Nondestructive Wireless Monitoring of Early-Age Concrete Strength Gain Using an Innovative Electromechanical Impedance Sensing System

C. P. Providakis,E. V. Liarakos,E. Kampianakis

doi:10.1155/2013/932568

C. P. Providakis, E. V. Liarakos + Show 1 more

Open Access

https://doi.org/10.1155/2013/932568

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Abstract

Monitoring the concrete early-age strength gain at any arbitrary time from a few minutes to a few hours after mixing is crucial for operations such as removal of frameworks, prestress, or cracking control. This paper presents the development and evaluation of a potential active wireless USB sensing tool that consists of a miniaturized electromechanical impedance measuring chip and a reusable piezoelectric transducer appropriately installed in a Teflon-based enclosure to monitor the concrete strength development at early ages and initial hydration states. In this study, the changes of the measured electromechanical impedance signatures as obtained by using the proposed sensing system during the whole early-age concrete hydration process are experimentally investigated. It is found that the proposed electromechanical impedance (EMI) sensing system associated with a properly defined statistical index which evaluates the rate of concrete strength development is very sensitive to the strength gain of concrete structures from their earliest stages.

Highlights

Since accurate field measurements of early-age concrete properties, such as setting time, in-place strength gain, and shrinkage stresses, are crucial to in situ quality control of concrete, various techniques have been proposed including Windsor and pullout probe tests, ultrasonic pulse velocity, impact-echo method, microwave method, and maturity method [1]
The Wireless USB 2.0 Extender will automatically establish a wireless connection between the Wireless USB 2.0 Sender unit and the Wireless USB 2.0 Receiver unit once power is applied to both units and they are located within their operating range
C1, C2, and C3 with dimensions of 150 × 150 × 150 mm, which is normally used for compressive strength evaluation, were prepared for this experiment comprising of type I Portland cement (C), water (W), well-graded washed sand (FA), middle-size aggregates (MA), and gravel coarse aggregate (CA)

Summary

Introduction

Since accurate field measurements of early-age concrete properties, such as setting time, in-place strength gain, and shrinkage stresses, are crucial to in situ quality control of concrete, various techniques have been proposed including Windsor and pullout probe tests, ultrasonic pulse velocity, impact-echo method, microwave method, and maturity method [1]. In the study of Park and Kim [11], a series of efforts were presented to confirm the applicability of the EMI technique using both wired and wireless sensing systems based on AD5933 chip for monitoring on the strength development during the curing process of concrete They extended the previous researches for multifunctional and environment-friendly uses in the impedance-based structural health monitoring (SHM) process, the main drawback of this work was that their first impedance measurement should be carried out 3 days after concrete mixing because before 3 days, the piezoelectric sensors could not be attached completely to the fresh concrete surface, since concrete behaves almost like a liquid at its very early stages. This coupling property (between the electrical and mechanical impedance) of the PZT patch is utilized for strength gain monitoring, which enables one to measure the impedance changes (and strength changes) in concrete during curing

Experimental Implementation

Results and Discussion

Conclusions