1. Key Laboratory of Building Safety and Energy Efficiency of Ministry of Education, Hunan University, Changsha 410082, China 2. National Center for International Research Collaboration in Building Safety and Environment, Hunan University, Changsha 410082, China 3. College of Civil Engineering, Hunan University, Changsha 410082, China 4. Chonfar Engineering and Technology Co. Ltd, Changsha 410000, China 5. Hubei Dayukou Chemical Co. Ltd, Zhongxiang 431911, China
New sodium polyacrylate modified bentonite-sand-phosphogypsum (PMB-S-PG) impermeable material was developed for PG slag field or roadbed impermeable layers, which can provide a new idea for multiple ways to dispose PG. The properties of impermeability and shear strength for PMB-S-PG, raw bentonite-sand-phospho gypsum (RB-S-PG) and sodium polyacrylate modified bentonite-sand (PMB-S) under the drying-wetting (DW) cycles were compared, and the micro-mechanisms of the impermeability and the strength weakening for the specimens under the action of DW cycles were investigated by scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) tests. Results showed that the coefficients of permeability for the RB-S-PG, PMB-S-PG and PMB-S specimens increased by 146.50, 6.14 and 1.59 times after 9 DW cycles, respectively, indicating that the PMB can effectively improve the resistance of the specimens for DW cycles. The relationship of the shear strength for three specimens was as follows: PMB-S-PG>RB-S-PG>PMB-S, indicating that the PG and the PMB both helped to improve the shear strength of the specimens. The shear strength of the specimens showed a change trend of decreasing first and then stabilizing with the increasing number of DW cycles. By the MIP tests, it was found that the pore structure of the PMB-S-PG specimen changed from single-peak to three-peaks structure with the increasing number of DW cycles. The pore volume and number corresponding to the particle size of the three peaks increased continuously, which led to the weakening of interparticle cementation, but the increment of the pore volume of the specimen decreased gradually. In the effect of DW cycles, the properties of impermeability and strength for the specimen first weakened and then tended to be stable.
Tab.1Physical and chemical indexes of washed and original phosphogypsum
指标
wB/%
指标
wB/%
SiO2
62.839
MgO
3.224
Al2O3
16.337
K2O
1.331
Fe2O3
5.817
TiO2
1.331
CaO
5.399
P2O5
0.255
Na2O
3.614
—
—
Tab.2Chemical composition of bentonite
材料
wP/%
wL/%
IP
Gs
mF/(100 mL·(2g)?1)
聚合物改性膨润土
105.06
598.36
493.30
2.39
72.0 (去离子水)
膨润土
132.35
336.41
201.06
2.68
31.5 (去离子水)
Tab.3Physical property of bentonite and polymer-modified bentonite
试样
wB
MDD/(g·cm?3)
wopt/%
PMB
RB
Sand
PG
PMB-S-PG
10
10
40
50
1.50
24.7
RB-S-PG
10
10
40
50
1.61
22.3
PMB-S
10
10
90
0
1.52
20.3
Tab.4Results of different specimens for compaction tests
Fig.2Particle size distribution of specimens and materials
Fig.3SEM images of three specimens
Fig.4Curves of coefficient of permeability for specimens under different DW cycles
Fig.5Variation of shear strength curves for specimens under different DW cycles
Fig.6Curves of cohesion and internal friction angle for specimens under different DW cycles
Fig.7Cumulative mercury curve for specimen PMB-S-PG under different DW cycles
Fig.8Pore distribution curves for specimen PMB-S-PG under different DW cycles
[1]
