## 1 Introduction  
There is no doubt that cementitious composites shape the civil engineering industry, as they are the most widely used materials, more than steel and wood combined, for construction purposes [1]. Due to their physical-mechanical parameters, concrete and mortar provide architects and builders with a wide range of applications. There is a great need and interest in research aiming at reducing the carbon footprint of cementitious composites. Mortar, on which this research is focused, can be defined as a composite material, consisting of small-size aggregates and a binder (a mixture of hydraulic cement and water). Among its components, the greatest threat to the environment is the production of Portland cement, upon which most hydraulic types of cement employed today are based [2]. Additionally, cement plants generating power cause cement production to be a leading source of carbon dioxide atmospheric emissions. It is estimated that cement production is responsible for 5% of global emissions of carbon dioxide [3]. Due to the global warming problem, the cement industry is facing the problem of improvement and adaptation to new conditions of reducing its carbon footprint. One of the possibilities for making mortar more eco-friendly is the partial replacement of cement with fly ash. Fly ash can be collected in the dust collection systems that remove particles from the exhaust gases of power plants that burn pulverized coal. It is generally finer than Portland cement and consists mostly of small spheres of a glass of complex composition involving silica, ferric oxide, and alumina [4]. Due to control standards, fly ash cannot be released into the atmosphere and must be stored at coal power plants or placed in landfills. This creates the opportunity for recycling and a reduction in waste. The replacement of cement with fly ash can be beneficial for mortar parameters, decreasing the shrinkage and increasing its resistance to aggressive factors, frost resistance, fracture toughness, and the interfacial zone around the aggregate [5]. Usually, the replacement does not exceed 30% of the binder because of the longer setting time, lower early strength, and altered durability. Higher fly ash contents (high volume fly ash concrete, cementless ash concrete) require alkalization of the hardening process [6]. Another step into sustainable mortars is the addition of granite powder, which is waste arising from the rock-crushing process, as a partial cement replacement. In accordance with the literature survey, there is a huge potential for granite powder as a replacement for natural fine aggregates [7]. Granite powder application in concrete can contribute not only to reducing landfills but also improving workability, stiffness, strength, and the packing density of the aggregate [8] compared to ordinary aggregates and Portland cement mortars. Similarly to fly ash, the addition of granite powder beyond 30% caused a strength decrease, according to the literature [9]. The conscious choice of ingredient type and amount, additives, and admixtures allows us to obtain different types of mortar, prepared for a specific task to fulfill. This research is focused on studying mortar with its surface subjected to dynamic loading with fly ash and/or granite powder as the partial cement replacement. One of the most important parameters when dealing with scuffing, scratching, wearing down, marring, or rubbing away the surface is abrasion resistance [10]. The significant impact of it on mortar's surface durability has been proved by several pieces of research [11; 12]. The abrasion resistance of mortar depends on parameters such as paste hardness, aggregate hardness, aggregate/paste bond, and most importantly, compressive strength [13]. Other practices such as curing and surface finishing techniques can also have a strong influence on it [14]. Knowledge of the abrasion mechanism may be useful in the design of elements exposed to contact with moving objects such as industrial floors, slabs, pavement, roads, airport aprons, etc.