碱激发粉煤灰固化淤泥微观机制研究
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摘要
为解决硅酸盐水泥等传统固化剂高能耗、高CO_2排放和高污染等问题,采用新型低碳碱激发粉煤灰胶凝材料对淤泥进行固化处理,开展养护龄期、激发剂类型及掺量多种因素影响下固化淤泥无侧限抗压强度、X射线衍射、扫描电镜、热重和压汞试验,通过分析抗压强度、化学成分、断面形貌及孔隙结构等宏微观特性,揭示碱激发粉煤灰固化淤泥强度性状演变规律与微观机制。结果表明:碱激发粉煤灰可有效提高固化淤泥无侧限抗压强度,Na OH,Na_2Si O_3·9H_2O激发效能优异,Na_2CO_3激发效果相对有限。碱性OH~-作用于粉煤灰玻璃体内外,受激发经"溶解–聚合"形成不同聚合度的硅铝酸盐聚合物凝胶N-A-S-H,黏结细颗粒从而提高固化淤泥整体强度。碱激发剂掺量升高,引起N-A-S-H凝胶生成量增多、热重质量损失增多、团粒内孔隙更多地转化为颗粒间孔隙,导致固化淤泥微观结构更加致密、整体性更强,宏观上表现为力学特性大幅改善。上述结果揭示了碱激发粉煤灰固化淤泥宏微观特征演变过程,建立了碱激发粉煤灰内在化学反应诱发固化淤泥性能改良的全过程模型,可为碱激发粉煤灰替代水泥用于淤泥固化提供理论依据。
To mitigate the thorny problems associated with traditional Portland cement production in terms of energy consumption,CO_2 emissions and air pollution,a favorable alternative option-novel and low-carbon alkali-activated industrial by-products is proposed for sludge solidification.Based on unconfined compressive strength,X-ray diffraction,scanning electron microscopy,thermogravimetric and mercury intrusion porosimetry tests,a systematical study has been performed to analyze the mechanical strength,hydration product,section morphology,thermal stability and micropore structure of alkali-activated fly ash solidified sludge and to reveal finally their strength evolution and microstructural mechanisms.The test results demonstrate that the compressive strength of dredged sludge is significantly enhanced owning to the incorporation of alkali-activated fly ash.Compared to Na_2CO_3,Na OH and Na_2SiO_3·9H_2O have gained much more attention because of their excellent performance to activate the potential activity of fly ash.Through the OH~-attack to the inner and outer glass sphere structure,fly ash is effectively activated by dissolution-polymerization to form aluminosilicate polymer gels N-A-S-H with different degrees of polymerization,binding fine particles together to increase the overall strength of solidified sludge.The increase in alkali activator content leads to an elevated production amount of N-A-S-H gels,an increase in thermogravimetric weight loss and a transformation of inter-aggregate pores to inter-particle pores.The above changes produce a denser micropore structure and better integrity,which promotes significantly the strength performance of solidified sludge.The obtained results deepen the understanding of macro-and microcharacteristics of alkali-activated fly ash solidified sludge,and establish the full microscopic reaction model of alkali-activated fly ash to clarify the intrinsic micro-mechanisms for strength improvement and to provide the theoretical basis for partial replacement of Portland cement by alkali-activated fly ash in sludge solidification.
