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钢丝网或纤维网增强超高性能混凝土双向板弯曲性能

邓宗才, 鹿宇浩, 桂营金

邓宗才, 鹿宇浩, 桂营金. 钢丝网或纤维网增强超高性能混凝土双向板弯曲性能[J]. 复合材料学报, 2022, 39(10): 4757-4768. DOI: 10.13801/j.cnki.fhclxb.20211022.002
引用本文: 邓宗才, 鹿宇浩, 桂营金. 钢丝网或纤维网增强超高性能混凝土双向板弯曲性能[J]. 复合材料学报, 2022, 39(10): 4757-4768. DOI: 10.13801/j.cnki.fhclxb.20211022.002
DENG Zongcai, LU Yuhao, GUI Yingjin. Flexural properties of ultra high performance concrete reinforced with steel wire mesh or fiber mesh[J]. Acta Materiae Compositae Sinica, 2022, 39(10): 4757-4768. DOI: 10.13801/j.cnki.fhclxb.20211022.002
Citation: DENG Zongcai, LU Yuhao, GUI Yingjin. Flexural properties of ultra high performance concrete reinforced with steel wire mesh or fiber mesh[J]. Acta Materiae Compositae Sinica, 2022, 39(10): 4757-4768. DOI: 10.13801/j.cnki.fhclxb.20211022.002

钢丝网或纤维网增强超高性能混凝土双向板弯曲性能

基金项目: 北京市教委科技重点资助项目(KZ201810005008).
详细信息
    通讯作者:

    邓宗才,博士,教授,博士生导师,研究方向为超高性能混凝土及其结构 E-mail:dengzc@bjut.edu.cn

  • 中图分类号: TU376

Flexural properties of ultra high performance concrete reinforced with steel wire mesh or fiber mesh

  • 摘要: 为研究钢丝网或纤维网对混杂纤维超高性能混凝土(Ultra-high performance concrete,UHPC)板弯曲性能的影响,进行了四边简支双向板弯曲试验。UHPC中短切纤维为:单掺钢纤维、钢纤维分别与聚乙烯醇纤维、玻璃纤维、玄武岩纤维混掺等。研究参数为:钢丝网与玻璃纤维网层数、孔径、混掺纤维比例等。结果表明,单掺体积分数为1.5vol%的钢纤维时,铺设3层和4层钢丝网的UHPC板的极限承载力和25 mm挠度处的能量吸收值较2层分别提升14.9%、32.3%和14.1%、25.2%;孔径较小的钢丝网对UHPC板承载力和韧性提升明显。当混杂纤维总体积分数为1.5vol%且钢丝网2层时,混掺1.0vol%钢纤维和0.5vol%聚乙烯醇纤维对UHPC板增强增韧效果更好,0.5vol%钢纤维与1.0vol%玻璃纤维或玄武岩纤维混掺较0.5vol%钢纤维与1.0vol%聚乙烯醇纤维混掺对改善板峰后持荷能力更有利,即钢纤维与较高弹性模量非金属纤维混掺有利于提高裂后承载力。与玻璃纤维网相比,铺设钢丝网的UHPC板在峰后延性更好。提出了以素UHPC板峰值荷载挠度作为初裂挠度的韧性指标评定方法,该方法可表征网格和纤维对UHPC板裂后韧性的贡献。基于网格有效利用率概念,建立了板抗弯承载力计算方法,理论值与试验值吻合良好。
    Abstract: To study the influence of steel wire mesh on the bending properties of ultra-high performance concrete (UHPC) slabs, a bending test of simply supported two-way slabs with four sides was carried out. The chopped fibers in UHPC ware: Steel fiber and steel fiber were mixed with polyvinyl alcohol fiber, glass fiber and basalt fiber, respectively. The research parameters were: Number of layers of wire mesh and glass fiber mesh, pore size and proportion of blended fibers. The results show that when UHPC is single-doped with 1.5vol% steel fiber, the ultimate bearing capacity and energy absorption at 25 mm deflection of UHPC slabs with 3 layers and 4 layers are increased by 14.9%, 32.3% and 14.1%, 25.2%, respectively compared with UHPC slabs with 2 layers of steel wire mesh. When the total volume fraction of hybrid fibers is 1.5vol% and the steel wire mesh is 2 layers, the blending of 1.0vol% steel fiber and 0.5vol% polyvinyl alcohol fiber has better reinforcing and toughening effect on UHPC slabs, and the UHPC slab mixed with 0.5vol% steel fiber and 1.0vol% glass fiber or basalt fiber has a stronger ability to maintain load after peak load than 1.0vol% polyvinyl alcohol fiber, namely the mixing of steel fiber with higher modulus of elasticity non-metallic fiber is advantageous to increase the post-cracking bearing capacity. Compared with glass fiber mesh, UHPC slabs with steel mesh have better ductility after peak load. A method for evaluating the flexibility of UHPC slabs with peak load deflection as initial cracking parameter was proposed, which can characterize the contribution of mesh and fibers to the post-crack toughness of UHPC slabs. Based on the concept of effective utilization of mesh, the theoretical value is in good agreement with the experimental value by calculating the bending capacity.
  • 重金属对水环境的污染是当今面临的最严重的一类环境污染,主要由采矿、冶金、电镀、石油化工和纺织业等行业的发展引起的[1-2]。与有机污染物不同,重金属污染具有不可降解性。未经处理的或未处理完全的含重金属废水排放到环境中,会通过生物累积危害到食物链的各环节,破坏生态平衡。Cd(II)是一种典型的毒性极大的重金属离子,美国环保署将其列为B1类致癌物,对人体的肾脏有极大的危害[3-4]。因此,工业废水中Cd(II)的去除是至关重要的。

