Comparison of Alkali-Silica Reaction Gel Behavior in Mortar at Microwave Frequencies


Alkali-silica reaction (ASR) is one common cause of concrete deterioration and has been a growing concern for decades. Water, in the presence of reactive aggregates used to make concrete, plays a major role in the formation, sustainment, and promotion of this reaction. In this process, free water becomes bound within ASR gel, resulting in expansion and deterioration of concrete. Devising a test approach that is sensitive to the state of water (free or bound) has the potential to become a method-of-choice for ASR detection and evaluation, since such measures can be used to detect ASR and potentially quantify reaction progression. Microwave signals are sensitive to the presence of water, since the water relaxation frequency occurs in this frequency range. Recently, microwave nondestructive evaluation techniques have shown great potential to evaluate and distinguish between ASR-affected mortar samples and those without ASR gel. Given the complex chemistry of ASR products, their behavior is expected to differ at different microwave frequency bands. To evaluate the sensitivity of different frequencies to the presence of ASR, dielectric constant measurements were conducted at R-band (1.7-2.6 GHz), S-band (2.6-3.95 GHz), and X-band (8.2-12.4 GHz). This paper presents the measured results for mortar samples made with reactive and nonreactive aggregates. The measurement results and subsequent analyses aid in a better understanding of the microwave signals interaction with ASR-affected cement-based materials. Moreover, the results indicate that S-band appears to be the most appropriate frequency band for ASR evaluation in the microwave regime.


Electrical and Computer Engineering

Keywords and Phrases

Aggregates; Concrete Aggregates; Concrete Testing; Concretes; Deterioration; Frequency Bands; Microwave Frequencies; Mortar; Nondestructive Examination; Permittivity; Signal Detection; Silica; Alkali-Silica Reaction; Cement Based Material; Concrete Deterioration; Dielectric-Constant Measurements; Different Frequency; Microwave Non-Destructive Testing; Non-Destructive Evaluation Techniques; Relaxation Frequency; Microwaves; Alkali-Silica Reaction (ASR) Gel; Concrete; Dielectric Constant; Microwave Nondestructive Testing

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Article - Journal

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© 2015 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jul 2015