Effect of Glass Fiber and Rubber on the Properties of Expansive Soil and Its Utilization as Subgrade Reinforcement in Road Application

: Expansive soil is a problematic material for construction due to its high potential for volume change, which can cause damage to road infrastructure. This study aims to investigate the effect of glass fi - ber and rubber on the properties of expansive soil and its suitability as subgrade reinforcement in road applications. The maximum dry density (MDD), optimum moisture content (OMC), and Cali - fornia Bearing Ratio (CBR) were evaluated for varying percentages of glass fiber and rubber in the soil. The results showed that the addition of glass fiber and rubber had a positive effect on the soil properties. The MDD and CBR increased with increasing fiber and rubber content, while the OMC decreased. Additionally, the reinforced soil exhibited a significant improvement in strength com - pared to the unreinforced soil. The study suggests that the incorporation of glass fiber and rub - ber can enhance the performance of expansive soil as subgrade reinforcement in road applications.


Introduction:
Expansive soil is a type of soil that exhibits significant volume changes due to changes in moisture content.This type of soil is widespread and is found in many parts of the world.Expansive soil is problematic for construction due to its high potential for volume change, which can cause damage to road infrastructure.The damage caused by expansive soil can be severe and can result in costly repairs.One solution to mitigate the impact of expansive soil on road infrastructure is to reinforce the soil using various materials.In this study, the effect of glass fiber and rubber on the properties of expansive soil and its utilization as subgrade reinforcement in road application was investigated.

Literature Review:
Expansive soils are a significant problem for pavement design and construction.The presence of expansive soils in subgrade layers can lead to significant pavement damage and, ulti mately, pavement failure.Therefore, the stabilization of expansive soils is necessary to improve pavement performance.One potential solution to this problem is the use of reinforcement materials, such as glass fibers and rubber, to improve the strength and stability of the soil.Glass fibers have been shown to be an effective reinforcement material for expansive soils.A study conducted by Sharma and Singh (2016) investigated the effect of glass fibers on the engineering properties of expansive soil.The study found that the addition of glass fibers to the soil resulted in an increase in the maximum dry density and a decrease in the optimum moisture content, indicating improved compaction characteristics.In addition, the study found that the addition of glass fibers improved the California Bearing Ratio (CBR) and the Unconfined Compressive Strength (UCS) of the soil.Rubber has also been studied as a reinforce-ment material for expansive soils.A study conducted by Lee and Shin (2013) investigated the effect of crumb rubber on the properties of expansive soil.The study found that the addition of crumb rubber to the soil resulted in an increase in the maximum dry density and a decrease in the optimum moisture content.Additionally, the study found that the addition of crumb rubber improved the CBR of the soil.In addition to improving soil properties, the use of glass fibers and rubber in soil stabilization can provide an alternative solution for the disposal of plastic waste.A study conducted by Akinmusuru et al. (2017) investigated the use of recycled low-density polyethylene (LDPE) and waste tire rubber as stabilizing agents for expansive soils.The study found that the use of these waste materials improved the CBR and UCS of the soil while also reducing the amount of waste materials that would otherwise be sent to landfills.Overall, the use of reinforcement materials such as glass fibers and rubber can provide a cost-effective and environmentally friendly solution for the stabilization of expansive soils in pavement applications.The results of the studies mentioned above suggest that the addition of these materials can improve soil properties and pavement performance while also providing an alternative solution for the disposal of waste materials.

Methodology:
The study was conducted in the laboratory using expansive soil samples collected from a construction site in the Amman region.Glass fiber and rubber were added to the soil at varying percentages, and the effect on the soil properties was measured.The maximum dry density (MDD) and optimum moisture content (OMC) were determined using the standard Proctor compaction test.The California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCCT) were measured using the standard test methods.

Materials:
The study utilized an expansive soil collected from a site in Amman.The soil was classified as an A-7-6 soil according to the Unified Soil Classification System (USCS).The soil was tested for its physical and geotechnical properties, including the maximum dry density (MDD), optimum moisture content (OMC), and California Bearing Ratio (CBR).The effect of glass fiber and rubber on these properties was investigated.The glass fiber used in this study was obtained from waste glass and had a length of 12mm and a diameter of 0.2mm.The rubber used was obtained from discarded tires and was ground to a size of 4.75mm.The soil was reinforced with varying percentages of glass fiber (0%, 0.5%, 1%, and 1.5%) and rubber (0%, 1%, 5%, and 9%).The MDD, OMC, and CBR were determined for each reinforced soil sample.The strength of the reinforced soil was evaluated using the Unconfined Compression Strength (UCS) test.The UCS test was conducted for varying percentages of glass fiber in the reinforced soil.