To mitigate the thorny problems associated with traditional Portland cement production in terms of energy consumption,CO_2 emissions and air pollution,a favorable alternative option-novel and low-carbon alkali-activated industrial by-products is proposed for sludge solidification.Based on unconfined compressive strength,X-ray diffraction,scanning electron microscopy,thermogravimetric and mercury intrusion porosimetry tests,a systematical study has been performed to analyze the mechanical strength,hydration product,section morphology,thermal stability and micropore structure of alkali-activated fly ash solidified sludge and to reveal finally their strength evolution and microstructural mechanisms.The test results demonstrate that the compressive strength of dredged sludge is significantly enhanced owning to the incorporation of alkali-activated fly ash.Compared to Na_2CO_3,Na OH and Na_2SiO_3·9H_2O have gained much more attention because of their excellent performance to activate the potential activity of fly ash.Through the OH~-attack to the inner and outer glass sphere structure,fly ash is effectively activated by dissolution-polymerization to form aluminosilicate polymer gels N-A-S-H with different degrees of polymerization,binding fine particles together to increase the overall strength of solidified sludge.The increase in alkali activator content leads to an elevated production amount of N-A-S-H gels,an increase in thermogravimetric weight loss and a transformation of inter-aggregate pores to inter-particle pores.The above changes produce a denser micropore structure and better integrity,which promotes significantly the strength performance of solidified sludge.The obtained results deepen the understanding of macro-and microcharacteristics of alkali-activated fly ash solidified sludge,and establish the full microscopic reaction model of alkali-activated fly ash to clarify the intrinsic micro-mechanisms for strength improvement and to provide the theoretical basis for partial replacement of Portland cement by alkali-activated fly ash in sludge solidification.
引文
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[8]杨爱武,闫澍旺,杜东菊,等.碱性环境对固化天津海积软土强度影响的试验研究[J].岩土力学,2010,31(9):2 930-2 934.(YANGAiwu,YAN Shuwang,DU Dongju,et al.Experimental study of alkaline environment effects on the strength of cement soil of Tianjin marine soft soil[J].Rock and Soil Mechanics,2010,31(9):2 930-2 934.(in Chinese))
[9]易耀林,李晨,孙川,等.碱激发矿粉固化连云港软土试验研究[J].岩石力学与工程学报,2013,32(9):1 820-1 826.(YI Yaolin,LI Chen,SUN Chuan,et al.Test on alkali-activated ground granulated blast-furnace slag(GGBS)for Lianyungang soft soil stabilization[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(9):1 820-1 826.(in Chinese))
[10]吴燕开,胡晓士,胡锐,等.烧碱激发钢渣粉在淤泥质土中的试验研究[J].岩土工程学报,2017,39(12):2 187-2 194.(WU Yankai,HU Xiaoshi,HU Rui,et al.Experimental study on caustic sodaactivated steel slag powder in muddy soil[J].Chinese Journal of Geotechnical Engineering,2017,39(12):2 187-2 194.(in Chinese))
[11]孙秀丽,童琦,刘文华,等.碱激发粉煤灰和矿粉改性疏浚淤泥力学特性及显微结构研究[J].大连理工大学学报,2017,57(6):622-628.(SUN Xiuli,TONG Qi,LIU Wenhua,et al.Study of microstructure and mechanical properties of dredged silt solidified using fly ash and slag stimulated by alkali[J].Journal of Dalian University of Technology,2017,57(6):622-628.(in Chinese))
[12]崔源声.中国粉煤灰利用现状及2050年展望[C]//2014亚洲粉煤灰及脱硫石膏综合利用技术国际交流大会.朔州:[s.n.],2014:1-4.(CUI Yuansheng.Utilization status of fly ash in China and prospects for 2050[C]//Proceedings of the Annuel Meeting of Coal Ash Asia2014.Shuozhou:[s.n.],2014:1-4.(in Chinese))
[13]DUXSON P,LUKEY G C,DEVENTER J V.Thermal evolution of metakaolin geopolymers:part 1-Physical evolution[J].Journal of Non-Crystalline Solids,2006,352(52/54):5 541-5 555.
[14]SHEAR D L,OLSEN H W,NELSON K R.Effects of desiccation on the hydraulic conductivity versus void ratio relationship for a natural clay[R].Washington D C:National Academy Press,1993:1 365-1 370.
[15]FERNáNDEZ-JIMéNEZ A,PALOMO A,CRIADO M.Microstructure development of alkali-activated fly ash cement:a descriptive model[J].Cement and Concrete Research,2005,35(6):1 204-1 209.
[2]LI Z J,DING Z,ZHANG Y S.Development of sustainable cementitious materials[C]//International Workshop on Sustainable Development and Concrete Technology.Ames USA:Iowa State University,2004:55-76.
[3]DAVIDOVITS J.Global warming impact on the cement and aggregates industries[J].World Resource Review,1994,6(2):263-278.
