新型外包钢组合梁受弯承载力理论分析

结合一种新型外包钢组合梁的试验,进行了这种组合梁抗弯承载力的研究,推导出了各种配筋情况下正截面抗弯承载力的计算公式,计算结果与试验符合较好,最后给出设计建议。     

盐污染混凝土电化学除盐研究

采用电化学除盐的方法对盐污染混凝土进行除盐试验,结果表明在除盐早期,混凝土中氯离子排除量主要与电流密度和混凝土中氯离子的含量直接相关,电化学除盐后混凝土内部的氯离子含量呈由里及外逐渐增大的趋势;而上下两端面的氯离子含量较少,中间段的较高。     

混凝土泵液压系统能量损耗研究

从理论和试验两方面对混凝土输送泵液压系统能量损耗问题进行研究,系统分析导致能量损耗的主要因素以及对混凝土泵产品使用可靠性产生的影响.在HBTS80型混凝土输送泵上对其液压系统能量损耗情况进行试验研究,找出主要的能量损耗源以及系统能量损耗随负载、泵送方式、主液压泵使用性能等的变化规律,提出减小能量损耗的措施.     

混凝土砌块墙增强方法

本文简要介绍国外通过足尺试验证明已有的普通配筋墙体的抗震性能较差,必须在墙体两边按一定间距用螺栓固定外部钢板的方法增加抗震能力。     

Particle-based characterization of Ottawa sand: Shape,size, mineralogy,and elastic moduli

The success of computational materials science models for cement and concrete, at the micrometer-to-millimeter scale, is based on careful characterization of the two main starting materials – cement and aggregates. Concrete is a complex material, and models based on over-simplified chemical, geometrical, and topological assumptions have limits on the behavior they can realistically simulate. In this paper, a sample of Ottawa sand was carefully characterized, since this material is used in laboratories all around North America as the specified sand for many standard tests, including what is possibly the most highly-used ASTM test of all in the field of cement-based materials, C-109, the mortar cube strength test. Particle shape and size distributions were acquired via a combination of X-ray tomography, spherical harmonic analysis, sieve analysis, microscopy and image analysis, and laser diffraction. Quantitative X-ray diffraction showed that the Ottawa sand used was very pure α−quartz with 1% amorphous content. Elastic moduli information at the particle level was obtained via instrumented nanoindentation. Polarized light microscopy showed that the particles that were indented were single crystals. Results for the Young's modulus, E, of Ottawa sand were E = 110 GPa ± 5 GPa (assumed Poisson's ratio of 0.08), in agreement with other nanoindentation results for Ottawa sand in the literature but more than one standard deviation larger than the results obtained from isotropic averages of the elastic moduli tensor of α−quartz, measured by ultrasonic and Brillouin scattering techniques and averaged in various ways. This kind of disagreement has been seen for other minerals as well as α−quartz, and indicates that nanoindentation measurement of elastic moduli for particulate minerals used in cement and concrete and other applications must be used with some care. This characterization procedure can now be confidently employed for any class of sand or gravel particle that is desired to be used in a three-dimensional mortar or concrete model.     

Leaching behaviour of major and trace elements from concrete: Effect of fly ash and GGBS

The leaching of major and trace elements from concrete made with Portland cement, fly ash and GGBS (ground granulated blast-furnace slag) was studied using pH static availability and tank leach tests. The release of substances during the tank leach test occurs by surface dissolution of phases at the concrete surface and diffusion inside the concrete, the amounts depending on the phases controlling solubility and concrete porosity. Alkali release is controlled by diffusion and is thus reduced by lower water/binder ratios and the replacement of Portland cement by fly ash. Ca, Al and S release occurs mainly by surface dissolution of portlandite and AFt/AFm, respectively. The release of V is determined by surface dissolution of V substituted ettringite and/or calcium vanadate. Although fly ash can increase the total V content of concrete, enhancing release, only 2% of the total V content in concrete was available for release.     

铁路20m预应力活性粉末混凝土T形梁预应力传递长度研究

为尝试研究RPC在结构设计及应用方面的情况,通过建立ANSYS有限元模型进行了相关计算,对端块预应力传递长度进行了分析与研究,得出了在特定条件下的预应力传递长度,可为RPC今后在结构领域中的应用与研究提供参考.     

Fatigue Properties of RPC under Cyclic Loads of Single-stage and Multi-level Amplitude

Fatigue properties of Reactive Powder Concrete (RPC) under axial compression of single-stage and multi-level amplitude in cycles were studied. The tests reveal the fatigue life, the strain and residual life of the RPC samples. Through the analysis of the test results under cyclic loads of single amplitude, the S-N curve of RPC and the evolution rule of macro-damage of RPC were presented, which can be divided into latency stage, stable development stage and instability development stage according to the evol...     

Cement content determination through selective stain in hardened concrete

A cement quantification method has been developed in Ø 15 × 30 cm concrete specimens applying selective stain. A tannic acid–tartaric acid solution was used to stain the cement paste.This paper explains the procedure to determine the quantity of cement in the samples: the reagents utilised for the stain, preparation, cutting and stain of the specimens, the capture and treatment of images of the stained samples, and the preparation of the calibration curves.Next, we assess the accuracy of this method and include the resolution of a practical case in which a comparison is drawn between the values obtained through the application of this method and those obtained using a ‘reference’ method.     

泵式混凝土湿喷机液压系统设计

介绍了泵式混凝土湿喷机的液压系统组成、工作原理及设计特点。