Results and Discussion:
The results of the study showed that the addition of glass fiber and rubber had a positive effect on the soil properties.The MDD increased with increasing fiber and rubber content, as shown in Figures 1 and 5, respectively.The highest MDD was obtained for the soil reinforced with 1.5% glass fiber and 0% rubber.The OMC decreased with increasing fiber and rubber content, as shown in Figures 2 and 4, respectively.The lowest OMC was obtained for the soil reinforced with 1.5% glass fiber and 9% rubber.The CBR increased with increasing fiber and rubber content, as shown in Figures 3 and 6 effect of glass fiber on maximum dry density tively.The highest CBR was obtained for the soil reinforced with 1.5% glass fiber and 5% rubber.California Bearing Ratio (CBR) is an essential parameter for subgrade soil design.The effect of the glass fiber and rubber on the CBR of the soil is presented in Figure 3 and Figure 6, respectively.
It can be observed that as the percentage of glass fiber and rubber in the soil increases, the CBR also increases.The increase in CBR can be attributed to the improvement in the maximum dry density and optimum moisture content due to the addition of glass fiber and rubber.The addition of glass fiber and rubber also helps to reduce the plasticity of the soil, which in turn improves the CBR of the soil.The maximum CBR value of 22.9% was obtained for the soil reinforced with 1.5% glass fiber, while the maximum CBR value of 20.96% was obtained for the soil reinforced with 5% rubber.The comparison between the effects of glass fiber and rubber on CBR is presented in Figure 7.It can be observed that the CBR of the soil reinforced with 1% crumb rubber is slightly higher than the CBR of the soil reinforced with 1% glass fiber.However, the CBR of the soil reinforced with 1.5% glass fiber is significantly higher than the CBR of the soil reinforced with 5% rubber.Therefore, it can be concluded that glass fiber is a more effective reinforcement material for improving the CBR of expansive soil.

Unconfined Compressive Strength (UCS)
The relationship between the glass fiber percentage in reinforced soil and the UCS is presented in Figure 8.It can be observed that as the percentage of glass fiber in the soil increases, the UCS also increases.The increase in UCS can be attributed to the improvement in the maximum dry density and optimum moisture content due

Figure (5): effect of rubber content on maximum dry density
to the addition of glass fiber.The addition of glass fiber also helps to reduce the plasticity of the soil, which in turn improves the soil's UCS.
The maximum UCS value of 98.41 kPa was obtained for the soil reinforced with 4% glass fiber.
The result of the study showed that the addition of both glass fiber and crumb rubber to the expansive soil improved the engineering properties of the soil, making it more suitable for subgrade reinforcement in road applications.The following sections discuss the effects of glass fiber and rubber on the properties of the expansive soil.

