# Experimental Study on the Influence of Snow-Melting Agents on Fiber-Reinforced Cemented Soil under Freezing-Thawing Cycles

Authors: Lina Xu; Xu Ding; Shuang Sun; Hao Gu; Lei Niu; Yang Chen
Journal: Advances in Materials Science and Engineering
 (2023)

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## Abstract

To explore the effect of snow-melting agents on the glass fiber-reinforced cemented soil under freezing-thawing cycles, three widely used snow-melting agents, including potassium acetate, magnesium chloride, and sodium sulfate, were used in this article. The effects of snow-melting agent types on the apparent damage, mass loss, and mechanical properties of fiber-reinforced cemented soil under freezing-thawing cycles were analyzed through salt freezing and unconfined compressive strength tests. The results show that the snow-melting effect of potassium acetate is the best, the snow-melting effect of magnesium chloride is the second, and the snow-melting effect of sodium sulfate is the worst. Notably, as the number of freezing-thawing cycles increases, the strength of the test block decreases to varying degrees. After the fifth freezing-thawing cycle, the strength of the block without fiber decreased by 61.30%, 70.22%, and 81.58% in clear water, potassium acetate, and magnesium chloride solution, respectively, while the test block in sodium sulfate solution lost its bearing capacity. A series of studies proved that the snow-melting agent with sodium sulfate as the main component has the most apparent erosion effect on the cemented soil, followed by magnesium chloride, and the erosion effect of potassium acetate is the weakest. The incorporation of glass fiber can effectively improve the resistance of the cemented soil under the action of various salt solution erosion and freezing-thawing coupling and has a significant effect on slowing the development of surface cracks, improving peak strength, and reducing the mass loss rate. This research will provide theoretical support for the design of subgrade and the selection of snow-melting agents in cold areas.


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## Body

## 1. Introduction

The cemented soil composite material has been widely used in road subgrade engineering and foundation treatment due to its low cost, short construction period, and high compressive strength [1, 2]. In recent years, scholars at home and abroad have tried to add fibers to the cemented soil to improve its performance [3–7]. Niu et al. [8] found that the unconfined compressive strength of the reinforced cemented soil is closely related to the length and the content of fibers, and the dispersion of the fiber in the test block also has a specific influence on its strength. Additionally, Lu et al. [9] proved that adding fibers can improve the compressive strength and ductility of the cemented soil and reduce the development of cracks by studying the mechanical properties of the fiber-reinforced cemented soil. Furthermore, Li et al. [10] studied the effect of different fiber contents on the performance of the cemented soil and clarified that adding fibers to the cemented soil can substantially improve its strength.To reduce traffic safety problems caused by road snow during winter in Northeast China, snow-melting agents are often added to deal with the snow and ice on the road surface. However, the frequent use of snow-melting agents such as chloride, acetate, and sulfate in road snow removal is bound to adversely affect the mechanical properties of the subgrade [11]. The cemented soil, utilized as a standard roadbed filler, is vulnerable to various environments (freezing-thawing cycles and solution erosion), resulting in poor stability and durability problems [12–14]. Chen et al. [15] researched the cemented soil’s shear strength and found that the compressive strength decreased with the increase of freezing-thawing cycles. Zhang and Duan [16] discussed that with the increase in freezing-thawing cycles, the unconfined compressive strength and relative dynamic elastic modulus of cement soil at different ages decreased. Additionally, Cui et al. [17] explored the effects of the curing period and freezing-thawing cycles on compressive strength, the mass loss rate, and deformation modulus. They proved that under the influence of freezing-thawing cycles and cement hydration reactions, the properties of the cemented soil under different curing ages were significantly different. Ning et al. [18] studied the erosion effect of various kinds and concentrations of chemical solution and different pH values on the cemented soil piles and proved that different types, concentrations, and pH values significantly affected the mechanical properties of cemented soil piles. Zhang et al. [19] analyzed the destruction of the cemented soil by different concentrations of chlorine salt and obtained the internal action mechanism of chlorine salt on the destruction of the cemented soil by electron microscope analysis. Furthermore, by studying the erosion mechanism of sulfate on the cemented soil, Emidio and Flores [20] expounded that the erosion of sulfate increased the permeability of the cemented soil and reduced the shear modulus.To improve the adverse effects of the external environment on the cemented soil, many scholars have investigated these parameters to achieve results beneficial for this field. Changizi et al. [21] demonstrated that after nine freezing-thawing cycles, the unconfined compressive strength (UCS) and shear strength of clay treated with 1.0% nano-SiO2 were 16% and 21% more than natural clay, which was not subjected to the freezing-thawing cycles. Xu et al. [22, 23] also proposed that incorporating the basalt fiber or glass fiber into the cemented soil can effectively improve the ability of the cemented soil to resist freezing-thawing cycles and reduce its strength loss under freezing-thawing cycles through experimental research. Kravchenko et al. [24] and Li et al. [25] highlighted that incorporating fibers in the cemented soil can improve its peak stress and residual strength under freezing-thawing cycles. Furthermore, Zhang et al. [26] verified that the uniform incorporation of fibers in the cemented soil could improve its tensile and compressive strength. He [27] obtained a series of conclusions by studying fiber-reinforced loess’ mechanical properties under freezing-thawing cycles. These findings demonstrated that the strength and deformation of fiber-reinforced loess are better than those of plain loess after freezing-thawing cycles. Therefore, fibers improve the strength of soil and constrain deformation. From the study of Ahmadi et al. [28, 29], SEM images’ observations reflected that thermal stresses due to freeze and thaw periods caused whiskers’ growth from nano-SiO2 surfaces. The whiskers and glass fiber modify clayey soil’s strength properties and structure by creating filamentary networks on nano and macro scales, respectively. Furthermore, glass fiber produces less strength than popular additives such as lime and cement. However, it emits very low carbon dioxide into the environment compared to other additive materials. Li et al. [30], through the study of the mechanical properties and the pore structure of tailings in seasonal frozen areas, pointed out that the shear strength of tailings generally decreases with the increase of the freezing-thawing cycle time.At present, scholars mainly focus on the mechanical properties of the fiber-reinforced cemented soil subject to freezing and thawing cycles, drying and wetting cycles, and the influence of salt solution erosion environment on cemented soil. However, there are few studies on the impact of cemented soil subgrade by snow-melting agents in cold areas. Based on this, to study the mechanism of cemented soil subgrade subjected to salt-freezing cycles in cold areas, three common snow-melting agents (potassium acetate, magnesium chloride, and sodium sulfate) were utilized to prepare solutions with the same concentration (0.2 mol/L). The mechanical properties and mass loss of glass fiber-reinforced cemented soil under different snow-melting agent solution environments and freezing-thawing cycles were investigated through a series of salt-freezing tests. The purpose of this article is to analyze the effects of the snow-melting agent type, fiber incorporation or not, and freezing-thawing cycles on the strength, apparent quality, and stress-strain curve of the cemented soil. The results of this study point out the degree of damage of different snow-melting agents on the fiber-reinforced cemented soil and provide theoretical support for relevant scientific research to provide a reference for practical engineering applications of road snow removal and soil subgrade reinforcement in cold areas.


## 2. Test Materials and Preparation

### 2.1. Test Materials

The test soil is from a foundation pit in Jingyue district, Changchun City, Jilin province. As shown in Figure1, the soil sample is silty clay with a yellowish-brown color, and its basic property parameters are shown in Table 1. The basic properties of Dinglu ordinary Portland cement (strength grade P.O.42.5) produced by the Changchun Yatai Group are shown in Table 2. The apparent state of the glass fiber produced by the China Stone Group is shown in Figure 2, and the basic properties are shown in Table 3. The test was carried out following the Cement Soil Mix Design Specification provisions (JGJ/T 233-2011). The mass incorporation ratio of cement was 0.1, the water-cement ratio was 0.5, and the mass incorporation ratio of the glass fiber was 0.1%. Additionally, the fiber length was 6 mm. According to the previous test results, the glass fiber mass incorporation ratio was 0.1% and the fiber length was 6 mm [23].Figure 1
Test soil photo.Table 1
Basic properties of the test soil.
ParametersValuesSpecific gravity2.71Liquid limit water content (%)40.91Plastic limit water content (%)24.84Liquidity index0.52Plastic index16.07Table 2
Basic properties of cement.
ParametersValuesSpecific surface area (m2∙kg)345Initial setting time (h)2Final setting time (h)2.5Flexural strength of cement mortar (MPa)3 d528 d8Compressive strength of cement mortar (Mpa)3 d2428 d49Figure 2
Glass fiber photo.Table 3
Basic properties of the glass fiber.
ParametersValuesDiameter (μm)5–30Length (mm)6Tensile strength (MPa)2800Elasticity modulus (GPa)86Density (g·cm−3)2.4–2.76Softening point (°C)1000


