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Effect of Fly-ash and Silica Fume on the Properties of Concrete Exposed to High Temperature 粉煤灰和硅灰对高温混凝土性能的影响
Pub Date : 2008-01-01 DOI: 10.21608/absb.2007.11107
M. Taher
The development of high temperatures in concrete could cause a number of effects that have been shown to be determining to long-term concrete performance. High temperatures in concrete increase the rate of hydration, thermal stresses, the tendency for drying shrinkage cracking, permeability, and decrease of long-term concrete strengths and durability as a result of cracking. The objective of this study is to investigate the effects of using fly-ash and silica fume on the strength and absorption of cement concrete and pozzolanic cement concrete in hot condition. The cement concrete and pozzolanic cement concrete specimens containing fly-ash or silica fume were first cured in water for a periods of 1, 3, 7, 28, 90 and 180 days then exposed to high temperature 45°C ( maximum summer temperature in Egypt and Arabian Gulf countries) in oven for 2,8,12 and 24 hours. The effect of fly-ash and silica fume contents on the absorption capacity of concrete specimens was evaluated by measuring 48-hours absorption and volume of permeable voids. The specimens were also tested for compressive strength and moisture content. The results show an increase in the compressive strength of cement concrete and pozzolanic cement concrete with increasing both curing and exposing temperature time. The absorption of theses concretes decreased with time of curing and increased with exposing temperature time The absorption of both fly-ash and silica fume cement concrete specimens decreased significantly at early stages (3-7days) of curing. While the absorption of cement concrete specimens were effected significantly by exposing temperature period, no significant change in the absorption of pozzolanic cement concretes due to increasing exposing temperature period was observed, especially after 7 days of curing. The volume of permeable voids also decreased with curing. The highest reduction in the absorption and volume of voids was observed in the fly-ash concrete specimens.
高温在混凝土中的发展可能会导致许多影响,这些影响已被证明是决定混凝土长期性能的因素。混凝土中的高温增加了水化速率、热应力、干燥收缩开裂的趋势、渗透性,并由于开裂而降低了混凝土的长期强度和耐久性。本研究的目的是探讨粉煤灰和硅灰在高温条件下对水泥混凝土和火山灰水泥混凝土强度和吸收率的影响。首先将含有粉煤灰或硅灰的水泥混凝土和火山灰水泥混凝土试件在水中固化1、3、7、28、90和180天,然后在烤箱中暴露于45°C(埃及和阿拉伯海湾国家夏季最高温度)的高温下2、8、12和24小时。通过测定48小时吸收量和渗透孔洞体积,评价粉煤灰和硅灰掺量对混凝土试样吸附能力的影响。试样还进行了抗压强度和含水率测试。结果表明:水泥混凝土和火山灰水泥混凝土的抗压强度随养护温度和暴露时间的增加而增加;混凝土的吸收量随养护时间的延长而减小,随暴露温度的延长而增大。粉煤灰和硅灰水泥混凝土试样的吸收量在养护初期(3 ~ 7d)均显著降低。暴露温度期对水泥混凝土试样的吸收有显著影响,而火山灰水泥混凝土的吸收不受暴露温度期的影响,特别是养护7天后。可渗透空隙的体积也随着固化而减小。粉煤灰混凝土试样的吸收量和空隙体积减小幅度最大。
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引用次数: 0
In-situ carbon content adjustment in polymer-derived Si/C/N ceramics by reactive heat treatment. Calculations of the pyrolysis product composition 反应热处理原位调整聚合物基Si/C/N陶瓷中的碳含量。热解产物组成计算
Pub Date : 1999-01-01 DOI: 10.1016/s0140-6701(01)80600-7
D. Galusek, S. Reschke, R. Riedel
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引用次数: 1
Effect of Calcining Temperature of Kaolinite Clay on the Properties of Portland Cement Pastes Containing Metakaolin 高岭土煅烧温度对偏高岭土硅酸盐水泥体性能的影响
Pub Date : 1900-01-01 DOI: 10.21608/absb.2007.11149
M. Taher, A. Y. El-Sayed, O. A. Farghaly, M. Shatat
Metakaolin (MK) is a highly reactive pozzolan produced by calcination of kaolinite clay at high temperature. It has a high specific surface, which makes it very suitable as a cementing material in concrete. The utilization of calcined clay, in the form of MK, as a pozzolanic material for mortar and concrete has received considerable attention in recent years. This interest is part of the widely spread attention directed towards the utilization of wastes and industrial by-products in order to minimize Portland cement (PC) consumption, the manufacture of which being environmentally damaging. Another reason is that mortar and concrete, which contain pozzolanic materials, exhibit considerable enhancement in durability properties. In this investigation, the physicochemical properties of artificial pozzolanic cement pastes containing MK produced by calcination of kaolinite clay at different temperatures (700, 800, 900, and 1000°C) were studied. PC was partially substituted for by 0, 5,10,15 and 20 % ofMK by weight at different calcining temperatures. The characteristics of prepared mortars were investigated after curing in water for different periods (3, 7, 28 and 90 days) by determination of compressive strength and total porosity. The hydration kinetics was evaluated by determination of free lime contents. IR spectroscopic analysis was used to investigate the change in structure of mortars after curing. The change in morphology and microstructure of some hardened pastes were investigated by scanning electron microscopy (SEM) tests.
偏高岭土是由高岭土在高温下煅烧而成的高岭土。它具有很高的比表面,这使得它非常适合作为混凝土中的胶结材料。近年来,将煅烧粘土以MK的形式作为火山灰材料用于砂浆和混凝土的研究受到了广泛的关注。这种兴趣是对废物和工业副产品的利用的广泛关注的一部分,以便尽量减少波特兰水泥的消耗,这种水泥的生产对环境有害。另一个原因是砂浆和混凝土中含有火山灰材料,在耐久性方面表现出相当大的增强。在本研究中,研究了高岭石粘土在不同温度(700、800、900和1000℃)下煅烧制备的含MK的人工火山灰水泥浆体的物理化学性质。在不同的煅烧温度下,分别用0、5、10、15和20%的mk代替部分PC。通过测定砂浆的抗压强度和总孔隙率,研究了砂浆在水中养护3、7、28和90 d后的特性。通过测定游离石灰含量来评价水化动力学。采用红外光谱分析研究了砂浆养护后的结构变化。采用扫描电镜(SEM)研究了硬化膏体的形貌和显微结构变化。
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引用次数: 2
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Silicates Industriels
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