Abstract

In this work, multi-walled carbon nanotubes (MWCNTs) have been synthesized using a modified method of solid-phase pyrolysis. The MWCNTs are effectively dispersed using a simple and facile method such as ultrasonic energy without and with surfactant for two different sonication times (15 min and 40 min). In the present study, the effect of MWCNT concentration (0.001, 0.01, 0.05, 0.1 wt.%) on the compressive strengths of cement mortars has been investigated. Compressive tests were carried out on an automatic pressure machine (C089) with a loading rate of 0.5 kN/s at the age of 7 days and 28 days. It is shown that the optimal value of the nanotubes' concentration does not exist in the case of 15 min of sonication time, whereas the optimal value for 40 min of sonication time without and with surfactant is 0.01%. Moreover, in the absence of surfactants, the strength of the specimen over 7 days of hardening increased by 13%, and by 19.5% in the presence of surfactants. The compressive strength for a curing period of 28 days increased by 6.3% and 13.8%, respectively.