Study on Strength Properties and Microstructure Characteristics of Straw Ash Improved Clay Liner Material

Abstract: In view of the low utilization rate of straw resources and the poor strength of landfill high quality GCL geosynthetic clay liner materials, straw ash modified clay is used as a new liner material. It can be obtained through compaction test, unconfined compression test and microstructure test. After the addition of straw ash, the strength of the soil is obviously increased, and the internal structure of the soil is more reasonable. 10% of the ash content of the straw can achieve the best mechanical strength effect.

Keywords: straw ash; GCL geosynthetic clay liner factory price; maximum dry density; optimal moisture content; axial stress

introduction

With the progress of human society, the treatment of domestic garbage has gradually been standardized GCL geosynthetic clay liner for sale. Today, domestic garbage is mainly treated by means of sanitary landfill or incineration and landfill. In the course of operation, the traditional domestic landfill is affected by multiple factors such as temperature and water flow, which can easily cause cracking of the clay liner in the landfill, causing serious damage to the production and living environment around the landfill [ 1].

Many scientists have improved traditional clay high quality GCL geosynthetic clay liner in a variety of ways. Liu Jisheng [2] tried to use fly ash to improve loess as a landfill liner material; Wang Yong [3], et al. studied GCL geotechnical materials. It is found that the geotechnical material has the characteristics of shearing and compressive resistance, and can delay the aging of the cushioning system for a certain period of time, thereby achieving the purpose of reducing the degree of cracking GCL geosynthetic clay liner manufacturers. Scientists have also tried to modify landfill clay liners using materials such as red mud and rice husks [4, 5]. The study found that the straw ash particles obtained after the straw treatment have a small composition and a certain strength.

In this paper, straw ash is mixed with traditional clay to make straw ash modified clay material. The maximum dry density and optimum moisture content of straw ash modified material are determined by the compaction test GCL geosynthetic clay liner for sale. The compressive properties of the straw ash modified material are determined by the unconfined compression test. The anti-shrinkage characteristics of the modified clay material under the action of water flow were measured by expansion and shrinkage test, and the microstructure was examined by scanning electron microscopy.

1 Test materials and methods

1.1 Test materials
The clay used in the test was taken from a construction site in Jiangxia District of Wuhan City. The soil was taken out and placed in a sample bag high quality GCL geosynthetic clay liner, sealed and preserved. After testing GCL geosynthetic clay liner manufacturers, the content of heavy metals and dangerous substances in the soil met the relevant national regulations and belonged to uncontaminated soil. The basic physical properties and chemical composition of clay are shown in Tables 1 to 2. The straw fiber used in the experiment was taken from a farm in Huanggang City and was used after being crushed.

Table 1 Basic physical properties of clay

Table 2 Chemical composition of clay

1.2 Test methods
The straw obtained by the experiment was manually crushed and placed in a muffle furnace, the temperature was adjusted to 800 ° C, and the straw ash was obtained after incineration for 2 hours, and placed in a vacuum desiccator for storage. The clay used in the test was dried in a blast oven at 105 ° C, and the mass was weighed every 1 h until the mass difference was less than 0.05%, and the mass was considered to be constant high quality GCL geosynthetic clay liner, and it was taken out and stored for use. The straw ash is blended into the clay at a mass ratio of 5%, 10%, and 15%, and uniformly mixed to obtain a straw ash-modified clay.

According to the geotechnical test procedure (SL237-011-1999), the compaction test was carried out on the modified clay with different straw ash content by using the compactor. The light compaction bucket was selected in the test, and the compaction function per unit volume was 592.2kJ/m3. According to the compaction curve, the maximum value is the optimal moisture content and the maximum dry density value GCL geosynthetic clay liner factory price. According to the geotechnical test procedure (SL237-020-1999), the unconfined compressive strength of the straw ash-modified clay was determined by a strain-controlled unconfined compression instrument.

The microstructure of the modified clay sample after the compressive strength test was scanned by scanning electron microscopy to determine the microstructure change of the straw ash-modified clay GCL geosynthetic clay liner manufacturers, and the magnification was set to 5,000 times.

2 Test results and discussion

2.1 Maximum dry density and optimum moisture content
The compaction curves of different ash ash-modified clays are shown in Figure 1. The maximum dry density and optimum moisture content are shown in Table 3.