刘宁, 徐文龙 湿堆磷石膏渣场黏土防渗层效果分析[J]. 环境工程, 2011, 29 (2): 91- 95 LIU Ning, XU Wenlong Effectiveness of clay liner in seepage control for wet phosphogypsum stacks[J]. Environmental Engineering, 2011, 29 (2): 91- 95
[2]
崔荣政, 白海丹, 高永峰, 等 磷石膏综合利用现状及“十四五”发展趋势[J]. 无机盐工业, 2022, 54 (4): 1- 4 CUI Rongzheng, BAI Haidan, GAO Yongfeng, et al Current situation of comprehensive utilization of phosphogypsum and its development trend of 14th Five-Year Plan[J]. Inorganic Chemicals Industry, 2022, 54 (4): 1- 4
[3]
LI B X, LI L, CHEN X, et al Modification of phosphogypsum using circulating fluidized bed fly ash and carbide slag for use as cement retarder[J]. Construction and Buliding Materials, 2022, 338: 127630
doi: 10.1016/j.conbuildmat.2022.127630
[4]
CUADRI A A, MORENO S, ALTAMAR C L, et al Phosphogypsum as additive for foamed bitumen manufacturing used in asphalt paving[J]. Journal of Cleaner Production, 2021, 283: 124661
doi: 10.1016/j.jclepro.2020.124661
[5]
CHERNYSG Y, YAKHNEKO E, CHUBUR V, et al Phosphogypsum recycling: a review of environmental issues, current trends, and prospects[J]. Applied Sciences-Basel, 2021, 11 (4): 1575
doi: 10.3390/app11041575
[6]
CHEN M S, LIU P, KONG D W, et al Influencing factors of mechanical and thermal conductivity of foamed phosphogypsum-based composite cementitious materials[J]. Construction and Buliding Materials, 2022, 346: 128462
doi: 10.1016/j.conbuildmat.2022.128462
[7]
MARTIN D F, DOORIS P M, SUMPTER D Environmental impacts of phosphogypsum vs. borrow pits in roadfill construction[J]. Journal of Environmenal Science and Health Part A: Toxic/Hazardous Substances and Environmenal Engineering, 2001, 36 (10): 1975- 1982
[8]
ZHANG B L, CHEN K S, ZHANG K, et al Mechanical properties and modification mechanism of phosphogypsum stabilized soil[J]. SN Applied Sciences, 2022, 4 (8): 1- 19
[9]
JIN S X, ZHAO Z H, JIANG S F, et al. Comparison and summary of relevant standards for comprehensive utilization of fly ash at home and abroad [C]// IOP Conference Series: Earth and Environmental Science . Bristol: IOP, 2021: 012006.
[10]
LIU X D, JIN Z W, JING Y H, et al Review of the characteristics and graded utilisation of coal gasification slag[J]. Chinese Journal of Chemical Engineering, 2021, 35 (7): 92- 106
[11]
XU H Q, ZHU W, QIAN X D, et al Studies on hydraulic conductivity and compressibility of backfills for soil-bentonite cutoff walls[J]. Applied Clay Science, 2016, 132: 326- 335
[12]
DOLEY C, DAS U K, PHUKAN P K, et al A study on use of Brahmaputra river sand as a liner material for municipal landfills[J]. IOSR Journal of Mechanical and Civil Engineering, 2016, 13 (4): 91- 96
doi: 10.9790/1684-1304029193
[13]
ABDELLAH D, MOHAMED K G, IDRISS G Effect of water and leachate on hydraulic behavior of compacted bentonite, calcareous sand and tuff mixtures for use as landfill liners[J]. Geotechnical and Geological Engineering, 2017, 35 (6): 2677- 2696
doi: 10.1007/s10706-017-0270-4
[14]
OZHAN H O Determination of mechanical and hydraulic properties of polyacrylamide-added bentonite-sand mixtures[J]. Bulletin of Engineering Geology and The Environment, 2021, 80: 2557- 2571
doi: 10.1007/s10064-020-02062-9
[15]
周正兵, 王钊, 王俊奇. GCL: 一种新型复合土工材料的特性及应用综述[J]. 长江科学院院报, 2002, (1): 35-38. ZHOU Zhengbing, WANG Zhao, WANG Junqi. An overview about preoperties and application if a new geocomposite : GCL [J]. Journal of Yangze River Scientific Rearch Institute , 2002, (1): 35-38.
