Effect of partial replacement of geopolymer binder materials on the fresh and mechanical properties: A review

The growth of demand for concrete raises concerns about the consumption of natural resources and ordinary Portland cement. Geopolymer composites show promise as a sustainable alternative for conventional cement concrete. Considering the wide range of potential geopolymer composites applications (including suitability for transportation infrastructure, underwater applications, repair and rehabilitation of structures as well as recent developments in 3D printing), the desired fresh and mechanical properties of the geopolymer composite may vary between applications: for example, rapid setting can be a merit for certain applications and a demerit for others. Therefore, the desired fresh and mechanical properties (e.g., workability, setting time, compressive strength, etc.) can be controlled for a given geopolymer source material through its partial substitution by natural or by-product materials. Recognizing the critical role of various replacement materials in enhancing the potential applications of geopolymer composites, the present review was undertaken to quantify and understand the effect of partial replacement by fly ash, metakaolin, kaolin, red mud, slag, ordinary Portland cement, and silica fume on the setting time, workability, compressive strength and flexural strength of various source materials addressed in the literature. The review also provides insights into research gaps in the field to promote future research.     

Performance characteristics of concrete based on a ternary calcium sulfoaluminate–anhydrite–fly ash cement

This paper reports an assessment of the performance of concrete based on a calcium sulfoaluminate–anhydrite–fly ash cement combination. Concretes were prepared at three different w/c ratios and the properties were compared to those of Portland cement and blast-furnace cement concretes. The assessment involved determination of mechanical and durability properties. The results suggest that an advantageous synergistic effect between and ettringite and fly ash (Ioannou et al., 2014) was reflected in the concrete’s low water absorption rates, high sulfate resistance, and low chloride diffusion coefficients. However, carbonation depths, considering the dense ettringite-rich microstructure developed, were higher than those observed in Portland cement concretes at a given w/c ratio. It was concluded that the amount of alkali hydroxides present in the pore solution is as important factor as the w/c ratio when performance of this type of concrete is addressed.     

Back-analysis of geotechnical parameters on PVD-improved ground in the Mekong Delta

This study presents a back-analysis of geotechnical parameters on prefabricated vertical drain improved ground at a site in the Mekong Delta. Various time?settlement behaviors that reflected different clay thicknesses and loading patterns were observed. The total surface settlement behavior at several monitoring locations was simulated using an updated exponential method that considered staged construction. The analyzed results were validated by substituting the values into a theoretical solution for radial consolidation. The estimated theoretical behaviors were comparable with the monitored behaviors. The geotechnical parameters were back-analyzed by applying the previously analyzed results to various theoretical and empirical formulas. However, the use of extensometer data that were installed at large intervals produced different values of the geotechnical properties. Furthermore, finite element analysis supported the back-analyzed total settlement behaviors and nearly disregarded the application of the geotechnical properties that were obtained using either surface or subsurface settlement data. However, settlements and excess pore pressures in the sublayers were not successfully predicted even when the geotechnical properties were adjusted. Thus, subsurface instruments that can be installed closely in thick clay deposits are required to reliably reevaluate the variations in geotechnical properties along a certain depth.     

电力变压器动稳定破坏的分析和对策

对大型电力变压器绕组在变压器发生外部短路时所受的辐向力和轴向力进行了分析和计算，比较了国内外不同的计算方法和得出的不同结果。     

大掺量粉煤灰轻质墙体砌块的研制

大掺量粉煤灰轻质墙体砌块是以粉煤灰为主要原材料 ,普通硅酸盐水泥为胶凝材料 ,配以各种外加剂 ,经发泡剂发泡 ,在常温、常压条件下养护而成。具有重量轻、导热系数小、抗冻性高以及粉煤灰掺量大、成型方便、工艺简单、投资小、见效快等优点。     

关于变压器二次额定电压的计算

推导了变压器二次负载电压的计算公式,建议由此公式代替以往原理书中惯用的近似公式。利用此公式绘制和分析了不同功率因数额定负载时的相量轨迹图。     

新型全密封阻爆式油纸电容套管

介绍了一种新型全密封阻爆式油纸电容套管及其性能和特点。     

变压器和电抗器声级测量方法的对比分析

介绍了变压器、电抗器声级测量方法－－声压法和声强法，并对影响测量结果的各种因素进行了对比分析。     

基于LabWindows/CVI的某型飞机FBW飞行试验台设计与实现

主要阐述了某型飞机EBW飞行试验台的LabWindows／CVI实现。在分析EBW组成及信号交联关系的基础上，设计了PCI总线结构的系统硬件；提出了测试库与测试引擎相结合的编程方法，并着重阐述了测试引擎的实现方法。     

变压器的经济运行与节电

基于变压器的节电与变压器的运行有着密切的关系，阐述了实现变压器经济运行的方法与措施。