Page 151 - New Trends in Green Construction

SENSORS FOR THE NON-DESTRUCTIVE CHARACTERIZATION OF CONCRETE DURABILITY
Fabiano Tavares, Rubén Beltrán, Mercedes Sánchez
Keywords: Ad-hoc sensors , non-destructive, concrete, durability 1. Introduction
The ongoing research presented in the present study deals with the remote monitoring of the durability parameters related to the reinforced concrete structures performance as a highly promising alternative for the non-destructive characterization of concrete (Barroca, 2013).
The general objective of the study is the design, development, fabrication and implementation of integrated wireless sensor systems to be embedded for the continuous monitoring of the concrete performance through the measurement of multiple variables in real-time: temperature, humidity content, resistivity, pH, presence of chloride ions, etc.
Different types of sensors are being developed, using the electrical resistivity as an indirect parameter for evaluating both the fresh state properties of concrete and the hardened concrete properties. The resistivity is used as the indirect parameter for evaluating the concrete moisture content (Cheng, 20068; Steinberg, 2016) and for detecting the penetration of aggressive agents from the concrete surface (chloride ions and/or carbonation depth, even adapting resistivity and RH/T probes in the same sensing module to obtain the simultaneous variation of the different variables). A remote data-acquisition system is also being implemented in the integrated sensor.
2. Material and methods
The ongoing research is on its very first stages and preliminary tests of two different types of sensors have been carried out:
a) A miniaturized two-point sensor for evaluating the setting process of concrete mixes has been tested on laboratory conditions.
b) An array of 5 sensors for assessing the water exchange through the concrete surface has been tested for both the uptake and the loss of water.
3. Results and conclusions
In the figure below, the results concerning the ability of the sensor array for detecting the water penetration through a dried concrete surface are included. It can be derived from the figure that the electrical resistance values decrease at different times depending on the depth of each sensor, with longer times of response for the deeper sensors.
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