Page 135 - New Trends in Green Construction

USING GRAPHENE OXIDE AS MEANS OF IMPROVEMENT OF CONCRETE: A BRIEF REVIEW
Pedro Raposeiro da Silva, Luís Evangelista
Keywords: Portland cement, concrete, graphene oxide, Mechanical property 1. Introduction
Nowadays, the use of nanomaterials (NM) to improve the performance of cement and concrete matrixes constitutes a potential alternative to the exclusive use of Portland cement (PC). Similarly, there is currently no doubt in the construction industry (CI) about the pressing need to reduce the consumption of PC. The CI represents the world's third-largest industrial energy consumer, and the component related to the production of PC alone represents 7% of the carbon dioxide (CO2) emissions globally (OECD, 2018). PC is undoubtedly the most used material in construction in terms of its relative volume. Raw materials for PC production are generally plentiful and they are also available throughout the world. It is possible to state that, , at this moment, there is no other material with the same availability as the PC, which might be able to fulfil the construction’s technical requirements as the concrete’s main component. In this sense, it is imperative that the cement industry obtains viable technical solutions that allow the reduction of PC consumption. That reduction can be achieved either by its direct replacement with another material (e.g. using fly ash), or by improving the cement and concrete matrix performance with the addition of new materials, such as NM. This second option is quite interesting, since it allows u s to maintain the cement and concrete matrix properties/characteristics, reducing PC consumption by adding a tiny amount of a NM.
2. Nanomaterials
The NM evolution has allowed the production of new cement-based nanocomposites with previously unimaginable properties. In general, NM can be grouped into three main types: the zero-dimensional (0D) nanoparticles, such as nanosilica; the one-dimensional (1D) nanofibres, such as carbon nanotubes and, lastly, the most recent two-dimensional (2D) nanosheet, i.e., graphene oxide (GO) (Chuah et al., 2014). These materials, especially the 1D and 2D NM, have the ability to, in very small dosages, strengthen the cement and concrete matrix through the reinforcement and pore refinement. This allows conventional cement composites to achieve higher performance levels, or to maintain the same performance levels while decreasing PC consumption (Yang et al., 2017).
3. Graphene oxide
In the particular case of GO, we are in the presence of one of the most recent advances in materials science, with enormous potential to be used as nano-sized additive for cementitious materials (Tong et al., 2016). The GO shows a number of unusual properties, namely: super-high specific surface area, ultra-high strength and elastic modulus (Wang et al., 2017); excellent thermal, electrical and optical conductivity (Wang et al., 2017); since it easily forms composites with polymer and ceramic materials and contains a large concentration of hydroxyl, epoxide, carboxyl and carbonyl functional groups that are compatible with water and, for this reason, it is highly dispersible in polar liquids (Saafi et al., 2015). Its introduction in the production of cement and concrete implies
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New Trends in Green Construction