    去除水中Cd(II)常用方法有混凝-絮凝、微生物、膜分离、吸附等。其中吸附法因其效果好、成本低、工艺简单等优点成为最常用的方法[5-8]。海藻酸钠(SA)是一种天然多糖,可与CaCl2溶液交联形成一种吸附性能极好的水凝胶材料—海藻酸钙CaAlg(CA)。以CA为基材的小球在重金属的吸附方面效果显著[9]。氧化石墨烯(GO)是石墨多次化学氧化后得到的含有大量羟基和羧基的常见改性材料。它具有极高的比表面积和电负性,这些特性也使其成为一种理想的重金属离子吸附材料[10]。将SA、致孔剂和GO混合后再与CaCl2交联,GO的含氧基团也能参与到交联过程,从而使三者形成有机统一的多孔材料,而且各组分间的相互作用更强,这对其吸附性能和力学性能都有很大的提升。

    在吸附过程,相对于球型吸附剂,膜上的吸附位点能够更准而快地捕捉重金属离子[11]。将GO与致孔剂共混在SA溶液中,与CaCl2交联制得的GO/CA水凝胶复合膜将会是一种优良的重金属离子吸附剂。由于SA良好的成膜性[12],此复合膜还可用作膜过滤技术。将其吸附性能与截留性能结合,从而可在实际水处理工程中达到更好的应用效果。目前还没有关于它对重金属离子吸附性能的相关公开报道。

    本文将制备一种新型的GO/CA复合膜材料,用于探究其对Cd(II)的吸附性能和吸附机制。将吸附前后的GO/CA水凝胶复合膜进行表征;并探究常见的变量因素对其吸附容量的影响。还将引入吸附动力学、吸附等温线来分析其吸附机制。

    海藻酸纳(Sodium alginate,分析纯)、硝酸镉(Cd(NO3)2,分析纯)、HNO3(分析纯),购于国药化学试剂有限公司;天然鳞片石墨,购于南京先丰纳米有限公司;尿素(Urea)、CaCl2、KMnO4、NaNO3 H2O2,分析纯,均购于天津科密欧化学试剂有限公司;浓HCl、浓H2SO4,分析纯,均购于成都科隆化学品有限公司。

    将2.5 g SA和2.5 g尿素加入100 mL超声均匀的GO(制备参考文献[13])溶液(0.3 wt%),室温下用磁力搅拌器以400 r/min的速率搅拌36 h。搅拌均匀的铸膜液在室温下静置36 h以脱除气泡。将铸膜液倒在玻璃板上,用刮膜棒将其铺平后将玻璃板平行地放入2.5 wt%的CaCl2溶液中交联。膜从玻璃板脱落后取出玻璃板。复合膜在48 h后取出,以达到交联完全和尿素溶出的目的。将交联完全的膜用去离子水洗脱后即可置于1 wt%的CaCl2溶液中保存备用。为制备纯CA水凝胶膜,将2.5 g SA和2.5 g尿素加入100 mL去离子水中,其余步骤同上。

