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蒸养条件对电解锰渣水泥胶砂力学性能与微观形貌的影响

付勇, 乔宏霞, 冯琼, 薛翠真, 李言奇, 贾振宇

付勇, 乔宏霞, 冯琼, 等. 蒸养条件对电解锰渣水泥胶砂力学性能与微观形貌的影响[J]. 复合材料学报, 2024, 41(12): 6826-6843. DOI: 10.13801/j.cnki.fhclxb.20240326.001
引用本文: 付勇, 乔宏霞, 冯琼, 等. 蒸养条件对电解锰渣水泥胶砂力学性能与微观形貌的影响[J]. 复合材料学报, 2024, 41(12): 6826-6843. DOI: 10.13801/j.cnki.fhclxb.20240326.001
FU Yong, QIAO Hongxia, FENG Qiong, et al. Effect of steam curing conditions on mechanical properties and microstructure of electrolytic manganese residue cement mortar[J]. Acta Materiae Compositae Sinica, 2024, 41(12): 6826-6843. DOI: 10.13801/j.cnki.fhclxb.20240326.001
Citation: FU Yong, QIAO Hongxia, FENG Qiong, et al. Effect of steam curing conditions on mechanical properties and microstructure of electrolytic manganese residue cement mortar[J]. Acta Materiae Compositae Sinica, 2024, 41(12): 6826-6843. DOI: 10.13801/j.cnki.fhclxb.20240326.001

蒸养条件对电解锰渣水泥胶砂力学性能与微观形貌的影响

基金项目: 国家自然科学基金(U21A20150;52178216);国家自然科学基金青年基金(52008196;52108219);甘肃省科技计划(23JRRA799;23JRRA813);重庆市科技局重点项目(cstc2021jscx-jbgs0029)
详细信息
    通讯作者:

    乔宏霞,博士,教授,博士生导师,研究方向为固废资源化利用 E-mail: qiaohongxia@lut.edu.cn

  • 中图分类号: TU528;TB333

Effect of steam curing conditions on mechanical properties and microstructure of electrolytic manganese residue cement mortar

Funds: National Natural Science Foundation of China (U21A20150; 52178216); Youth Fund of the National Natural Science Foundation of China (52008196; 52108219); Gansu Provincial Science and Technology Programme Grants (23JRRA799; 23JRRA813); Key Projects of Chongqing Science and Technology Bureau (cstc2021jscx-jbgs0029)
  • 摘要:

    本文研究了不同煅烧温度(200℃和800℃)电解锰渣(EMR)火山灰活性及掺入0wt%、10wt%、20wt% EMR水泥胶砂在80℃蒸汽养护7 h、7 d和标准养护3 d、28 d条件下力学性能、水化产物与孔隙特征分布。采用低场核磁共振技术、XRD定量表征及SEM微观形貌共同揭示了EMR对水泥胶砂的水化产物、孔径分布及孔隙率等影响规律,并探究了不同养护条件对EMR水泥胶砂水化进程的影响。结果表明:800℃煅烧EMR火山灰活性明显高于200℃煅烧火山灰活性,当800℃煅烧EMR替代量为10wt%时,初凝、终凝时间和标准稠度用水量分别为对照组的1.52、1.06和1.05倍,而蒸养7 h、7 d抗压强度分别高于标准养护3 d和28 d抗压强度,而抗折强度仅仅在蒸养7 d时高于对照组17.3%;纯水泥胶砂的水化产物主要为纤维状水化硅酸钙(C-S-H)凝胶和片状氢氧化钙(CH),而EMR水泥胶砂中由于硫酸盐含量较高,除了上述水化产物之外,在蒸养或标准养护条件下均可观察到石膏相与针棒状钙矾石(AFt)的存在,标准养护28 d时,CH、AFt和无定性含量分别为14.50%、11.75%和46.25%,与蒸养7 d衍射峰基本相似。另外,蒸汽养护7 h与标准养护3 d对比孔隙率减少1.44%,蒸养7 d与标准养护28 d对比孔隙率减少0.06%。综上,蒸汽养护可以提高800℃煅烧EMR火山灰活性,同时还可以加速EMR水泥胶砂的水化进程和细化其内部孔结构,进而提高胶砂的力学性能。

     

    Abstract:

