Abstract
The potential effects of curing age on the self-sensing (piezoresistivity) capability of carbon-based Engineered Cementitious Composites (ECC) specimens are under focus in the present study. This non-structural feature can be regarded as one of the best solutions for continuously monitoring of infrastructures in terms of damage and deformations. Carbon fibers which are a micro-scale electrically conductive material were added to the ECC matrix and well dispersed to create the electrically conductive network. This network is responsible for sensing the applied loads on the prismatic specimens. The self-sensing behavior of electrically conductive prismatic specimens under four-point monotonic flexural loading was investigated and compared with dielectric ECC specimens at four ages of curing (7, 28, 90 and 180 days). The results showed that the developed multifunctional cementitious composites can sense the changes in the applied flexural stresses and the resultant mid-span deflection along the adopted curing ages with an improvement in the later ages.
Highlights
The concrete, which is the main material in the construction of several structures and infrastructures around the world, suffers from of a lot of risks resulting from the applied loads, as well as, from the surrounding weather conditions, which caused, as a whole, a decline in the serviceability index of these structures
In the present study, the method that was described in ASTM standard C 1018 – 97 and suggested by kim et al [15] was utilized to identify this point at the stress/deflection curve. This method takes into account the fact that the point which is located at the end of the straight line and the beginning of the non-linear line of the stress/deflection curve is the point of the occurring of the first crack
The simplest way that was explained by Naaman [14] to represent the deflection hardening behavior was used in the present study. He showed that the deflection hardening of the prismatic specimens can be measured by utilizing the ductility index (DI) which is the ratio of the mid-span deflection at the ultimate strength point and the mid-span deflection at the first cracking point based on a condition that the ultimate stress must be greater than the first cracking stress
Summary
The concrete, which is the main material in the construction of several structures and infrastructures around the world, suffers from of a lot of risks resulting from the applied loads, as well as, from the surrounding weather conditions, which caused, as a whole, a decline in the serviceability index of these structures. It was presented figuratively that the fractional change in electrical resistance reached up to around 225% at compressive strain of 1.9×10-3 and compressive stress of 39 MPa at 7 days of curing age These results can be seen, within the study of Chung [4]. Chen and Chung [2] examined the capability of mortars reinforced by 0.2-4.2 vol.% and concretes contain 0.2-1.1 vol.% of short carbon fiber (CF) to act as a strain sensor via electrical probing under static and cyclic compression, tension and flexure loadings at 7 days age. The experimental results of cyclic loadings of all fabricated types of three-point bending specimens showed that the relationships between fractional change in electrical resistance and strain measured at top and bottom of specimens were linear. Electrically conductive chopped carbon fibers (CF) in micro-scale were used to fabricate the multifunctional cementitious composites (MCC)
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