[4]DING Y,DAI J G,SHI C J.Mechanical properties of alkali-activated concrete:a state-of-the-art review[J].Construction and Building Materials,2016,127:68-79.
[5]史迪,张文生,孙俊民,等.硅钙渣制备碱激发胶凝材料的实验研究[J].硅酸盐通报,2015,34(8):2 334-2 339.(SHI Di,ZHANGWensheng,SUN Junmin,et al.Preparation of alkali-activated cementitious materials with calcium silicate slag[J].Bulletin of the Chinese Ceramic Society,2015,34(8):2 334-2 339.(in Chinese))
[6]杨长辉,蒲心诚,吴芳.碱矿渣水泥砂浆的碱集料反应膨胀研究[J].硅酸盐学报,1999,27(6):651-657.(YANG Changhui,PUXincheng,WU Fang.The studies on alkali aggregate reaction of alkali-activated slag cement mortars[J].Journal of the Chinese Ceramic Society,1999,27(6):651-657.(in Chinese))
[7]SHI C J,ROY D,KRIVENKO P.Alkali-activated cements and concretes[M].New York:Taylor and Francis,2006:6-26.
[8]杨爱武,闫澍旺,杜东菊,等.碱性环境对固化天津海积软土强度影响的试验研究[J].岩土力学,2010,31(9):2 930-2 934.(YANGAiwu,YAN Shuwang,DU Dongju,et al.Experimental study of alkaline environment effects on the strength of cement soil of Tianjin marine soft soil[J].Rock and Soil Mechanics,2010,31(9):2 930-2 934.(in Chinese))
[9]易耀林,李晨,孙川,等.碱激发矿粉固化连云港软土试验研究[J].岩石力学与工程学报,2013,32(9):1 820-1 826.(YI Yaolin,LI Chen,SUN Chuan,et al.Test on alkali-activated ground granulated blast-furnace slag(GGBS)for Lianyungang soft soil stabilization[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(9):1 820-1 826.(in Chinese))
[10]吴燕开,胡晓士,胡锐,等.烧碱激发钢渣粉在淤泥质土中的试验研究[J].岩土工程学报,2017,39(12):2 187-2 194.(WU Yankai,HU Xiaoshi,HU Rui,et al.Experimental study on caustic sodaactivated steel slag powder in muddy soil[J].Chinese Journal of Geotechnical Engineering,2017,39(12):2 187-2 194.(in Chinese))
[11]孙秀丽,童琦,刘文华,等.碱激发粉煤灰和矿粉改性疏浚淤泥力学特性及显微结构研究[J].大连理工大学学报,2017,57(6):622-628.(SUN Xiuli,TONG Qi,LIU Wenhua,et al.Study of microstructure and mechanical properties of dredged silt solidified using fly ash and slag stimulated by alkali[J].Journal of Dalian University of Technology,2017,57(6):622-628.(in Chinese))
[12]崔源声.中国粉煤灰利用现状及2050年展望[C]//2014亚洲粉煤灰及脱硫石膏综合利用技术国际交流大会.朔州:[s.n.],2014:1-4.(CUI Yuansheng.Utilization status of fly ash in China and prospects for 2050[C]//Proceedings of the Annuel Meeting of Coal Ash Asia2014.Shuozhou:[s.n.],2014:1-4.(in Chinese))
[13]DUXSON P,LUKEY G C,DEVENTER J V.Thermal evolution of metakaolin geopolymers:part 1-Physical evolution[J].Journal of Non-Crystalline Solids,2006,352(52/54):5 541-5 555.
[14]SHEAR D L,OLSEN H W,NELSON K R.Effects of desiccation on the hydraulic conductivity versus void ratio relationship for a natural clay[R].Washington D C:National Academy Press,1993:1 365-1 370.
[15]FERNáNDEZ-JIMéNEZ A,PALOMO A,CRIADO M.Microstructure development of alkali-activated fly ash cement:a descriptive model[J].Cement and Concrete Research,2005,35(6):1 204-1 209.