    The pozzolanic activity of electrolytic manganese residue (EMR) at different calcination temperatures (200℃ and 800℃), and the distribution of mechanical properties, hydration products, and pore characteristics of cement mortar with 0wt%, 10wt% and 20wt% EMR, subjected to 80℃ steam curing for 7 h and 7 d, as well as standard curing for 3 d and 28 d, were studied. The effects of EMR on the hydration products, pore size distribution and porosity of cement mortar were revealed by low field nuclear magnetic resonance technology, XRD quantitative characterization and SEM microstructure. The effects of different curing conditions on the hydration process of EMR cement mortar were also investigated. The results show that the pozzolanic activity of EMR calcined at 800℃ is significantly higher than that of EMR calcined at 200℃. When the substitution amount of EMR calcined at 800℃ is 10%, the initial setting time, final setting time and water requirement of normal consistency are 1.52, 1.06 and 1.05 times than that of the control group, respectively. The compressive strength of steam-cured 7 h and 7 d is higher than that of standard-cured 3 d and 28 d, respectively, while the flexural strength is only 17.3% higher than that of the control group at 7 d. The hydration products of pure cement mortar are mainly fibrous hydrate calcium silicate (C-S-H) and sheet-like calcium hydroxide (CH), while in EMR cement mortar, due to the high sulfate content, in addition to the above hydration products, the presence of gypsum phase and needle shaped ettringite (AFt) can be observed under steam curing or standard curing conditions. The CH, AFt and amorphous contents are 14.50%, 11.75% and 46.25% after 28 d of standard curing. These values are similar to the diffraction peaks after 7 d of steam curing. In addition, the porosity of steam-cured 7 h is 1.44% lower than that of standard curing 3 d, and the porosity of steam-cured 7 d is 0.06% lower than that of standard curing 28 d. In summary, steam curing can improve the pozzolanic activity of EMR calcined at 800℃, accelerate the hydration process, and refine the internal pore structure, thereby improving the mechanical properties of the mortar.

     

  • 碳纤维增强聚合物复合材料(CFRP)具有高强、质轻、抗疲劳性能好和施工方便等优点,目前不仅被广泛应用于钢筋混凝土结构的加固中,同时也用在砌体结构的加固中[1-6]。CFRP加固砌体结构是通过CFRP与砌体材料界面间的粘结力,使两种材料组合在一起协同工作并传递荷载。因此,CFRP与砌体材料之间良好的粘结性能是保证CFRP与砌体结构共同受力变形的基础[7-8]。关于CFRP加固砌体结构,国内外学者做了大量研究,而关于CFRP-砌体界面性能只有少部分学者进行了研究并提出不同的界面粘结-滑移模型,这些模型基本上能准确模拟粘结界面的受力情况[9],但对于冻融环境下界面粘结-滑移模型未见公开报道。在冻融环境中,粘土砖的性能会随着时间的推移有所退化,在一定程度上会影响界面粘结性能,最终引起不可避免的耐久性问题[10-12]。因此,对冻融循环作用下CFRP与粘土砖之间粘结性能进行相应研究具有十分重要的意义。

    通过简单可靠的单剪试验探究了冻融循环作用下CFRP-粘土砖界面在外力作用的破坏过程及破坏形态,得到了界面剥离承载力在循环作用下的变化规律,通过试验测得的应变得到了冻融循环过程中剪应力的发展及分布规律,并给出了考虑冻融循环影响的界面粘结-滑移关系。

    试验所使用碳纤维增强聚合物复合材料(CFRP)和树脂均为上海滠口实业有限公司生产,其主要性能如表1所示。试验所使用粘土砖的抗压强度平均值为9.28 MPa,吸水率约为17.58%,平均密度约为1 700 kg/m3。试验所用胶粘剂为SKO-碳纤维浸渍胶,其主要性能如表2所示。

    表  1  碳纤维增强聚合物复合材料(CFRP)的性能
    Table  1.  Properties of carbon fiber reinforced polymer(CFRP)
    SampleTensile
    strength/MPa
    Modulus/
    GPa
    Elongation/
    %
    Thickness/
    mm
    CFRP ≥3 500 220 1.458 0.111
    下载: 导出CSV 
    | 显示表格
    表  2  粘结树脂的性能
    Table  2.  Properties of impregnation resin
    Tensile shear strength/MPaTensile strength/GPaCompressive strength/MPaBending strength/MPaPositive tensile bond strength/MPaModulus/MPaElongation/%
    24.2940.1273.6272.954.442 605.72.45
    下载: 导出CSV 
    | 显示表格

    本试验选用的粘土砖尺寸为235 mm×115 mm×55 mm,CFRP片材粘贴在粘土砖的一个表面(如图1所示),CFRP粘贴尺寸设计为6种规格,试件的具体参数如表3所示。

    图  1  单剪试验试件
    Figure  1.  Single shear specimens
    表  3  CFRP-粘土砖单剪试验试件参数
    Table  3.  Specimen parameters of CFRP-clay brick specimens for single shear test
    CFRP size(Length×width)/mmNumber of CFRP-clay brick specimen
    0 cycle20 cycles40 cycles60 cycles80 cycles
    80×50 5 5 5 5 5
    100×80 5 5 5 5 5
    80×80 5 5 5 5 5
    100×80 5 5 5 5 5
    80×100 5 5 5 5 5
    100×100 5 5 5 5 5
    下载: 导出CSV 
    | 显示表格

