Paper Information

Journal:   MODARES CIVIL ENGINEERING JOURNAL   JUNE 2017 , Volume 17 , Number 2 #F0067; Page(s) 1 To 9.
 
Paper: 

CONSTRUCTION AND EVALUATION OF DAMAGE DETECTION SENSOR CONSISTENT WITH CONCRETE PAVEMENT

 
 
Author(s):  ADRESI M., HASSANI A.*, SOLEIMANI M.R., YAZDIAN A.
 
* CIVIL AND ENVIRONMENTAL DEPARTMENT, TARBIAT MODARES UNIVERSITY
 
Abstract: 

Structural Health Monitoring (SHM) provides a way to evaluate safety and durability of a structure during its service life in order to ensure the serviceability and sustainability. Therefore, the sensor technology is a critical part to operate SHM system for recording relevant data through its lifespan. Sensor is a device capable of identifying the probability or the value of parametric changes and showing them as a relevant output (typically electrical or optical signal). Making materials electrically conductive may be useful in many different ways such as creating piezoresistive sensors with the ability to acquire stress-strain or load-displacement data or creating sensors with the ability to acquire data on the extent of damage to the concrete. The piezoresistive sensor is capable of detecting the applied forces to the structure based on the changes in the electrical resistance. But the damage detection sensor operates based on the contacting conduction of CNTs. This means that by increasing the amount of CNTs in concrete, a three-dimensional contacting network of CNTs is built. When the amount of CNTs exceeds the percolation threshold, the contacting conduction will affect the electrical conduction of nano-composites. One of the most significant and economical types of the sensor is the damage detection sensor which is provided by mixing conductive fibers (such as carbon nanotubes (CNT)) with concrete. For preparing damage detection sensor, CNTs and surfactants were mixed in the water for 10 minutes using a magnetism stirrer at 5000 rpm. Then, the mix was prepared at one ultrasonic energy dispersion. The cement and CNTs were added to high-speed mixer to be uniformly mixed. After adding aggregate to the mixer, the concrete was placed in pre-oiled molds and by applying appropriate vibration, any trapped air was released. The specimens were cured for 28 days and they were tested under the static loading by Instron-Tech. test equipment. In order to remove the effect of polarization - which is due to the movement of free ions in the concrete sensor during the measurement - an alternating current generator was used to nullify this phenomenon. After preparing the sensors, two main factors affecting the performance of concrete sensors are the amount of CNTs and their dispersion quality in the mixture. The goal of this study is to determine the optimum amount of CNTs with regard to the combined effects of the surfactant and the CNTs dispersion quality on the performance of the sensor. In this regard, various criteria such as sensitivity of the sensor (Se), the Absolute prediction errors as electrical criteria and flexural strength as mechanical criteria are involved. The results demonstrate that the sensor provided by 0.15 wt% CNTs, superplasticizer and SDS as a surfactant has the best performance. Also, the static criteria indicates that the quality of the dispersion (using proper surfactant material) and the amount of CNTs are effective on the sensitivity and the Absolute of the prediction errors, respectively.

 
Keyword(s): CONCRETE SENSOR, CARBON NANOTUBES, MECHANICAL PROPERTIES, ELECTRICAL PROPERTIES, CONCRETE
 
References: 
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