Nanotechnology has brought significant innovations in science and engineering. Nanomaterials could change the face of modern construction because they are more resistant, more durable and have notable features. Concrete is a material widely used in construction industry worldwide. Carbon nanotube has been considered a new and outstanding material in nanoscience field with great potential application in the construction industry. The study presented in this paper, aims at assessing how carbon nanotubes can affect cement composites and so the concrete, in terms of microstructure and physical-mechanical properties. Three different ratios of carbon nanotubes have been searched: 0.20%, 0.40% and 0.60%. Tests were carried out with the ultrasound technique, measuring the propagation delay of the signal thought the specimens of cementitious materials with and without CNT, to reach the dynamic modulus of elasticity.