Response of Nano-Reinforced Cementitious Composites Using Natural and Commercial Dispersants ^†

An efficient and promising approach from economy point of view to effectively disperse Multi-walled carbon nanotubes (MWCNTs) in cementitious environment has been devised. The natural organic extract from species of indigenously known ‘keekar’ trees scattered along tropical and sub-tropical countries; is found as an exceptional replacement to the non-natural commercial surfactant. In the initial phase ideal content of surfactant was explored in relation with the added content of MWCNTs using ultra-violet spectroscopy. The experimental investigations were then extended to five formulations containing 0.0, 0.025, 0.05, 0.08 and 0.10 MWCNTs by weight percent of cement. It was observed that the natural surfactant produced efficient dispersion at much reduced cost (>14% approx.) compared with the commercial alternate. The estimated weight efficiency factor ‘ϕ’ was found 6.5 times higher by the proposed sustainable replacement to the conventional with remarkable increase of 23% in modulus of rupture on 0.08 wt% addition of MWCNTs. Besides, strength enhancement the dispersed MWCNTs also improved the first crack and ultimate fracture toughness by 51.5% and 35.9%, respectively. The field emission scanning electron microscopy of the cryofractured samples revealed efficient dispersion of MWCNTs in the matrix leading to the phenomenon of effective crack bridging and crack branching in the composite matrix. Furthermore, the proposed scheme significantly reduced the early age volumetric shrinkage by 39% to mitigate early age micro-cracks encouraging long lasting deteriorations from durability prospects.