Fig.1 Compaction curve of different dosage of straw ash modified clay

Table 3 Maximum dry density and optimum moisture content

It can be seen that with the increase of water content, the compaction curve first increases and then decreases. Under the same water content condition, with the increase of straw ash content, the dry density value increases first and then decreases, and the straw ash is mixed high quality GCL geosynthetic clay liner. The modified clay with a volume of 10% has the largest maximum dry density, reaching 1.656 g/cm3, which is 1.72% higher than the sample with 0% straw ash content. When the straw ash content continues to increase to 15%, the maximum dry density increases to 1.659 g/cm3, which is 0.18% lower than the sample with 10% straw ash content. The optimum moisture content of each sample is close to 21.9%-22.4%. It can be seen that after adding straw ash, the degree of compaction of the sample is increased GCL geosynthetic clay liner factory price, the connection between the particles is tighter, the structure of the particle skeleton is gradually revealed, and the maximum dry density value is also increased, and the mechanical strength is enhanced. However, when the amount of straw ash added exceeds 10%, the maximum dry density value increases little, and the interparticle voids gradually become saturated.

2.2 Unconfined compressive strength
The unconfined compressive strength of the modified clay with different straw ash content is shown in Fig. 2.

It can be seen that with the increase of axial strain, the axial stress first increases and then decreases GCL geosynthetic clay liner manufacturers. The maximum axial stress of the straw ash sample is 11.4 kPa, and the axial strain continues to increase. The stress change is not obvious, and the soil sample enters a hardened state. After the incorporation of straw ash GCL geosynthetic clay liner for sale, the maximum axial stress value of the sample increased significantly GCL geosynthetic clay liner factory price. The maximum axial stress of the 5%, 10%, and 15% soils was 17.2 kPa, 18.8 kPa, and 18.4 kPa, respectively. The sample is 50.9%~64.9% larger, and the compressive strength of the soil increases obviously. After reaching the maximum axial stress, the axial stress of the soil sample decreases and the softening phenomenon is obvious.

Fig.2 Unconfined compressive strength of clay with different dosage of straw ash

It can be seen that with the addition of straw ash, the compressive properties of the soil are obviously improved, the compressive strength value is increased, the structure of the granular components is more reasonable, and the pores of the particles are filled with straw ash, which plays an obvious skeleton supporting structure high quality GCL geosynthetic clay liner. The difference of the maximum axial stress between the 10% straw ash content and the 15% straw ash content is small. The increase in the strength of the straw ash content is less than 10%, which is similar to the compaction test results.

2.3 Microstructure
A scanning electron microscope image of the straw ash-modified clay is shown in Fig. 3.

It can be seen that when the straw ash is not added, the soil particle fragments are densely distributed and the pore filling is small, but the strength is greatly affected because there is no supporting system. The image of adding straw ash is shown in Figure b to Figured GCL geosynthetic clay liner manufacturers. The straw ash particles are relatively small and the surface is rough. It can be seen that the genus is uniformly distributed in the image, and a small number of pores appear inside the soil, and the ash particles are wrapped. In clay GCL geosynthetic clay liner for sale, the distribution of the pore structure is more reasonable, and the arrangement of soil debris is gradually converted from the original surface arrangement to the point-point arrangement.

According to the results obtained from the compaction test and the unconfined compression test, the mechanical strength of the straw ash is increased after the addition of straw ash GCL geosynthetic clay liner factory price. It can be seen that the straw ash forms an obvious skeleton support system in the clay particles GCL geosynthetic clay liner manufacturers, and the soil structure is uniform and reasonable, vertical and horizontal. The pressure resistance is significantly enhanced.

Figure 3 Scanning electron microscope image of different dosage of straw ash modified clay

When the straw ash material continues to increase GCL geosynthetic clay liner factory price, the pore volume in the soil reaches a critical value GCL geosynthetic clay liner for sale. Under the action of high strength pressure, part of the support structure is damaged, which indirectly affects the compressive strength of the soil, which results in the ash content of the straw being greater than 10%. The increase in strength is not obvious.

3 Conclusion

(1) With the increase of straw ash content, the dry density value increased first and then decreased. The maximum dry density of modified clay with 10% straw ash content was 1.656 g/cm3.
(2) After the straw ash was mixed, the maximum axial stress value of the sample increased significantly GCL geosynthetic clay liner for sale. The maximum axial stress of the 5%, 10%, and 15% soils was 17.2 kPa, 18.8 kPa, and 18.4 kPa, respectively.
(3) After the addition of straw ash, the distribution of the pore structure of the modified clay is more reasonable, and the arrangement of the residual parts of the soil is gradually converted from the original surface arrangement to the point-dot arrangement.