## 1 Introduction
Workability is always an essential characteristic of mortar mixtures in general. Numerous researchers acknowledge the drawbacks of construction that result from the incorporation of GO. It is due to the hydrophilic functional groups or extensive surface area of GO, which can absorb a significant amount of water during the construction process [1]. Nevertheless, the primary reason for the detrimental impact of GO on the fluidity of the mortar is the significant quantity of free water that the flocculation process captures [11]. In a similar manner, the Van der Waals attraction of the nanosheets causes the cement particles to adhere to one another, thereby decreasing the fluidity of the mixture. GO is deposited on the surface of the cement particles [12]. In terms of the dispersion capacity of GO in a cement mixture, numerous studies that have been conducted thus far have demonstrated that the addition of a modest quantity of GO can significantly improve the mechanical characteristics of cement-based substances. However, dispersing GO well in the mixture is always a challenge [13; 14; 15] because this directly affects the mechanical properties and durability of the composite material. Alternatively, if GO flocculation occurs, it will result in the formation of voids and zones of low strength within the mixture. It will have detrimental impacts on the material's qualities. In addition, the mass production of GO is also a question mark that needs to be harmonized with the local context of cement-based materials. Generally, new materials must compensate for the expenses related to cultural, production, and training adjustments. If the specified criteria are not fulfilled, the utilization of the novel substance, notwithstanding its exceptional performance, is restricted in its potential uses, with no exemption for GO specifically. Meanwhile, many studies have shown that fly ash (FA) is a common mineral additive and is often used to improve workability and increase the strength of mortar and conventional concrete [16; 17]. However, some properties of fly ash also need to be noted before being put into use. Type F fly ash was selected according to ASTM C618 due to its widespread use in construction materials and its compatibility with the cementitious matrix. Derived from bituminous and anthracite coals, Type F fly ash has a lower calcium content compared to Type C fly ash, making it more suitable for the specific objectives of this study, which aims to enhance the mechanical properties and durability of cement mortar. Loss on ignition (LOI) is the total content of unburned carbon residue. The most adverse effect of using fly ash with a high carbon content is the need for a higher water demand, which creates more porosity upon hardening, thereby reducing compressive strength compared to standard mixtures. To ensure good performance, fly ash must be processed so that the loss on ignition content is less than 6%, as specified by ASTM C618. Therefore, this paper focuses on investigating the effects of GO and FA on the workability and durability of mortar. The correlation between each parameter is also analyzed and discussed using experimental and mathematical methods.