단일벽 탄소나노튜브(SWCNT) 분산 용액을 혼입한 시멘트 페이스트의 기초적 물성 평가

Abstract

A lot of efforts has been made to increase the properties of high performance concrete (HPC) since the use of HPC gained popularity in many construction sites. Although many different approaches can be applied to make the performance of HPC much superior to those conventional concrete, this work aims to utilize single-walled carbon nanotube (SWCNT) to make HPC. Since SWCNT is a material with excellent mechanical properties, durability, and unique functionalities, it has a strong potential to be a key material to enhance the current level of concrete technology. However, the use of SWCNT has not been even attempted in construction business mainly due to its excessively high price. In addition, its hydrophobic characteristics, which pristine SWCNT is naturally coagulated when added to the aqueous solution, also make it difficult to be used because water is always used to make cement based materials. To resolve such problem, a theoretical concept called “core-shell” structural model has been adapted in this work. It is to use amphiphilic macromolecules whose hydrophobic part attaching to the SWCNT whereas its hydrophilic part facing with water, thereby making SWCNT equally dispersed in aqueous solution. High energy sonication was used to separate SWCNT bundles in surfactant solution, ultracentrifugation was applied to remove carbon impurities, and the presence of SWCNT in aqueous solution was verified by Raman spectroscopy. Sodium deoxycholate (DOC), air entraining agent (AEA), and superplasticizer (SP) were chosen as surfactants. To make cement paste specimens, 10% of deionized water in the mixture was replaced by aqueous SWCNT solution. According to the experimental results, the use of SWCNT solution clearly increased both the 28 day compressive and flexural strengths. It was also found that the type of surfactant used to make SWCNT solution affected the mechanical properties of the cement paste. DOC was found to be a better option than AEA and SP to make SWCNT solution for cement paste. Finally, FE-SEM (Field Emission-Scanning Electron Microscope) analyses were performed on a fractured surfaces of cement paste samples in order to observe the dispersion condition of SWCNT in hardened cement paste. The FE-SEM results showed that SWCNT was uniformly dispersed in cement paste. Therefore, it is believed that aqueously dispersed SWCNT solution can be used as a promising material to make high performance concrete.