# Influence of Waste Filler on the Mechanical Properties and Microstructure of Epoxy Mortar
## 1 Introduction  
Cement mortar comprises Portland cement, fine aggregates, and water, whereas Portland cement concrete comprises the same components as mortar and coarse aggregate. Portland cement mortar is primarily used in masonry work because of its better hardening and adhesion capabilities. Portland cement concrete is used mainly as a constructive material because of its cheap cost, high strength, and easier utilization [1]. Both Portland cement mortar and cement concrete are porous and can be easily intensified by surrounding factors such as shrinkage, expansion, salinity, and acidity. These factors can easily damage its mechanical, physical, and permeation resistance properties. To overcome the mentioned drawback of mortar and concrete, epoxy is widely used as a substitute in modern concrete technology. In recent years, the addition of epoxy has been used in the combination of mortar and concrete [2]. Epoxy mortar is commonly used as construction material to fix flaws and damages on concrete structures, due to its quick curing, high strength, outstanding bonding, low permeability, and exceptional chemical resistance. Furthermore, epoxycomposites with concrete could be a practical manufacturing of railroad sleepers (substitute for industrial flooring) [3] and overlays for pavement [4]. Epoxy resin is comparatively expensive, which is the main barrier to the epoxy composite's widespread acceptance as opposed to concrete made with regular Portland cement. As a result, numerous investigations have been carried out to establish the ideal epoxy resin proportion. Using an epoxy matrix with a resin-to-filler ratio of 60:40, epoxy concrete can be made with evenly distributed particles. Using the Taguchi approach [5], the ideal design under a temperature exposure of \(-15\)\({}^{\circ}\)C was found to have 14% epoxy resin content along with coarse aggregates ranging from 9.5 mm to 19 mm. For epoxy mortar, 18% by weight was reported to be the ideal epoxy resin content, because higher epoxy resin resulted in a reduction in compressive strength. Addition of epoxy results in improved physical, thermal, and mechanical properties for epoxy-based polymer mortar. It is observed that an increase in the mass fraction of epoxy could improve the mechanical properties of the epoxy-based polymer mortar. The use of waste as environment-friendly building materials has been a common research strategy due to growing awareness of sustainable development [6; 7]. To decrease the use of natural resources and enhance the mechanical qualities of epoxy resin, various waste products have been added to it. Blast furnace slag [8], fly ash [9], sand washing wastes [10], silica fume [11], palm oil fuel ash [12], recycled short-milled carbon fibers [13], red mud [14], and recycled crumb rubber particles [15] are all fillers that have been examined in the past. The most widely utilized micro fillers among these waste products are fly ash and silica fume because they have high fineness and a low thermal coefficient and are cheap, non-toxic, widely available, and compatible with other components of epoxy resin. Epoxy resin attracted particular attention from researchers in building materials due to its extraordinary properties, such as high strength resistance to a chemical attack in aggressive environments, good adhesion, permeability, and a controllable setting time [2]. The epoxy mortar's mechanical strength increased as the epoxy resin content increased. By taking samples of a composition of 20% fly ash (FA) and 80% ground coal burning ash (GCBA), it was observed that the mechanical strength increased from 32 MPa to 38 MPa, but it decreased as the as the epoxy resin content increased from 10% to 30% [16]. In some cases, industrial waste materials may have properties that make them suitable for specific applications. For example, steel slag may be used as a construction aggregate due to its durability and strength [17]. Marble dust may be used as a filler in concrete to improve its workability and reduce the amount of cement needed [18].