Effect of Glass Fiber on the Properties of Expansive Soil
The effect of glass fiber on the maximum dry density (MDD), optimum moisture content (OMC), and California bearing ratio (CBR) of the expansive soil is shown in  (1), the maximum dry density (MDD) of the soil increased with an increase in the percentage of glass fiber.The MDD increased from 1.92 g/cm3 for the unreinforced soil to 1.75 g/cm3 for the soil reinforced with 1.5% glass fiber.This increase in MDD can be attributed to the filling of the voids in the soil by the glass fibers, which leads to a denser and more compacted soil.Figure (2) shows the effect of glass fiber on the optimum moisture content (OMC) of the soil.The OMC increased with an increase in the percentage of glass fiber.The OMC increased from 10.3% for the unreinforced soil to 14.97% for the soil reinforced with 1.5% glass fiber.This increase in OMC can be attributed to the hydrophilic nature of the glass fiber, which tends to absorb moisture from the soil and thereby increase the water content.Figure (3) shows the effect of glass fiber on the California bearing ratio (CBR) of the soil.
The CBR increased with an increase in the percentage of glass fiber.The CBR increased from 13% for the unreinforced soil to 22.9% for the soil reinforced with 1.5% glass fiber.This increase in CBR can be attributed to the reinforcement provided by the glass fiber, which improves the load-bearing capacity of the soil.
The dry density and moisture content of the unreinforced soil and the soil reinforced with glass fiber are shown in Table 1.As shown in the table, the dry density of the soil increased with an increase in the percentage of glass fiber.
The moisture content of the soil also increased with an increase in the percentage of glass fiber.
The effect of rubber on the maximum dry density (MDD), optimum moisture content (OMC), and California bearing ratio (CBR) of the expansive soil is shown in  and rubber significantly improved the MDD and OMC of the expansive soil.Figure 1 and Figure 2 show the effect of glass fiber on the MDD and OMC, respectively.The MDD increased from 1.92 g/cm³ for the unreinforced soil to 1.75 g/cm³ for the soil reinforced with 1.5% glass fiber.The OMC increased from 10.3% for the unreinforced soil to 14.97% for the soil reinforced with 1.5% glass fiber.Figure 3 shows the effect of glass fiber on the CBR of the soil.The CBR increased from 13% for the unreinforced soil to 22.9% for the soil reinforced with 1.5% glass fiber.Table 1 shows the dry density and moisture content for the unreinforced and reinforced soils with glass fiber.Similarly, the addition of rubber significantly improved the MDD and OMC of the expansive soil.Figure 4 and Figure 5 show the effect of rubber on the OMC and MDD, respectively.The MDD increased from 1.92 g/cm³ for the unreinforced soil to 1.73 g/cm³ for the soil reinforced with 9% rubber.The OMC decreased from 10.3% for the unreinforced soil to 8.42%.Furthermore, it was observed that the addition of glass fibers led to an increase in CBR value, as shown in Figure (3).The CBR value increased from 13% for unreinforced soil to 22.9% for soil reinforced with 1.5% glass fiber.This indicates that the use of glass fiber as subgrade reinforcement can improve the load-bearing capacity of expansive soils and make them more suitable for road construction.
Table 1 shows the effect of glass fiber on the dry density and moisture content of the soil.As the percentage of glass fiber increased, the dry density of the soil also increased, while the moisture content decreased.For example, the dry density increased from 1.71 g/cm3 for unreinforced soil to 1.55 g/cm3 for soil reinforced with 1% glass fiber.Similarly, the moisture content decreased from 11% for unreinforced soil to 10.1% for soil reinforced with 0.5% glass fiber.This indicates that the addition of glass fiber can improve the compaction characteristics of the soil, which is important for subgrade reinforcement in road construction.The effect of rubber on the properties of expansive soil and its utilization as subgrade reinforcement in road application was also investigated.Figure (4) shows the effect of rubber content on the optimum moisture content (OMC) of the soil.
The OMC decreased with an increase in rubber content.For example, the OMC decreased from 10.3% for unreinforced soil to 8.42% for soil reinforced with 9% rubber.This indicates that the addition of rubber can improve the stability of the soil and reduce its susceptibility to moisture changes.Figure (5) shows the effect of rubber content on the maximum dry density (MDD) of the soil.The MDD increased with an increase in rubber content up to a certain limit, beyond which it started to decrease.For example, the MDD increased from 1.92 g/cm3 for unreinforced soil to 1.8 g/cm3 for soil reinforced with 5% rubber, but then decreased to 1.73 g/cm3 for soil reinforced with 9% rubber.This indicates that the addition of rubber can improve the compaction characteristics of the soil up to a certain limit, beyond which its effectiveness decreases.Figure ( 6) shows the effect of rubber content on the CBR value of the soil.The CBR value increased with an increase in rubber content up to a certain limit, beyond which it started to decrease.For example, the CBR value increased from 13% for unreinforced soil to 20.96% for soil reinforced with 5% rubber, but then decreased to 17.01% for soil reinforced with 9% rubber.This indicates that the addition of rubber can improve the load-bearing capacity of the soil up to a certain limit, beyond which its effectiveness decreases.
Table 2 shows the effect of rubber on the dry density and moisture content of the soil.As the percentage of rubber increased, the dry density of the soil also increased up to a certain limit, beyond which it started to decrease, while the moisture content decreased.For example, the dry density increased from 1.71 g/cm3 for unreinforced soil to 1.85 g/cm3 for soil reinforced with 1% rubber, but then decreased to 1.54 g/ cm3 for soil reinforced with 5% rubber.Similarly, the moisture content decreased from 11% for unreinforced soil to 10.57% for soil reinforced with 1% rubber, but then decreased to 10.
Table 3 presents a comparison between crumb rubber and glass fiber reinforcement on unconfined compressive strength (UCS) values of a soil sample.UCS is a measure of the strength of a soil sample when subjected to compressive loading without any lateral restraint.
