水泥砂浆在主动围压下的动态力学性能

水泥砂浆等脆性材料的力学性能与所受围压的大小密切相关。为了研究水泥砂浆在围压下的动态力学性能,研制了适于分立式Hopkinson压杆加载的主动围压装置,最大预加载主动围压大于30 MPa。实验得到了水泥砂浆在不同围压、不同应变率下的轴向应力应变曲线,发现材料在围压作用下抗压强度和韧性大大提高并且整体进入了伪塑性,而材料的应变率效应也是显著的。     

高应变率下水泥砂浆劈拉强度试验研究

采用直径为74 mm的分离式霍普金森压杆(SHPB)设备对水泥砂浆在高应变率下的抗拉力学特性进行试验研究,受载试件采用平台巴西圆盘试样。通过控制不同气压,获得了50/s~342/s应变率范围内的水泥砂浆动态抗拉力学性能。为了凸显平台巴西圆盘试样的合理性,试验结果还与传统的巴西圆盘试样进行了对比。试验结果表明,水泥砂浆的劈拉强度,峰值应变及弹性模量随应变率的提高而提高,试验得出的动态强度增长因子(DIF)值随应变率的变化趋势与欧洲-国际混凝土协会(CEB)提出的模型比较吻合。破坏模式与应变率有一定关系,剪切破坏区的大小随着应变率的提高而提高。作为间接测量准脆性材料抗拉力学性能的方法,平台巴西圆盘试样优于巴西圆盘试样。     

碳化对水泥石和砂浆的结构及砂浆渗透性的影响

用压汞法、扫描电子显微镜、X射线衍射及渗透高度法研究了碳化对水泥石和水泥砂浆的孔结构和显微结构及砂浆渗透性的影响．结果表明,碳化生成的碳酸钙在毛细孔中沉积后会堵塞毛细孔或将大的毛细孔分割成小孔,使水泥石和水泥砂浆总孔隙率降低、孔径细化,从而可提高砂浆抗渗性．     

移动化趋势下实体商业营销思考

随着移动互联网和智能手机的飞速发展,移动化趋势已成为不可逆转的时代潮流。移动化趋势为因网络发展而受到冲击的实体商业提供了新的发展机遇。通过对消费者行为的探究,证明了在手机终端开展移动营销的必要性。选取了微信和品牌App两个适宜开展移动营销的平台,通过对平台特点的分析,找到了实体商业在营销方式及营销模式上的新机遇。并结合案例分析提出了在相应平台开展营销活动的建议,为实体商业在移动化趋势下的营销发展提供了参考。     

基于细观力学方法的混凝土热膨胀系数预测

建立混凝土材料的有效性质与微结构参数之间的关系,是混凝土材料优化设计的基础。本文用细观力学方法对复合材料宏观有效热膨胀系数进行研究,得到了含有一球形夹杂物的无限大介质在均匀变温作用下的应力场。假定混凝土为由骨料和砂浆基质组成的二相复合材料,根据混凝土宏观体积热膨胀量与组成混凝土的各相介质细观体积热膨胀量相等的原则,采用基于Mori-Tanaka方法的混凝土宏观有效剪切模量,推导出混凝土有效热膨胀系数的解答。对稀疏解法、自洽方法和有限单元数值试验结果的比较说明,本文提出的基于自洽方法的混凝土宏观有效热膨胀系数的理论公式能够较好的描述混凝土的热学特性,该方法可以推广到多相复合材料宏观有效热膨胀系数的预测中。     

Mortar physical properties evolution in extrusion flow

Extrusion is not a common way to form firm cement-based material. Due to material frictional behaviour, drainage phenomenon appears and leads to process blockage. The properties of the extrusion multiphase flow of such specific materials have to be highlighted to understand the properties of the process flow. An extrudible mortar is formulated according to extrusion criteria provided by literature tests developed to describe the evolution of the paste undergoing extrusion. To study the relationship between flow properties, extrusion force and material consolidation, a technique based on the measurement of paste hardness in the billet zone is developed. Measurements of the local paste density and flow visualisation are also performed. Results show that in the range of used ram velocities, filtration occurs between fluid and solid phases. This creates zones of preferential flow and of non-flowing consolidated material. Paper presented at the 3rd Annual European Rheology Conference held on April 27–29, 2006, Crete, Greece.     

Physicochemical Characteristics of Styrene-Butadiene Latex- modified Mortar Composite vis-à-vis Preferential Interactions

The interaction between styrene-butadiene rubber (SBR) film and the ions from C₂S and C₃S hydration of Portland cement mortar composites has been evaluated by Fourier Transform Infrared Spectroscopy (FTIR), and the morphology of the composites characterized with scanning electron microscopy (SEM). The specimen used was cured for 28 days. FTIR spectrum supports the interaction of SBR with cement in the composite. Compressive strength, bulk density and water absorption properties of the cured composites were tested. Addition of SBR latex in Portland cement mortar increases the compressive strength and decreases the water absorption. Bulk density study revels interface formation in the composite. The role of the interface in relation to compressive strength of the composite has been discussed. A simple Matrix System model is shown to account composition dependence of bulk density.     

5·12大地震后砖混结构房屋抗震加固技术探讨

通过两个工程实例,分别说明了教学楼、住宅两种不同用途的砖混结构房屋在具体的加固改造中所采用的如加设钢筋混凝土翼墙、钢筋砂浆带圈梁、双面钢筋网加固基础及板端和板边的结构措施,以通过实际的技术运用为抗震加固的工程实践提供了安全分析和抗震加固设计的思路,为类似工程提供借鉴和参考的依据。     

YDS高抗冲磨环氧砂浆的研究与应用

在YDS高渗透环氧化学灌浆材料的基础上,开发了一类新型高抗冲磨环氧砂浆。介绍了YDS高抗冲磨环氧砂浆的制备方法,探讨了环氧基液和环氧砂浆的主要性能。结果表明,YDS环氧砂浆不仅具有优异的抗渗耐腐蚀性能,而且其抗冲耐磨性能也非常好,抗冲磨强度最高达到400h/(kg/m2)以上,应用前景广泛。     

A regularized domain decomposition method with Lagrange multiplier

In this paper, we are concerned with the nonoverlapping domain decomposition method with Lagrange multiplier for three-dimensional second-order elliptic problems with no zeroth-order term. It is known that the methods result in a singular subproblem on each internal (floating) subdomain. To handle the singularity, we propose a regularization technique which transforms the corresponding singular problems into approximate positive definite problems. For the regularized method, one can build the interface equation of the multiplier directly. We first derive an optimal error estimate of the regularized approximation, and then develop a cheap preconditioned iterative method for solving the interface equation. For the new method, the cost of computation will not be increased comparing the case without any floating subdomain. The effectiveness of the new method will be confirmed by both theoretical analyzes and numerical experiments. The work is supported by Natural Science Foundation of China G10371129.