The Flexural Strengths and Characteristics of the Cement-based Composite Reinforced with Acid-treated Multi-walled Carbon Nanotubes

Carbon nanotubes/cement composite is a novel functional material.Acid-oxidization is applied to modify the surface of multi-walled carbon nanotubes (MWCNTs),and afterwards,the cement-based composites reinforced with MWCNTs or AT-MWCNTs (MWCNTs/CC,or AT-MWCNTs/CC) are prepared with surfactant ultrasonic dispersion and subsequent mix-casting method.Their flexural strengths are acquired with three-point bending test method,the surface characteristics of MWCNTs,AT-MWCNTs,MWCNTs/CC and AT-MWCNTs/CC are compared and analyzed with FT-IR apparatus,and the microstructures of MWCNTs/CC and AT-MWCNTs/CC are observed by SEM.The results show that,the flexural strength of MWCNTs/CC is lower than that of the reference,but AT-MWCNTs with surface modification exhibits good reinforcement to the matrix,and the enhancement amplitude of the strength of AT-MWCNTs/CC with respect to that of the reference is up to 23.1%,and the homogeneity is better.Many hydrophilic active groups are found on the surface of AT-MWCNTs,which is hardly found on the surface of MWCNTs,and the correspondent absorption peaks of AT-MWCNTs/CC are much richer.SEM micrographs show that most MWCNTs have only weak bonding with loose hydration product,while there is many hydration products encapsulating AT-MWCNTs,exhibiting strong bonding force and good interfacial bond between AT-MWCNTs and the dense hydration product.