Studies on combined effect of superplasticizer modified graphene oxide and carbon nanotubes on the physico-mechanical strength and electrical resistivity of fly ash blended cement mortar

In the present study, functionalized carbon nanotubes (FCNT), graphene oxide (GO) and their Hybrid as reinforcing material in the fly ash blended cement nanocomposites (FCNCs in 30:70 ratio of FA to cement) has been investigated for enhanced mechanical performance. It was observed that addition of 0.02% GO and 0.02% FCNT by weight of blend in FCNCs showed an improvement in its compressive strength by 35.6% and 24.5%, respectively. However, compressive strength was improved synergistically by 46.7% for 0.02% mHCN-FCNC (i.e. 37.1 MPa) (superplasticizer modified GO thorn FCNT in 1:1) after 90 days of curing with respect to the control sample. The enhancement in tensile strength found was 16.0%, 53.6% and 74.0% for FCNT, GO and HCNs, respectively. The compressive strength as well as tensile strengths found for mHCN-FCNC were comparable or even better as compared to the 100% OPC based mortar specimen (i.e. 37.6 MPa), making the practical applications possible for FA based cementitious nanocomposites in the construction industry. For 0.02% mHCN-FCNC, BET (Brunauer-Emmett-Teller) results showed a decrease in the pore volume by 9.1% whereas an increase in electrical resistivity by 41.7%, which shows the densification of FA blended mortar as compared to control sample. The improved hydration of fly ash blended mortar has also been shown by techniques such as FESEM (Field emission-Scanning electron microscopy) and XRD (X-Ray diffraction) studies which represent the consumption of fly ash particles by the cement hydration products i.e. portlandite and further resulting in the formation of dense calcium silicate hydrate gel via secondary pozzolanic reaction. So, the present study provides a sustainable path to the green and economical FA cement based materials that are competent to the OPC based cement materials in every aspect.