Development of Carbon Nanotube (CNT) reinforced ultra high strength cement-based coating

Abstract

Concrete plays an important role in construction industry. Due to the increasing demand of high performance and durable concrete, there is a need to develop Ultra High Performance Concrete (UHPC) which is of ultra high compressive strength as compared to conventional concrete. However, UHPC has its drawbacks in terms of tensile strength and brittleness. Hence, these encourage the development of high strength and better performance concrete and create the need to research on the use of Carbon Nanotube (CNT) as nanoreinforcement effectively in UHPC. This is because CNT was believed to be able to further improve concrete’s mechanical properties due to its impressive characteristics.

In this study, cement was replaced by different amount of Ground Granulated Blast Furnace Slag (GGBS) in concrete design mix. Effect of GGBS on UHPC and its mechanical properties was investigated to develop an optimum design mix. Two types of CNT were then incorporated into the optimum mix of UHPC to understand effects of CNT and its dispersion method. Compressive and flexural strength tests were carried out to determine the effects of both GGBS and CNT’s improvement on UHPC’s mechanical properties by comparing with control mix’s strength.

Experimental results demonstrated that additional of GGBS in UHPC does not achieve higher compressive strength than control mix’s strength. However, it increases the flexural strength of UHPC. Additionally, mechanical properties of CNT-UHPC can be enhanced only if the dispersion method of CNT is effective in ensuring no agglomeration occurs and good bonding exists between the CNT and cement matrix. Image and microscopic analysis have shown that GGBS is able to reduce amount of air voids and give a denser microstructure of UHPC.