**1. Introduction**

The use of ordinary Portland cement (OPC) by replacing it with recycled cement in certain proportions is an interesting issue for sustainable environmental awareness [1,2]. During cement production, a high amount of energy is consumed, and a high amount of carbon dioxide (CaO2) is released into the atmosphere [3]. Therefore, cement additives are of interest to reduce cement production [4,5]. Waste is generally defined as residues from industrial production processes, residues arising from the transfer, or product residues that have completed their economic life [6–14]. With the development of modern cities, the decrease in natural resources, climate change, and increasing awareness of environmental protection, there is an urgent need to develop building materials that will reduce greenhouse gas emissions [2,15]. Waste glass powder (WGP), which is increasing with the effect of industrialization and the increase in urban transformation, attracts the attention of researchers as a concrete additive material due to its economic and mechanical performance effects [4,5,16–21]. Since there is no regular storage area for waste glass, it increases the risk of soil and water pollution due to its oxidation effect. Therefore, the use of recycled glass in concrete production will provide significant contributions to reducing environmental problems [2,3,22,23].

According to ASTM C618-19, 2019, since waste glass consists of a large amount of calcium and an amorphous structure, it can be ground into powder to obtain pozzolanic material or cement additive [24–26]. Therefore, WGP can be used in concrete production by replacing it with cement in certain proportions [2]. Recent studies show that replacing 15–25% glass powder with cement increases the mechanical properties of concrete [6,15,21]. Aliabdo et al. used 25% substitution with cement to investigate the mechanical effect of WGP in concrete as a cement substitute. According to the results obtained, it was observed that the void ratio and density of the samples decreased, while the tensile and compressive strengths increased [27]. Al Saffar et al. in their study to test the interaction of WGP, added cement mortar with other materials and found that the compressive strength of the samples increased as the glass powder addition rate increased. They obtained the highest strength with the addition of 25% glass powder [15]. Elaqra et al. (2019) added 4% by weight to the mix to investigate the effect of WGP on fresh and hardened concrete. They found that as the amount of WGP increased, the machinability increased, and the maximum compressive strength was reached with the addition of 20% WGP at 28 days of cure [28]. It is well known that in the case of fine grinding of soda–lime glass, the reactivity of pozzolanic increases as the particle size decreases [29]. Zhang et al. in their study to examine the effect of WGP particle size on the mechanical and microstructures of concrete, found that the particle size distribution of WGP has a significant effect on the properties of WGPbased concrete [30]. Shao et al. in their experimental study to observe the effect of finely ground WGP on the compressive strength of concrete found that the pozzolanic reactivity increases as the WGP particle size decreases. They found that WGP, with a particle size of 38 μm, was replaced by 30% with cement, resulting in 4.1 MPa greater compressive strength [31]. It was found that WGP pozzolanic reactivity was replaced by 0, 15, 30, 45, and 60% of weight cement, while below 30% the concrete compressive strength did not decrease due to the pozzolanic reaction between WGP cement hydration products. In fact, with the addition of 60% WGP, the resistance to chloride ion and water penetration increased continuously, while the concrete compressive strength increased by around 85% [32]. In the study by Peril and Sangle, it was observed that when WGP was mixed with 30% cement, an increase in compressive strength between <38 μm and <75 μm was between 20% and 10% [33]. Khatib et al. found in their study that there was a 1.2% increase in concrete compressive strength with the addition of 10% WGP [34]. In a similar study, Madandoust and Ghavidel found that the compressive strength of the control sample was higher than the concrete with glass powder added at every stage, the compressive strength of both samples increased with aging [35]. In their study, Tejaswi et al. stated that the compressive strength increased by 1.5% with the addition of 10% WGP. However, they found that the compressive strengths were at equal levels when 20% was substituted [36]. Vasudevan et al.

observed a 1.05% increase in concrete compressive strength when 20% WFP addition was <90 μm [37]. Schwarz et al. found that the addition of 20% WGP increased the compressive strength by 19% when <75 μm [38]. They state that while the strength decreases as a result of the 7-day compressive strength test, the compressive strength does not change as a result of the 28- and 91-day tests <75 μm. In addition to strength performance, the failure processes of brittleness materials are also important. Some researchers have studied the failure processes of brittleness materials [39,40]. Since the risk of fracture will increase under sudden loads, it is beneficial to take measures to increase elastic behavior.

Dust and particles from soda glass were mostly used in previous studies. However, its usability in concrete was investigated by replacing fine aggregate in self-compacting concrete with waste particles obtained from cathode ray tubes. The results had a positive effect on the durability properties of concrete [41]. Past studies have shown that ground glass powder can increase the pozzolanic reactivity of secondary cementitious materials. Therefore, the granule size of the ground glass powder has important effects [42,43]. Ahmet et al. examined different methods of using waste glass in concrete and stated that particle size, substitution ratio, and chemical composition have important effects on the mechanical durability of concrete. For example, as the grain size decreases, workability becomes more difficult but pozzolanic and strength increase [44]. The particle size of the waste glass, which must be taken into account during the mix design, may affect the active silica reaction depending on the rate of substitution.

Solid waste management is an important issue for most developing countries [45]. Instead of storing or disposing of waste materials such as glass, plastic, and metal, reusing or recycling has become a more attractive option. Waste glass has started to be widely preferred for concrete production in civil engineering applications in recent years. Since the employing of waste glass in concrete can assist to reduce environmental pollution, protect natural resources and produce low-cost concrete, WGP can be preferred instead of either natural aggregates or cement due to its pozzolanic effect. Although many studies have been conducted on this subject, there are differences in the results obtained from the literature. Thus, there still remains a need to investigate the mechanical behavior of concrete with partial substitution of waste glass and the ideal dosage of it. Based on this motivation, an experimental study was carried out on some test specimens. Analytical solution proposals have been developed according to the data obtained from the experimental study. The proposed formulas will serve as a guide for researchers and manufacturers and will accelerate future studies to be more effective.

#### **2. Experimental Program**

In this study, the main aim is to investigate the effect of glass powder when it is replaced with cement. Furthermore, the effects of all replacements with glass are investigated. Nine mixes including the reference were designed. C represents cement replacement, MIX represents cement, fine aggregate, and coarse aggregate replacement. Table 1 summarizes the sample properties. For the MIX design, each type of material was replaced with certain amounts of recycled glass. The size of fine aggregates is 1 mm to 4 mm and the corresponding waste glass was 1.7 mm to 4 mm. Size of coarse aggregate size was selected as 5–12 mm and the corresponding waste glass was also 5–12 mm. The particle size of cement particles was between 0.02 mm to 0.1 mm and the size of glass waste powder was 0.1–0.2 mm. Figure 1 demonstrates the used aggregates and cement and also their replacements which are glass powder and glass grains. Figure 2 demonstrates the recycled glass in concrete.