### 2.2. Selection of the Snow-Melting Agent

The principle of snow-melting agents is to use the solubility, hygroscopicity, and low freezing point characteristics of its main components to reduce the freezing point of the mixed liquid and inhibit ice formation. The standard snow-melting agent components are potassium, acetate, and chloride [31]. Combined with the snow-melting agents applied in road engineering, most are compound snow-melting agents containing multiple components. To eliminate multifactor interference, magnesium chloride, sodium sulfate, and potassium acetate as the active components of snow-melting agents were used as experimental agents. The snow-melting agent solution in this article adopts 95% potassium acetate analytical pure powder produced by Xilong Science Co., Ltd., 99% magnesium chloride analytical pure powder produced by Tianjin Beichen Fangzheng Reagent Factory, and 95% sodium sulfate analytical pure powder produced by Guoyao Group Chemical Reagent Co., Ltd. The potassium acetate solution, magnesium chloride solution, and sodium sulfate solution were configured with a 0.2 mol/L concentration. The apparent morphology of each reagent is shown in Figure 3.Figure 3
Appearance of snow-melting agents (a) potassium acetate; (b) magnesium chloride; (c) sodium sulfate.
(a)(b)(c)


### 2.3. Specimen Preparation

According to the requirements of “Cement Soil Mix Design Specification” (JGJ/T 233-201), a cube test block with a size of 70.7 mm × 70.7 mm × 70.7 mm was prepared. After manually mixing, mold loading, and vibration, it was cured in a natural state for 1 d and watered and covered with plastic film for 3 d, and then the mold was removed. Finally, the specimens were placed in room temperature water for 28 d. The specific preparation process is shown in Figure4. The specific preparation steps are described as follows:(1)
The dried soil and cement were thoroughly mixed by manual mixing until uniform (Figures4(a) and 4(b)).(2)
The glass fiber was sprinkled into the mixture and then manually mixed evenly until all the glass fiber was mixed to ensure that the fiber had a good dispersion effect in the soil (Figure4(c)).(3)
The water is added and mixed for 2 min (Figure4(d)).(4)
The mixture was loaded into the mold (Figure4(e)), and a vibration table was selected to discharge the air bubbles in the sample. The vibration frequency of the vibration table was 2860 times/min (Figure 4(f)).(5)
After the vibration was completed, the excess part was scraped off to ensure that the top surface was flat, and then the samples were covered with plastic film for maintenance.Figure 4
Preparation process of specimens is (a) mixing cement and soil; (b) dry mixing; (c) incorporation of fibers; (d) mixing with water; (e) molding; (f) vibration compaction.


### 2.4. Salt Freezing Cycle Test Scheme

After the specimens were cured for 28 d, the specimens were subjected to the salt-freezing cycle test. The specific steps of the salt-freezing cycle test are as follows:(1)
Soak the specimens in four solutions (water, potassium acetate, magnesium chloride, and sodium sulfate) with a concentration of 0.2 mol/L for 72 h.(2)
After soaking, the specimens were taken out, the surface water was dried, and the specimen’s weight was recorded.(3)
The specimens were frozen for 24 h at −18°C and then placed in the corresponding solution for thawing for 24 h. This process was one salt-freezing cycle. Each group was set up with 8 salt-freezing cycles. This test included 64 groups. The specific scheme is given in Table4.(4)
After each salt-freezing cycle, the specimens were weighed and tested for compressive strength.Table 4
Test plan.
TypesFiber content (%)Number of freezing-thawing cyclesWater0, 0.10, 1, 2, 4, 5, 6, 7, and 8Magnesium chloride solution0, 0.10, 1, 2, 4, 5, 6, 7, and 8Potassium acetate solution0, 0.10, 1, 2, 4, 5, 6, 7, 8Sodium sulfate solution0, 0.10, 1, 2, 4, 5, 6, 7, and 8


### 2.5. Unconfined Compressive Strength Test

Unconfined compressive strength was tested using a microcomputer servo pressure tester (WAW-600 k) produced by Changchun Kexin Test Instrument Co., Ltd. The instrument was controlled by displacement at a constant speed, and the loading speed was designated as 0.1 mm/s. The data acquisition of unconfined compressive strength was completed using an automatic acquisition system matched with the WAW-600 universal testing machine, and the collected data include load and displacement. The microcomputer servo pressure testing machine is shown in Figure5.Figure 5
Microcomputer servo pressure testing machine.


## 2.1. Test Materials

The test soil is from a foundation pit in Jingyue district, Changchun City, Jilin province. As shown in Figure1, the soil sample is silty clay with a yellowish-brown color, and its basic property parameters are shown in Table 1. The basic properties of Dinglu ordinary Portland cement (strength grade P.O.42.5) produced by the Changchun Yatai Group are shown in Table 2. The apparent state of the glass fiber produced by the China Stone Group is shown in Figure 2, and the basic properties are shown in Table 3. The test was carried out following the Cement Soil Mix Design Specification provisions (JGJ/T 233-2011). The mass incorporation ratio of cement was 0.1, the water-cement ratio was 0.5, and the mass incorporation ratio of the glass fiber was 0.1%. Additionally, the fiber length was 6 mm. According to the previous test results, the glass fiber mass incorporation ratio was 0.1% and the fiber length was 6 mm [23].Figure 1
Test soil photo.Table 1
Basic properties of the test soil.
ParametersValuesSpecific gravity2.71Liquid limit water content (%)40.91Plastic limit water content (%)24.84Liquidity index0.52Plastic index16.07Table 2
Basic properties of cement.
ParametersValuesSpecific surface area (m2∙kg)345Initial setting time (h)2Final setting time (h)2.5Flexural strength of cement mortar (MPa)3 d528 d8Compressive strength of cement mortar (Mpa)3 d2428 d49Figure 2
Glass fiber photo.Table 3
Basic properties of the glass fiber.
ParametersValuesDiameter (μm)5–30Length (mm)6Tensile strength (MPa)2800Elasticity modulus (GPa)86Density (g·cm−3)2.4–2.76Softening point (°C)1000


## 2.2. Selection of the Snow-Melting Agent

The principle of snow-melting agents is to use the solubility, hygroscopicity, and low freezing point characteristics of its main components to reduce the freezing point of the mixed liquid and inhibit ice formation. The standard snow-melting agent components are potassium, acetate, and chloride [31]. Combined with the snow-melting agents applied in road engineering, most are compound snow-melting agents containing multiple components. To eliminate multifactor interference, magnesium chloride, sodium sulfate, and potassium acetate as the active components of snow-melting agents were used as experimental agents. The snow-melting agent solution in this article adopts 95% potassium acetate analytical pure powder produced by Xilong Science Co., Ltd., 99% magnesium chloride analytical pure powder produced by Tianjin Beichen Fangzheng Reagent Factory, and 95% sodium sulfate analytical pure powder produced by Guoyao Group Chemical Reagent Co., Ltd. The potassium acetate solution, magnesium chloride solution, and sodium sulfate solution were configured with a 0.2 mol/L concentration. The apparent morphology of each reagent is shown in Figure 3.Figure 3
Appearance of snow-melting agents (a) potassium acetate; (b) magnesium chloride; (c) sodium sulfate.
(a)(b)(c)


## 2.3. Specimen Preparation

According to the requirements of “Cement Soil Mix Design Specification” (JGJ/T 233-201), a cube test block with a size of 70.7 mm × 70.7 mm × 70.7 mm was prepared. After manually mixing, mold loading, and vibration, it was cured in a natural state for 1 d and watered and covered with plastic film for 3 d, and then the mold was removed. Finally, the specimens were placed in room temperature water for 28 d. The specific preparation process is shown in Figure4. The specific preparation steps are described as follows:(1)
The dried soil and cement were thoroughly mixed by manual mixing until uniform (Figures4(a) and 4(b)).(2)
The glass fiber was sprinkled into the mixture and then manually mixed evenly until all the glass fiber was mixed to ensure that the fiber had a good dispersion effect in the soil (Figure4(c)).(3)
The water is added and mixed for 2 min (Figure4(d)).(4)
The mixture was loaded into the mold (Figure4(e)), and a vibration table was selected to discharge the air bubbles in the sample. The vibration frequency of the vibration table was 2860 times/min (Figure 4(f)).(5)
After the vibration was completed, the excess part was scraped off to ensure that the top surface was flat, and then the samples were covered with plastic film for maintenance.Figure 4
Preparation process of specimens is (a) mixing cement and soil; (b) dry mixing; (c) incorporation of fibers; (d) mixing with water; (e) molding; (f) vibration compaction.


