Mechanical Characteristics and Self-Monitoring Technique of Smart Cementitious Mixtures with Carbon Fiber and Graphite Powder as Hybrid Functional Additives

Abstract

In this paper, the self-sensing properties of cementitious composites under compressive loads were investigated by utilizing hybrid functional fillers, which are responsible for creating an electrical network that is used to build the self-sensing capability within the traditional cement-based mixtures. Most of the previous works depict the self-sensing capability with the aid of one type of functional fillers or fibers. The present paper attempts to utilize two types of functional fillers, representing a gap filling within the subject. Four hybrid proportions of Graphite (G) (wt.%) and carbon fibers (CF) (vol.%) were introduced. These are (0.5, 1.0), (1.0, 0.75), (1.5, 0.50) and (2.0, 0.25) respectively. In addition to carbon-based materials, polypropylene, polyolefin, and steel fibers are used as reinforcing fibers. One type of fiber was utilized in each manufactured mixture with a constant rate of 2% by volume of the mixture. A plain mixture without functional fillers has also been manufactured. The samples were non-destructively tested by an ultrasonic device before a uniaxial compression test was performed. To verify the self-sensing properties of the manufactured samples, the electrical resistance of the samples was recorded during load application each second. The self-sensing behavior was better for mixtures containing high dosages of graphite with respect to the fractional change in electrical resistivity (FCER). Steel and polyolefin fibers showed good results in terms of compressive strength behavior. However, polypropylene fibers showed the lowest compression strength among all types of reinforcing fibers used.