Mechanism of cement-stabilized soil polluted by magnesium sulfate
来源期刊：中南大学学报(英文版)2015年第5期
论文作者：HAN Peng-ju WANG Shuai Frank Y. Chen BAI Xiao-hong
文章页码：1869 - 1877
Key words：unconfined compression strength (UCS); magnesium sulphate (MS); X-ray diffraction (XRD); microstructure; energy dispersive spectrometer (EDS)
Abstract: In order to simulate and study the mechanism of cement stabilized soils polluted by different contents of magnesium sulfate (MS), a series of tests were conducted on the cemented soil samples, including unconfined compression strength (UCS) tests of blocks, X-ray diffraction (XRD) phase analysis of powder samples, microstructure by scanning electronic microscopy (SEM), element composition by energy dispersive spectrometry (EDS), and pore distribution analysis by Image Processed Plus 6.0 (IPP 6.0) software. The UCS test results show that UCS of cemented soils reaches the peak value when the MS content is 4.5 g/kg. While, the UCS for Sample MS4 having the MS content of 18.0 g/kg is the lowest among all tested samples. Based on the EDS analysis results, Sample MS4 has the greater contents for the three elements, oxygen (O), magnesium (Mg) and sulfur (S), than Sample MS1. From the XRD phase analysis, C-A-S-H (3CaO·Al2O3·3CaSO4·32H2O and 3CaO·Al2O3·CaSO4·18H2O), M-A-H (MgO·Al2O3·H2O), M-S-H (MgO·SiO2·H2O), Mg(OH)2 and CaSO4 phase diffraction peaks are obviously intense due to the chemical action associated with the MS. The pore distribution analysis shows that the hydrated products change the distribution of cemented soil pores and the pores with average diameter (AD) of 2-50 μm play a key role in terms of the whole structure of cemented soil. The microscopic structure of the cemented soil with MS exhibits the intertwined and embedded characteristics between the cement and granular soils from the SEM images of cemented soils. The microstructure analysis shows that the magnesium sulfate acts as the additive, which is beneficial to the soil strength when the MS content is low (i.e., Sample MS2). However, higher MS amount involving a chemical action makes samples crystallize and expand, which is adverse to the UCS of cemented soils (i.e., Sample MS4).
HAN Peng-ju(韩鹏举)1, 2, WANG Shuai(王帅)1, Frank Y. Chen(陈幼佳)1, 2, BAI Xiao-hong(白晓红)1
(1. College of Architecture and Civil Engineering, Taiyuan University of Technology, Taiyuan 030024, China;
2. Department of Civil Engineering, The Penn State University, Harrisburg, PA 17057, USA)
Abstract:In order to simulate and study the mechanism of cement stabilized soils polluted by different contents of magnesium sulfate (MS), a series of tests were conducted on the cemented soil samples, including unconfined compression strength (UCS) tests of blocks, X-ray diffraction (XRD) phase analysis of powder samples, microstructure by scanning electronic microscopy (SEM), element composition by energy dispersive spectrometry (EDS), and pore distribution analysis by Image Processed Plus 6.0 (IPP 6.0) software. The UCS test results show that UCS of cemented soils reaches the peak value when the MS content is 4.5 g/kg. While, the UCS for Sample MS4 having the MS content of 18.0 g/kg is the lowest among all tested samples. Based on the EDS analysis results, Sample MS4 has the greater contents for the three elements, oxygen (O), magnesium (Mg) and sulfur (S), than Sample MS1. From the XRD phase analysis, C-A-S-H (3CaO·Al2O3·3CaSO4·32H2O and 3CaO·Al2O3·CaSO4·18H2O), M-A-H (MgO·Al2O3·H2O), M-S-H (MgO·SiO2·H2O), Mg(OH)2 and CaSO4 phase diffraction peaks are obviously intense due to the chemical action associated with the MS. The pore distribution analysis shows that the hydrated products change the distribution of cemented soil pores and the pores with average diameter (AD) of 2-50 μm play a key role in terms of the whole structure of cemented soil. The microscopic structure of the cemented soil with MS exhibits the intertwined and embedded characteristics between the cement and granular soils from the SEM images of cemented soils. The microstructure analysis shows that the magnesium sulfate acts as the additive, which is beneficial to the soil strength when the MS content is low (i.e., Sample MS2). However, higher MS amount involving a chemical action makes samples crystallize and expand, which is adverse to the UCS of cemented soils (i.e., Sample MS4).
Key words:unconfined compression strength (UCS); magnesium sulphate (MS); X-ray diffraction (XRD); microstructure; energy dispersive spectrometer (EDS)
