I hereby declare that this manuscript, entitled "Triose shear behavior of cement-treated sand under high confining pressures", is the result of my own work, except for quotations and citations duly acknowledged. However, due to the environmental problems associated with the use of OPC, its replacement with calcium sulfoaluminate (CSA) cement offers great promise for soil improvement because it is less harmful to the environment. Nevertheless, previous studies have investigated the effects of CSA cement on the mechanical behavior of cemented sand; researchers still need to make efforts to study the behavior of sand treated with CSA cement under high confining pressure.
For this purpose, a triaxial consolidated drainage (CD) test was performed at high confining pressure to verify the shear strength and mechanical properties of the CSA-treated sand. In addition, SEM analysis was performed to learn more about the substructure of the tested samples. Experimental conditions including effective stresses of 1500 kPa and 3, 5 and 7% CSA cement content were used in this research.
Finally, the test results showed that the effective stresses and the percentage of CSA cement present in the samples significantly influence the mechanical behavior of the CSA-treated sand under high confining pressures. I sincerely thank my supervisor, Assistant Professor Alfred Satyanagi, for his help, input and guidance in this research project. I would like to take this opportunity to thank my senior colleagues, Shynggys Abdiali and Nazerke Sagidullini, and the entire team of technicians working in the Advanced Research Laboratory of Soil Mechanics at Nazarbayev University for all the help and encouragement they have given me throughout the entire my research.
Introduction
Introduction
Definition of the problem
Aim and Objective
Literature review
- Introduction
- Principles of Soil Stabilization
- Methods of Soil Stabilization
- Mechanical Stabilization
- Chemical Stabilization
- Stabilization of soil with CSA cement
- Triaxial Behavior of cemented treated-sand
16] studied the aftermath of freezing and thawing on the development of strength in sand treated with CSA cement. Experimental procedures such as UCS and UPV were performed on test specimens treated with 2, 5, 7 and 10% CSA cement by dry weight of sand. According to the research, an increase in freeze-thaw cycles reduced the strength of samples treated with CSA cement.
In this research, the test specimens were treated with CSA and OPC at 3%, 5% and 7% of the total mass of dry sand. Moreover, the early stiffness and strength of the test specimens treated with CSA and OPC also increased with an increase in fine particles. The researchers concluded that the choice of stabilizing materials for the treatment of the sand affects the effect of small particle sand treated with CSA and OPC.
UCS was used to determine the strength of cemented sand treated by the researchers with both CSA and OPC. Nevertheless, the test samples treated with CSA cement showed even better strength development than the samples treated with OPC. Furthermore, test specimens treated with CSA under dry curing conditions showed higher early strength growth than those with OPC due to the presence of ettringite in CSA. However, samples treated with OPC had somewhat high ultimate strength.
Laboratory tests of UPV and UCS were used to check the growth of strength in soils treated with CSA. The conclusions of the study showed that the CSA-treated samples developed their strength faster than the OPC-treated samples after one day of curing. Amini and Hamidi [25] investigated the mechanical properties of sand and gravel mixture treated with cement.
35] investigated the effect of cementation on the mechanical behavior of a sand sample treated with cement. Therefore, several CD-triaxial experiments were performed to determine the mechanical properties of samples treated with different cements (OPC and lime). However, samples treated with cement and zeolite were stiffer than those treated with cement alone.
In addition, the cement content increases the maximum deviator stress and the initial stress. Furthermore, the shear strength of cemented sand increased significantly with increasing effective stress.
Materials and Methodology
- Materials used
- Sample preparation
- Testing system
- Test procedure
Figures 3.2 and 3.3 show photographs of quartz sand and CSA cement used for the study. According to the standard compression test [41], water was added and the mixture was stirred for ten minutes. To facilitate the process of extruding the test samples, oil was applied to the inner surfaces of the cylindrical steel molds.
25 rammer blows were used to compact each of the three layers. The tops of the initial and second layers were sacrificed to avoid problems with smooth densified surfaces and to ensure adequate surface-to-surface contact before placement and compaction of the next layer [42]. Due to the significant increase in the CSA strength of the cemented soils, the curing period was set to 7 and 14 days.
A picture of the completed high-pressure triaxial cell is shown in Figure 3.5, along with the test setup. GDSlab Control Software, Data Logger, Speed Control Load Frames, Pressure/Volume Controllers, Speed Control Load Frames, PWP/Axial Displacement Sensor, Top Cap, Back and Cell Pressure/Volume Controllers (ADVDPC) and Triaxial Cell are some parts of the ETAS system. The load was transferred to the system from the base of the loading frame using a digital hydraulic force actuator.