    用扫描电镜(SEM,JMS6510LV, Japan)和透射电镜(TEM, JEM-2100, Japan)来表征GO/CA水凝胶复合膜是否制备成功;将GO/CA水凝胶复合膜裁成10 cm×1 cm的样本条,用拉力测定仪(电子单纱强力仪,HD021NS,南通宏大实验仪器有限公司)进行力学性能测试,每个样品测10次,取平均值;用称重法计算GO/CA水凝胶复合膜的平均孔径:先将膜片浸没在去离子水中24 h,取出后用滤纸擦干表面水分。将此湿膜片称重,通过称重法[13]确定其孔隙率ε,再用Guernout-Elford-Ferry公式[13]计算平均孔径r;两种复合膜的水通量使用小型平板纳滤错流过滤系统在25℃、0.1 MPa的条件下进行测定。试验前,在0.15 MPa的压力下用去离子水预压,用通量计算公式[13]计算通量;GO/CA水凝胶复合膜的表面官能团用傅里叶衰减全反射红外光谱仪(FTIR-ATR, Thermoelectroncorp, iS50, 美国)测定。

    本文将探究溶液pH、Cd(II)初始离子浓度、接触时间、温度等因素对GO/CA水凝胶复合膜吸附性能的影响。溶液的pH用0.1 mol/L HNO3溶液调节。每组实验均将300 mL Cd(NO3)2溶液置于500 ml的烧杯中,然后加入复合膜片0.06 g,用保鲜膜封存静置。在固定时间,每次从同一位置的上层溶液用滴管吸取5 mL的样品,并测定其Cd(II)浓度。达到吸附平衡后,用镊子将膜片夹出。Cd(II)在膜上的吸附量按下式计算:

    Vnt(i)=Vnt(i1)5 (1)
    Qnt=ni=1(Cnt(i1)Cnt(i))Vnt(i1)m (2)

    式中:Qnt是在时间t的吸附容量(mg·g−1);Cnt是第i次采样时的Cd(II)浓度(mg·L−1);Vnt(i)是第i次取样时Cd(NO3)2溶液的体积(mL);m是用于吸附的GO/CA水凝胶复合膜的重量(g)。溶液中的Cd(II)浓度由电感耦合等离子体发射光谱仪(ICP-5000,聚光科技(杭州)股份有限公司)测定。

    为探究pH的影响,将溶液pH分别调至3、4、5、6、7,在初始离子浓度为80 mg·L−1、温度为318 K的条件下进行吸附;为探究GO的影响,在pH=7、288 K、初始离子浓度50 mg·L−1的条件下,分别将0.06 g的CA膜和GO/CA水凝胶复合膜加入Cd(NO3)2溶液进行静态吸附实验;为探究初始离子浓度的影响,在pH=7、318 K的条件下,配制梯度浓度(10、40、80 mg·L−1)的溶液进行静态吸附实验;为探究温度和接触时间的影响,在初始离子浓度为50 mg·L−1、pH=7的条件下,设置三组温度(288 K、303 K、318 K)的静态吸附实验;为探究GO/CA水凝胶复合膜的再生性,在pH=7,初始浓度为80 mg·L−1的条件下进行5个吸附-解吸循环。选取0.4 mol/L HCl溶液作为洗脱剂,洗脱后用去离子水冲洗。置于CaCl2溶液中12 h恢复强度后,进入下一循环。

    为探究吸附过程的动力学规律,引入伪一级、伪二级、Elovich动力学模型[1]和颗粒内扩散模型[2];引入Freundlich和Langmuir模型[2]对吸附过程进行拟合来探究Cd(II)在GO/CA水凝胶复合膜上的平衡吸附;由复合膜本身的性质及其对重金属离子的吸附特点可知,吸附过程存在离子交换。定量检测吸附平衡后的Cd(NO3)2溶液,确定溶液中Ca(II)的增加量,来判定Cd(II)与Ca(II)的离子交换在吸附中所占的比例。RLN分别为单独定义的一个无量纲常数和Freundlich液相吸附等温指数。

    用傅里叶红外衰减全反射红外光谱仪定性表征吸附Cd(II)前后的GO/CA水凝胶复合膜。对吸附Cd(II)前后的GO/CA水凝胶复合膜喷金处理后进行X射线能谱分析(XPS K-Alpha Thermo, AlKα)。

    GO/CA水凝胶复合膜的表面形貌和微观结构如图1(a)图1(b)所示。从图1(a)可以看出,GO/CA水凝胶复合膜表面平整,有烘干留下的褶皱。从图1(b)可以看出,在水凝胶均匀的网络骨架结构上有片层状的GO,两者均匀地结合,说明成功制备了GO/CA水凝胶复合膜。

