# Use of Lignin, Waste Tire Rubber, and Waste Glass for Soil Stabilization
## 3 Specim Preparation and Test Methods  
The complete experimental program of this study is shown in Figure 4. The low-plasticity clay, the glass powder, and the lignin were placed in an oven at 105 \({}^{\circ}\)C for 24 h to remove the moisture and dry completely. A standard compaction test was conducted to determine the optimum water content and maximum dry unit weight of all predetermined mix ratios for experimental studies. The standard compaction test was performed according to ASTM D 2216 [52] and Turkish standard TS 1900-1 [48] for different mix ratios. In the standard compaction test, water was gradually added to the soil samples. Each moistened sample was then placed in a standard compaction mold with a diameter of 105 mm and a height of 115.5 mm. The soil was compacted in three layers, with each layer having approximately the same mass. Each layer was compacted by 25 blows with a 2.5 kg hammer dropped from a height of 305 mm above the sample. This procedure was repeated three to five times, adding more and more water to the soil. The relationship between dry density and water content observed in these tests allowed the maximum dry density and optimum water content to be determined. For sample preparation, the clay soil was mixed with lignosulfonate, glass powder, and rubber tires in different ratios (three different mixtures for lignocellulosic and five different mixtures for rubber tires), using the dry weights of the materials for the mixtures. The mixing ratio of the additives was chosen on the basis of previous studies [53; 54; 55; 56] in which each type of waste was tested in different ratios. All specimens were compacted at standard Proctor compaction energy and optimum water content. The specimens were also prepared at optimum water content for uniaxial compressive strength, California Bearing Ratio, and dynamic triaxial testing. The compositions of the specimens with the different mixtures are shown in Table 2.  
To assess geotechnical properties, unconfined compressive strength (UCS) tests were conducted on soil samples stabilized with various waste additives. These samples, prepared at optimum moisture content, were molded into specific dimensions using sample molds. The UCS test is used to evaluate the strength of soil stabilization mixtures and to understand the impact of additives on soil strength. The test followed the procedures outlined in TS 1900-2 [57] and ASTM D 698 [58] with a strain rate of 1% per minute maintained throughout. Figure 4: Experimental program with flow chart. The soil mixtures containing glass powder, rubber tire crumbs, and lignocellulosic were compacted using a standard Proctor mold. After compaction, the specimens were extracted from the mold with a sharpened brass tube having an inner diameter of 38 mm and a height of 76 mm. Three specimens were prepared for each mixing ratio. These test specimens were then wrapped in plastic foil and covered with a damp cloth to maintain moisture, and the cloth was moistened daily. The specimens were cured for periods of 7 and 28 days. The UCS results reported are the average values obtained from the three tests conducted on each mixture. In determining the proportions of waste materials added to the mixtures, an approach has been adopted that aims to reuse the maximum amount of waste possible, taking into account both the positive contribution of the waste materials used to engineer the properties of the soils and sustainability. Curing times longer than 7 and 28 days are expected to increase the strength properties of the mixtures. However, in this study, tests were carried out with the most common curing times (7 and 28 days) and the results evaluated. The California Bearing Ratio (CBR) value is a critical factor in road pavement design, as it correlates with the required pavement thickness. A lower CBR value necessitates a thicker pavement, whereas a higher CBR value allows for a thinner pavement. The CBR test follows the standards set by ASTM D 1883 [59] and TS 1900-2 [57].