The ADVDPC used in this research has a compressive capacity of 4 MPa, the weight cell has a capacity of 50 kN, and the triaxial cell has a compressive capacity of 4 MPa. 5 (a) Schematic diagram of the ETAS (b) Picture of the High Pressure triaxial cell inside the loading frame. After completion of the curing period, the test specimen was placed on top of the pedestal of the ETAS triaxial cell's base.
A pair of sealing rings was placed between the test specimen and the base plate to prevent cell oil. To achieve saturation, the sample was flushed with water that was deaerated from top to bottom for two hours, with a back pressure of ten kPa lower than the average effective stress (swelling pressure).
Results and Discussions
- Stress-strain relationship of the CSA cemented sand
- Failure characteristics
- Stress-dilatancy relationship of the CSA-treated samples
- SEM observation
Therefore, the q-εa behavior of the treated samples changes from ductile to brittle as the CSA cement content increases. The volumetric strain curves of the tests performed on the CSA treated sand samples at a confining pressure of 1500 kPa are also compared in Figure 4.3. It can be seen from Figure 4.3 (a) that all test specimens showed compression at an effective stress of 1500 kPa.
Therefore, with an increase in cement content, the compressive behavior of sand at high effective load decreases. Therefore, the CSA cement content and high confining pressure significantly affected the q-εa and εv-εa behavior of CSA-treated sand [e.g. Therefore, the peak state of each test accurately captures the failure state of the treated sand samples.
The failure conditions of all experiments performed in this study are shown in Figure 4.4. Nevertheless, as the percentage of cement increases, the failure envelopes of the treated samples become more and more bent. Furthermore, Figure 4.4 shows that an increase in the curvature of the failure envelope occurs along with an increase in the amount of CSA cement content.
The shear strength of the tested samples can be defined as a function of the friction angle and the cohesion intercept when considering the cohesion-friction properties. Furthermore, Figure 4.5 shows that the interparticle cohesion of the treated samples increases with cement concentration. It occurs due to the inherent geometric limitations of the tissue against the pressure applied during shearing.
Consequently, the dilatancy of the CSA-treated sample can be affected by the presence of CSA cement, which strengthens the bond between the sand particles after treatment. Furthermore, the volumetric strain curves of the investigated samples show that an increase in confining pressure suppresses the dilation rate. It shows the influence of density on the bond breaking and particle crushing of the CSA treated samples.
This finding is consistent with the results of previous experimental research that was conducted on cemented sand [8, 10].
Conclusions
Bagheripour, “Stabilization of oily contaminated clay soils using new materials: Micro and macrostructural investigation,” Geomechanics and Engineering, vol. White, "Cement, lime and fly ash in stabilization of expansive soils: performance evaluation and comparison," Journal of Materials in Civil Engineering, vol. Afaque Khan, “A review article on comparative study of soil stabilization with widely used admixtures such as lime, cement, fly ash and bitumen emulsion,” International Journal of Engineering Trends and Technology, vol.
Yu, "Drained behavior of cemented sand in high-pressure triaxial compression tests," Geomechanics and Geoengineering, vol. Consoli, "Characterization of cemented sand in triaxial compression," Journal of geotechnical and geoenvironmental engineering, vol. Wanatowski, "The effect of highly confining pressure on the behavior of fiber reinforced sand," Geotechnical engineering journal of the SEAGS &.
Moon, “Effect of cyclic freeze-thaw on the strength and durability of sand stabilized with CSA cement,” in The 2020 World Congress on Advances in Civil, Environmental, & Materials Research, 2020. Moon, “Characterization of CSA-cemented sand via discrete element method", in AIP Conference Proceedings, 2021, vol. Moon, "Performance of cement stabilized sand subjected to freeze-thaw cycles", Geomechanics and Engineering, vol.
Ku, “CSA-treated sand for geotechnical application: microstructure analysis and rapid strength development,” Journal of Materials in Civil Engineering, vol. Ku, “Effect of fine particles on the strength and stiffness of cement-treated sand,” Granular Matter, vol. Moon, “Stabilization of silty sand with CSA cement under freeze-thaw cycles,” in Proceeding of the 10th International Conference on Physical Modeling in Geotechnics (ICPMG.
34; The potential of limestone dust to improve the stabilization of saline soils containing sulfate," in IOP Conference Series: Materials Science and Engineering, 2021, vol. Hamidi, "Triaxial shear behavior of a cement-treated sand-gravel mix," Journal of Rock Mechanics and Geotechnics , vol.