    图  1  氧化石墨烯/海藻酸钙水凝胶( GO/CA)复合膜的表面形貌(a)、透视特征(b)及官能团的变化(c)
    Figure  1.  Surface morphology (a), perspective characteristics (b) and functional groups (c) of graphene oxide/calcium alginate hydrogel( GO/CA) hydrogel composite membrane

    纯CA膜和GO/CA水凝胶复合膜的红外光谱如图1(c)所示。可见,加入GO后,膜表面官能团的类型未发生变化。在3 300 cm−1附近的特征峰为—OH的伸缩振动峰,1 600和1 400 cm−1附近的特征峰为羧酸盐的反对称和对称伸缩峰,1 300 cm−1附近为C—H的伸缩振动峰,1 000 cm−1附近的峰为C—O的伸缩振动峰。而对于GO,羧基的特征峰位于1 723和1 618 cm−1。以上结果也说明了加入到铸膜液中的GO,参与了制膜过程的交联反应,从而使其由羧基状态转化成了羧酸盐状态。

    表1是CA和GO/CA水凝复合膜的渗透性能。可以看出,加入GO后,膜的孔隙率和平均孔径都明显地增大。这是由于加入GO使水凝胶骨架之间有更大的支撑空间,进而膜的内部结构更加立体。内部孔隙率的增加也提升了膜的输水性能,从而使膜的水通量增大。

    表  1  CA膜和GO/CA水凝复合膜的渗透性能
    Table  1.  Permeability of CA membrane and GO/CA hydrogel composite membrane
    MembraneMean pore size/nmPoriness/%Water flux/(L·m-2h-1)
    CA10.686.514.7
    GO/CA12.690.118.1
    下载: 导出CSV 
    | 显示表格

    CA膜和GO/CA水凝复合膜的力学性能如表2所示。可以看出GO的加入明显提升了其机械强度。这是由于GO加入后,三者相互交联,形成比CA膜更稳定的结构。

    表  2  CA膜和GO/CA水凝复合膜的力学性能
    Table  2.  Mechanical properties of the CA membrane and GO/CA hydrogel composite membrane
    MembraneElongation at break/%Fracture energy/(kJ·m−2)Stress/MPa
    CA9534914
    GO/CA143651 725
    下载: 导出CSV 
    | 显示表格

    图2(a)是CA膜和GO/CA水凝胶复合膜吸附性能的比较。可以看出,在添加GO后,膜的吸附性能明显提升。由于加入GO,膜表面有了更多的吸附位点(含氧基团),提高了膜的吸附能力。且加入GO会增大膜的孔隙率,为吸附提供更大的空间。

    图  2  GO (a)、pH ((b)、(c))、初始浓度(d)、温度(e)和循环次数(f)对GO/CA 膜吸附容量的影响
    Figure  2.  Effect of GO (a), pH ((b), (c)), initial concentration (d), temperature (e), cycle times (f) on adsorption capacity of GO/CA hydrogel composite membrane

    溶液初始pH值对GO/CA水凝胶复合膜吸附性能的影响如图2(b)所示。可以看出在低pH时,吸附效果较差。随pH升高,吸附容量逐渐增大,在pH为6~7时保持稳定。这是由于pH影响膜的表面电性。GO/CA水凝胶复合膜表面有大量羧基等含氧基团。在溶液中H+浓度较大时(pH<pKa (3.38~3.65)[14]),含氧基团被质子化,使膜表面带正电。这严重影响带正电的重金属离子与膜的静电吸引作用,阻碍了吸附反应。随着pH升高,膜表面质子化逐渐消失,负电性恢复,吸附容量也逐渐增加,在pH=6~7时达到稳定。从Cd(II)离子种类分布(图2(c))可看出,pH升到弱碱性时,Cd(II)的水解增强,形成氢氧化物甚至会出现沉淀,这会影响吸附反应的进行。因此pH=6~7是最适宜的条件。

    图2(d)为Cd(II)初始浓度不同时GO/CA水凝胶复合膜的吸附量。可以看出吸附量与浓度成正相关。由于离子浓度较大,溶液对金属离子会产生更强的驱动力[15]。较大的离子浓度,还会使离子与GO/CA水凝胶复合膜之间有更大的碰撞几率和接触密度[16]。这些是吸附的有利因素,因此Cd(II)初始浓度与吸附量呈正相关。

