Use of Near-Field Microwave Reflectometry to Evaluate Steel Fiber Distribution in Cement-Based Mortars


Nonuniform distribution of fibers in steel fiber-reinforced cement-based materials can lead to heterogeneous hardened properties directly impacting mechanical properties. Given the highly conductive and strong scattering characteristics of steel fibers at microwave frequencies, near-field microwave reflectometry can offer an effective and robust methodology for evaluating steel fiber content and distribution in these materials. This paper evaluates the steel fiber distribution in fiber-reinforced cement-based mortar (FRCM) using near-field microwave reflectometry. The statistical properties of the microwave reflection experiments conducted at 3 and 10 GHz were correlated with fiber content and distribution in FRCM samples made with various fiber contents ranging from 0 to 3%. Image analysis techniques were also implemented to assess fiber distribution on cut surfaces at different thicknesses. The results of the microwave reflection properties are found to correlate well with fiber density determined from image analysis on hardened samples and fiber homogeneity obtained from freshly cast prism samples. A 3D microwave image of sample with 3% fiber content exhibited relatively high nonuniform image intensity.


Electrical and Computer Engineering

Second Department

Civil, Architectural and Environmental Engineering

Keywords and Phrases

Cements; Conductive Materials; Fiber Reinforced Materials; Fibers; Hardening; Image Analysis; Microwaves; Mortar; Nondestructive Examination; Reflection; Reflectometers; Reinforced Plastics; Reinforcement; Steel Testing; Fiber Distribution; Fiber Reinforced Cement; Image Analysis Techniques; Microwave Non-Destructive Testing; Microwave Reflection Properties; Microwave Reflectometry; Non-Uniform Distribution; Statistical Properties; Steel Fibers; Cement; Microwave Radiation; Mortar; Nondestructive Testing; Reflectometry; Steel; Fiber Clumping; Microwave Nondestructive Testing; Steel Fiber

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


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© 2017 American Society of Civil Engineers (ASCE), All rights reserved.

Publication Date

01 Jul 2017