Synergetic effect of multiwalled carbon nanotubes on mechanical and deformation properties of engineered cementitious composites: RSM modelling and optimization

Engineered cementitious composites (ECC) have outstanding energy absorption and ductility, but their primary drawbacks continue to be their poor elastic modulus and severe drying shrinkage. Therefore, the incorporation of multiwalled carbon nanotubes (MWCNTs) to mitigate the stated drawbacks and also the influence of MWCNTs on the mechanical characteristics of ECC has been examined. However, the primary goal of this research investigation is to apply the response surface methodology (RSM) modelling for optimizing multiple objectives, effectively handling variable interactions, and achieving significant improvements. A total of thirteen mixtures were produced through RSM modelling using two input factors including different concentrations of MWCNTs at 0.05 %, 0.065 %, and 0.08 %, as well as varying concentrations of PVA fiber at 1 %, 1.5 %, and 2 %. The central composite design (CCD) technique of RSM modelling was used in the production of these mixtures. The results demonstrated that the incorporation of 0.05 % MWCNTs and 1 to 1.5 % PVA fiber together considerably enhanced all of the characteristics of the ECC. The optimum compressive strength, flexural strength, tensile strength, and modulus of elasticity of the ECC were recorded by 74.28 MPa, 14.14 MPa, 5.51 MPa, and 31.10 GPa at 0.05 % MWCNTs at 28 days correspondingly. Furthermore, the drying shrinkage is getting decreased as the extent of MWCNTs increases in ECC. It has been concluded that the use of 0.05 % of MWCNTs and 1 % to 1.5 % of PVA fiber provided good outcomes for construction purposes.