    图2(e)为不同温度下时间与吸附量的关系。可以看出,吸附量随时间先迅速增长后缓慢增长,最后趋于稳定。这是由于吸附初期离子浓度大且空余吸附位点多。随吸附位点逐渐被占据,吸附速度减缓,在20 h达到平衡。由此可认为吸附最佳时间为20 h。还可知,吸附量与温度正相关。但当温度上升到一定值后其影响变小,这是由于膜表面吸附位点数量固定,吸附位点达到饱和,吸附量就基本保持稳定,不会再随温度升高而增大。

    图2(f)所示,解吸次数对GO/CA水凝胶复合膜吸附Cd(II)有一定的影响,但在5次吸附-解吸循环后仍能保持70%的吸附量,说明复合膜具有可重复利用性。在经过吸附-解吸循环后,膜的吸附量下降的原因是:吸附过程中,不可逆吸附占据一定的比例,使这部分吸附位点难以循环利用;且解吸过程具有不完全性,这也使膜在再吸附过程失去一部分吸附能力,使吸附量下降。

    初始浓度C0不同时,GO/CA水凝胶复合膜吸附Cd(II)动力学拟合结果如图3(a)~3(d)表3所示。在低浓度下,吸附过程与伪一级动力学模型更一致。拟合优度R2更接近于1,平衡吸附量Qe拟合值更接近于实验数据。而Cd(II)浓度增加到40 mg·L−1以上时,吸附过程则更符合伪二级吸附动力学模型。图3(d)是颗粒内扩散模型结果,可以看出复合膜吸附Cd(II)明显地分为了三个阶段:表面吸附阶段、颗粒内部扩散阶段和吸附平衡阶段。其中表面吸附阶段的反应时长为4 h,颗粒内扩散阶段的反应时长为16 h,因此第二阶段被认为是吸附过程的速率控制阶段,说明此吸附过程是颗粒内扩散为主的三阶段吸附[17]

    图  3  GO/CA水凝复合膜吸附动力学((a)~(d))及等温线((e)、(f))模型拟合图
    Figure  3.  Adsorption kinetics((a)-(d))and isotherm ((e), (f)) model fitting diagram of GO/CA hydrogel composite membrane
    表  3  Cd(II)的初始浓度C0不同时GO/CA水凝复合膜吸附性能的动力学模型拟合参数
    Table  3.  Kinetic model parameters of GO/CA hydrogel composite membrane adsorption at different initial concentration C0 of Cd(II)
    C0/(mg·L−1)Pseudo-first order kinetic modelPseudo-second order kinetic modelElovich model
    k1/min−1Qe/(mg·g−1)R2k2/min−1Qe/(mg·g−1)R2ABR2
    100.1530 51.370.99990.0826 57.280.987434.53−4.4970.964 1
    400.3131140.00.99190.0116147.50.9993113.7−7.5790.9785
    800.4497211.90.98040.0066224.10.9993135.3−22.170.9714
    Notes: C0—Initial concentration of Cd(II); R2—Goodness; Qe—Adsorption capacity at adsorption equilibrium; k1, k2 and A—Constant of kinetic models, respectively; B—Coefficient of elovich kinetic models.
    下载: 导出CSV 
    | 显示表格

    图3(e)3(f)表4是不同温度下GO/CA水凝胶复合膜吸附Cd(II)等温线拟合结果。可以看出,此吸附过程更符合Langmuir模型,由于拟合优度R2更接近于1,说明吸附过程属于单层吸附[18]。计算得到在288、303和318 K时RL均在0~1范围内,说明GO/CA水凝胶复合膜吸附Cd(II)是有利吸附。Freundlich模型的R2都大于0.9,其参数有较大参考价值。通过拟合得到的N分别为1.79、2.77和3.15,可判断吸附过程属于物理吸附。

    表  4  GO/CA水凝胶复合膜吸附Cd(II)的吸附等温线模型参数
    Table  4.  Isothermal adsorption model parameters of Cd(II) adsorbed by GO/CA hydrogel composite membrane
    Temper-
    ature/K
    Freundlich isothermLangmuir isotherm
    kfNR2klQm/(mg·g−1)R2
    28813.811.7870.94450.176685.400.9914
    30347.992.7700.96180.2168161.80.9952
    31847.673.1470.95890.3146173.60.9981
    Notes: kf—Capacity factor of Freundlich; N—Liquid phase adsorption isotherm index of Freundlich; k1—Langmuir constant of affinity point; Qm—Adsorption capacity of single layer.
    下载: 导出CSV 
    | 显示表格

