Use of Carbon Nanotubes to Improve Fracture Toughness of Polymer Concrete

Abstract

Bridge deck overlays often require materials that are durable and easy to apply and that have a long fatigue life. In many applications, polymer concrete (PC) has been chosen not only because it meets such requirements but also because it offers additional features such as high friction. However, the service life of PC overlays is reduced, and cracking occurs because of the continuous increase in traffic loads. This paper investigates the use of multiwalled carbon nanotubes (MWCNTs) to improve the fracture toughness and fatigue service life of PC. Pristine MWCNTs (P-MWCNTs) and MWCNTs functionalized with carboxyl (COOH-MWCNTs) were used at 0.0- (neat), 0.5-, 1.0-, 1.5-, and 2.0-wt.% contents. Three-point bending tests of notched beams were carried out in which the loading rate was controlled by crack mouth opening displacement. Direct tension tests were also used to examine the effect of MWCNTs on the tensile properties of PC. The results showed that MWCNTs improved the fracture toughness of PC by up to 56% and 112% for P-MWCNTs and COOH-MWCNTs, respectively. Samples prepared with P-MWCNTs showed increased ductility; samples with COOH-MWCNTs provided increased tensile strength. Microstructural analysis with a scanning electron microscope and Fourier transform infrared spectroscopy revealed how different types of MWCNTs at different weight contents influenced the behavior of PC.