Multiwall carbon nanotubes (MWCNTs) dispersion & mechanical effects in OPC mortar & paste: A review

Abstract

The incorporation of multiwalled Carbon nanotubes (MWCNTs) and their dispersion procedures such as the use of surfactant agents, functionalization, and ultrasonication have been intensively implemented to improve the mechanical and durability properties of ordinary Portland cement (OPC) mortar and paste. Many studies stated significant enhancements in the mechanical properties of OPC mortar or paste; however, others showed impairments. The review observed the preparation techniques for dispersion and mixing MWCNTs with dry materials such as cement and sand. The recent studies regarding the implementation of MWCNTs on the mechanical properties of OPC paste and mortar were reviewed. These properties include compressive, tensile, flexural strengths, and elastic modulus. A statistical approach was conducted to observe the effects of the MWCNTs' amendment on the mechanical properties of Portland cement paste and mortar. The results showed that there is no consistent preparation technique for the dispersion of MWCNT. The ultrasonication, used in most studies either alone or as a surfactant combination, was the most effective technique for dispersion when the sonication duration was between 20 and 45 min. The statistical mechanical property observations revealed that the majority of compressive strength enhancements were below 40% (approximately 91% of the data) regardless of the MWCNTs %. The improvement in strength below 40% was 74% of the data for tensile/flexural strength of mortar. For cement paste, 50% of the enhancements were equal to or below a 40% increase. However, some studies showed impairments in the mechanical properties of OPC composites when MWCNTs were incorporated. Most reduction in compressive strength was below 40% compared to mortar and cement with 0% MWCNTs.