    在吸附达到平衡后,测定溶液中出现的Ca(II)的浓度为2.32 mg·L−1。由此可知离子交换作用在吸附过程占了较大的比重,经计算得到物理作用力吸附、离子交换作用及溶液中剩余的未被吸附的Cd(II)的比例分别是59.94%、32.33%、7.72%。

    图4是吸附Cd(II)前后GO/CA水凝胶复合膜的FTIR图谱。在3 232、1 586、1 407和1 019 cm−1处的四个特征峰分别代表—OH、羧基上的—C=O和—C—OH及C—O的伸缩振动峰。证明膜表面有大量羟基和羧基等亲水基团。吸附后,四个特征峰的位置分别移动到3 208、1 577、1 408和1 023 cm−1,强度也轻微地降低。没有新的特征峰出现,说明吸附过程发生了配位反应或离子交换[19-20]。这表明化学吸附可能占有一定的比重,但Cd(II)在GO/CA水凝胶复合膜上的吸附仍然以物理吸附作用为主。

    图  4  GO/CA水凝胶复合膜的FTIR图谱
    Figure  4.  FTIR spectra of GO/CA hydrogel composite membrane

    图5是GO/CA水凝胶复合膜吸附Cd(II)前后的XPS能谱。图5(a)为吸附前后复合膜的XPS全谱。可以看出,吸附重金属离子后,Ca2+的吸收峰强度减弱,且在405 eV出现新的吸收峰,即Cd 3d的吸收峰图5(b)。证明吸附反应发生,也证明了Ca2+与Cd2+发生了离子交换作用。图5(c)为吸附前后膜的C元素的XPS拟合分峰结果。吸附后,羧基和羟基的强度减弱,峰位置也发生变化,说明复合膜中的羟基、羧基等基团参与了吸附过程,与金属离子形成了配合物。

    图  5  GO/CA水凝胶复合膜吸附Cd(II)的XPS能谱
    Figure  5.  XPS spectra of GO/CA hydrogel composite membrane adsorption of Cd(II)

    (1)成功制备了氧化石墨烯(GO)/海藻酸钙(CA)水凝胶复合膜。加入GO提高了GO/CA复合膜的力学性能、平均孔径、水通量及吸附性能。复合膜对Cd(II)的吸附性能良好,拟合得到的最大吸附量为173.61 mg·g−1,平衡时间为20 h。最适pH为6~7,吸附量与初始离子浓度、接触时间、温度都成正相关。

    (2) GO/CA水凝胶复合膜对重金属离子Cd(II)的吸附过程符合Langmuir吸附等温线模型,属于单层有利的物理吸附。在低离子浓度,吸附过程遵循伪一级吸附动力学,在较高浓度遵循伪二级吸附动力学,是以颗粒内扩散为控速步骤的三阶段吸附。

    (3)经过5个吸附-解吸循环,GO/CA水凝胶复合膜对Cd(II)的吸附量仍能保持原吸附量的70%,证明了其可重复利用性。

  • 图  1   钢丝网格 (a) 和玻璃纤维网格 (b)

    Figure  1.   Steel wire mesh (a) and glass fiber mesh (b)

    图  2   UHPC双向板浇筑步骤

    Figure  2.   UHPC two-way slabs pouring steps

    图  3   不同层数网格在UHPC双向板内的高度示意图

    Figure  3.   Schematic diagram of height of mesh with different layers in the UHPC two-way slabs

