保护层厚度对混凝土中钢筋锈蚀的影响

混凝土中的钢筋锈蚀破坏是混凝土结构失效破坏的最主要原因.通过电化学测定,研究了保护层厚度对钢筋锈蚀的影响,研究表明:增大混凝土保护层厚度能有效延缓混凝土中钢筋的锈蚀,延长钢筋开始锈蚀的时间,保护层厚度越大,越能延长钢筋开始锈蚀的时间;进入钢筋开始锈蚀阶段后,保护层比较厚的混凝土中钢筋锈蚀速率增长的较慢;在稳定锈蚀阶段,保护层厚度越大.稳定腐蚀电流密度就越小,保护层厚度和稳定腐蚀电流密度存在一定的函数关系,且数据相关性良好.     

混凝土碳化的影响因素及其控制措施的探讨

混凝土的碳化是指混凝土中原呈碱性的氢氧化钙在大气中受到二氧化碳和水分的作用逐渐变成呈中性的碳酸钙的过程。经过碳化的混凝土，表面强度、密度能有所提高，但由于碳化一般均在结构表面，深度不大，故对整体结构强度影响不大。混凝土碳化后会产生体积收缩，当收缩应力超过混凝土表面抗拉强度时，会在表面产生裂缝。潮湿空气进入裂缝使裂缝处的混凝土碳化收缩，继而使裂缝向混凝土内部发展。当裂缝穿透混凝土保护层到达钢筋时，混凝土失去对钢筋的保护作用，钢筋开始生锈。钢筋锈蚀后，锈蚀产生的体积开始膨胀，从而对周围的混凝土产生膨胀应力，锈蚀越严重，铁锈越多，膨胀力越大，最后导致混凝土开裂形成顺筋裂缝，最终有可能影响结构安全。     

浅谈水工隧洞混凝土钢筋锈蚀的预防与处理

在水工隧洞中相对湿度较大，导致钢筋出现锈蚀的时间提前以及锈蚀程度加重，钢筋锈蚀对结构的耐久性影响极大，会引起工程和建筑物的安全稳定问题。结合某输水隧道工程，分析隧道工程钢筋锈蚀的主要原因，并提出了通过调节保护层厚度、降低混凝土水灰比、掺加引气减水剂等措施预防隧洞混凝土钢筋锈蚀，同时提出锈蚀后应采取的处治措施，以保证结构的耐久性。     

芜湖长江大桥泵送粉煤灰混凝土耐久性研究

本文研究了粉煤灰对混凝土抗碳化性能、抗冻融性能及其对钢筋锈蚀的影响。研究结果表明:掺粉煤灰混凝土的碳化深度略大于不掺粉煤灰的同龄期混凝土,但其抗冻性能优良,并对钢筋无锈蚀危害。     

钢筋混凝土构件耐久性的初步探讨

针对钢筋混凝土构件出现的钢筋锈蚀、保护层脱落、混凝土碳化、构件出现裂纹进行数据检测,从而为治理病害提供依据,防止事故发生,提高混凝土结构及构件的耐久性。     

弯曲应力作用下不同钢筋种类和保护层厚度珊瑚混凝土的钢筋锈蚀研究

通过自制设备对珊瑚混凝土构件进行弯曲应力加载试验，研究弯曲应力对珊瑚混凝土中不同保护层厚度下不同种类钢筋锈蚀的影响程度。通过ABAQUS有限元分析软件模拟钢筋珊瑚混凝土构件模型在弯曲应力作用下的应力大小和受力状态，并采用极化曲线、电化学阻抗谱分析对比分析不同种类钢筋在弯曲应力作用下的锈蚀情况。结果表明：自制设备可以较好地模拟弯曲应力和海洋环境耦合作用下的钢筋锈蚀情况；钢筋的耐腐蚀性能会随着弯曲应力的增大而降低；在一定保护层厚度范围(0～30 mm),增大弯曲应力对钢筋锈蚀的影响显著，但当保护层增大到一定程度(50 mm)时，增大弯曲应力对钢筋锈蚀的影响逐渐变小；弯曲应力对钢筋的影响程度由强到弱依次为HPB400钢筋、镀锌钢筋、304不锈钢钢筋。     

芜湖长江大桥泵送煤灰混凝土耐久性研究

本文研究了粉煤灰对混凝土抗碳化性能，抗冻融性能及其对钢筋锈蚀的影响。研究结果表明：掺粉煤灰混凝土的碳化深度略大于不掺粉煤灰的同龄期混凝土，但其抗冻性能优良，并对钢筋无锈蚀危害。     

粉煤灰混凝土钢筋锈蚀影响因素研究

通过实验室加速钢筋锈蚀的方法,运用半电池电位法,研究了水胶比、粉煤灰掺量、保护层厚度和阳离子类型对混凝土钢筋锈蚀的影响。结果表明,减小水胶比,增加粉煤灰掺量(0-40%),增大保护层厚度,均可以有效提高钢筋抗锈蚀能力,但当粉煤灰掺量大于40%时,钢筋抗锈蚀能力则变差;阳离子类型对钢筋锈蚀有显著的影响,与Na Cl相比,Ca Cl2明显加快了混凝土内钢筋的锈蚀。     

混凝土保护层厚度检测工作探讨

混凝土保护层厚度是制约桥梁使用寿命的一个关键因素,良好的保护层控制既可以有效防止钢筋外露而造成钢筋的锈蚀,又可以确保结构受力达到设计的意图,真正发挥钢筋混凝土构件的作用。在公路桥梁施工检测中,随着电子科技的高速发展,检测手段不断提高并且越来越准确,特别是混凝土保护层的检测,是每个施工项目必检的一项。     

电镀车间砼结构腐蚀机理及加固

针对石家庄市某厂房电镀车间鉴定中混凝土结构钢筋锈蚀状况及其损坏特征，分析其腐蚀机理，即当混凝土保护层被完全碳化，其pH值降至约9．5时，钝化膜就会遭到破坏，在有氧和水的作用下．钢筋就会锈蚀。提出了防治对策，同时对侵蚀后的加固处理方案进行探讨。     

Insect antifeedant properties of anthranoids from the genusVismia

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.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

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.     

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.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

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.     

2007～2008年世界塑料工业进展

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.     

2005～2006年国外塑料工业进展

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。