A compensated magnetic probe for steel fiber reinforced concrete monitoring

Abstract

SFRC, steel fiber reinforced concrete, is a widely employed material in building construction. The fibers assure a better mechanical behavior with respect to plain concrete. Testing the material "on the site" represents a very important goal. In particular, there is a strong need to have a reliable measurement method available which allows assessing information about size, orientation and concentration of the fibers. Currently, the measurement techniques present some important restrictions (laboratory applications only, sensitivity to the humidity, complexity, cost etc). This paper presents a new approach, based on a simple, low-cost sensor employing a Cshaped ferrite core. Four coils have been wound on it: two provides the generation of the magnetic flux and two allow picking up the emf. By leaning the probe on the SFRC surface and by measuring the variation of the mutual inductance between the two pairs of winding, it is possible to discriminate the average orientation of the fibers, and to obtain information about their concentration. It has also been proven that the size and the geometrical properties of the fibers result in a variation of the power losses.

Low Frequency Electrical and Magnetic Methods for Non-Destructive Analysis of Fiber Dispersion in Fiber Reinforced Cementitious Composites: An Overview

“…Methods which employ a probe sensitive to the magnetic properties of the steel fibers has been recently proposed and validated [22–24]. They rely on the fact that the steel fiber reinforced concrete is a mixture of two materials with very different magnetic permeability.…”

Electrical resistivity measurements to determine the steel fiber content of concrete

“…Other methods based on inductivity (see, e.g., Refs. [36][37][38][39][40][41][42][43][44][45][46] or permittivity (see, e.g., Refs. [47][48][49][50][51][52][53][54] are also used in scientific research but cannot be realized yet in the process of construction of huge elements or even buildings.…”

Fibre Distribution Characterization of Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) Plates Using Magnetic Probes

“…The C-shape ferromagnetic probe test was proposed by Faifer et al [ 20 ]. However, the main focus of their research was on the theoretical background modelling and derivation of the probe, for example, the simulation of flux density of the probe [ 21 ].…”