原材料理化性质对碱激发粉煤灰/矿渣早期性能的影响
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摘要
原材料的物理化学性能是影响碱激发材料工程性能的重要因素,为了研究不同粉煤灰与矿渣对碱激发粉煤灰/矿渣复合体系反应的影响,选取了广东省内5种粉煤灰与4种高炉矿渣粉为原材料,对其化学活性及物理性能进行表征,并借助等温量热仪、扫描电子显微镜和MIP等测试方法对反应放热、微观形貌及微观结构进行表征。结果表明,在低钙粉煤灰中比表面积对碱激发粉煤灰/矿渣复合体系的影响显著,粉煤灰比表面积过大,导致反应液相环境不足,灰体颗粒反应不充分,材料凝结快,反应热低,微观结构松散,样品抗压强度低;而低钙粉煤灰的化学活性对碱激发复合体系性能的影响并不明显。同时发现粉煤灰中Ca O含量越高,体系凝结越快,早期反应放热越高,对应样品7 d抗压强度越高。矿渣的碱度系数是影响碱激发粉煤灰/矿渣性能的重要参数,矿渣碱度系数越高,反应诱导期时间越短,生成凝胶所对应的放热峰出现时间提前且峰值越高,累计放热量越高,碱激发材料微观结构越致密,对应样品抗压强度越高。而当矿渣碱度系数相差不大时,矿渣中Mg O对碱激发反应促进作用比CaO更强。
The physical and chemical properties of raw materials are important factors that affect the engineering property of alkali-activated materials.Five kinds of fly ash and four kinds of blast furnace slag in Guangdong Province were chosen for study.Their chemical and physical properties were characterized.The hydration heat,morphology and microstructure of alkali-activated materials were studied by using 8-channel TAM auto isothermal calorimeter,scanning electron microscopy(SEM)and MIP method.The results showed that,for low calcium fly ash,the physical properties like the specific surface area,was found as one significant factor affecting the property of AAFS.Fly ash with higher surface area resulted in a lack of reaction liquid in alkaline environment,and insufficient reaction of the particles.Thus the AAFS exhibited faster setting and lower cumulative heat release.Meanwhile,the gels grew on the surface of the particles result in a looser microstructure and lower compressive strength.The reactivity of low calcium fly ash has no obvious effect on the performance of alkali-activated composite system.The study also found that fly ash with higher CaO content showed a shorter setting time and greater cumulative heat release,corresponding to higher compressive strength at 7 d,but the development of strength at later age was slow.The alkalinity of the slag was found as an important index indicating the reactivity for alkali activation.Slag with a higher alkalinity had not only shorter induction period,but higher and earlier exothermic peak corresponding to the gel formation.Meanwhile the AAFS showed a greater cumulative heat release and denser microstructure,corresponding to a higher compressive strength.When slag had similar alkalinity coefficient,the effect of Mg O in slag on alkali activation reaction is stronger than that of CaO.
The physical and chemical properties of raw materials are important factors that affect the engineering property of alkali-activated materials.Five kinds of fly ash and four kinds of blast furnace slag in Guangdong Province were chosen for study.Their chemical and physical properties were characterized.The hydration heat,morphology and microstructure of alkali-activated materials were studied by using 8-channel TAM auto isothermal calorimeter,scanning electron microscopy(SEM)and MIP method.The results showed that,for low calcium fly ash,the physical properties like the specific surface area,was found as one significant factor affecting the property of AAFS.Fly ash with higher surface area resulted in a lack of reaction liquid in alkaline environment,and insufficient reaction of the particles.Thus the AAFS exhibited faster setting and lower cumulative heat release.Meanwhile,the gels grew on the surface of the particles result in a looser microstructure and lower compressive strength.The reactivity of low calcium fly ash has no obvious effect on the performance of alkali-activated composite system.The study also found that fly ash with higher CaO content showed a shorter setting time and greater cumulative heat release,corresponding to higher compressive strength at 7 d,but the development of strength at later age was slow.The alkalinity of the slag was found as an important index indicating the reactivity for alkali activation.Slag with a higher alkalinity had not only shorter induction period,but higher and earlier exothermic peak corresponding to the gel formation.Meanwhile the AAFS showed a greater cumulative heat release and denser microstructure,corresponding to a higher compressive strength.When slag had similar alkalinity coefficient,the effect of Mg O in slag on alkali activation reaction is stronger than that of CaO.
