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This research studied an innovative method for improving the properties of fly ash–based geopolymer mortar by using ultrafine two-dimensional (2D) graphitic carbon nanoplatelets (GCNPs) derived from sustainable biomass sources. These low-cost and eco-friendly GCNPs were synthesized through a thermochemical process involving biomass-derived sucrose solution. Both fly ash and GCNPs were processed and activated to optimize their performance in the geopolymerization process. The graphitic carbon reinforced geopolymer mortar (GCGPM) composite was optimized by employing different dosages of GCNPs (0, 0.1, 0.2, 0.3% [by weight of binder]), and the resulting GCGPM was examined through various instrumental analyses. It was observed that the addition of GCNPs results in reduced workability of the geopolymer mortar. Importantly, the maximum compressive strength of the GCGPM was significantly enhanced, up to 34.21%, with a 0.2% GCNPs addition over a 28-day curing period. Furthermore, incorporating 0.1% GCNPs into the composite led to an increased composite density, resulting in a substantial reduction of water absorption, up to 76.49%. These outcomes hold promise for achieving a more compact microstructure through the integration of GCNPs into geopolymer composites. The study suggests that novel synthesized GCNPs can effectively and sustainably enhance the properties of geopolymer composites in a cost-effective manner. [ABSTRACT FROM AUTHOR]

This paper evaluates the effect of the addition of nanocalcium carbonate (NC) and nanosilica (NS) on chloride-induced corrosion, chloride diffusion, chloride permeability, and service life of high-volume slag (HVS) and high-volume slag–fly ash (HVS-FA) blended concretes containing more than 70% blast furnace slag (BFS) and combined BFS and FA as the partial replacement of ordinary Portland cement (OPC). Compared to the control OPC concrete, the HVS and HVS-FA concretes containing NC and NS exhibited superior compressive strengths in all curing ages up to 365 days. Superior performance against chloride permeability, chloride diffusion, and chloride-induced corrosion are also observed in both HVS and HVS-FA concretes due to the addition of both nanomaterials. Among NS and NC, the concretes containing NC performed much better than the concrete mixes with NS. Significant extension of service life is also observed in both HVS and HVS-FA concretes by the inclusion of both nanomaterials. [ABSTRACT FROM AUTHOR]

An analytical model for the design of strain-hardening and multiple-cracking behavior of engineered cementitious composites (ECC) containing hybrid fibers is proposed. The model predicts first crack strength and ultimate bridging strength of hybrid fiber ECC. The model also predicts the minimum (critical) volume fraction of fibers required to exhibit strain-hardening and multiple-cracking behavior in uniaxial tension. The model is verified with the experimental results of hybrid fiber ECC specimens. A parametric study is also performed, using this model, to evaluate the effects of fiber length, diameter, and interfacial bond strength on the first crack strength, the ultimate bridging strength and the critical volume fraction of fibers. It is shown that the critical volume fraction of fibers in hybrid fiber composites can be optimized by proper selection of fiber length, diameter, and interfacial bond strength. Low modulus fibers are found to have a more pronounced effect on the strain-hardening and multiple-cracking behaviors of hybrid fiber composites compared to high modulus fibers. The hybrid fiber concept is found to offer additional freedom in the design variables compared to composite containing one type of fiber. [ABSTRACT FROM AUTHOR]