Repair Mortars Incorporating Multiwalled Carbon Nanotubes: Shrinkage and Sodium Sulfate Attack

AbstractThis study investigates the effect of multiwalled carbon nanotubes (MWCNTs) on the shrinkage and expansion caused by sodium sulfate attack in repair mortars; repair mortar behavior in the fresh state and the compressive strength are also measured. Three repair mortars are studied: 0.0% MWCNTs (reference), mortar from two different manufacturers. Shrinkage and sulfate attacks are evaluated according to current standards. The carbon nanotube increases the compressive strength by approximately 19.5% and decreases the fluidity. Shrinkage occurs more intensely in MWCNT-embedded mortars, although results show similar behavior between the two types of MWCNTs. The MWCNTs increase the expansion due to attack by sodium sulfate, indicating that this material may be harmful when the cementitious composite is in contact with these aggressive agents (sodium sulfate).