Aluminosilicate materials are generally considered electrical insulators. In order to achieve enhanced electrical conductivity these materials must doped with suitable conductive admixtures such as carbon black. These composites gain the importance in the new field of applications such as self-sensing materials or self-monitoring structures. This paper presents a study on self-sensing properties of alkali-activated slag composite with 2 and 4% of carbon black as conductive filler during repeated flexural and till fracture loading in the configuration of three-point bending test. The results showed that best performance of the self-sensing properties was achieved with 4% of carbon black, though both the compressive and flexural strengths were deteriorated.
The development of smart materials is a basic prerequisite for the development of new technologies enabling the continuous non-destructive diagnostic analysis of building structures. Within this framework, the piezoresistive behavior of fly ash geopolymer with added carbon black under compression was studied. Prepared cubic specimens were doped with 0.5, 1 and 2% carbon black and embedded with four copper electrodes. In order to obtain a complex characterization during compressive loading, the electrical resistivity, longitudinal strain and acoustic emission were recorded. The samples were tested in two modes: repeated loading under low compressive forces and continuous loading until failure. The results revealed piezoresistivity for all tested mixtures, but the best self-sensing properties were achieved with 0.5% of carbon black admixture. The complex analysis also showed that fly ash geopolymer undergoes permanent deformations and the addition of carbon black changes its character from quasi-brittle to rather ductile. The combination of electrical and acoustic methods enables the monitoring of materials far beyond the working range of a strain gauge.
Alkaline activated binders showing enhanced piezoresistive properties have recently attracted increased interest in research of their application in smart self-sensing components. This study is focused on metakaolin geopolymer mortar doped with 0.05 and 0.10% carbon nanotubes, a conductive filler that effectively increases electrical conductivity without considerable deterioration of mechanical properties. Self-sensing performance of composites incorporated with electrodes and attached strain gauge was tested during different regimes of compressive loading cycles with continuous monitoring of strain and resistivity. Although the differences in sensitivity and repeatability were observed, all samples including the reference material have shown good response to applied loading.
Materials with enhanced electrical properties are widely studied concerning their future application in smart or self-sensing constructions. Carbon black is known as one of the inexpensive multipurpose admixtures used in polymeric materials. This study is focused on the application of carbon black in fly ash geopolymer mortar to enhance its conductivity and other electrical properties. Geopolymer samples were prepared with the carbon black content from 0.5 to 4.0% to evaluate their performance in selected electrical properties (conductivity, resistance, capacitance). Further investigations included its influence on the mechanical properties (compressive and flexural strength) and microstructure of the binder (mercury intrusion porosimetry, SEM). Despite the considerable improvement in conductivity, the amount of conductive filler over 2% was also associated with increased porosity and reduced compressive strengths.
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