USE OF CARBON NANOTUBES IN THE RETROFITTING OF REINFORCED CONCRETE BEAMS WITH AN OPENING AND THE EFFECT OF DIRECT FIRE ON THEIR BEHAVIOUR

Abstract

Carbon nanotubes (CNTs) are used to enhance the performance of nano-composites because of
their high strength and remarkable physical properties. An experimental study was designed to investigate the
use of CNTs in a ferrocement mix as an advanced technique for externally retrofitting for shear zone opening
of reinforced concrete beams. The main parameters in this work are opening size, ferrocement techniques
(CNTs and wire mesh), and fire exposure. The ferrocement technique is used to retrofit the reduction of open
beams strength, whether exposure to fire occurred or not. The burned beams are loaded at 30 kN at room
temperature and then subjected to a direct fire, followed by cooling with water before the load was finally
increased to failure. In addition, the strength reduction of the test specimens was increased during firing with
an increase in the opening size; strengthening with ferrocement decreased this reduction, deflection, and change
in crack pattern shape and improved beam ductility. Carbon nanotubes improve the efficiency of retrofitting
by ferrocement compared to the use of steel wire mesh in the ferrocement mix.