R Keshavarz - Fars Nov Cement Company and Department of Polymer Engineering, Darab Branch
A Mohebbi - Department of Polymer Engineering, Darab Branch, Islamic Azad University, Darab, Iran
J Morshedian - Iran Polymer and Petrochemical Institute, Tehran, Iran

Carbon nanotubes (CNTs) are hollow tubular channels, which produced in form of either single wall (SWCNTs) or multi walls (MWCNTs). Carbon nanotubes have great mechanical properties. Due to their high flexibility, CNTs acts as shock absorber and protect buildings and concrete constructions against collapsing.In this study the presence of carbon fibers with composition of 0.5 wt% in cement was compared with the effect of MWCNTs treated with carboxylic functional groups with composition of 0.05 and 0.1 wt% in cement. Several samples of concrete with uniform distribution of carbon fiber and MWCNTs in a mixture of cement, sand and water were prepared. The effect of carbon fiber and carbon nanotubes on the properties of concrete strength were investigated using compressive and bending tests. The morphological changes of the microstructure were analyzed by electron microscopy images.Results show that in presence of MWCNTs the compressible and bending strength of concrete nanocomposites were increased more than 30% and 13% respectively. Further by adding carbon fiber to the composite concrete the bending strength was increased up to 7.64 %, while the compressible strength of concrete was reduced. Also, MWCNTs were led to improvement of microstructure porosity of concrete composite and therefore more solid and more compressed concrete composite were created. The treated MWCNTs in concrete composite were generated more contact surface to transferring of forces. As a result, these connections were led to better MWCNTs surface bonding with concrete matrix to prevent it from growth of defects

Cement, Reinforced Concrete, Carbon Nanotube, Compressible and Bending Strength