## 2.4. Salt Freezing Cycle Test Scheme

After the specimens were cured for 28 d, the specimens were subjected to the salt-freezing cycle test. The specific steps of the salt-freezing cycle test are as follows:(1)
Soak the specimens in four solutions (water, potassium acetate, magnesium chloride, and sodium sulfate) with a concentration of 0.2 mol/L for 72 h.(2)
After soaking, the specimens were taken out, the surface water was dried, and the specimen’s weight was recorded.(3)
The specimens were frozen for 24 h at −18°C and then placed in the corresponding solution for thawing for 24 h. This process was one salt-freezing cycle. Each group was set up with 8 salt-freezing cycles. This test included 64 groups. The specific scheme is given in Table4.(4)
After each salt-freezing cycle, the specimens were weighed and tested for compressive strength.Table 4
Test plan.
TypesFiber content (%)Number of freezing-thawing cyclesWater0, 0.10, 1, 2, 4, 5, 6, 7, and 8Magnesium chloride solution0, 0.10, 1, 2, 4, 5, 6, 7, and 8Potassium acetate solution0, 0.10, 1, 2, 4, 5, 6, 7, 8Sodium sulfate solution0, 0.10, 1, 2, 4, 5, 6, 7, and 8


## 2.5. Unconfined Compressive Strength Test

Unconfined compressive strength was tested using a microcomputer servo pressure tester (WAW-600 k) produced by Changchun Kexin Test Instrument Co., Ltd. The instrument was controlled by displacement at a constant speed, and the loading speed was designated as 0.1 mm/s. The data acquisition of unconfined compressive strength was completed using an automatic acquisition system matched with the WAW-600 universal testing machine, and the collected data include load and displacement. The microcomputer servo pressure testing machine is shown in Figure5.Figure 5
Microcomputer servo pressure testing machine.


## 3. Results and Discussion

### 3.1. Snowmelt Effect Analysis

The snow-melting effect analysis test was carried out under the outdoor condition in the middle and late December of Changchun City, Jilin province, China. The outdoor temperature was −19°C during the time of the test. Three snow samples with a mass of 60 g were taken. Following snow collection, 10 g of 99% analytical pure powder of various test agents (magnesium chloride, potassium acetate, and sodium sulfate) was mixed with the same amount of snow samples to simulate the melting effect of multiple types of snow-melting agents on snow samples under normal road snow removal conditions. The experimental design time was 0, 10, 30, and 60 min, and the snow-melting effect is shown in Figure6.Figure 6
Snow-melt effect diagram for (a) magnesium chloride (10 g); (b) potassium acetate (10 g); (c) sodium sulfate (10 g).
(a)(b)(c)It can be seen from Figure6 that the snow-melting effect of the snow-melting agent was more prominent with increased time. Simultaneously, the snow-melting effect of potassium acetate was the most significant, the snow-melting effect of magnesium chloride was second, and the snow-melting effect of sodium sulfate was the worst. On the one hand, the reason for the abovementioned situation is that after the snow-melting agent is dissolved in water (snow), the freezing point of salt water becomes lower than that of water at 0°C [32]. Additionally, the lowest freezing point of magnesium chloride is about −20°C, the lowest freezing point of potassium acetate is about −30°C, and the lowest freezing point of sodium sulfate is −5°C [33]. Therefore, the lower the freezing point, the better the snow-melting effect. On the other hand, experiments have demonstrated that the solubility of potassium acetate is higher than that of magnesium chloride below 0°C. At the same time, sodium sulfate is not easy to dissolve in water at low temperatures [33]. Therefore, the higher the solubility at low temperatures, the higher the ion concentration in water. So as the liquid vapor pressure of water decreases, the solid vapor pressure of ice remains unchanged. To achieve the state of the solid-liquid vapor pressure of the ice-water mixture, the ice and snow melt are critical factors in the difference in snow-melting effects among the three.


### 3.2. Apparent Morphological Analysis

Figure7 shows the apparent photos of the glass fiber-reinforced cemented soil after 0, 2, 4, and 6 freezing-thawing cycles in a water environment. Figure 8 shows the apparent photos of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles in water, potassium acetate solution, magnesium chloride solution, and sodium sulfate solution.Figure 7
The apparent characteristics of the glass fiber-reinforced cemented soil in a water environment (a) after 0 cycles; (b) after 2 cycles; (c) after 4 cycles; (d) after 6 cycles.
(a)(b)(c)(d)Figure 8
The apparent characteristics of the glass fiber-reinforced cemented soil in a salt solution environment after 5 cycles in (a) water; (b) potassium acetate; (c) magnesium chloride; (d) sodium sulfate.
(a)(b)(c)(d)Figure7 shows that the surface cracking phenomenon of the cemented soil in the water environment is more apparent with the increase in freezing-thawing cycles. After 2 cycles, pores gradually appeared on the surface. After 6 freezing-thawing cycles, the surface of the specimens was cracked. Due to the low temperatures, the water in the pores changes to ice, leading to increased expansion stress. When the expansion stress exceeds the tensile strength of the cemented soil, small internal cracks will occur. When it is melted again, more water enters the crack, and the crack increases when it is frozen again. Damage occurs gradually through repeated freezing-thawing cycles [34].It can be seen from Figure8 that after the same number of freezing-thawing cycles, there are small cracks on the surface of the specimens in water, and there is no apparent damage as a whole. The specimens soaked in potassium acetate solution have small cracks and holes, but the overall structure is dense. The ones soaked in magnesium chloride solution have obvious cracks and peeling on the surface. Furthermore, the sodium sulfate solution had the most apparent destructive effect on the specimens, and the specimens had large cracks and falling blocks. Thus, it can be seen that sodium sulfate and magnesium chloride solution have a more serious erosive effect on the specimens, while potassium acetate has a less erosive effect.Figures9 and 10 are the internal photos of the glass fiber-reinforced cemented soil and the cemented soil without glass fibers after soaking in water, potassium acetate solution, magnesium chloride solution, and sodium sulfate solution after 5 freezing-thawing cycles. As shown in Figures 9 and 10, there is no crystal precipitation inside the specimens in a water environment following 5 freezing-thawing cycles. The crystal precipitated from the specimens soaked in potassium acetate solution is a smaller dotlike distribution and less precipitation. The substance is mainly formed by the intrusion of potassium acetate into the internal water loss of the specimens. Due to the acetate ion belonging to the acid ion of the weak acid, it is weak in the reaction process with the hydration product of the cement [35]. It is a balanced reaction, so the damaging effect of acetate on the cemented soil is negligible. Additionally, the distribution of the precipitated substances in the specimens soaked in magnesium chloride solution is relatively concentrated and becomes an apparent block. The main component of the precipitated substances is calcium chloride hexahydrate formed by the reaction of magnesium chloride with calcium hydroxide, a cement hydration product. The formation of this substance expands the cracks inside the specimens. At the same time, the combination of magnesium ions and hydroxide ions reduces the pH value of the solution. Importantly, it reduces the formation of hydrated calcium silicate and hydrated calcium aluminate. In contrast, magnesium ions react with silicon dioxide in the cement to form MgO·SiO2·H2O, which reduces the gelation of hydrated calcium silicate, thus weakening the cementation force of cement and causing damage to the test block [36]. The specimens soaked in sodium sulfate solution precipitate more dense substances. This is likely due to the sulfate ions in the solution reacting with some cations (such as potassium, calcium, and sodium ions) in cement and soil to generate new minerals and gypsum, which makes the internal substances precipitate more. Furthermore, because sulfate is a strong acid radical ion, the test block is greatly affected by acid erosion, resulting in the deterioration of the overall strength of the test block or even leading to rupture.Figure 9
Internal characteristics of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles in (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)Figure 10
Internal characteristics of the cemented soil without glass fibers after 5 freezing-thawing cycles in (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)