    参照CECS 146—2003[13]中相关要求将CFRP粘贴在粘土砖表面。为防止粘土砖出现局部拉剪破坏,粘结CFRP时在加载端留出30 mm非粘结区,制作完成的试件如图1所示,标准试件示意图如图2所示。

    图  2  CFRP-粘土砖试件示意图
    Figure  2.  Diagram of CFRP-clay bricks specimen

    冻融循环试验参照GB/T 2542—2012[14]进行。将试件清理干净,在鼓风干燥箱内烘干达到质量要求后,将其在20℃的水中浸泡24 h后取出拭干水分,在冷冻箱内温度降至−15℃时开始计时。每次冷冻时间为3 h,融化2 h,控制冷冻温度为(−17±2)℃,融化水的温度控制在(15±2)℃。冻融循环次数分别取0次、20次、40次、60次和80次。

    所有试件的单剪试验均在济南恒思盛大仪器有限公司生产的WDW-50微机控制电子万能试验机上通过自制单剪试验盒进行(如图3(a)所示),通过电脑控制加载速度,由荷载传感器输出CFRP与粘土砖的粘结荷载,CFRP的应变值通过江苏东华DH3816静态应变测试系统采集(如图3(b)所示)。为了使CFRP片材在加载过程中受力均匀,在试件加载端片材上下各粘贴一层30 mm长的CFRP加强片,加强片与试件同宽。加载过程采用位移控制,加载速率为0.5 mm/min。在CFRP试件拉伸前,先施加约为破坏荷载5%的预拉荷载(约为0.4 kN),检查夹具、拉力机和应变采集系统运行是否正常。

    图  3  CFRP-粘土砖试件纵向拉伸试验系统
    Figure  3.  Longitudinal tensile test system for CFRP-brick specimens

    试验发现,在经过若干次冻融循环后,CFRP-烧结粘土试件界面发生了较为明显的变化,以粘贴长度×宽度为80 mm×50 mm的单剪试件为例,图4为不同冻融循环作用下CFRP-烧结粘土砖界面破坏情况。可知,室温下试件破坏发生后,CFRP片材上粘有大颗粒粘土砖碎屑(如图4(a)所示);冻融20次和40次的试件破坏后,CFRP片材上粘有的粘土砖颗粒较小(如图4(b)所示);冻融60次后,其中2个试件破坏面较40次严重,界面上粘有大量粘土砖颗粒(如图4(c)所示),另1个试件与冻融40次的形态基本相同;冻融80次后,试件破坏发生在粘土砖,界面发生剪切破坏(如图4(d)所示),说明冻融循环作用对界面粘结性能有不利影响。

    图  4  不同冻融循环作用下CFRP-烧结粘土砖界面破坏情况
    Figure  4.  Interface failure modes of CFRP-sintered clay brick under different freeze-thaw cycles

    表4为粘贴长度×宽度为80 mm×50 mm的CFRP-粘土砖单剪试件试验结果。可以看出,随着冻融次数的增加,界面承载力逐渐降低,60次冻融后减小了约12%,表明冻融循环作用对CFRP-粘土砖的界面承载力有着不利影响。因此,当使用CFRP对粘土砖结构进行加固时,如果是在北方寒冷地区应适当考虑界面粘结折减系数。

    表  4  CFRP-粘土砖界面承载力平均值和降低幅度
    Table  4.  Average interfacial bearing capacity and reduction of CFRP-brick specimens
    CFRP size(Length×width)/mmInterfacial baring capacity/kNDecrease of bearing capacity/%
    0 cycle20 cycles40 cycles60 cycles80 cycles0 cycle20 cycles40 cycles60 cycles80 cycles
    80×50 7.63 7.52 6.85 5.93 5.34 1.44 10.22 22.28 30.01
    100×50 7.95 7.88 7.07 6.95 6.43 0.88 11.07 12.58 19.12
    120×50 8.12 8.15 7.26 7.06 6.65 –0.37 10.59 13.05 18.10
    80×80 12.40 12.00 11.40 11.00 10.30 3.23 8.06 11.29 16.94
    100×80 13.00 12.80 12.30 11.60 10.50 1.54 5.38 10.77 19.23
    120×80 13.50 13.20 12.50 11.70 11.00 2.22 7.41 13.33 18.52
    下载: 导出CSV 
    | 显示表格

