Abstract
Graphene oxide (GO) is a potential material to be used as a nano-reinforcement in cement matrix. However, a prerequisite for GO to fulfill its function in the cement matrix is homogeneous dispersion. In this study, the effects of three different dispersing agents (DAs), including polycarboxylate-based high range water reducer (P-HRWR), naphthalene-based high range water reducer (N-HRWR), and air entraining agent (AEA) on the dispersion of GO in aqueous solution, simulated concrete pore solution (SCPS), and suspension of cement pastes were sequentially investigated. Results showed that the dispersion effect of GO in aqueous solutions was improved with different DAs. However, the homogeneous dispersion of GO in aqueous solution re-agglomerated in SCPS and suspension of cement pastes. It was concluded that as the cement content and pH of aqueous solutions increased, GOs re-agglomerated and precipitated in an alkaline solution. A possible mechanism was proposed in this study and it was believed that electrostatic interactions and steric hindrance provided by the P-HRWR further made GOs stable in aqueous solutions. The ions and pH of cement pastes increased with the increasing amount of cement, which caused the separation of P-HRWR from GOs. Therefore, GOs were re-agglomerated and absorbed on the surface of the cement particles, resulting in GOs sedimentation.
Highlights
Modern concrete technology is shifting towards a high-performance application with a desire to be sustainable [1,2]
Dispersion State of Graphene oxide (GO) in Cement Paste. These results provided the evidence that dispersing agents had a positive effect on GO dispersion in During the dispersion process of GO in simulated concrete pore solution (SCPS) solution, cations in SCPS
The following conclusions concerning GO stability and agglomeration were made: The following conclusions concerning GO stability and agglomeration were made: (1) The dispersion of GO in aqueous solutions was positively influenced by P-HRWA, N-HRWA, (1) The dispersion of GO in aqueous solutions was positively influenced by P-HRWA, N-HRWA, and air entraining agent (AEA), respectively; among the dispersing agents (DAs), the AEA provided the most improvement of dispersion and AEA, respectively; among the DAs, the AEA provided the most improvement of dispersion in aqueous solutions
Summary
Modern concrete technology is shifting towards a high-performance application with a desire to be sustainable [1,2]. Nano-materials have shown to improve the micro-structure and comprehensive performance of cement-based composites [3,4,5,6]. Several studies on self-sensing cement composites which uses nanocomposites have been reported [7,8,9]. Nano-modified cement-based materials are the main technical ways for developing ultra-high-performance concrete (UHPC). The development of nano-carbon-based materials (carbon nano-tubes, graphene, graphene oxide, etc.) and zero-dimensional nanoparticles (nano-SiO2 , nano-CaCO3 , nano-Al2 O3 , etc.) has demonstrated that the microstructure and mechanical performance of concrete can be improved significantly [14,15,16]
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