### 3.3. Mass Loss Rate

The mass loss rate is a ratio ofthe difference between the mass of the specimen before and after the freezing-thawing cycle to that before freezing-thawing cycle. After each salt-freezing cycle, the mass loss rate of the specimens can be calculated according to the following equation:(1)∆Mn=M0−MnM0×100%,where ∆Mn is the mass loss rate; Mn is the mass of the specimen after the salt-freezing cycle; and M0 is the initial mass of the specimen without the salt-freezing cycle.The quality of the specimen adopted the average of the measured quality of three specimens, and the standard deviation ranges between 0.03 and 0.06. Table5 shows the mass loss rate of the specimens under different freezing-thawing cycles. Notably, the negative number in the table indicates that the quality has increased. Some specimens are loose and disintegrated after multiple freezing-thawing cycles, and the quality cannot be measured, expressed as “/”.Table 5
Mass loss rate of the specimens under different freezing-thawing cycles.
Number of freezing and thawing cyclesGlass fiber-reinforced cemented soilCemented soil without fibersWaterPotassium acetateMagnesium chlorideSodium sulfatenWaterPotassium acetateMagnesium chlorideSodium sulfate0−0.49%−0.55%−0.97%−0.92%−0.56%−0.58%−0.54%−1.02%2−1.02%−0.83%−1.86%0.16%0.22%0.01%0.17%−0.59%4−0.70%−1.08%3.11%10.75%2.83%4.20%8.05%16.49%62.05%2.08%7.67%—5.03%5.62%13.06%—83.64%4.16%10.06%—————It can be seen from Table5 that when the freezing-thawing cycle is 0, the mass of each specimen increases slightly to varying degrees due to the immersion in various solutions for 72 h. However, after several freezing-thawing cycles, the specimens begin to crack, slag off, and block off, resulting in a gradual decrease in mass, and the mass loss rate gradually changes from negative to positive. In contrast, the mass loss rate of the specimens increases with the number of freezing-thawing cycles. Under the same number of cycles, the mass loss rate of the specimens with fiber is significantly lower than that without fiber in the same solution. The specimens without added fiber have been completely destroyed after the eighth freezing-thawing cycle, which shows that incorporating the fiber effectively improves the ability of the specimens to resist freezing-thawing damage and salt solution erosion. Notably, under the same number of cycles, the mass loss rate of the specimens is sodium sulfate solution > magnesium chloride solution > potassium acetate solution > water.


### 3.4. Effect of Freezing-Thawing Cycles on Unconfined Compressive Strength

The compressive strength in this part is the average of the measured values of three specimens, with a standard deviation between 0.04 and 0.08. Figure11 shows the strength loss rate of the specimens after 5 freezing-thawing cycles. Figure 12 shows the relationship between unconfined compressive strength and the number of freezing-thawing cycles of the cemented soil without the fiber. As demonstrated in Figure 11, compared with the strength of the specimen before the freezing-thawing cycle, the strength of the specimens in water decreases by 61.30%, the ones in potassium acetate solution decreases by 70.22%, the ones in magnesium chloride solution decreases by 81.58%, and the ones in sodium sulfate solution lost their bearing capacity. The erosion damage of the specimens is more serious, resulting in many falling blocks and losing the bearing capacity after 7 cycles. Therefore, the number of freezing-thawing cycles in Figure 11 shows 7 cycles. Importantly, Figure 12 shows that with the increase in the number of freezing-thawing cycles, the unconfined compressive strength of the cemented soil continues to decline and the downward trend is pronounced. After 5 cycles, the strength of all the specimens tended to be stable. It can be seen that the damaging effect of freezing-thawing cycles is significant for the specimens eroded by different types of solutions, and the strength value and the decreased value are different due to the difference in the erosion environment.Figure 11
Strength loss rate after the fifth freezing-thawing cycle.Figure 12
Relationship between unconfined compressive strength and number of freezing-thawing cycles of the cemented soil without fibers.


### 3.5. Effect of the Fiber

#### 3.5.1. Fiber Influence Strength Ratio

To further study the influence of glass fibers on the frost resistance of the cemented soil, the fiber influence strength ratio is introduced in [22]. The strength ratio formula was calculated according to the following equation:(2)ω=in,fin,pwhere ω is the fiber influence strength ratio; in,f is the unconfined compressive strength value of the glass fiber-reinforced cemented soil subject to freezing-thawing cycles in a water environment; in,p is the unconfined compressive strength value of the cemented soil without the glass fiber in a water environment; n represents the number of freezing-thawing cycles; f represents the cemented soil with the glass fiber; and p represents the cemented soil test block without glass fiber.Figure13 shows the fiber influence strength ratio. As noted in Figure 13, the fiber influence strength ratio in a clear water environment is less than 1 in the early time because the strength of glass fiber-reinforced cement is slightly lower than that of the cemented soil without fibers after 28 days of curing. With the increasing number of freezing-thawing cycles, the fiber influence strength ratio is greater than 1 after 4 cycles, indicating that the fiber’s existence inhibits the freezing-thawing cycle’s damaging effect on the specimens. Therefore, the strength loss of the fiber-reinforced cemented soil is less than that of the cemented soil without the fiber.Figure 13
Fiber influence strength ratio in a water environment.


#### 3.5.2. Effect of Fiber on Unconfined Compressive Strength

Figure14 shows the strength loss rate of the cemented soil in a water environment. According to Figure 14, the strength loss rate of the glass fiber-reinforced cemented soil is 42.86% and the strength loss rate of the cemented soil without the glass fiber is 61.30%. These findings demonstrate that incorporating the fiber improves the soil’s bonding performance and suppresses the loss of strength of the specimens subject to freezing-thawing cycles. Figure 15 shows the specimens’ damage curve under different freezing-thawing cycles in a water environment. It can be seen from Figure 15 that with the increase in freezing-thawing cycles, the unconfined compressive strength of the specimens without the glass fiber decreased significantly. Furthermore, the unconfined compressive strength of the glass fiber-reinforced cemented soil decreased significantly at the beginning of the freezing-thawing cycle and then tended to be stable after 2 freezing-thawing cycles.Figure 14
Strength loss rate of cement-soil test block after the 5th freezing-thawing cycle in a clean water environment.Figure 15
The damage curve of specimens under different freezing-thawing cycles.Dispersion of fibers in the specimen is an important factor affecting the strength of the specimen. Uneven dispersion and bunching of fibers were found during the mixing process, as shown in Figure16. As a result, the initial strength of the cemented soil with fibers is lower than that without fibers, as shown in Figure 15. When the glass fiber is incorporated into the cemented soil, the glass fiber will form a network that will increase the friction resistance between the soil particles and prevents the formation and expansion of micropores and crack lines under the freeze and thawing conditions [29]. Thus, the strength of the cemented soil with fiber decreases slowly under the action of freezing-thawing cycles. Furthermore, the strength of the cemented soil with fibers is higher than that without fibers in the middle and late periods of Figure 15, which proves the effect of fiber reinforcement.Figure 16
The fiber bundle phenomenon.


#### 3.5.3. Relationship between Strain and Stress

Figure17 shows the stress-strain relationship curve of the glass fiber-reinforced cemented soil and the cemented soil without fiber after 5 freezing-thawing cycles in a water environment. It can be seen from Figure 17 that the peak strength of the glass fiber-reinforced cemented soil was 2.7878 Mpa, the peak strength of the cemented soil without the fiber was 2.4043 Mpa, and the peak difference between the two was 0.3835 Mpa. Therefore, these findings indicate that incorporating the fiber increases the peak strength of the test block.Figure 17
Relationship between strain and stress of specimens in water environment (after 5 freezing-thawing cycles).Figure18 shows the vertical strain cloud diagram of the glass fiber-reinforced cemented soil and the cemented soil without glass fibers in the water environment after 5 freezing-thawing cycles using digital image correlation technology. As seen in Figure 18, in the later loading stage, the internal strain of the glass fiber-reinforced cemented soil is concentrated at the center and no apparent cracks have appeared. The cemented soil without fiber shows an inclined strain concentration zone below and noticeable damage cracks appear. This indicates that the incorporation of fibers increases the tensile strength of the cemented soil, limits the development of cracks, and thus increases the strength of the test block.Figure 18
Vertical strain cloud diagram of specimen in water environment (after 5 freezing-thawing cycles) for (a) glass fiber-reinforced cemented soil and (b) cemented soil without fibers.
(a)(b)


