Abstract
This study analyzed the influence of carbon nanotubes (CNTs) on the carbonation conductive cementitious composites. Two powder types of CNT, multi-walled and single-wall CNTs, were employed to give the cement mortar the conductivity, and four tests including the accelerated carbonation, compressive and flexural strength, electrical resistance, and porosity tests were carried out. To intentionally accelerate the carbonation, the prismatic specimens of conductive cement composites were fabricated and stored in the controlled environmental chamber at a constant temperature of 20 ± 2 °C, constant relative humidity of 60 ± 5%, and carbon dioxide (CO2) concentration of 5% for 12 weeks. It was observed that carbonation resulted in only chemical damage so that there was no change in the electrical resistance value of conductive cementitious mortar that had undergone a carbonation attack.
Highlights
The quality degradation of concrete structures is generally caused by the continuous occurrence of various types of environmental factors [1]
Carbonation occurs in the cement mortar as the calcium hydroxide (Ca(OH)2 ) in cement reacts with CO2 from the atmosphere and water in the pore
Greater than that of MW and the carbonation rate of conductive cement mortar increased by 150% as the amount of carbon nanotubes (CNTs) was doubled in the mixture
Summary
The quality degradation of concrete structures is generally caused by the continuous occurrence of various types of environmental factors [1]. As the carbonized concrete or cementitious composite is neutralized, the reinforcing bars inserted inside reinforced concrete structures are prone to corrosion, and the corroded reinforcement generates internal cracks due to its volume expansion. As this process progresses for long periods of time, such cracks that occur on the surface of the structure pose a great threat to structural safety. Underground structures, such as a subway structure, are exposed to a CO2 concentration of more than 660 ppm and high humidity at 60–70%, which promotes carbonation [10,11]
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