Improved simultaneous adsorption of Cu(II) and Cr(VI) of organic modified metakaolin-based geopolymer

In this paper, a metakaolin-based mesoporous geopolymer (GP-CTAB) was used as adsorbent for Cu(II) and Cr(VI) through a novel and simple synthetic route using cetyltrimethylammonium bromide (CTAB) as an organic modifier. The application of GP-CTAB for the simultaneous removal of metal anions and cations in aqueous solution was studied for the first time. The results of X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Brunauer, Emmett and Teller (BET), and Barrett, Joyner, and Halenda (BJH) methods indicate that GP-CTAB is still geopolymer even in the presence of quaternary ammonium salt cations. The material was tested to simultaneously adsorb Cu(II) and Cr(VI) from an aqueous solution. The results show that GP-CTAB can adsorb anions simultaneously without sacrificing the adsorption properties of heavy metal cations, which is superior to conventional geopolymers. The maximum theoretical adsorption capacity of GP-CTAB for Cu(II) and Cr(VI) was 108.2 mg/g and 95.3 mg/g in the binary system, respectively. It was also found that the presence of Cu(II) in the solution promoted the adsorption of Cr(VI). Given this characteristic of GP-CTAB, it has shown great application prospects in the prevention and control of heavy metal pollution.     

3D X-ray Micro-CT Analysis of Rebar Corrosion in Reinforced Concrete Subjected to a Chloride-Induced Environment

The paper presents experimental investigations of the concrete covers’ protective ability to counteract rebar corrosion in reinforced concrete cubes. The concrete sample was subjected to a chloride-induced environment to get corroded and combined with an un-corroded sample. The chloride-accelerated technique can induce a high degree of corrosion within a controlled time. Moreover, detailed and thorough experimental measurements and analyses of reinforcement loss due to corrosion and its influence on concrete microstructure, were studied through 3D X-ray micro-computed tomography. The rebar outside the concrete was heavily corroded due to the chloride-accelerated test, whereas, only local surface corrosion products appeared inside the concrete. It turned out that the concrete cover showed protective ability to counteract the reinforcing-steel corrosion mechanism despite the accelerated corrosion environment. Moreover, the bond strength between the reinforcement rebar and concrete was not visibly affected since the failure force in the pull-out test and failure mechanisms, observed by 3D X-ray micro-CT, were similar for corroded and un-corroded samples. The failure occurred due to radial cracks with a maximum width equal to approximately 0.25 mm.     

基于修正压力场理论的再生混凝土梁抗剪承载力计算方法研究

基于修正压力场理论分析有腹筋再生混凝土梁的剪切破坏机理,建立了更接近有腹筋再生混凝土梁实际受力的抗剪模型,并通过考虑再生骨料有效粒径和受箍筋作用下的裂缝宽度与构件裂缝处应力的联系,分析了再生骨料咬合力对梁斜截面抗剪性能的影响,提出了再生混凝土梁极限抗剪承载力的计算方法.此外,本文将理论结果与课题组自制的6根再生混凝土梁...     

组合式十字形钢管混凝土柱偏压力学性能试验研究

设计了一种由槽钢和方形钢管拼焊形成的组合式十字形钢管混凝土柱,将其灵活地布置在框架结构的中节点,可使柱肢与填充墙等厚,有效地提高建筑使用面积。共制作了6根组合式十字形钢管混凝土柱试件,考虑了偏心距和长细比两种变化参数。通过对其进行偏心受压试验研究,考察了试件的破坏形态和荷载-挠度曲线,并分析了其在不同偏心距和长细比下的荷载-应变曲线发展规律。结果表明:组合式十字形钢管混凝土柱中钢管和槽钢对混凝土的约束作用强,表现为较高的延性系数;偏心距或长细比越大,试件的极限承载力及弹性刚度越小,且偏心距越大延性越好,长细比对延性影响不显著;在受拉侧纵向应变基本上符合平截面假定,在受压侧纵向应变不符合平截面假定。     

不同材料弹体超声速侵彻钢筋混凝土靶的结构破坏对比实验

设计了超声速钻地结构弹,采用203 mm口径的火炮,开展了25 kg量级弹体在1100~1300 m/s速度范围内侵彻钢筋混凝土靶的实验研究,应用数值仿真对弹体侵彻钢筋混凝土靶的过程进行了模拟计算。基于实验和仿真结果,对超声速侵彻条件下两种金属材料弹体的结构响应、质量损失等问题进行了分析。结果表明:在超声速侵彻钢筋混凝土靶的过程中,两种金属材料的弹体结构变形破坏形式主要为头部侵蚀和侧壁磨蚀,头部侵蚀量的大小与弹体壳体材料有关,高强度G50钢材料更适合用于1200 m/s速度量级的超声速侵彻环境。对出现的“径缩”现象作了初步分析,并对今后工程应用的结构弹体设计提出了指导意见。     

