Durability, mechanical properties and rebar corrosion of slag-based cement concrete modified with graphene oxide

The application of nanomaterial to concrete is an innovative approach to enhancing mechanical properties and durability. In fthis work, the combined additions of graphene oxide nano-platelets (GO) to concrete mix formulated to use ground granulated blast furnace slag (GGBFS) as a substitute for Portland cement (PC) for use in salt-rich environments is studied. The need arises in both off-shore structures and also places coming to contact with brine due to de-icing of road structures or the geological peculiarities specific to saline terrain. The physical, mechanical, chloride, and water permeability and electrical conductivity tests on the developed concrete are compared with those of ordinary concrete under conditions of varying temperature and water pressure. The addition of GGBFS is known to improve the mechanical properties of concrete specimens. Results from the present work show that the addition of no more than 0.1 wt% GO to 50 wt% GGBFS substituted concrete increases the after-curing compressive strength by 40 %, and flexural strength by 60 %. The electrical conductivity of the 90-day cured samples as a measure of chloride permeability dropped from nearly 4000 Coulombs in ordinary concrete to roughly 1100 Coulombs for the modified concrete indicating a nearly 70 % reduction. Accelerated C-S-H gelation, followed by Ca(OH)2 crystallization after GO addition, combined with altered pore structure from the addition of finely milled slag. The nucleation mechanism is affected such that the average pore diameter falls to 6.2 nm from 11.4 nm in the PC concrete. The low porosity thus established is reflected in the measured improvements in strength, resistance to water absorption, chloride permeability, and the overall enhanced corrosion performance. Calorimetric conductivity, thermogravimetric analysis (TGA), and differential thermogravimetric (DTG) analysis under nitrogen from 105 to 1000 degrees C, total porosity and pore size distribution using Mercury Intrusion Porosimetry (MIP) with a maximum pressure of 200 MPa, X-ray diffraction, linear polarization and electrochemical impedance spectroscopy (EIS) corrosion test results further corroborate that the addition of 0.1 % by weight of GO improved the physical, durability, and corrosion resistance properties of GGBFS concrete.