氧化镁微膨胀混凝土性能研究

研究了氧化镁水泥混凝土的物理、力学、变形等性能．结果表明：在混凝土中掺入氧化镁使其自生体积膨胀，其膨胀具有延迟性的特点；混凝土的抗压强度随氧化镁掺量的增加而降低；混凝土的自生体积变形随氧化镁掺量的增加而增大；养护温度越高，自生体积变形越大；氧化镁掺量对混凝土的干缩变形及绝热温升没有明显影响．     

用统计连续理论研究混凝土的力学性能

混凝土材料可看成由骨料，水泥水化物和砂浆组成的三相非均质材料，或看成由骨料和细砂组成的二相非均质材料，本文提出了等效常数的概念，把混凝土看成随机非均匀连续介质，用统计连续理论研究其力学性能，并给出了计算等效弹性模量的公式。     

Study of the Reflected (Albedo) Secondary Gamma Radiation from Different Materials

The experimental measurements of the reflected (albedo) component of the secondary gamma radiation have been carried out for cylindrical samples of graphite, ilmenite limonite concrete and iron of different thicknesses. A collimated beam of neutrons emitted from one of the horizontal channels of the ET-RR-1 reactor have been used. A single stilbene crystal scintillator applying zero crossover technique for the differentiation between gamma and neutron pulses have been utilized. The measured pulse height spectra were transformed to energy spectra. It was shown that the reflected secondary gamma rays increase with the increase of the material thickness then becomes constant. The reflected secondary gamma rays increase also with the increase of the used material density.

Die refleklierte (Albedo) Kompononte der sekundären Gammastrahlung wurde an zylindrischen Proben unterschiedlicher Dicke von Graphit, Ilmenit-Limonit-Zement und Eisen gemessen. Dazu iwurde cin gerichteter Neutronenstrahl verwendet, der aus cinem der horizontalen Kanäle des ET-RR-1 Reaktors emittiert wurde. Ein einzelner Stilbenkristall-Szintillalor wurde zur Unterscheidung der Gamma- und Neutronenimpulse eingesetzt. Es konnte gezeigt werden, daβ die reflektieten sekundaren Gammastrahlen mit der Materialdicke zunächst zunehmen und schlieβlich einen konstanten Wert errcichen. Der reflektierte Anteil der sekundären Gammastrahlen steigt ebenfalls mit der Dichte des verwendeten Materials an.     

马岭河特大桥承台温度控制方案

大体积砼须采取相应技术措施妥善处理内外温差,合理解决温度应力并控制裂缝。介绍了在塔座施工中采取的温度控制措施、实施过程及效果,并结合实际观测数据对大体积砼施工通过外掺剂的使用,优化砼原材料,优化砼配合比等措施更好地掌握用山砂施工大体积砼。     

Solid-state Al and Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

Partially deuterated Ca₃Al₂(SiO₄)_y(OH)_12−4y-Al(OH)₃ mixtures, prepared by hydration of Ca₃Al₂O₆ (C₃A), Ca₁₂Al₁₄O₃₃ (C₁₂A₇) and CaAl₂O₄ (CA) phases in the presence of silica fume, have been characterized by ²⁹Si and ²⁷Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca₃Al₂(OH)₁₂ and Al(OH)₃ phases were detected. From the quantitative analysis of ²⁷Al NMR signals, the Al(OH)₃/Ca₃Al₂(OH)₁₂ ratio was deduced. The incorporation of Si into the katoite structure, Ca₃Al₂(SiO₄)_3−x(OH)_4x, was followed by ²⁷Al and ²⁹Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of ²⁷Al MAS-NMR components associated with Al(OH)₆ and Al(OSi)(OH)₅ environments. The ²⁹Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From ²⁹Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures.     

静态旋转侵彻混凝土力学仿真与实验研究

为研究静态旋转侵彻过程中力学和结构参数之间的匹配关系,按照经典切削理论建立了静态旋转侵彻混凝土的经验公式,应用LS-DYNA软件对其作用过程进行了数值仿真。利用正交实验法进行了静态旋转侵彻混凝土模拟实验,并利用经典Levenberg-Marquardt算法拟合经验公式,得到了轴向力和扭矩、侵彻量、旋转侵彻体直径和旋转速度之间的经验关系。实验结果表明:经验公式与仿真结果相符合,旋转侵彻体直径对轴向力的影响较大,进给量对扭矩的影响较大,钻速对轴向力及扭矩的影响较小。     

混凝土开孔梁实验研究

在建筑结构中采用混凝土 (RC/PC)开孔梁 ,使各种管道、线路等从构件孔中穿过 ,可以有效地节约建筑空间 作者在前期工作的基础上 ,通过 1 0根足尺混凝土 (RC/PC)开孔梁的实验研究 ,对混凝土 (RC/PC)开孔梁的强度、刚度、变形、裂缝开展等特性进行了详细的探讨 研究中考虑了静定梁、超静定梁、单孔、双孔、普通混凝土梁、预应力混凝土梁、对比试验、仿真试验、实测试验等多种情况 ,最后给出了相应的设计计算建议