    图  4   试验加载和测量装置

    Figure  4.   Loading and measuring arrangement

    LVDT—Linear variable displacement transducer

    图  5   双向板加载方式示意图

    Figure  5.   Loading mode of two-way board

    P—Load

    图  6   铺设SWM的UHPC板荷载-挠度曲线

    Figure  6.   Load-deflection curve of UHPC slabs with SWM

    图  7   不同网格层数UHPC板破坏形态

    Figure  7.   Failure modes of UHPC slabs with different mesh layers

    图  8   SWM或GFM增强UHPC板破坏形态示意图

    Figure  8.   Schematic diagram of failure modes of UHPC slabs with SWM or GFM

    图  9   不同SWM层数UHPC板荷载-挠度曲线

    Figure  9.   Load-deflection curves of UHPC slabs with different SWM layers

    图  10   不同SWM孔径UHPC板荷载-挠度曲线

    Figure  10.   Load-deflection curves of UHPC slabs with different SWM aperture

    图  11   不同纤维种类UHPC板荷载-挠度曲线

    Figure  11.   Load-deflection curves of UHPC slabs with different fiber types

    图  12   不同网格种类UHPC板荷载-挠度曲线

    Figure  12.   Load-deflection curves of UHPC slabs with different mesh types

    图  13   不同SWM层数UHPC板能量吸收值

    Figure  13.   Energy absorption value of UHPC slabs with different SWM layers

    图  14   不同SWM孔径UHPC板能量吸收值

    Figure  14.   Energy absorption value of UHPC slabs with different SWM aperture

    图  15   不同纤维种类UHPC板能量吸收值

    Figure  15.   Energy absorption value of UHPC slabs with different fiber types

    图  16   不同网格种类UHPC板能量吸收值

    Figure  16.   Energy absorption value of UHPC slabs with different mesh types

    图  17   UHPC双向板矩形截面受弯承载力计算图

    Figure  17.   Calculation diagram of bending capacity of rectangular section of UHPC two-way slabs

    fc—Axial compressive strength; ft—Axial tensile strength; h0—Effective height of section; Mu−Theoretical bending capacity; a—Distance from the mesh resultant point in the tension zone to the edge of the bottom section of the slab; b—Calculated width of the slab; α1—Equivalent rectangular stress diagram coefficient of compression zone, take 0.88; β—Equivalent rectangular stress diagram coefficient of tensile zone, take 0.35; xc—Height of compression zone; xt—Equivalent rectangular stress height of tension zone; fte—Mesh effective stress; k—Ratio of x to xc; Af—Total section area of grid; h—Height of slab; x—Equivalent rectangular stress height of compression zone

    表  1   钢丝网和玻璃纤维网力学性能参数

    Table  1   Mechanical property parameters of steel wire mesh and glass fiber mesh

    Mesh nameTensile strength/MPaElastic modulus/GPaMonofilament area/mm2Elongation/
    %
    SWM5822000.7852.6
    GFM2200790.2903.0
    下载: 导出CSV

    表  2   超高性能混凝土(UHPC)基体配合比

    Table  2   Composition ratio of ultra-high performance concrete (UHPC)

    Matrix typeCementSilicaMineral powderRiver sandWater
    consumption
    UHPC1.0000.1820.6212.1820.327
    下载: 导出CSV

    表  3   SWM或GFM增强UHPC双向板试件编号与分组方案

    Table  3   Specimen number and grouping scheme of UHPC reinforced with SWM or GFM

    Group categorySpecimen numberDosage and type
    of fiber
    Number of mesh layers
    The first
    group
    U1-S2-121.5vol% SF2
    U1-S3-121.5vol% SF3
    U1-S4-121.5vol% SF4
    The second groupU1-S2-121.5vol% SF2
    U1-S2-201.5vol% SF2
    U1-S3-121.5vol% SF3
    U1-S3-201.5vol% SF3
    U1-S4-121.5vol% SF4
    U1-S4-201.5vol% SF4
    The third groupU1-S2-201.5vol% SF2
    U2-S2-201.0vol% SF+0.5vol% PVA2
    U3-S2-200.5vol% SF+1.0vol% PVA2
    U4-S2-200.5vol% SF+1.0vol% GF2
    U5-S2-200.5vol% SF+1.0vol% BF2
    The fourth
    group
    U1-S2-121.5vol% SF2
    U1-S2-201.5vol% SF2
    U1-G2-51.5vol% SF2
    Notes: In specimen number, Un represent UHPC types; Sn/Gn represent SWM or GFM types and number of mesh layers; The next number represents the mesh aperture. Such as, U1-S2-12 represents UHPC slab with 2 layers of steel wire mesh with 12 mm aperture and 1.5vol% steel fiber volume fraction.
    下载: 导出CSV

    表  4   短切纤维性能参数

    Table  4   Performance parameters of chopped fibers

    Fiber typeDiameter/µmTensile strength/MPaDensity/(g·cm−3)Elastic modulus/GPaLength/mm
    Steel fiber20029507820513
    Polyvinyl alcohol4016001.335-4012
    Glass fiber1817002.687218
    Basalt fiber2032002.690-11020
    下载: 导出CSV

