforced concrete. In combination with a suitable FEM model, concretes with fibre contents up 80 kg/m3 were analysed to derive a first model to assess the actual fibre content of steel fibre reinforced concretes. After a calibration of the literature’s equation by use of an adjusted aspect ratio for the analysis of drilling cores, the estimation of the fibre content is possible with high accuracy for the tested material combination. The results show that the newly developed test method is suitable for the rapid and non-destructive structural diagnosis of the fibre content of steel fibre reinforced concrete based on drilling cores using electrical resistivity measurements.

Highlights

With the help of an optimised experimental setup, this study focuses on the validation of electrical resistivity as a novel approach to assess the fibre content and orientation of drilling cores extracted from concrete plates with fibre contents up to 80 kg/m3
As already seen for the cubic specimens, increase the fibreresults, content results in a between the results of different fibre contents and the is much lower for the drilling lower electrical resistivity
The basic test setup was already developed, and the FEM model was constructed in ing cores

Summary

Introduction

Academic Editors: Diego Gino and Gabriele Bertagnoli. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Based on a recently developed easy-to-use test setup [1], a new application to assess the steel fibre content of existing structures based on the electrical resistivity analysis of drilling cores is described in this two-part study. In the first part (see [2]), the test setup was adapted. A new numerical model was generated to simulate the flow of the alternating current, which enables the calculation of the electrical resistivity in different specimen directions. An in-depth literature review on the methods concerning the determination of the steel fibre content is presented in [1,2]

Methods

Results

Discussion

Conclusion