    从试验及文献分析可知,造成界面承载力降低的原因主要有两点:(1)冻融作用导致粘土砖自身材料强度降低而引起CFRP-粘土砖试件粘结强度降低;(2) CFRP-粘土砖之间的胶体面层的粘结性能退化。由于CFRP的特殊构造,其聚合物基体的孔径较小,冻融循环作用下,其孔隙中的水不会冻结[15]。因此,可能是胶体吸水后,在冻融作用下,当溶胀和温度应力共同作用时,界面产生微裂纹,从而导致介质水在界面上冻结产生应力。

    由于本次试验在CFRP-粘土砖试件加载端预留了30 mm非粘结区,所有CFRP-粘土砖试件均是CFRP与粘土砖之间发生界面剥离而破坏的,没有发生CFRP布的撕裂破坏,也没有发生粘土砖的拉剪破坏。

    所有CFRP-粘土砖试件剥离破坏是由纤维布传递荷载到粘土砖,从而使粘土砖内部产生的微小裂缝逐渐发展导致的。对于没有经过冻融循环的CFRP-粘土砖试件,其破坏过程是初始加载时除了碳纤维布开始绷紧外,试件并无明显变化,加载端的应变基本呈线性增加;当荷载增加至剥离荷载的40%左右时,可以听到“噼啪声”,加载端附近的应变迅速增加,粘土砖内部微裂缝逐渐开展,试件开始发生局部粘结破坏,总的粘结面积开始减少;随着荷载的进一步增大,应变急速增加,剥离深度也在加大,距离加载端较远处应变片的应变也逐渐增大,说明剥离逐渐向自由端发展。当剩余的粘结面积不足以抵抗荷载时,破坏瞬间发生。而在冻融循环作用下,破坏具有相似性,只是由于粘土砖与胶层之间的界面被削弱、粘土砖材料本身强度降低,开裂速度较未经循环试件更迅速,破坏更突然。

    粘土砖为多孔材料,在水冻作用下,粘土砖内部孔隙中的水分子会出现冻结现象,造成孔隙体积膨胀,从而使粘土砖内部出现较大的微孔隙损伤和拉应力,使砖体的缝隙和节理出现加深和扩大;当粘土砖处于融化状态时,粘土砖内部微孔隙会出现迁移现象。当粘土砖在不同温度下进行反复冻结和溶解时,张力使孔隙壁的损伤不断加剧,最终造成砖体损伤。这种损伤反映到CFRP-粘土砖的粘结上,便会出现粘结退化现象。

    图5为不同冻融循环作用下粘土砖孔隙度变化。图6为不同冻融循环作用下粘土砖弛豫时间T2谱分布。从图5可以看出,随着冻融循环次数的增加,粘土砖的孔隙度逐渐增大。由图6可知,随着冻融循环次数的增加,T2谱的峰值向右移动,说明大孔径比例增加,冻融使冻胀力逐渐大于颗粒间的粘聚力,造成砖样的孔隙发育和扩展程度加剧。

    图  5  不同冻融循环作用下粘土砖孔隙度变化曲线
    Figure  5.  Change curve of clay brick porosity under different freezing-thawing cycles
    图  6  不同冻融循环作用下粘土砖的弛豫时间T2谱分布
    Figure  6.  Relaxztion time T2 distribution of clay bricks under different freezing-thawing cycles

    由CFRP-粘土砖单剪试验结果分析可知,冻融作用下,粘结界面破坏模式的变化与粘土砖微观变化是相统一的(如图4所示)。从单剪试件的破坏过程可以看出,不同冻融次数下,CFRP-粘土砖试件破坏后,粘土砖的表层破坏模式不尽相同。未经冻融的CFRP-粘土砖试件以CFRP粘结区域内靠近加载端部位的粘土砖剪切破坏为主。剪切破坏面被拉出的近似三角形粘土砖块与CFRP粘结较好,其余部位CFRP粘有大量被拉下的粘土砖碎屑与颗粒,破坏面一般在粘土砖基层一侧,深度约为2~5 mm。经过冻融循环的CFRP-粘土砖试件在冻融次数较低时,破坏模式与未受冻融的CFRP-粘土砖试件基本一致,冻融达到40次后,在加载端出现三角破坏区的概率随之减小,破坏以界面剥离破坏为主;当冻融时间达到60次时,所有试件均为剥离破坏,加载端不再出现三角破坏区,在CFRP上粘下的粘土砖层越来越均匀;当冻融时间达到80次时,在加载端出现类似三角区域的破坏情况,说明粘土砖的强度减弱。