    表  5   SWM或GFM增强UHPC板初裂、峰值荷载及其挠度

    Table  5   Initial crack, peak load and deflection of UHPC slabs with SWM or GFM

    Specimen numberPcr/kNδcr/mmPm/kNδm/mm
    U1-S2-1261.761.5080.153.79
    U1-S3-1264.881.8492.067.76
    U1-S4-1272.952.50106.058.53
    U1-S2-2057.931.4472.793.43
    U1-S3-2061.151.6480.307.32
    U1-S4-2068.352.0588.738.86
    U2-S2-2051.341.4877.083.49
    U3-S2-2052.721.5365.593.47
    U4-S2-2045.971.5760.7313.02
    U5-S2-2043.151.3957.6211.93
    U1-G2-530.560.8573.146.53
    Notes: Pcr—Initial crack load;δcr—Deflection at initial crack load;Pm—Peak load;δm—Deflection at peak load.
    下载: 导出CSV

    表  6   SWM或GFM增强UHPC板不同挠度处能量吸收计算值

    Table  6   Calculated values of energy absorption for different deflections of UHPC slabs with SWM or GFM

    Specimen
    number
    Qcr/JQm/JQ2/JQ5/JQ15/JQ25/J
    U1-S2-1254.78226.4288.71321.551084.371769.73
    U1-S3-1274.39578.5884.55329.841229.862019.31
    U1-S4-1294.82676.1060.43315.281332.852215.37
    U1-S2-2044.57180.3680.03290.77934.061480.90
    U1-S3-2061.06490.5483.62306.651087.161762.61
    U1-S4-2082.41656.3679.01320.161181.461965.45
    U2-S2-2041.32178.8771.49292.22959.041501.36
    U3-S2-2040.85156.7866.52254.19805.111139.25
    U4-S2-2036.30673.0456.85213.34785.481206.25
    U5-S2-2036.15578.5863.19211.76759.311191.33
    U1-G2-512.83327.6152.35218.20744.56
    Notes: Qcr and Qm—Energy absorption values at the initial crack and peak load deflection of UHPC slabs, respectively; Q2, Q5, Q15, Q25—Energy absorption value of UHPC slabs with deflection of 2 mm, 5 mm, 15 mm and 25 mm, respectively.
    下载: 导出CSV

    表  7   SWM或GFM增强UHPC板硬化指数和韧性指标

    Table  7   Hardening index and toughness index of UHPC slabs with SWM or GFM

    Specimen numberIShT15T25
    U1-S2-121.30141.68231.86
    U1-S3-121.42160.82264.70
    U1-S4-121.45174.38290.50
    U1-S2-201.26121.90193.86
    U1-S3-201.31142.05230.92
    U1-S4-201.30154.46257.61
    U2-S2-201.50125.19196.55
    U3-S2-201.24104.94148.90
    U4-S2-201.32102.35157.72
    U5-S2-201.3498.91155.75
    U1-G2-52.3996.97
    Notes: ISh—Hardening index; T15—Toughness index at 15 mm deflection; T25—Toughness index at 25 mm deflection.
    下载: 导出CSV

    表  8   各UHPC板抗弯承载力计算结果

    Table  8   Calculation results of bending capacity of UHPC slabs

    Specimen
    number
    fc/MPaft/MPah0/mmεcfte/MPaλ/%Mu
    /(kN·m)
    Me
    /(kN·m)
    Me/Mu
    U1-S2-1298.816.3743.50.003913279.7382.09.9610.021.006
    U1-S3-1298.816.3741.00.003972595.6764.910.9511.131.017
    U1-S4-1298.816.3738.50.004012199.3355.011.5413.261.198
    U1-S2-2098.816.3743.50.003533908.7397.77.819.101.165
    U1-S3-2098.816.3741.00.003653205.4480.18.8210.041.138
    U1-S4-2098.816.3738.50.003852740.1068.59.3911.091.227
    U2-S2-2091.126.4943.50.003533871.3596.37.739.641.247
    U3-S2-2090.786.1143.50.003413681.4492.07.368.201.114
    U4-S2-2086.525.9543.50.003393570.4989.37.147.591.064
    U5-S2-2083.065.8943.50.003383480.9187.06.977.201.034
    U1-G2-598.816.3745.00.004092027.7378.07.248.621.191
    Notes:fc—Axial compressive strength; ft—Axial tensile strength; h0—Effective height of section; εc—Compressive strain of concrete; fte—Mesh effective stress; λ—Effective utilization of mesh; Mu—Theoretical bending capacity; Me—Experimental bending capacity.
    下载: 导出CSV
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出版历程
  • 收稿日期:  2021-08-23
  • 修回日期:  2021-10-11
  • 录用日期:  2021-10-11
  • 网络出版日期:  2021-10-25
  • 刊出日期:  2022-08-21

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