### 3.6. Effect of the Snow-Melting Agent Type

#### 3.6.1. Snow-Melting Agent Influence Strength Ratio

To explore the influence of the erosion environment on the glass fiber-reinforced cemented soil, the snow-melting agent influence strength ratioα is introduced. This strength ratio denotes the peak strength of the specimens in the water environment to the peak strength of the specimens in different environments after freezing-thawing cycles. The strength ratio is calculated by the following equation:(3)α=in,win,dwhere α is the ratio of the unconfined compressive strength of the specimens in the water environment after freezing-thawing cycles to the unconfined compressive strength of the specimens in different environments; in,w is the unconfined compressive strength of the glass fiber-reinforced cemented soil in the water environment after freezing-thawing cycles; in,d is the unconfined compressive strength of the glass fiber-reinforced cemented soil in different saline environments after freezing-thawing cycles, and n represents the numbers of the freezing-thawing cycle; w represents the water environment; d represents the salt solution environment.Figure19 shows the snow-melting agent’s influence strength ratio and the number of freezing-thawing cycles. It can be seen from Figure 19 that the snow-melting agent influence strength ratio of the specimens in sodium sulfate solution was the highest in the early stage of the freezing-thawing cycle. In contrast, the specimens in the sodium sulfate solution lost its strength after 5 freezing-thawing cycles, indicating that the sodium sulfate solution eroded the specimens rapidly and the deterioration effect was severe. The strength ratio of magnesium chloride began to be greater than 1 after the second freezing-thawing cycle. It then showed an upward trend, indicating that the magnesium chloride solution had a strong erosion effect on the specimens and significantly affected their deterioration. Furthermore, the overall strength ratio of the specimens in the potassium acetate solution was close to 1 during 8 freezing-thawing cycles, indicating that the potassium acetate solution had a weak effect on the strength deterioration of the test block.Figure 19
The relationship between the snow-melting agent influences the strength ratio and the number of freezing-thawing cycles.


#### 3.6.2. Relationship between Strain and Stress

Figure20 is the stress-strain relationship curve of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles. Figure 20 shows that the peak stress of the specimens in the potassium acetate solution was slightly different from the peak stress of the specimens in the water environment. In contrast, the peak strength of the specimens in the magnesium chloride and sodium sulfate solution decreased significantly. Compared with the specimens in the water environment, the peak strength of the specimens in the magnesium chloride solution decreased by 69.81%, and the peak strength in the sodium sulfate solution decreased by 83.17%. The strain corresponding to the peak strength of the specimens in the magnesium chloride solution and sodium sulfate solution was larger, the stress-strain curve had no noticeable stress drop, and the whole was a ductile failure, suggesting that the test block tended to the nature of the soil.Figure 20
Stress-strain relationship curve of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles.Figure21 is the vertical strain cloud diagram of the glass fiber-reinforced cemented soil in four different solution environments after 5 freezing-thawing cycles. As demonstrated in Figure 21, the internal strain of the specimens in water and potassium acetate solution is concentrated at the center, the range is small, and there is no apparent strain zone causing cracks at the edge. Additionally, the range of the strain zone in the magnesium chloride solution increased. Furthermore, the strain zone of the test block in the sodium sulfate solution was the largest, and there was roughly a tilt through the strain concentration zone.Figure 21
Vertical strain cloud diagram of glass fiber-reinforced cemented soil in salt solution environment after 5 cycles: (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)


### 3.7. Modulus of Deformation

To better describe the deformation of the glass fiber-reinforced cemented soil under salt solution erosion and freezing-thawing cycles, the deformation modulus E50 is introduced. The definition formula of deformation modulus is shown in the following equation:(4)E50=σu2εwhere E50 is the deformation modulus of the specimen (MPa), σu is the peak stress of specimen (MP), and ε is the strain corresponding to half peak stress of the specimen.Figure22 shows the relationship between the deformation modulus and the number of freezing-thawing cycles of the glass fiber-reinforced cemented soil soaked in water and 0.2 mol/L potassium acetate, magnesium chloride, and sodium sulfate solutions. As displayed in Figure 22, as the number of freezing-thawing cycles increases, the deformation modulus of the test block gradually decreases. After the 2 freezing-thawing cycles, the deformation modulus decreased greatly, in which the pilot block of water and sodium sulfate solution decreased by 114.33 MPa and 100.58 MPa, respectively. Additionally, the trend is flat after 5 freezing-thawing cycles. Furthermore, at this time, the deformation modulus of the pilot block of water, potassium acetate, magnesium chloride, and sodium sulfate solution decreased by 185.94 MPa, 206.98 MPa, 175.47 MPa, and 101.37 MPa, respectively, compared with the initial value. Therefore, the comprehensive analysis shows that the relationship between deformation modulus is water > potassium acetate > magnesium chloride > sodium sulfate.Figure 22
Relationship between the deformation modulus and the number of freezing-thawing cycles of the glass fiber-reinforced cemented soil.


## 3.1. Snowmelt Effect Analysis

The snow-melting effect analysis test was carried out under the outdoor condition in the middle and late December of Changchun City, Jilin province, China. The outdoor temperature was −19°C during the time of the test. Three snow samples with a mass of 60 g were taken. Following snow collection, 10 g of 99% analytical pure powder of various test agents (magnesium chloride, potassium acetate, and sodium sulfate) was mixed with the same amount of snow samples to simulate the melting effect of multiple types of snow-melting agents on snow samples under normal road snow removal conditions. The experimental design time was 0, 10, 30, and 60 min, and the snow-melting effect is shown in Figure6.Figure 6
Snow-melt effect diagram for (a) magnesium chloride (10 g); (b) potassium acetate (10 g); (c) sodium sulfate (10 g).
(a)(b)(c)It can be seen from Figure6 that the snow-melting effect of the snow-melting agent was more prominent with increased time. Simultaneously, the snow-melting effect of potassium acetate was the most significant, the snow-melting effect of magnesium chloride was second, and the snow-melting effect of sodium sulfate was the worst. On the one hand, the reason for the abovementioned situation is that after the snow-melting agent is dissolved in water (snow), the freezing point of salt water becomes lower than that of water at 0°C [32]. Additionally, the lowest freezing point of magnesium chloride is about −20°C, the lowest freezing point of potassium acetate is about −30°C, and the lowest freezing point of sodium sulfate is −5°C [33]. Therefore, the lower the freezing point, the better the snow-melting effect. On the other hand, experiments have demonstrated that the solubility of potassium acetate is higher than that of magnesium chloride below 0°C. At the same time, sodium sulfate is not easy to dissolve in water at low temperatures [33]. Therefore, the higher the solubility at low temperatures, the higher the ion concentration in water. So as the liquid vapor pressure of water decreases, the solid vapor pressure of ice remains unchanged. To achieve the state of the solid-liquid vapor pressure of the ice-water mixture, the ice and snow melt are critical factors in the difference in snow-melting effects among the three.