    图7为CFRP-粘土砖界面承载力随冻融循环次数的变化曲线。由表4图7可知,随着冻融循环次数的增加,CFRP-粘土砖界面承载力总体呈下降趋势,而后期的下降速度要快于前期。同时,还可以看到,在CFRP的粘结宽度及冻融循环次数相同的情况下,当粘结长度从80 mm增加至120 mm时,CFRP-粘土砖界面承载力增加的幅度并不大,但当粘结宽度从50 mm增加到80 mm时,CFRP-粘土砖界面承载力却提高了60%~70%,说明CFRP的粘结宽度是影响界面承载力的主要因素之一,与以混凝土为基材的复合材料结果相似[16-18]

    图  7  CFRP-粘土砖的界面承载力曲线
    Figure  7.  Interfacial capacity curves of CFRP-clay bricks

    在不考虑相关几何参数因素对试件界面粘结性能的影响下,通过界面粘结强度平均值来考察界面在冻融循环作用下的劣化情况,界面粘结强度平均值计算如下:

    τf=PuA (1)

    式中:τf为试件平均粘结强度(MPa);Pu为CFRP-粘土砖界面承载力(kN);A为粘结面积(mm2)。

    图8为CFRP-粘土砖界面平均粘结强度曲线。可知,平均粘结强度曲线根据长度和宽度组合分为三组,同一长度不同宽度的图形在位置上比较接近,再次证明粘结宽度对承载力的贡献较大,即只要保证粘结长度足够,CFRP-粘土砖试件的平均粘结强度基本和粘结宽度呈正相关关系。

    图  8  CFRP-粘土砖界面平均粘结强度曲线
    Figure  8.  Average bonding strength curves of CFRP-clay brick interface

    由于试验无法得到粘结界面上任意点的应变值,因此在计算中以两个相邻应变片之间的平均剪应力作为界面剪应力。由于CFRP非常薄,可以假定CFRP在轴向力方向上的应力σf在横截面内是均匀分布的,并假定相邻两应变片间的应变线性分布,现取长度为微元长度dx的CFRP单元作为对象进行研究,CFRP-烧结粘土砖界面单元体剪应力分布如图9所示。

    图  9  CFRP-粘土砖界面单元体剪应力分布
    Figure  9.  Shear stress distribution of CFRP-clay brick interface

    由力的平衡条件可以得到粘结剪应力的计算公式为

    τ(x)=dFbfdx=dσfdxtf=Eftfdεxdx=Eftfεi+1εiΔxi (2)

    式中:F为界面承载力;bftfEfεi分别为CFRP片材的宽度、厚度、弹性模量和应变。

    由于各个试件剪应力的分布具有一定相似性,因此以粘贴长度×宽度为80 mm×50 mm的单剪试件为例,其不同冻融循环作用下的剪应力分布如图10所示。可知,当荷载较小时,剪应力的峰值出现在加载端,而粘结剪应力只分布在距加载端20 mm左右的范围内;当荷载逐渐增加时,加载端附近的剪应力也随之逐渐增加,增加到峰值后剪应力开始向远端传递,此时的剪应力集中分布在一定区域内,区域外剪应力几乎为零,这一区域即为有效粘结区域,该区域的长度称为“有效粘结长度”,本试验中有效粘结长度基本保持不变,大约为60~80 mm,且其不随CFRP粘结尺寸及冻融循环次数而变化,说明随着荷载的增加,有效粘结区域在破坏过程中会以近似不变的长度由加载端向自由端平行移动,从而使剥离区域逐渐增加,直至试件破坏,与CFRP-混凝土试件的研究结果一致[19-20]

    图  10  不同冻融循环作用下CFRP-粘土砖界面剪应力分布
    Figure  10.  Shear stress distribution of CFRP-clay brick under different freeze-thaw cycles

    为建立准确可靠的粘结-滑移曲线,需要进一步了解界面剥离机制及破坏过程中粘结剪应力与滑移值的变化情况,即ττmaxss0曲线。其中,滑移值为CFRP与粘土砖的位移差,计算如下:

    s(x)=s(0)+x0ε(u)du (3)

    式中:s(0)为最大剪应力对应的滑移值;s(x)为CFRP上任一点滑移值;ε为应变值。

    关于粘结-滑移关系,目前国内外学者对纤维增强聚合物复合材料(FRP)-混凝土界面深入研究较多,而对于FRP-粘土砖的研究鲜见报道。粘结-滑移模型的提出有试验方法、有限元模拟方法、理论推导方法等,图11为几种典型粘结-滑移关系模型曲线。由图11(a)可以看到,直角三角形模型属于早期模型,把界面近似看做弹性体,缺点是忽略了界面在加载后期的软化行为;由图11(b)~11(d)可知,粘结-滑移关系模型均为两阶段曲线模型,曲线由上升段和下降段组成,目前对CFRP-混凝土界面的研究大多采用该类型曲线模型。通过对比发现,图11(d)的Popovics模型比较适合本试验数据,如下式:

