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矿物掺合料对混凝土氯离子结合能力的影响(英文) 总被引:4,自引:0,他引:4
用自然扩散法测定了混凝土中的总氯离子和自由氯离子浓度,计算了普通混凝土、粉煤灰混凝土和矿渣混凝土的氯结合能力,研究了矿物掺合料的掺量、暴露时间、养护龄期对混凝土氯结合能力的影响.结果表明:随着矿物掺合料掺量的增大,粉煤灰混凝土氯离子结合能力的变化趋势是先上升后下降,矿渣混凝土的氯离子结合能力则急剧增强;混凝土的氯离子结合能力与暴露的氯盐溶液种类有关,而与暴露时间无关,并且随着混凝土的标准养护龄期的延长而不断增强.因此,对于实际氯盐环境中的混凝土结构,建议采用最佳掺量25%的粉煤灰混凝土或者高掺量矿渣混凝土,同时加强潮湿养护,有利于提高混凝土结构的服役寿命. 相似文献
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针对城市地下环境下氯盐和硫酸盐对超高性能混凝土共同侵蚀下SO42-和Cl-的扩散规律和侵蚀机理,配置侵蚀溶液在完全浸泡和喷雾循环条件下进行模拟试验研究,测定了离子浓度、孔径尺寸等数据,并对微观形貌进行分析。研究结果表明:完全浸泡与喷雾环境下,UHPC中氯离子、硫酸根离子含量扩散规律符合Fick第二扩散定律;90d完全浸泡条件下30%硅灰掺量UHPC中氯离子、硫酸根离子平均含量比普通混凝土低46.5%、37.2%,喷雾循环90次条件下30%硅灰掺量UHPC中氯离子、硫酸根离子平均含量比普通混凝土低37.2%、44.0%;含30%硅灰掺量UHPC的氯离子、硫酸根含量远低于掺量20%、10%硅灰掺量的UHPC。 相似文献
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通过再生混凝土在3.5%NaCl、3.5%Na2SO4、3.5%NaCl+3.5%Na2SO4和水四种溶液中的冻融循环试验,分析再生混凝土在同浓度不同种类盐碱溶液中经过不同冻融次数后(N)的质量变化(△m)和动弹性模量变化(△E) ,绘制N-△m和N-△E的曲线.同时,设置单掺10%、20%粉煤灰和2%、4%硅灰为对照组,研究粉煤灰和硅灰组分别在3.5%NaCl和3.5%Na2SO4环境下混凝土的抗冻性能规律.结果表明:氯盐环境中,随冻融次数的增加,混凝土表面剥削、开裂现象明显,质量和动弹性模量损失严重,而硫酸盐环境中,冻融前期混凝土内部生成水化产物使质量增加,表面膨胀开裂,后期质量和动弹性模量急剧下降,与浓度3.5%氯盐盐冻相比,硫酸盐盐冻动弹性模量损失更大.冻融破坏强度由强到弱排序为氯盐冻、硫酸盐冻、复合盐冻、水冻;掺入粉煤灰后,氯盐环境下的混凝土抗冻性反而下降,10%掺量优于20%掺量.掺入硅灰后,硫酸盐环境下再生混凝土抗冻性提高,破坏程度要比水冻小,4%掺量优于2%掺量;最后分析了混凝土腐蚀机理. 相似文献
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我国西部地区盐湖分布广泛,土壤及地下水中含有高浓度硫酸盐、镁盐及氯盐,与衬砌喷射混凝土发生一系列物理化学反应,造成喷射混凝土单层永久衬砌结构耐久性能下降.为系统研究盐湖卤水侵蚀喷射混凝土耐久性能退化规律,以5%Na2 SO4+5%MgSO4+3.5%NaCl混合溶液为侵蚀介质,采用干湿交替法,分别模拟盐湖卤水及隧道衬砌侵蚀方式,开展喷射混凝土耐久性试验.通过测试混凝土相对动弹性模量、质量变化率、相对抗压强度、损伤层厚度及混凝土中离子含量,研究卤水侵蚀喷射混凝土耐久性能退化规律.结果表明,高水胶比、未掺粉煤灰及高粉煤灰掺量喷射混凝土和模筑混凝土物理力学性能退化速度快,损伤层厚度快速增大,钢纤维可显著提升喷射混凝土抗侵蚀性能.随着侵蚀的进行,混凝土中水溶性钙离子及混凝土pH值下降,水溶性钠离子和氯离子含量增大,酸溶性硫酸根离子含量快速增大.混凝土表面水化产物含量降低,密实度下降,损伤层厚度增大,物理力学性能退化. 相似文献
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矿物掺合料对混凝土中氯离子渗透性的影响 总被引:16,自引:1,他引:15
采用可蒸发水含量法、氯离子渗透快速实验法,研究了粉煤灰、硅灰、粉煤灰与硅灰复合掺入及不同龄期等条件制备的混凝土的孔结构、结合氯离子性能及渗透性的变化规律,探讨了掺粉煤灰、硅灰混凝土的孔结构、结合氯离子性能对其氯离子渗透性的影响.结果表明:粉煤灰、硅灰对混凝土的孔结构、结合氯离子性能及氯离子渗透性均存在不同程度的影响.对于掺粉煤灰、硅灰的混凝土,在胶凝材料水化前期,主要是混凝土的孔结构变化引起其6h库仑电量下降;而在胶凝材料水化中后期,主要是混凝土孔结构变化与混凝土对氯离子的结合共同作用导致其6h库仑电量降低.混凝土的孔结构改善及其对氯离子的结合是导致混凝土中氯离子渗透性降低的重要原因. 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively.
There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized.
High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without
the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of
fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to
achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic
SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve
F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender
particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing,
and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing
or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually
preserves suspension stability during freezing.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago,
IL. Tied for first place in The John A. Gordon Best Paper Competition. 相似文献
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Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US
In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae
and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted
in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures
(release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species
(Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species
to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were
exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of
separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles
from the southeastern region of the US. 相似文献
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Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed. 相似文献
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中蓝晨光化工研究院有限公司《塑料工业》编辑部 《塑料工业》2009,37(3)
收集了2007年7月~2008年6月世界塑料工业的相关资料,介绍了2007~2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍. 相似文献
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中蓝晨光化工研究院《塑料工业》编辑部 《塑料工业》2007,35(3):1-25,67
收集了2005年7月~2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、通用热固性树脂(酚醛、聚氨酯、不饱和树脂、环氧树脂)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。 相似文献