## 3.2. Apparent Morphological Analysis

Figure7 shows the apparent photos of the glass fiber-reinforced cemented soil after 0, 2, 4, and 6 freezing-thawing cycles in a water environment. Figure 8 shows the apparent photos of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles in water, potassium acetate solution, magnesium chloride solution, and sodium sulfate solution.Figure 7
The apparent characteristics of the glass fiber-reinforced cemented soil in a water environment (a) after 0 cycles; (b) after 2 cycles; (c) after 4 cycles; (d) after 6 cycles.
(a)(b)(c)(d)Figure 8
The apparent characteristics of the glass fiber-reinforced cemented soil in a salt solution environment after 5 cycles in (a) water; (b) potassium acetate; (c) magnesium chloride; (d) sodium sulfate.
(a)(b)(c)(d)Figure7 shows that the surface cracking phenomenon of the cemented soil in the water environment is more apparent with the increase in freezing-thawing cycles. After 2 cycles, pores gradually appeared on the surface. After 6 freezing-thawing cycles, the surface of the specimens was cracked. Due to the low temperatures, the water in the pores changes to ice, leading to increased expansion stress. When the expansion stress exceeds the tensile strength of the cemented soil, small internal cracks will occur. When it is melted again, more water enters the crack, and the crack increases when it is frozen again. Damage occurs gradually through repeated freezing-thawing cycles [34].It can be seen from Figure8 that after the same number of freezing-thawing cycles, there are small cracks on the surface of the specimens in water, and there is no apparent damage as a whole. The specimens soaked in potassium acetate solution have small cracks and holes, but the overall structure is dense. The ones soaked in magnesium chloride solution have obvious cracks and peeling on the surface. Furthermore, the sodium sulfate solution had the most apparent destructive effect on the specimens, and the specimens had large cracks and falling blocks. Thus, it can be seen that sodium sulfate and magnesium chloride solution have a more serious erosive effect on the specimens, while potassium acetate has a less erosive effect.Figures9 and 10 are the internal photos of the glass fiber-reinforced cemented soil and the cemented soil without glass fibers after soaking in water, potassium acetate solution, magnesium chloride solution, and sodium sulfate solution after 5 freezing-thawing cycles. As shown in Figures 9 and 10, there is no crystal precipitation inside the specimens in a water environment following 5 freezing-thawing cycles. The crystal precipitated from the specimens soaked in potassium acetate solution is a smaller dotlike distribution and less precipitation. The substance is mainly formed by the intrusion of potassium acetate into the internal water loss of the specimens. Due to the acetate ion belonging to the acid ion of the weak acid, it is weak in the reaction process with the hydration product of the cement [35]. It is a balanced reaction, so the damaging effect of acetate on the cemented soil is negligible. Additionally, the distribution of the precipitated substances in the specimens soaked in magnesium chloride solution is relatively concentrated and becomes an apparent block. The main component of the precipitated substances is calcium chloride hexahydrate formed by the reaction of magnesium chloride with calcium hydroxide, a cement hydration product. The formation of this substance expands the cracks inside the specimens. At the same time, the combination of magnesium ions and hydroxide ions reduces the pH value of the solution. Importantly, it reduces the formation of hydrated calcium silicate and hydrated calcium aluminate. In contrast, magnesium ions react with silicon dioxide in the cement to form MgO·SiO2·H2O, which reduces the gelation of hydrated calcium silicate, thus weakening the cementation force of cement and causing damage to the test block [36]. The specimens soaked in sodium sulfate solution precipitate more dense substances. This is likely due to the sulfate ions in the solution reacting with some cations (such as potassium, calcium, and sodium ions) in cement and soil to generate new minerals and gypsum, which makes the internal substances precipitate more. Furthermore, because sulfate is a strong acid radical ion, the test block is greatly affected by acid erosion, resulting in the deterioration of the overall strength of the test block or even leading to rupture.Figure 9
Internal characteristics of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles in (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)Figure 10
Internal characteristics of the cemented soil without glass fibers after 5 freezing-thawing cycles in (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)


## 3.3. Mass Loss Rate

The mass loss rate is a ratio ofthe difference between the mass of the specimen before and after the freezing-thawing cycle to that before freezing-thawing cycle. After each salt-freezing cycle, the mass loss rate of the specimens can be calculated according to the following equation:(1)∆Mn=M0−MnM0×100%,where ∆Mn is the mass loss rate; Mn is the mass of the specimen after the salt-freezing cycle; and M0 is the initial mass of the specimen without the salt-freezing cycle.The quality of the specimen adopted the average of the measured quality of three specimens, and the standard deviation ranges between 0.03 and 0.06. Table5 shows the mass loss rate of the specimens under different freezing-thawing cycles. Notably, the negative number in the table indicates that the quality has increased. Some specimens are loose and disintegrated after multiple freezing-thawing cycles, and the quality cannot be measured, expressed as “/”.Table 5
Mass loss rate of the specimens under different freezing-thawing cycles.
Number of freezing and thawing cyclesGlass fiber-reinforced cemented soilCemented soil without fibersWaterPotassium acetateMagnesium chlorideSodium sulfatenWaterPotassium acetateMagnesium chlorideSodium sulfate0−0.49%−0.55%−0.97%−0.92%−0.56%−0.58%−0.54%−1.02%2−1.02%−0.83%−1.86%0.16%0.22%0.01%0.17%−0.59%4−0.70%−1.08%3.11%10.75%2.83%4.20%8.05%16.49%62.05%2.08%7.67%—5.03%5.62%13.06%—83.64%4.16%10.06%—————It can be seen from Table5 that when the freezing-thawing cycle is 0, the mass of each specimen increases slightly to varying degrees due to the immersion in various solutions for 72 h. However, after several freezing-thawing cycles, the specimens begin to crack, slag off, and block off, resulting in a gradual decrease in mass, and the mass loss rate gradually changes from negative to positive. In contrast, the mass loss rate of the specimens increases with the number of freezing-thawing cycles. Under the same number of cycles, the mass loss rate of the specimens with fiber is significantly lower than that without fiber in the same solution. The specimens without added fiber have been completely destroyed after the eighth freezing-thawing cycle, which shows that incorporating the fiber effectively improves the ability of the specimens to resist freezing-thawing damage and salt solution erosion. Notably, under the same number of cycles, the mass loss rate of the specimens is sodium sulfate solution > magnesium chloride solution > potassium acetate solution > water.


## 3.4. Effect of Freezing-Thawing Cycles on Unconfined Compressive Strength

The compressive strength in this part is the average of the measured values of three specimens, with a standard deviation between 0.04 and 0.08. Figure11 shows the strength loss rate of the specimens after 5 freezing-thawing cycles. Figure 12 shows the relationship between unconfined compressive strength and the number of freezing-thawing cycles of the cemented soil without the fiber. As demonstrated in Figure 11, compared with the strength of the specimen before the freezing-thawing cycle, the strength of the specimens in water decreases by 61.30%, the ones in potassium acetate solution decreases by 70.22%, the ones in magnesium chloride solution decreases by 81.58%, and the ones in sodium sulfate solution lost their bearing capacity. The erosion damage of the specimens is more serious, resulting in many falling blocks and losing the bearing capacity after 7 cycles. Therefore, the number of freezing-thawing cycles in Figure 11 shows 7 cycles. Importantly, Figure 12 shows that with the increase in the number of freezing-thawing cycles, the unconfined compressive strength of the cemented soil continues to decline and the downward trend is pronounced. After 5 cycles, the strength of all the specimens tended to be stable. It can be seen that the damaging effect of freezing-thawing cycles is significant for the specimens eroded by different types of solutions, and the strength value and the decreased value are different due to the difference in the erosion environment.Figure 11
Strength loss rate after the fifth freezing-thawing cycle.Figure 12
Relationship between unconfined compressive strength and number of freezing-thawing cycles of the cemented soil without fibers.


## 3.5. Effect of the Fiber

### 3.5.1. Fiber Influence Strength Ratio

To further study the influence of glass fibers on the frost resistance of the cemented soil, the fiber influence strength ratio is introduced in [22]. The strength ratio formula was calculated according to the following equation:(2)ω=in,fin,pwhere ω is the fiber influence strength ratio; in,f is the unconfined compressive strength value of the glass fiber-reinforced cemented soil subject to freezing-thawing cycles in a water environment; in,p is the unconfined compressive strength value of the cemented soil without the glass fiber in a water environment; n represents the number of freezing-thawing cycles; f represents the cemented soil with the glass fiber; and p represents the cemented soil test block without glass fiber.Figure13 shows the fiber influence strength ratio. As noted in Figure 13, the fiber influence strength ratio in a clear water environment is less than 1 in the early time because the strength of glass fiber-reinforced cement is slightly lower than that of the cemented soil without fibers after 28 days of curing. With the increasing number of freezing-thawing cycles, the fiber influence strength ratio is greater than 1 after 4 cycles, indicating that the fiber’s existence inhibits the freezing-thawing cycle’s damaging effect on the specimens. Therefore, the strength loss of the fiber-reinforced cemented soil is less than that of the cemented soil without the fiber.Figure 13
Fiber influence strength ratio in a water environment.


### 3.5.2. Effect of Fiber on Unconfined Compressive Strength

Figure14 shows the strength loss rate of the cemented soil in a water environment. According to Figure 14, the strength loss rate of the glass fiber-reinforced cemented soil is 42.86% and the strength loss rate of the cemented soil without the glass fiber is 61.30%. These findings demonstrate that incorporating the fiber improves the soil’s bonding performance and suppresses the loss of strength of the specimens subject to freezing-thawing cycles. Figure 15 shows the specimens’ damage curve under different freezing-thawing cycles in a water environment. It can be seen from Figure 15 that with the increase in freezing-thawing cycles, the unconfined compressive strength of the specimens without the glass fiber decreased significantly. Furthermore, the unconfined compressive strength of the glass fiber-reinforced cemented soil decreased significantly at the beginning of the freezing-thawing cycle and then tended to be stable after 2 freezing-thawing cycles.Figure 14
Strength loss rate of cement-soil test block after the 5th freezing-thawing cycle in a clean water environment.Figure 15
The damage curve of specimens under different freezing-thawing cycles.Dispersion of fibers in the specimen is an important factor affecting the strength of the specimen. Uneven dispersion and bunching of fibers were found during the mixing process, as shown in Figure16. As a result, the initial strength of the cemented soil with fibers is lower than that without fibers, as shown in Figure 15. When the glass fiber is incorporated into the cemented soil, the glass fiber will form a network that will increase the friction resistance between the soil particles and prevents the formation and expansion of micropores and crack lines under the freeze and thawing conditions [29]. Thus, the strength of the cemented soil with fiber decreases slowly under the action of freezing-thawing cycles. Furthermore, the strength of the cemented soil with fibers is higher than that without fibers in the middle and late periods of Figure 15, which proves the effect of fiber reinforcement.Figure 16
The fiber bundle phenomenon.