固相微萃取/气相色谱-质谱法对乌梅浸膏挥发性成分的分析研究

对乌梅浸膏挥发性物质的固相微萃取条件进行了研究。运用正交实验设计,比较了不同萃取头、平衡温度及采样时间对分析结果的影响,通过气相色谱-质谱(GC-MS)的分析监控,结合信息量最大原则,确定了固相微萃取的最佳条件:萃取纤维头为聚二甲基硅氧烷,平衡温度为70℃,采样时间45 min。通过GC-MS进行定性定量分析,共鉴定出38种成分,主要挥发性成分依次为糠醛(24.88%)、2-甲基-3-羟基苯甲醛(13.57%)和5-甲基糠醛(10.16%)。     

水泥聚苯模壳格构式混凝土墙体的抗侧性能试验及分析

论文介绍6片不同高宽比的水泥聚苯模壳格构式混凝土墙体在轴压力和水平往复侧推力作用下的试验,分析这种墙体的抗侧强度、刚度和延性等力学性能.试验表明,高宽比大于1的墙体破坏时表现为墙体跟部的单一水平裂缝,其他部位完好;高宽比3∶4的墙体破坏时存在多条通过格构梁柱的斜向裂缝,墙体裂缝分布密集,变形能力好.     

水下爆炸冲击荷载下混凝土重力坝的抗爆性能

在水下爆炸冲击荷载作用下,结构动力响应较之静态荷载和地震荷载作用下要复杂得多。通过大 量的数值模拟,探讨了混凝土重力坝在水下爆炸冲击荷载作用下,大坝高度、库前水位对大坝抗爆性能的影 响,为大坝抗爆性能评估和防护设计提供基础。数值计算中,构建了重力坝水下爆炸全耦合数值模型,并考虑 爆炸冲击作用下混凝土的高应变率效应。研究结果表明:对于混凝土重力坝,随着大坝高度的增加,大坝的抗 爆性能增强;库前水位对大坝的抗爆性能影响较大,通过降低库前水位可有效提高大坝的抗爆性能。     

NONLINEAR UNIFIED STRENGTH MODEL OF GEOMATERIALS

将材料的破坏归结为剪切破坏,每种材料对应于特定的剪切滑动面,抗剪强度为滑动面上正应力的函数,基于不同材料的强度特性将一系列的剪切滑动面统一起来,建立了岩土材料的非线性统一强度模型.非线性统一强度模型的滑动面为β应力空间内的等倾面,在β应力空间内的强度面为圆锥面;在普通应力空间内的强度面为一系列连续光滑、外凸的锥面,在偏平面上强度曲线涵盖了从下限Matsuoka-Nakai曲线到上限Drucker-Prager圆之间的所有区域,子午面上强度线为直线.非线性统一强度模型只有3个材料参数,参数都具有明确的物理意义,通过与国内外学者已取得的岩土类材料真三轴强度试验结果的比较,表明模型可适用于多种类型的材料,并合理描述其非线性强度特性.     

钨合金柱形弹超高速撞击水泥砂浆靶的侵彻深度研究

为探索钨合金柱形弹超高速撞击水泥砂浆靶的侵彻深度随撞击速度变化规律,利用二级轻气炮开展了?3.45 mm×10.5 mm的克级93 W钨合金柱形弹以1.82~3.66 km/s的速度撞击水泥砂浆靶的实验,利用CT图像诊断技术获得了侵彻深度和残余弹长随撞击速度的变化规律,对超高速撞击过程进行了数值模拟,结合数值模拟结果进一步分析了超高速撞击物理过程。结果表明:(1)超高速撞击条件下成坑是弹坑+弹洞型;(2)侵深-速度曲线呈现先增大后减小的现象,在弹速2.6 km/s附近存在侵彻深度极大值,约为8.5倍弹长,相对于中低速侵彻的深度并没有显著优势。(3)通过基于数值模拟得到的弹靶界面压力时程曲线将侵彻过程分为4个阶段,其中准定常侵彻阶段和第三侵彻阶段是决定总侵深的主要阶段。(4)随撞击速度增加,弹体侵蚀逐渐剧烈,此时准定常侵彻阶段的侵深变化不大,而第三侵彻阶段中的刚体侵彻部分大幅降低,导致总侵深大幅降低,使总侵深曲线呈现先增大后减小的现象。