引文
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[14]KUMAR S,KUMAR R,MEHROTRA S P.Influence of granulated blast furnace slag on the reaction,structure and properties of fly ash based geopolymer[J].Journal of Materials Science,2010,45(3):607-615.
[15]厉超.矿渣、高/低钙粉煤灰玻璃体及其水化特性研究[D].北京:清华大学,2011.
[16]万惠文,陈学兵,王君.矿渣成分及结构对潜在活性的影响[J].武汉理工大学学报,2009,31(4):101-103.
[17]胡张莉.碱激发矿渣粉煤灰水泥早期水化及收缩特性研究[D].长沙:湖南大学,2013.
[18]孙立萍.磨细矿粉活性激发的探讨[J].散装水泥,2012(3):41-42.
[19]徐彬,蒲心诚.矿渣玻璃体分相结构与矿渣潜在水硬活性本质的关系探讨[J].硅酸盐学报,1997(6):105-109.
[20]MA Y,HU J,YE G.The effect of activating solution on the mechanical strength,reaction rate,mineralogy,and microstructure of alkali-activated fly ash[J].Journal of Materials Science,2012,47(11):4568-4578.
[2]张祖华,姚晓,诸华军.硅酸钠模数对无机聚合物力学性能与微观结构的影响[J].南京工业大学学报(自然科学版),2011,33(1):52-56.
[3]MA Y.Microstructure and engineering properties of alkali activated fly ash-as an environment friendly alternative to portland cement[D].Delft:Delft University of Technology,2013.
[4]梁健俊,马玉玮,黄科,等.粉煤灰物理化学性能对碱激发材料的影响[J].硅酸盐通报,2016,35(8):2497-2502.
[5]陈晨,程婷,贡伟亮,等.粉煤灰地聚物反应体系下的反应影响因素分析[J].材料导报,2016,30(24):118-123.
[6]宋学锋,朱娟娟,邓倩倩.粉煤灰-矿渣基矿物聚物的强度影响因素及机理分析[J].硅酸盐通报,2016,35(3):943-947.
[7]DUXSON P,PROVIS J L.Designing precursors for geopolymer cements[J].Journal of the American Ceramic Society,2008,91(12):3864-3869.
[8]CHINDAPRASIRT P,JATURAPITAKKUL C,SINSIRI T.Effect of fly ash fineness on compressive strength and pore size of blended cement paste[J].Cement and concrete composites,2005,27(4):425-428.
[9]BERNAL S A,SAN N R,MYERS R J,et al.MgO content of slag controls phase evolution and structural changes induced by accelerated carbonation in alkali-activated binders[J].Cement and Concrete Research,2014(57):33-43.
[10]姚晓,诸华军,张祖华,等.碱激发体系与土聚水泥抗压强度的灰色关联[J].混凝土,2009(2):1-3.
[11]吴达华,吴永革,林蓉.高炉水淬矿渣结构特性及水化机理[J].石油钻探技术,1997(1):33-35,64.
[12]杨长辉,蒲心诚.论碱矿渣水泥及混凝土的缓凝问题及缓凝方法[J].重庆建筑大学学报,1996(3):68-73.
[13]LEE W K W,DEVENTER J S J V.The effect of ionic contaminants on the early-age properties of alkali-activated fly ash-based cements[J].Cement&Concrete Research,2002,32(4):577-584.
[14]KUMAR S,KUMAR R,MEHROTRA S P.Influence of granulated blast furnace slag on the reaction,structure and properties of fly ash based geopolymer[J].Journal of Materials Science,2010,45(3):607-615.
[15]厉超.矿渣、高/低钙粉煤灰玻璃体及其水化特性研究[D].北京:清华大学,2011.
[16]万惠文,陈学兵,王君.矿渣成分及结构对潜在活性的影响[J].武汉理工大学学报,2009,31(4):101-103.
[17]胡张莉.碱激发矿渣粉煤灰水泥早期水化及收缩特性研究[D].长沙:湖南大学,2013.
[18]孙立萍.磨细矿粉活性激发的探讨[J].散装水泥,2012(3):41-42.
[19]徐彬,蒲心诚.矿渣玻璃体分相结构与矿渣潜在水硬活性本质的关系探讨[J].硅酸盐学报,1997(6):105-109.
[20]MA Y,HU J,YE G.The effect of activating solution on the mechanical strength,reaction rate,mineralogy,and microstructure of alkali-activated fly ash[J].Journal of Materials Science,2012,47(11):4568-4578.