### 3.5.3. Relationship between Strain and Stress

Figure17 shows the stress-strain relationship curve of the glass fiber-reinforced cemented soil and the cemented soil without fiber after 5 freezing-thawing cycles in a water environment. It can be seen from Figure 17 that the peak strength of the glass fiber-reinforced cemented soil was 2.7878 Mpa, the peak strength of the cemented soil without the fiber was 2.4043 Mpa, and the peak difference between the two was 0.3835 Mpa. Therefore, these findings indicate that incorporating the fiber increases the peak strength of the test block.Figure 17
Relationship between strain and stress of specimens in water environment (after 5 freezing-thawing cycles).Figure18 shows the vertical strain cloud diagram of the glass fiber-reinforced cemented soil and the cemented soil without glass fibers in the water environment after 5 freezing-thawing cycles using digital image correlation technology. As seen in Figure 18, in the later loading stage, the internal strain of the glass fiber-reinforced cemented soil is concentrated at the center and no apparent cracks have appeared. The cemented soil without fiber shows an inclined strain concentration zone below and noticeable damage cracks appear. This indicates that the incorporation of fibers increases the tensile strength of the cemented soil, limits the development of cracks, and thus increases the strength of the test block.Figure 18
Vertical strain cloud diagram of specimen in water environment (after 5 freezing-thawing cycles) for (a) glass fiber-reinforced cemented soil and (b) cemented soil without fibers.
(a)(b)


## 3.5.1. Fiber Influence Strength Ratio

To further study the influence of glass fibers on the frost resistance of the cemented soil, the fiber influence strength ratio is introduced in [22]. The strength ratio formula was calculated according to the following equation:(2)ω=in,fin,pwhere ω is the fiber influence strength ratio; in,f is the unconfined compressive strength value of the glass fiber-reinforced cemented soil subject to freezing-thawing cycles in a water environment; in,p is the unconfined compressive strength value of the cemented soil without the glass fiber in a water environment; n represents the number of freezing-thawing cycles; f represents the cemented soil with the glass fiber; and p represents the cemented soil test block without glass fiber.Figure13 shows the fiber influence strength ratio. As noted in Figure 13, the fiber influence strength ratio in a clear water environment is less than 1 in the early time because the strength of glass fiber-reinforced cement is slightly lower than that of the cemented soil without fibers after 28 days of curing. With the increasing number of freezing-thawing cycles, the fiber influence strength ratio is greater than 1 after 4 cycles, indicating that the fiber’s existence inhibits the freezing-thawing cycle’s damaging effect on the specimens. Therefore, the strength loss of the fiber-reinforced cemented soil is less than that of the cemented soil without the fiber.Figure 13
Fiber influence strength ratio in a water environment.


## 3.5.2. Effect of Fiber on Unconfined Compressive Strength

Figure14 shows the strength loss rate of the cemented soil in a water environment. According to Figure 14, the strength loss rate of the glass fiber-reinforced cemented soil is 42.86% and the strength loss rate of the cemented soil without the glass fiber is 61.30%. These findings demonstrate that incorporating the fiber improves the soil’s bonding performance and suppresses the loss of strength of the specimens subject to freezing-thawing cycles. Figure 15 shows the specimens’ damage curve under different freezing-thawing cycles in a water environment. It can be seen from Figure 15 that with the increase in freezing-thawing cycles, the unconfined compressive strength of the specimens without the glass fiber decreased significantly. Furthermore, the unconfined compressive strength of the glass fiber-reinforced cemented soil decreased significantly at the beginning of the freezing-thawing cycle and then tended to be stable after 2 freezing-thawing cycles.Figure 14
Strength loss rate of cement-soil test block after the 5th freezing-thawing cycle in a clean water environment.Figure 15
The damage curve of specimens under different freezing-thawing cycles.Dispersion of fibers in the specimen is an important factor affecting the strength of the specimen. Uneven dispersion and bunching of fibers were found during the mixing process, as shown in Figure16. As a result, the initial strength of the cemented soil with fibers is lower than that without fibers, as shown in Figure 15. When the glass fiber is incorporated into the cemented soil, the glass fiber will form a network that will increase the friction resistance between the soil particles and prevents the formation and expansion of micropores and crack lines under the freeze and thawing conditions [29]. Thus, the strength of the cemented soil with fiber decreases slowly under the action of freezing-thawing cycles. Furthermore, the strength of the cemented soil with fibers is higher than that without fibers in the middle and late periods of Figure 15, which proves the effect of fiber reinforcement.Figure 16
The fiber bundle phenomenon.


## 3.5.3. Relationship between Strain and Stress

Figure17 shows the stress-strain relationship curve of the glass fiber-reinforced cemented soil and the cemented soil without fiber after 5 freezing-thawing cycles in a water environment. It can be seen from Figure 17 that the peak strength of the glass fiber-reinforced cemented soil was 2.7878 Mpa, the peak strength of the cemented soil without the fiber was 2.4043 Mpa, and the peak difference between the two was 0.3835 Mpa. Therefore, these findings indicate that incorporating the fiber increases the peak strength of the test block.Figure 17
Relationship between strain and stress of specimens in water environment (after 5 freezing-thawing cycles).Figure18 shows the vertical strain cloud diagram of the glass fiber-reinforced cemented soil and the cemented soil without glass fibers in the water environment after 5 freezing-thawing cycles using digital image correlation technology. As seen in Figure 18, in the later loading stage, the internal strain of the glass fiber-reinforced cemented soil is concentrated at the center and no apparent cracks have appeared. The cemented soil without fiber shows an inclined strain concentration zone below and noticeable damage cracks appear. This indicates that the incorporation of fibers increases the tensile strength of the cemented soil, limits the development of cracks, and thus increases the strength of the test block.Figure 18
Vertical strain cloud diagram of specimen in water environment (after 5 freezing-thawing cycles) for (a) glass fiber-reinforced cemented soil and (b) cemented soil without fibers.
(a)(b)


## 3.6. Effect of the Snow-Melting Agent Type

### 3.6.1. Snow-Melting Agent Influence Strength Ratio

To explore the influence of the erosion environment on the glass fiber-reinforced cemented soil, the snow-melting agent influence strength ratioα is introduced. This strength ratio denotes the peak strength of the specimens in the water environment to the peak strength of the specimens in different environments after freezing-thawing cycles. The strength ratio is calculated by the following equation:(3)α=in,win,dwhere α is the ratio of the unconfined compressive strength of the specimens in the water environment after freezing-thawing cycles to the unconfined compressive strength of the specimens in different environments; in,w is the unconfined compressive strength of the glass fiber-reinforced cemented soil in the water environment after freezing-thawing cycles; in,d is the unconfined compressive strength of the glass fiber-reinforced cemented soil in different saline environments after freezing-thawing cycles, and n represents the numbers of the freezing-thawing cycle; w represents the water environment; d represents the salt solution environment.Figure19 shows the snow-melting agent’s influence strength ratio and the number of freezing-thawing cycles. It can be seen from Figure 19 that the snow-melting agent influence strength ratio of the specimens in sodium sulfate solution was the highest in the early stage of the freezing-thawing cycle. In contrast, the specimens in the sodium sulfate solution lost its strength after 5 freezing-thawing cycles, indicating that the sodium sulfate solution eroded the specimens rapidly and the deterioration effect was severe. The strength ratio of magnesium chloride began to be greater than 1 after the second freezing-thawing cycle. It then showed an upward trend, indicating that the magnesium chloride solution had a strong erosion effect on the specimens and significantly affected their deterioration. Furthermore, the overall strength ratio of the specimens in the potassium acetate solution was close to 1 during 8 freezing-thawing cycles, indicating that the potassium acetate solution had a weak effect on the strength deterioration of the test block.Figure 19
The relationship between the snow-melting agent influences the strength ratio and the number of freezing-thawing cycles.


