Effects of silica fume on physicochemical properties and piezoresistivity of intelligent carbon black-cementitious composites. (30th October 2020)

• Record Type: Journal Article
• Authors: Dong, Wenkui; Li, Wengui; Guo, Yipu; He, Xuzhen; Sheng, Daichao
• Is Part Of: Construction & building materials. Volume 259(2020)
• Publication Date: 2020-10-30
• Subjects: Carbon black (CB) -- Silica fume (SF) -- Cementitious composite -- Piezoresistivity -- Physicochemical properties -- Electrical resistivity -- Microstructure; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2020.120399
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Electrical resistance and flowability of CB-cementitious composite decreased with the increase of SF. Both compressive and flexural strengths were increased and then decreased with the increase of SF. Denser microstructure and well-dispersed CB nanoparticles were observed with proper addition of SF. Hydration heat analysis indicated that the addition of SF can postpone cement hydration in the early stage. Piezoresistivity of CB-cementitious composite was improved with addition of SF, especially with 10% SF. Abstract: Carbon black (CB) filled cementitious composites as cement-based sensors with intrinsic piezoresistivity have the potential applications for structural health monitoring (SHM). Effect of silica fume (SF) replacement ratio on the physicochemical, mechanical and piezoresistive properties, and microstructure of CB-cementitious composite were experimentally investigated in this study. The results show that 5% or 10% replacement ratio of SF can improve the water impermeability, setting time and electrical conductivity, but decrease the fresh flowability. Cementitious composite with 10% SF exhibiteds excellent compressive and flexural strengths. Moreover, cement hydration in the acceleration stage decreased with the increase of SF content in the early stage, but the phase analysis after 28 days curing demonstrates that with the addition of SF, there are more hydrated products and less ettringite. In addition, the microstructures of cementitious composites without SF present more porous structures and CB agglomerations. In contrast, the amount of micropores or voids was significantly reduced by the addition of SF due to the physical filling effect and less CB agglomerations. In terms of piezoresistivity, SF can obviously improve the fractional changes of resistivity ( FCR ) under cyclic compression. With 10% SF, CB-cementitious composites as cement-based sensors exhibited excellent FCR and electrical stability, which will promote their development and application in the SHM for smart infrastructures.