A New Class of Carbon Nanotube: Polymer Concrete with Improved Fatigue Strength

Abstract

Polymer concrete (PC) has been used successfully as bridge deck overlays and in machine foundations. In such applications, PC is subjected to cyclic loading and thus is prone to fatigue failure. In this paper, we introduce a new method for improving the fatigue strength of PC using carbon nanotubes. To overcome the challenge of fatigue testing of concrete, a four point flexural displacement control test borrowed from Asphalt standards in AASHTO was used. In this test the displacement was ramped up from zero to 1.2 mm then the PC specimen (25 × 25 × 200 mm) was cycled between zero and 1.2 mm using a sinusoidal signal with a frequency of 0.5 Hz. Guided by AASHTO specifications, failure is defined as 50 % reduction in stiffness. Four PC mixes were tested. These mixes incorporated neat epoxy, and epoxy including 0.5, 1.0 and 1.5 % multi-walled carbon nanotubes (MWCNTs) by weight of epoxy resin. Damage in PC due to fatigue was evaluated with time. The experiments showed the ability of MWCNTs to improve fatigue strength by 61 and 100 % for PC incorporating 0.5 and 1.0 % MWCNTs respectively. PC incorporating 1.5 % MWCNTs reached 50,000 cycles without experiencing fatigue failure showing improvement above 520 %. Microstructural analysis of PC was conducted using scanning electron microscope (SEM) to explain the ability of MWCNTs to significantly improve fatigue strength of PC.