Enhancing the post-crack tensile strain capacity of Metakaolin- Portland Limestone Cement blend by using Carbon Nanotubes

Incorporating metakaolin (MK) into cementitious materials is known to enhance strength and stiffness, however, this yields a relatively brittle material with a significant loss of the ultimate strain capacity. To compensate for the loss in ductility, well-dispersed carbon nanotubes (CNTs) are incorporated in MK-Portland Limestone Cement (PLC) mortar to reinforce the Interfacial Transition Zone (ITZ) which is crucial for controlling the crack formation and propagation. Nanoscale imaging and mechanical property mapping at the ITZ between the nanomodified MK-PLC matrix and aggregates revealed that the local nanostructure and morphology of the ITZ were modified, resulting in an increase in the modulus of elasticity by 35.1%. Results of the three-point bending test on the notched beam specimens indicated a 1.5× higher tensile load-carrying capacity and an enhanced strain energy absorption capacity of the CNT-reinforced MK-PLC mortar compared to the MK-PLC mortar at both the pre-crack/elastic and post-crack stages of deformation.