## 3 Experimental Program
### Material Testing and Analysis Methods  
The experimental program encompassed a series of tests, including the determination of the oxide composition and examination of the particle mineralogy and morphology  
Figure 3: (**a**) Aging of BOF slags in laboratory conditions; (**b**) carbon oxide concentration measurement by AQ Expert Machine. of BOF slags through XRD, XRF, and grain-size analysis. Additional tests involved the assessment of aggregate properties, such as absorption, specific gravity, moisture content, soundness (sulfate attack and freeze and thaw tests), aggregate crushing value, and abrasion resistance. Moreover, an evaluation of the expansion potential of mortar bars containing BOF slag and river sand (at 14 and 28 days) was conducted to ascertain both the fresh and hardened properties of these mortar bars. As previously detailed, the research team had the opportunity to analyze the oxide composition of BOF slags using the Axios mAX X-ray fluorescence (XRF) spectrometer from PANalytical. This machine employs the SST-mAX X-ray tube, featuring close coupling and ZETA Technology. For both the X-ray fluorescence (XRF) and X-ray diffraction (XRD)  
Figure 4: Produced stockpiled BOF filler. Figure 5: The process of mixing two types of fillers (MP1 + BOF). Figure 6: “DAD-KT” thermostable adhesive additive. analyses, 45-micron-sized samples of BOF slags were prepared using a Proctor compaction apparatus. X-ray diffraction (XRD) analysis with Cu K\(\alpha\) radiation (utilizing the Rigaku SmartLab System) was employed, with a scan range set at 5-70\({}^{\circ}\) and a continuous scan type with a sampling interval of 0.03\({}^{\circ}\), allowing for the identification of the primary mineral constituents. The grain-size distributions of BOF steel slags and river sand conformed to ASTM 2007c, ASTM E 105, and ASTM E 122. The aggregate absorption, specific gravity, and moisture content of the BOF slag samples were determined within 3 days in accordance with ASTM C 127, ASTM C 128, and ASTM C556. The specific gravity of the BOF slags is expressed as the bulk specific gravity, bulk specific gravity (SSD) (saturated surface-dry), or the apparent specific gravity of the BOF samples. The specific gravity and absorption determination of the fine BOF aggregates were performed using the cone test. The aggregate soundness test followed the guidelines in ASTM C 88. Determining the resistance to freezing and thawing of the BOF slag samples involved the preparation of a 3% NaCl solution in accordance with LS-614. Both coarse and fine BOF samples were prepared similarly to the soundness test procedure. The BOF samples were placed in containers, and a 3% NaCl solution was added before subjecting them to environmental testing within the chamber at Nazarbayev University's Geotechnical laboratory. The BOF aggregate crushing value was determined following the guidelines of the BS 812-110. Samples of BOF slag retained on a 9.5 mm sieve were selected for the experiment and manually compacted within a cylinder mold (as shown in Figure 7). An expansion test was conducted in accordance with ASTM D 4792. BOF slag aggregates were compacted according to the D 1883 (Figure 8). Then, the samples in the CBR molds were placed inside a hot water bath at a temperature of 70 \(\pm\) 3 \({}^{\circ}\)C for a period of 14 days. During these 14 days, the volume expansion levels of the compacted specimens inside the water were recorded 4 times a day (Figure 8). Figure 8: Compacted BOF samples in CBR molds before testing and during testing for expansion. Figure 7: BOF sample before and after Compression Testing Machine. An accelerated mortar bar expansion test was performed in accordance with ASTM C 1260. BOF and river sand-added mortar bar specimens were placed in sealed containers filled with 1 M NaOH solution at 80 \({}^{\circ}\)C temperature, and also in sealed containers with water at an 80 \({}^{\circ}\)C temperature (Figure 9). The expansions of these mortar bars in two conditions were observed within 14 and 28 days.