Mechanical and microstructural properties of concrete incorporating high-strength graphene oxide-based geopolymer...

Artificial geopolymer aggregates (GPA) are environmentally friendly substitutes of natural aggregates. They assist in minimizing over-quarrying and reduce landfills. This paper was done to obtain high-strength graphene oxide-modified geopolymer aggregates (GO-GPA) in order to serve as coarse aggregates in concrete mixtures with water-to-binder ratios (w/b = 0.45). These aggregates obtained compressive strengths of paste more than 40 MPa. Examined and compared mechanical behavior of graphene oxide based geopolymer aggregate concrete (GPAC) and traditional natural aggregate concrete (NAC) on basis of mechanical behavior and failure properties. Intrinsic strength of GO-GPA was found to be lower than those of natural aggregates, but at w/b ratio of 0.45, GPAC improved compressive, splitting tensile and flexural strength by 8.0, 5.5 and 4.1 respectively. A failure mode analysis revealed that w/b ratios in which cracks in GPAC propagated were lower across aggregates and surrounding matrix, which is attributed to fact that material became bonded well. With rise in w/b ratio, crack propagation has mainly moved to aggregate-matrix interface. Conversely, mix proportions showed interfacial failure modes in NAC. Microstructural examination also verified formation of a denser and more cohesive interfacial transition zone (ITZ) in GPAC, especially at low w/b ratios. Results show that graphene oxide-enhanced geopolymer aggregates are potentially considered as a high-performance, sustainable alternative to conventional aggregates in construction of structural concrete. They also show that there is better mechanical performance and failure mechanisms of GPAC.