The table shows that the addition of 1% glass fiber to the soil sample increases the UCS from 27.8 to 75.3, which is a significant improvement.On the other hand, the addition of 1% crumb rubber to the soil sample increases the UCS to 42.7, which is also an improvement, but not as significant as the glass fiber.Table 4 shows the variations in maximum dry density (MDD), optimum moisture content (OMC), California Bearing Ratio (CBR), and unconfined compressive strength (UCS) of reinforced soil with different percentages of glass fiber.The values of MDD and UCS show an increasing trend with an increase in the percentage of glass fiber.On the other hand, the OMC shows a marginal increase with an increase in the percentage of glass fiber.The table also shows the effect of glass fiber reinforcement on the CBR value of the soil.It is observed that the CBR value of the soil increases with an increase in the percentage of glass fiber.This indicates that the soil becomes more resistant to deformation and better able to support loads with the addition of glass fiber reinforcement.It is interesting to note that the highest values of UCS and CBR are obtained at 1.5% glass fiber content.This suggests that 1.5% is the optimal percentage of glass fiber that can be added to the soil to enhance its mechanical properties.In summary, the results of Table 4 demonstrate that the addition of glass fiber can significantly improve the mechanical properties of soil.Moreover, the optimal percentage of glass fiber to be added to the soil can be determined by analyzing the variations in UCS, OMC, MDD, and CBR values at different percentages of glass fiber.Table 5 presents the relationship between the percentage of rubber content in reinforced soil and the corresponding UCS values.The ta-1.50% 1.00% 0.50% 0.00% strain (%) stress (Kpa) strain (%) stress (Kpa) strain (%) stress (Kpa) strain (%) stress (Kpa) 0 0 0 0 0 0 0 0 0.5 40.2 0.5 30.5 0.5 10.85 0.5 10.05   -------------------------------6.5 88.7 - -----------------------------------------------Table 3 -Relationship between glass fiber percentage in reinforced soil versus UCS ble displays the stress-strain behavior of reinforced soil at different levels of rubber content.The strain values are expressed as a percentage of deformation, while stress values are in kPa.The table shows that as the percentage of rubber content in the reinforced soil increases, the UCS value decreases.For example, at 0% rubber content, the UCS value is 0 kPa.However, at 5% rubber content, the UCS value drops to 51.6 kPa.This trend is observed throughout the table, indicating that the addition of rubber to the soil has a detrimental effect on the UCS value.It is also worth noting that the stress-strain behavior of reinforced soil changes with the percentage of rubber content.At lower rubber content levels, the stress-strain curve is more linear, whereas at higher rubber content levels, the curve becomes more nonlinear, indicating more ductile behavior.This is because the rubber particles act as energy dissipaters, absorbing the energy from applied loads and leading to more ductile behavior.In summary, Table 5 shows that the addition of rubber to reinforced soil has a negative effect on the UCS value but can lead to more ductile behavior at higher rubber content levels.The table provides valuable information for selecting the appropriate rubber content in reinforced soil, de-  ---------------5.5 49.5 5.5 40.2 5.5 24.8 - ---------------6 45.3 6 37.6 - -------------------------------6.5 39.1 - ---------------------------------------------- 6 presents the results of experiments conducted to investigate the effect of different percentages of rubber on the mechanical properties of reinforced soil.The table shows the values of the maximum dry density (MDD), optimum moisture content (OMC), California bearing ratio (CBR), and unconfined compressive strength (UCS) of the reinforced soil samples containing varying percentages of rubber.The results indicate that the addition of rubber to the soil mixture has a significant effect on the mechanical properties of the reinforced soil.As the percentage of rubber increases, the UCS and CBR values increase, while the MDD and OMC decrease.This is due to the fact that rubber particles occupy the void spaces in the soil mixture, which reduces the density of the soil and increases its porosity.The highest UCS value of 67.2 kPa was obtained for the sample containing 5% rubber, while the sample with 9% rubber had the highest CBR value of 17.01%.However, the MDD and OMC values decreased as the percentage of rubber increased, indicating that the addition of rubber to the soil mixture reduces its compaction and increases its water content.In summary, Table 6 shows that the addition of rubber to the soil mixture can improve the mechanical properties of the reinforced soil, but this improvement is accompanied by a decrease in the soil density and an increase in its water content.Therefore, the optimal percentage of rubber in the soil mixture should be carefully determined based on the specific engineering requirements and site conditions.
Table 7 provides a comparison between crumb rubber and glass fiber reinforced soil based on the UCS values.The UCS values of raw soil, 1% glass fiber reinforced soil and 1% rubber reinforced soil are presented in this table.The UCS value of the raw soil is 27.8 kPa, which is the lowest among the three types of soil.The UCS value of the 1% glass fiber reinforced soil is 75.3 kPa, which is significantly higher than the raw soil.On the other hand, the UCS value of the 1% rubber reinforced soil is 42.7 kPa, which is in between the values of raw soil and 1% glass fiber reinforced soil.This comparison suggests that glass fiber reinforcement is more effective in improving the UCS value of the soil than rubber reinforcement.Glass fibers are known for their high tensile strength and stiffness, which can contribute to improving the overall strength of the reinforced soil.On the other hand, rubber particles tend to deform and absorb energy when subjected to stress, which may result in a lower UCS value than glass fiber reinforcement.However, it is important to note that the choice of reinforcement material may depend on various factors, such as the application and environmental conditions.For example, in applications where flexibility and deformation tolerance are desired, rubber reinforcement may be a more suitable option than glass fiber reinforcement.

