Development of Next-Generation High-Ductility Engineered Cementitious Composites Using Hybrid Nano Fibers

Abstract

Engineered Cementitious Composites (ECC) are new generations of construction materials that can be used to overcome the brittleness and poor tensile properties of traditional concrete. This paper explores the synthesis of an innovative high-toughness ECC containing hybrid nano micro reinforcements such as polyvinyl alcohol fibres and multi-walled carbon nanotubes. In this research, attempts have been made to improve the mechanical properties, tensile toughness, crack resistance, and durability behaviour of ECC using different multi-scale reinforcement techniques. To develop hybrid ECC composites, ordinary Portland cement, class F fly ash, fine aggregate, superplasticizer, polyvinyl alcohol fibres, and multi-walled carbon nanotubes were utilized. To evaluate the effectiveness of reinforcement, different tests were performed on ECC composite specimens, including compressive test, tensile test, flexural test, chloride permeability test, and scanning electron microscope. The outcome of this investigation proved to be effective in enhancing the structural and durability properties of ECC. Of all the mixtures tested, the mixture named ECC-2 with 1.5% PVA fibres and 0.10% CNT gave the best results, having a compressive strength of 57.8 MPa, tensile strain of 6.2%, flexural strength of 9.3 MPa, and a decrease in chloride permeability by 41.98%. Scanning electron microscopy tests demonstrated that the inclusion of CNTs caused improved matrix densification, a decrease in porosity, decreased connectivity of pores, and an increase in interface bonding strength. It was further shown through statistical analysis that the test results were accurate, repeatable, and had low standard deviations. The combination of crack bridging at the micro level and crack arresting at the nano scale was found to be responsible for the excellent strain hardening property and better durability performance.