    图  11  几种典型粘结-滑移关系模型曲线
    Figure  11.  Typical bond-slip relationship curves of CFRP-clay brick interface
    ττmax (4)

    通过式(4)拟合效果较好(拟合系数n=3.032),可以较准确地表示CFRP-粘土砖面粘结-滑移的有关特征,如图12所示。可以看出,CFRP-粘土砖界面粘结-滑移曲线分为上升段和下降段,上升段为强化阶段,下降段为软化阶段。开始加载时,界面粘结剪应力和滑移均不大,粘结-滑移曲线近似呈线性关系,试件处于弹性状态;随着粘结剪应力逐步增大,粘结-滑移曲线表现出非线性,此时滑移量增加速度较剪应力增加速度要快,当界面逐渐达到最大剪应力,界面的粘结不足以抵抗剪应力时,试件开始出现滑移;当粘结剪应力增大至最大后,曲线进入下降段,此时剪应力下降速度和滑移量增加的速度均较快,且滑移量增加的速度越来越大,当粘结应力几乎为零时,滑移量达到最大值,此时CFRP和粘土砖在界面处完全剥离。对比Popovics曲线和实验数据可以发现,Popovics模型可以较好地描述CFRP-粘土砖界面粘结-滑移关系,上升段试验数据点几乎与Popovics模型曲线重合,下降段的试验数据分布于Popovics模型曲线两侧,但偏差较小,表明采用Popovics模型来描述CFRP-粘土砖界面的粘结-滑移本构关系是较准确的。

    图  12  CFRP-粘土砖界面粘结-滑移关系
    Figure  12.  Bond-slip relationship curves of CFRP-clay brick interface

    分析了冻融循环作用和粘结尺寸对CFRP-粘土砖界面承载力及粘结强度的影响,通过试验数据和理论比较,建立了考虑冻融循环影响下的CFRP-粘土砖界面粘结-滑移模型。

    (1)在冻融循环作用下,CFRP-粘土砖界面的破坏模式是由剪切破坏转变为粘结剥离破坏,剥离是从CFRP加载端开始逐渐向自由端发展。相对于长度,CFRP的宽度对试件界面承载力影响更为显著。

    (2)随着冻融循环次数的增加,CFRP-粘土砖界面承载力总体呈下降趋势,而后期的下降速度要快于前期。

    (3) CFRP-粘土砖界面粘结剪应力分布曲线具有相似性,当荷载水平逐渐增加,剪应力也随之逐渐增大,并从加载端向自由端传递,且所有剪应力集中分布在一定的“有效粘结区域”内,而区域外的剪应力几乎为零,有效粘结区域的长度约为60~80 mm,且与冻融循环次数无关。

    (4) CFRP-粘土砖界面粘结-滑移关系有明显的上升段和下降段,上升段为强化阶段,下降段为软化阶段,Popovics模型可以很好地描述CFRP-粘土砖的界面粘结-滑移关系。

  • 图  1   EMR的微观形貌

    Figure  1.   Microscopic morphology of EMR

    图  2   EMR的物相分析

    Figure  2.   Physical phase analysis by EMR

    图  3   OPC和EMR的粒径分布

    Figure  3.   Particle size distributions of OPC and EMR

    d50—The particle size corresponding to the cumulative passing of 50%

    图  4   OPC和EMR的傅里叶红外图谱

    Figure  4.   Fourier infrared spectra of OPC and EMR

    图  5   纯水泥浆体与EMR水泥浆体工作性能:(a)凝结时间;(b)标准稠度用水量与体积安定性

    Figure  5.   Working performance of pure cement paste and EMR cement paste: (a) Setting time; (b) Water requirement of normal consistency and soundness

    图  6   不同EMR掺入量时水泥胶砂抗压强度对比:(a) 10wt%;(b) 20wt%

    Figure  6.   Comparisons of compressive strength of cement mortar with different EMR dosages: (a) 10wt%; (b) 20wt%

    图  7   不同EMR掺入量时水泥胶砂抗折强度对比:(a) 10wt%;(b) 20wt%

    Figure  7.   Comparisons of flexural strength of cement mortar with different EMR dosages: (a) 10wt%; (b) 20wt%

    图  8   EMR200和EMR800 在40℃下固化8 d后的Frattini结果

    Figure  8.   Frattini results of EMR200 and EMR800 cured at 40℃ for 8 d

    [OH]—Concentration of OH; [CaO]—Concentration of CaO

    图  9   EMR200和EMR800 的Frattini试验与强度活性指数(SAI)试验相关性

    Figure  9.   Correlation between Frattini test and strength activity index (SAI) test for EMR200 and EMR800

