Lightweight screed containing cork granules: Mechanical and hygrothermal characterization

This paper presents the results of an experimental study on the use of expanded cork granule waste with cement-based mixtures to produce lightweight screeds as an overlay of a structural concrete slab. Lightweight screeds (LWSs) were made with Portland cement, sand, expanded cork granules (ECG) and water. These cork particles are industrial waste and are still a completely natural material even after industrial processing. The experiments were carried out on 3 cement dosages of 150 kg/m³, 250 kg/m³ and 400 kg/m³, incorporating expanded cork granules as replacement of part of the sand. Three additional mixtures without cork were prepared and used as reference. They had the same cement content as the lightweight ones. Hardened density, compressive strength, thermal conductivity, water vapor permeability, adsorption isotherms and water absorption by partial immersion of the mixtures were determined. Results show that the addition of expanded cork granules affects the screeds by decreasing their density, compressive strength and thermal conductivity while increasing their water vapor permeability.     

铁尾矿制备轻质隔热保温建筑材料的研究

介绍了新型轻质隔热保温材料的制备工艺,以铁尾矿、废旧聚苯乙烯泡沫为主要原料,普通硅酸盐水泥为胶凝剂,制备轻质隔热保温材料.试验研究表明,当铁尾矿/(水泥 铁尾矿)取40%、泡沫/(水泥 铁尾矿)取4%、水/水泥取0.48时,所制备的试块7 d抗压强度可达0.94 MPa,28 d抗压强度可达1.05 MPa,而干燥容重仅740.6 kg/m3,导热系数仅0.109 W/(m·K),为综合利用尾矿和废弃泡沫提供了一条新的技术途径.     

基于容器的Web运行环境轻量级虚拟化方法

Web运行环境、Web服务及Web应用的虚拟化是减轻Web操作系统安全风险的一种有效方法,然而Web运行环境的虚拟化仍然存在不少挑战,如：执行时间、资源负载和兼容性等。为解决Web操作系统在安全性、执行时间、资源负载和兼容性方面的问题,提出了一种Web运行环境轻量级虚拟化方法,采用Docker容器技术实现进程级别的隔离。本虚拟化方法可在一个基本内核上支持运行多种Web运行环境的容器。此外,为了减轻容器创建负载,提出了容器启动机制;为减轻系统资源负载,进行了系统的轻量化处理。在嵌入式设备的实验结果表明,该虚拟化方法在执行时间、资源负载及兼容性方面都具有较优表现。     

养护温度对高强轻集料混凝土强度和抗渗性的影响

研究了高强轻集料混凝土在高温养护条件下强度和抗渗性变化情况。Cl^-抗渗性采用电场加速方法;水抗渗性采用表面吸水法测试。结果表明,湿集料混凝土在50℃后强度就急速下降,而干集料混凝土85℃养护时温度下降不明显。混凝土Cl^-抗渗性和电阻随养护温度的提高而降低,且干集料混凝土的Cl^-抗渗性和电阻比湿集料混凝土要高得多。养护温度对水的渗透性无显著影响,但湿集料混凝土的吸水量要比干集料混凝土高出20％左右。干集料混凝土抗渗性好的原因是由于干集料的吸水作用使得混凝土过渡层变得致密所致。     

Alkali-silica reactivity of some frequently used lightweight aggregates

Lightweight aggregates (LWAs) are frequently used in concrete as well as in thermally insulating mortars and grouts, so that information on their alkali-silica reactivity (ASR) is very important. Four LWAs—expanded vermiculite, expanded clay, expanded glass and perlite—were studied regarding their ASR, using the following test methods: the accelerated mortar bar test (ASTM C 1260), the rapid chemical test (ASTM C 289) and the combined scanning electron microscopy-energy dispersive X-ray technique (SEM-EDX). According to these methods, neither the expanded vermiculite nor the expanded clay exhibited any potential ASR. On the other hand, in the case of the aggregates containing a glassy phase (expanded glass and perlite), the results of SEM-EDX analysis showed serious decomposition of aggregate texture due to ASR, although no deleterious expansion was observed in the accelerated mortar bar test. Therefore, suitable test criteria for ASR need to be defined for LWAs of this type when the AMBT method is used, as has already been suggested for slowly reactive aggregates in Australia.     

火工装置轻量化小型化研究

为满足航天器轻量化对火工装置的需求,对火工装置轻量化小型化开展研究,重点探讨火工装置轻量化小型化原则、轻量化小型化途径以及实施轻量化小型化研制工作的基本流程。以某切割器为例,开展轻量化小型化研制,并进行极限功能裕度和极限强度裕度试验。结果表明,优化后的切割器重量和体积均减小50%,并且满足功能要求。     

Determination of transient two-dimensional heat transfer in ventilated lightweight low sloped roof using Fourier series

In this paper, the analysis of transient two-dimensional (2D) heat transfer in low sloped roof with forced ventilated cavity made from lightweight building elements (LBE) is presented. For the heat transfer analysis the 2D numerical model, which was verified with experiments, was used. Forced ventilated cavity was configured in two different ways. In the first case the cavity was configured with coloured thin metal sheet and in the second case with thin metal sheet with added layer of thermal insulation and radiation barrier. Beside the influence of the ventilated cavity configuration on the transient 2D heat transfer in the LBE and on the cavity outlet air temperature also the influence of the LBE thickness, specific air flow rate through the cavity, inner air temperature and wind velocity was analysed. Multi-parametric equations for determination of Fourier series coefficients were formed. These coefficients were used for evaluation of transient 2D heat transfer on the inner side of the roof and cavity outlet air temperature for a clear day.     

Influence of steel fibres on strength and ductility of normal and lightweight high strength concrete

This paper presents the results of a series of experiments conducted to investigate the effectiveness of fibre inclusion in the improvement of mechanical performance of concrete with regard to concrete type and specimen size. Lightweight aggregate concrete and limestone aggregate concrete with and without steel fibres were used in the study. The compressive strength of the concrete mixes varied between 90 and 115 MPa and the fibre content was 1% by volume. Splitting tests on prisms and three-point bending test on notched beams were carried out on specimens of varying sizes to examine the size effect on splitting strength, flexural strength and toughness.

The experimental findings indicate that the low volume of fibre has little effect on compressive strength but improve remarkably splitting tensile strength, flexural strength and toughness. The increase in splitting tensile strength, flexural strength and toughness index for lightweight concrete seems much higher than that of normal aggregate concrete.

The size effect on prism splitting tensile strength is not significant beyond a critical (transition) size. There are apparent size effects on flexural strength and toughness index. As the specimen size increases, splitting and flexural strengths appear to decrease, and fracture behaviour tends to be more brittle.