### 3.6.2. Relationship between Strain and Stress

Figure20 is the stress-strain relationship curve of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles. Figure 20 shows that the peak stress of the specimens in the potassium acetate solution was slightly different from the peak stress of the specimens in the water environment. In contrast, the peak strength of the specimens in the magnesium chloride and sodium sulfate solution decreased significantly. Compared with the specimens in the water environment, the peak strength of the specimens in the magnesium chloride solution decreased by 69.81%, and the peak strength in the sodium sulfate solution decreased by 83.17%. The strain corresponding to the peak strength of the specimens in the magnesium chloride solution and sodium sulfate solution was larger, the stress-strain curve had no noticeable stress drop, and the whole was a ductile failure, suggesting that the test block tended to the nature of the soil.Figure 20
Stress-strain relationship curve of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles.Figure21 is the vertical strain cloud diagram of the glass fiber-reinforced cemented soil in four different solution environments after 5 freezing-thawing cycles. As demonstrated in Figure 21, the internal strain of the specimens in water and potassium acetate solution is concentrated at the center, the range is small, and there is no apparent strain zone causing cracks at the edge. Additionally, the range of the strain zone in the magnesium chloride solution increased. Furthermore, the strain zone of the test block in the sodium sulfate solution was the largest, and there was roughly a tilt through the strain concentration zone.Figure 21
Vertical strain cloud diagram of glass fiber-reinforced cemented soil in salt solution environment after 5 cycles: (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)


## 3.6.1. Snow-Melting Agent Influence Strength Ratio

To explore the influence of the erosion environment on the glass fiber-reinforced cemented soil, the snow-melting agent influence strength ratioα is introduced. This strength ratio denotes the peak strength of the specimens in the water environment to the peak strength of the specimens in different environments after freezing-thawing cycles. The strength ratio is calculated by the following equation:(3)α=in,win,dwhere α is the ratio of the unconfined compressive strength of the specimens in the water environment after freezing-thawing cycles to the unconfined compressive strength of the specimens in different environments; in,w is the unconfined compressive strength of the glass fiber-reinforced cemented soil in the water environment after freezing-thawing cycles; in,d is the unconfined compressive strength of the glass fiber-reinforced cemented soil in different saline environments after freezing-thawing cycles, and n represents the numbers of the freezing-thawing cycle; w represents the water environment; d represents the salt solution environment.Figure19 shows the snow-melting agent’s influence strength ratio and the number of freezing-thawing cycles. It can be seen from Figure 19 that the snow-melting agent influence strength ratio of the specimens in sodium sulfate solution was the highest in the early stage of the freezing-thawing cycle. In contrast, the specimens in the sodium sulfate solution lost its strength after 5 freezing-thawing cycles, indicating that the sodium sulfate solution eroded the specimens rapidly and the deterioration effect was severe. The strength ratio of magnesium chloride began to be greater than 1 after the second freezing-thawing cycle. It then showed an upward trend, indicating that the magnesium chloride solution had a strong erosion effect on the specimens and significantly affected their deterioration. Furthermore, the overall strength ratio of the specimens in the potassium acetate solution was close to 1 during 8 freezing-thawing cycles, indicating that the potassium acetate solution had a weak effect on the strength deterioration of the test block.Figure 19
The relationship between the snow-melting agent influences the strength ratio and the number of freezing-thawing cycles.


## 3.6.2. Relationship between Strain and Stress

Figure20 is the stress-strain relationship curve of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles. Figure 20 shows that the peak stress of the specimens in the potassium acetate solution was slightly different from the peak stress of the specimens in the water environment. In contrast, the peak strength of the specimens in the magnesium chloride and sodium sulfate solution decreased significantly. Compared with the specimens in the water environment, the peak strength of the specimens in the magnesium chloride solution decreased by 69.81%, and the peak strength in the sodium sulfate solution decreased by 83.17%. The strain corresponding to the peak strength of the specimens in the magnesium chloride solution and sodium sulfate solution was larger, the stress-strain curve had no noticeable stress drop, and the whole was a ductile failure, suggesting that the test block tended to the nature of the soil.Figure 20
Stress-strain relationship curve of the glass fiber-reinforced cemented soil after 5 freezing-thawing cycles.Figure21 is the vertical strain cloud diagram of the glass fiber-reinforced cemented soil in four different solution environments after 5 freezing-thawing cycles. As demonstrated in Figure 21, the internal strain of the specimens in water and potassium acetate solution is concentrated at the center, the range is small, and there is no apparent strain zone causing cracks at the edge. Additionally, the range of the strain zone in the magnesium chloride solution increased. Furthermore, the strain zone of the test block in the sodium sulfate solution was the largest, and there was roughly a tilt through the strain concentration zone.Figure 21
Vertical strain cloud diagram of glass fiber-reinforced cemented soil in salt solution environment after 5 cycles: (a) water environment; (b) potassium acetate environment; (c) magnesium chloride environment; (d) sodium sulfate environment.
(a)(b)(c)(d)


## 3.7. Modulus of Deformation

To better describe the deformation of the glass fiber-reinforced cemented soil under salt solution erosion and freezing-thawing cycles, the deformation modulus E50 is introduced. The definition formula of deformation modulus is shown in the following equation:(4)E50=σu2εwhere E50 is the deformation modulus of the specimen (MPa), σu is the peak stress of specimen (MP), and ε is the strain corresponding to half peak stress of the specimen.Figure22 shows the relationship between the deformation modulus and the number of freezing-thawing cycles of the glass fiber-reinforced cemented soil soaked in water and 0.2 mol/L potassium acetate, magnesium chloride, and sodium sulfate solutions. As displayed in Figure 22, as the number of freezing-thawing cycles increases, the deformation modulus of the test block gradually decreases. After the 2 freezing-thawing cycles, the deformation modulus decreased greatly, in which the pilot block of water and sodium sulfate solution decreased by 114.33 MPa and 100.58 MPa, respectively. Additionally, the trend is flat after 5 freezing-thawing cycles. Furthermore, at this time, the deformation modulus of the pilot block of water, potassium acetate, magnesium chloride, and sodium sulfate solution decreased by 185.94 MPa, 206.98 MPa, 175.47 MPa, and 101.37 MPa, respectively, compared with the initial value. Therefore, the comprehensive analysis shows that the relationship between deformation modulus is water > potassium acetate > magnesium chloride > sodium sulfate.Figure 22
Relationship between the deformation modulus and the number of freezing-thawing cycles of the glass fiber-reinforced cemented soil.


## 4. Conclusion

To quickly restore traffic after snow, snow-melting agents are overused, which leads to a certain degree of damage to the roadbed after spring melting and reduces the service life of the road and increases the maintenance cost in the later period. In this article, the apparent characteristics, mechanical properties, and mass loss of the cemented soil under salt-freezing cycles are studied, which provide a reference for the construction of roadbeds and the selection of snow-melting agents in cold areas, and the conclusion is as follows:(1)
With the increase in the number of freezing-thawing cycles, regardless of whether the glass fiber is added, the strength of the specimens is gradually reduced. From the apparent analysis, the test block began to suffer significant damage after 5 freezing-thawing cycles.(2)
The strength of the glass fiber-reinforced cemented soil and those without fiber decreased by 42.86% and 61.30%, respectively. Compared with that before the fifth freezing-thawing cycle, the addition of glass fibers is beneficial to alleviate the strength loss and mass loss rate of the cemented soil in the freezing-thawing cycle. Furthermore, this can effectively slow down the rate of test block damage and improve cemented soil’s corrosion and frost resistance.(3)
Among the common snow-melting agents, potassium acetate has the most significant snow-melting effect, followed by magnesium chloride, and sodium sulfate has the worst snow-melting effect. Under freezing-thawing cycles, the type of snow-melting agent dramatically influences cemented soil’s quality, strength, and deformation modulus. Notably, the relationship between the deterioration ability of the specimens is sodium sulfate > magnesium chloride > potassium acetate.(4)
the freezing-thawing cycle is an important factor affecting the stability and durability of the subgrade, so the freezing-thawing cycle should be fully considered in practical projects in cold areas. Notably, the use of sulfate snow-melting agents should be avoided, and acetate snow-melting agents can achieve the best effect of melting snow and protect subgrade material to a greater extent.The use of snow-melting agents will significantly reduce the durability of the roadbed, especially under the superposition of the freezing and thawing cycle, and the damage is more obvious. Importantly, fibers added to the cemented soil can slow down this damage. In the actual engineering, the type of snow-melting agent should be selected more carefully, and the appropriate fiber should be added to extend the roadbed’s service life.



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*Source: 9766539-2023-02-22.xml*