    R2—Fitness

    图  10   EMR200和EMR800在40℃的密封塑料瓶中养护1、3、7和28 d:(a)饱和石灰(SL)消耗试验;(b) SL消耗试验与Frattini试验相关性;(c) SL消耗试验与28 d活性指数(SAI)之间的相关性

    Figure  10.   EMR200 and EMR800 cured in sealed plastic bottles at 40℃ for 1, 3, 7 and 28 d: (a) Saturated lime (SL) consumption test; (b) Correlation between SL consumption test and Frattini test; (c) Correlation between SL consumption test and 28 d SAI

    图  11   蒸养7 h后E-0组试件的微观形貌和EDS能谱

    Figure  11.   Microstructure and EDS energy spectrum of E-0 group specimens after steam curing for 7 h

    CH—Calcium hydroxide; C-S-H—Calcium silicate hydrate

    图  12   蒸养7 h 后E200-10组试件的微观形貌和EDS能谱

    Figure  12.   Microstructure and EDS energy spectrum of E200-10 group specimens after steam curing for 7 h

    C3ASH—Hydrated garnet

    图  13   蒸养7 h后E800-10组试件的微观形貌和EDS能谱

    Figure  13.   Microstructure and EDS energy spectrum of E800-10 group specimens after steam curing for 7 h

    图  14   蒸养7 d 后E-0组试件的微观形貌和EDS能谱

    Figure  14.   Microstructure and EDS energy spectrum of E-0 group specimens after steam curing for 7 d

    图  15   蒸养7 d 后E200-10组试件的微观形貌和EDS能谱

    Figure  15.   Microstructure and EDS energy spectrum of E200-0 group specimens after steam curing for 7 d

    图  16   蒸养7 d 后E800-10组试件的微观形貌和EDS能谱

    Figure  16.   Microstructure and EDS energy spectrum of E800-0 group specimens after steam curing for 7 d

    图  17   标准养护28 d纯水泥胶砂E-0的水化产物

    Figure  17.   Hydration products of pure cement mortar E-0 after 28 d standard curing

    AFt—Ettringite

    图  18   标准养护28 d后E200-10的水化产物

    Figure  18.   Hydration products of E200-10 after 28 d standard curing

    图  19   标准养护28 d后E800-10的水化产物

    Figure  19.   Hydration products of E800-10 after 28 d standard curing

    图  20   不同养护条件下纯水泥胶砂与EMR水泥胶砂的XRD图谱

    Figure  20.   XRD patterns of pure cement mortar and EMR cement mortar under different curing conditions

    C3S—Tricalcium silicate; C2S—Dicalcium silicate; C4AF—Tetracalcium aluminoferrite; C3A—Tricalcium aluminate;

    图  21   标准养护28 d条件下纯水泥胶砂与EMR水泥胶砂:(a) XRD图谱;(b)水化产物含量

    Figure  21.   Pure cement mortar and EMR cement mortar under standard curing for 28 d: (a) XRD patterns; (b) Content of hydration products

    图  22   不同养护条件下纯水泥胶砂与EMR水泥胶砂横向弛豫时间T2图谱:(a) E-0;(b) E200-10;(c) E200-20;(d) E800-10;(e) E800-20;(f)孔隙率

    Figure  22.   The transverse relaxation time T2 spectra of pure cement mortar and EMR cement mortar under different curing conditions: (a) E-0; (b) E200-10; (c) E200-20; (d) E800-10; (e) E800-20; (f) Porosity

    d—Diameter size

    表  1   普通硅酸盐水泥(OPC)和电解锰渣(EMR)的化学组成

    Table  1   Chemical composition of ordinary portland cement (OPC) and electrolytic manganese residue (EMR) wt%

    Material Al2O3 SiO2 Fe2O3 CaO SO3 MgO Other
    OPC 6.57 19.34 3.22 47.95 1.23 1.58 4.06
    EMR200 11.85 39.72 5.92 10.07 24.47 1.22 6.75
    EMR800 10.79 37.03 6.66 12.29 24.60 1.24 7.21
    Notes: "EMR200" represents EMR calcined at 200℃; "EMR400" represents EMR calcined at 400℃.
    下载: 导出CSV

    表  2   EMR水泥胶砂的配比与养护条件

    Table  2   Proportioning and curing conditions of EMR cement mortar

    Sample OPC/g EMR/g Sand/g Water/g Curing condition
    E-0 450 0 1350 225 80℃ steam curing for 7 h (S7h);
    80℃ steam curing for 7 d (S7d);
    Standard curing 3 d (N3d);
    Standard curing 28 d (N28d)
    E200-10 405 45 1350 225
    E200-20 360 90 1350 225
    E800-10 405 45 1350 225
    E800-20 360 90 1350 225
    Notes: "E-0" indicates control specimen; E200-10, where "E200" indicates an EMR calcination temperature of 200℃, "10" indicates an EMR substitution rate of 10wt%, and other similar specimens.
    下载: 导出CSV