[16]
林海, 章玲玲, 阮晓波, 等 水化针刺GCL+GM复合衬里的单剪破坏特征[J]. 岩土工程学报, 2016, 38 (9): 1660- 1667 LIN Hai, ZHANG Lingling, YUAN Xiaobo, et al Simple-shear failure characteristics of hydrated needle punched GCL+GM composite liner[J]. Chinese Journal of Geotechnical Engineering, 2016, 38 (9): 1660- 1667
doi: 10.11779/CJGE201609013
[17]
徐超, 李志斌 针刺GCL内部剪切强度的试验研究[J]. 同济大学学报: 自然科学版, 2010, 38 (5): 639- 643 XU Chao, LI Zhibin Experimental research on internal shear strength of needle-punched GCL[J]. Journal of TongJi Univerisity: Natural Science, 2010, 38 (5): 639- 643
[18]
ARIFIN Y F The Permeability and shear strength of compacted claystone-bentonite mixtures[J]. International Journal of Geomate, 2021, 21 (84): 48- 61
[19]
SOBIT J, SINGH S K Strength and compaction analysis of sand-bentonite-coal ash mixes[J]. IOP Conference Series: Materials Science and Engineering, 2017, 225 (1): 012091
[20]
IRAVANIAN A, BILSEL H Tensile strength properties of sand-bentonite mixtures enhanced with cement[J]. Procedia Engineering, 2016, 143: 111- 118
doi: 10.1016/j.proeng.2016.06.015
[21]
MORRIS P H, GRAHAM J, WILLIAMS D J Cracking in drying soils[J]. Canadian Geotechnical Journal, 1992, 29: 263- 277
doi: 10.1139/t92-030
[22]
SEIPHOORI, A, FERRARI A, LYESSE L, et al Water retention behaviour and microstructural evolution of MX-80 bentonite during wetting and drying cycles[J]. Geotechnique, 2014, 64 (9): 721- 734
doi: 10.1680/geot.14.P.017
[23]
MICHELA D C, GEMMINA D E , ADAM B, et al. Effect of wet-dry cycles on polymer treated bentonite in seawater: swelling ability, hydraulic conductivity and crack analysis [J]. Applied Clay Science , 2017, 142: 52−59.
[24]
MICHAEL A M, SEUNGCHOEL Y, JEFFREY C E Hydraulic conductivity of model soil-bentonite backfills subjected to wet-dry cycling[J]. Canadian Geotechnical Journal, 2011, 48 (8): 198- 211
[25]
TANG, C S, CHEN Q, LENG T, et al Effects of wetting-drying cycles and desiccation cracks on mechanical behavior of an unsaturated soil[J]. Catena, 2020, 194: 104721
doi: 10.1016/j.catena.2020.104721
[26]
TU Y, ZHANG R, ZHONG Z, et al The strength behavior and desiccation crack development of silty clay subjected to wetting-drying cycles[J]. Frontiers in Earth Science, 2022, 10: 852820
doi: 10.3389/feart.2022.852820
[27]
ZENG L, YU H, GAO Q, et al Evolution of tensile properties of compacted red clay under wet and dry cycles[J]. KSCE Journal of Civil Engineering, 2022, 26 (2): 606- 618
doi: 10.1007/s12205-021-0527-6
[28]
杨微, 任孟健, 陈仁朋, 等 复杂环境条件下改性膨润土的抗盐性能[J]. 浙江大学学报: 工学版, 2021, 55 (10): 1885- 1893 YANG Wei, REN Mengjian, CHEN Renpeng, et al Salt resistance of modified bentonite in complex environment[J]. Journal of Zhejiang University: Engineering Science, 2021, 55 (10): 1885- 1893
熊峰, 杨宏伟, 吴益平, 等 干湿循环作用下滑带土孔隙结构与基质吸力响应规律研究[J]. 水利水运工程学报, 2018, (3): 95- 102 XIONG Feng, YANG Hongwei, WU Yiping, et al Response laws of pore structure and matrix suction of slip zone soils under action of wetting-drying cycles[J]. Hydro-Science and Engineering, 2018, (3): 95- 102
[34]
曾召田, 吕海波, 赵艳林, 等 膨胀土干湿循环过程孔径分布试验研究及其应用[J]. 岩土力学, 2013, 34 (2): 322- 328 ZENG Zhaotian, LU Haibo, ZHAO Yanlin, et al Study of pore size distribution of expansive soil during wetting-drying cycle and its application[J]. Rock and Soil Mechanics, 2013, 34 (2): 322- 328
[35]
吕海波, 汪稔, 赵艳林, 等 软土结构性破损的孔径分布试验研究[J]. 岩土力学, 2003, 24 (4): 573- 578 LU Haibo, WANG Ren, ZHAO Yanlin, et al Study of structure characteristics evolution of soft clay by pore size distribution test[J]. Rock and Soil Mechanics, 2003, 24 (4): 573- 578
doi: 10.3969/j.issn.1000-7598.2003.04.018
[36]
YANG W, ZHANG S Q, PAN X, et al Hydraulic properties of sodium polyacrylate-modified bentonite-sand mixtures[J]. Bulletin of Engineering Geology and the Environment, 2023, 82 (7): 250
doi: 10.1007/s10064-023-03255-8