UCS (Kpa) Series1
Based on Tables 3, 4, 5, 6, and 7, several conclusions can be drawn regarding the effect of different types and percentages of reinforcement on the mechanical properties of soil.Table 3 shows a comparison between crumb rubber and glass fiber based on the UCS values, where it can be observed that the UCS of soil reinforced with 1% glass fiber is higher than the UCS of soil reinforced with 1% rubber.This indicates that glass fiber reinforcement is more effective than rubber reinforcement in increasing the strength of the soil.Table 4 presents the MDD, OMC, CBR, and UCS of reinforced soil with different percentages of glass fiber.It can be observed that as the percentage of glass fiber increases, the UCS and CBR values also increase, indicating that higher percentages of reinforcement result in stronger and more durable soil.Table 5 shows the relationship between the rubber percentage in reinforced soil versus UCS.The results indicate that the UCS of the reinforced soil increases as the percentage of rubber increases up to a certain point, after which the UCS starts to decrease.Therefore, it can be concluded that the optimum rubber content for reinforced soil is around 3%.Table 6 displays the MDD, OMC, CBR, and UCS of reinforced soil with different percentages of rubber.The results indicate that the UCS and CBR values increase with the addition of rubber up to 5%, after which the values start to decrease.Therefore, it can be concluded that the optimum rubber content for reinforced soil is around 5%.Finally, Table 7 compares the UCS values of raw soil, soil reinforced with 1% glass fiber, and soil reinforced with 1% rubber.The results indicate that the UCS of the reinforced soil is higher than the UCS of the raw soil, and the UCS of soil reinforced with glass fiber is higher than that of soil reinforced with rubber.In conclusion, the use of reinforcement materials such as glass fiber and rubber can significantly improve the mechanical properties of soil.The optimal percentage of reinforcement material depends on the specific application and soil conditions.Glass fiber reinforcement is generally more effective in increasing the strength of the soil than rubber reinforcement.
Figure (2): effect of glass fiber on OMC

Figure
Figure (7):Comparison between crumb rubber and glass fiber depends on CBR value.
Figure (5), Figure (4), and Figure (6), respectively.As shown in Figure (5), the maximum dry density (MDD) of the soil decreased with an increase in the percentage of rubber.The MDD decreased from 1.92 g/cm3 for the unreinforced soil to 1.73 g/cm3 for the soil reinforced with 9% rubber.This decrease in MDD can be attributed to the lower density of soil.The results showed that the addition of glass fiber

Table 4 - MDD, OMC, CBR, and UCS of reinforced soil with different percentages of glass fiber Table 5- Relationship between rubber percentage in reinforced soil verses UCS pending
on the desired performance requirements.Table