    表  3   EMR200和EMR800在8 d时Frattini测试结果

    Table  3   Frattini test results of EMR200 and EMR800 at 8 d

    Material [OH]/
    (mmol·L−1)
    [CaO]/ (mmol·L−1) Theoretical
    Max[CaO]/
    (mmol·L−1)
    [CaO] reduction/%
    Sand 52.8 9.68 9.25 −4.4
    EMR200 58.9 6.34 7.97 20.45
    EMR800 54.0 6.30 8.79 28.3
    下载: 导出CSV
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  • 其他相关附件

  • 目的 

    研究了不同煅烧温度(200℃和800℃)电解锰渣(EMR)火山灰活性及掺入0wt%、10wt%、20wt% EMR水泥胶砂在80℃蒸养7 h、7 d和标准养护3 d、28 d条件下力学性能、水化产物与孔隙特征分布。

    方法 

    采用低场核磁共振技术、XRD定量表征及SEM微观形貌共同揭示了EMR对水泥胶砂的水化产物、孔径分布及孔隙率等影响规律,并探究了不同养护条件对EMR水泥胶砂水化进程的影响。结果表明:800℃煅烧EMR火山灰活性明显高于200℃煅烧火山灰活性,当800℃煅烧EMR替代量为10wt%时,初凝、终凝时间和标准稠度用水量分别为对照组的1.52、1.06和1.05倍,而蒸养7 h、7 d抗压强度分别高于标养3 d和28 d抗压强度,而抗折强度仅仅在蒸养7 d时高于对照组17.3%;纯水泥胶砂的水化产物主要为纤维状C-S-H和片状CH,而EMR水泥胶砂中由于硫酸盐含量较高,除了上述水化产物之外,在蒸养或标养条件下均可观察到石膏相与针棒状AFt的存在,标准养护28d时,CH、AFt和无定性含量分别为14.50%、11.75%和46.25%,与蒸养7 d衍射峰基本相似。另外,蒸养7 h与标准养护3 d对比孔隙率减少1.44%,蒸养7 d与标准养护28 d对比孔隙率减少0.06%。

    结论 

    综上,蒸养可以提高800℃煅烧EMR火山灰活性,同时还可以加速EMR水泥胶砂的水化进程和细化其内部孔结构,进而提高了胶砂的力学性能。

  • 电解锰渣(EMR)是电解金属锰生产时压滤和提纯过程中产生危险固体废弃物,其中含有Mn和NH3-N危险物质。目前还没有有效的方式处理大量堆存的EMR,只能通过填埋或指定区域堆存,这种处理方式不仅会污染周围土壤和水体,同时也会对人类健康造成严重威胁。因此,为了减少巨大的环境风险并为电解金属锰行业的可持续发展做出贡献,迫切的需要资源化利用EMR。

    本文通过煅烧方式来提高EMR火山灰活性和降低危险物质含量。将EMR作为矿物掺合料时,Mn和NH3-N的浸出在水泥体系提供的碱性环境和凝胶体系中可以完全封装和固定,使得浸出浓度远低于标准限值。另外重要的一点是EMR中石膏相含量较高,不仅严重影响了水泥体系的凝结时间、体积安定性及早期强度,且后期会导致耐久性较差。因此,本工作采用4种养护制度,分别为标养3 d、28 d和80 ℃蒸养7 h、7 d,旨在探明不同养护条件下石膏对水泥基材料水化反应及水化产物组成的影响。通过煅烧发现EMR在800 ℃煅烧时具有较好的火山灰活性,可以作为矿物掺合料使用,同时蒸养可以促进EMR水泥胶砂中C-S-H和CH的形成,另外还会形成石膏和AFt,有利于填充结构内部孔隙和缺陷,宏观表现为EMR水泥胶砂蒸养7 h、7 d的抗压强度分别高于标养3 d和28 d。因此,蒸养可以促使EMR水泥胶砂强度快速形成。

    火山灰活性评价与XRD的Rietveld定量分析(a) Frattini结果(b) SL消耗试验(c)水化产物定量分析对比

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出版历程
  • 收稿日期:  2024-01-23
  • 修回日期:  2024-02-27
  • 录用日期:  2024-03-06
  • 网络出版日期:  2024-04-15
  • 发布日期:  2024-03-27
  • 刊出日期:  2024-12-14

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