高强轻骨料混凝土拌合物性能及影响因素试验研究

采用粉煤灰等量取代水泥以及轻质砂代替普通砂,制备了高强轻骨料混凝土.通过试验研究了轻骨料吸水特性,颗粒类型和粒径,砂的细度模数,粉煤灰等级等因素对混凝土拌合物性能的影响,并且利用工业CT分析了骨料内部孔隙.结果表明,页岩陶粒充分预湿以后,轻骨料混凝土具有良好的流动性且经时损失小;圆球型陶粒混凝土相比于碎石型陶粒混凝土的拌合物性能更好,同时,粒径偏大的陶粒容易出现上浮现象.掺入超细粉煤灰的轻骨料混凝土拌合物性能有较大改善,掺入Ⅰ级粉煤灰试样的工作性相差不大,掺入Ⅱ级粉煤灰的试样的工作性有所降低;从拌合物性能优化的角度考虑,细度模数为2.4 ～2.8的砂较适合作为轻骨料混凝土用砂,且用轻质砂代替普通砂可使轻骨料混凝土容重大幅度降低.     

稻草纤维轻骨料混凝土力学性能影响因素研究

为了研究稻草纤维、粉煤灰的工程应用,进行了稻草纤维掺入下轻骨料混凝土力学性能试验研究,探索了同一配合比条件下纤维长度、掺量、形状、粉煤灰掺量、纤维夹层因素对轻骨料混凝土力学性能的影响.结果表明:纤维掺入后,粉煤灰陶粒混凝土抗压、劈裂抗拉强度有所降低,但抗冲击强度有所提高;纤维经NaOH溶液处理后,混凝土抗压、抗冲击强度得到了提高;纤维长度对混凝土强度影响不显著;用水泥质量15％以内的粉煤灰替代水泥,能够获得良好的流动性能和力学性能;纤维夹层位置对强度影响显著,底层抗冲击性能好,中间层抗压、抗拉性能好.基于线性回归分析,得出了植物纤维混凝土强度影响因素中纤维掺量>纤维形状>纤维长度的结论.     

高强轻骨料自密实混凝土的研究开发

高强轻骨料自密实混凝土不但具有良好的轻质、高强、隔热、保温、提高抗震性能,而且还要绿色环保.粉煤灰陶粒质量完好、颗粒圆涩、强度高、容重轻,适合高强高性能混凝土的要求.高强轻骨料自密实混凝土配合比的试验研究为施工应用搭设了桥梁.     

高密实轻骨料粉煤灰混凝土技术研究

依据高密实混凝土配合比设计方法,使用优质粉煤灰、磨细矿渣和普通粘土陶粒,可配制出和易性好、强度符合CL30要求的轻骨料混凝土。试验表明,复合掺加粉煤灰和磨细矿粉能提高轻骨料混凝土的和易性和强度,且此种高密实技术路线适合轻骨料混凝土。     

玻璃瓷粒轻骨料混凝土力学性能试验及配合比优化分析

为探究一种以玻璃瓷粒作为粗骨料的轻质混凝土材料的力学性能,通过正交试验对轻骨料混凝土进行了试验研究,分析了粗骨料类型、胶凝材料用量和水胶比等因素对混凝土力学性能的影响并进行了配合比优化.试验结果表明:玻璃瓷粒轻骨料混凝土的抗压强度和比强度均高于陶粒混凝土.其次,基于优化后的最佳配合比,测定玻璃瓷粒混凝土的坍落度、表观密度,并研究其抗压强度和抗拉强度.研究发现:玻璃瓷粒混凝土密度和力学性能均满足相关规范的要求,且抗压强度为陶粒混凝土的1.4倍.此研究可为玻璃瓷粒轻骨料混凝土的实际推广提供理论依据.     

自密实轻骨料混凝土工作性能和力学性能试验研究

自密实轻骨料混凝土是在自密实混凝土的基础上,用轻骨料代替普通骨料,采用一定混凝土配合比技术配制而成的一种新型高性能混凝土。本试验通过掺加不同量的粉煤灰制备自密实轻骨料混凝土,系统研究了胶凝材料用量及粉煤灰掺量对其工作性能和力学性能的影响。研究结果表明,混凝土坍落度为260mm时,坍落扩展度为650mm,此时的自密实轻骨料混凝土的工作性最好;当粉煤灰掺量为15%时,自密实轻骨料混凝土的后期强度达到最高,相比早期强度增大幅度达183%。     

中低强度高性能轻骨料混凝土试验研究

研究了中低强度高性能轻骨料混凝土的性能.通过正交试验,从水灰比、砂率、粉煤灰掺量、陶粒密度等级等方面分析,优化配比,得出了配制中低强度高性能轻骨料混凝土的各技术参数.     

陶粒混凝土的破坏损伤数值模拟

全轻陶粒混凝土作为一种常见的轻骨料混凝土,具有非常好的工程前景,特别是在高层建筑和装配式结构方面。然而,目前对于陶粒混凝土的研究主要在宏观层次。在细观层次上,将陶粒混凝土视为由陶粒、水泥砂浆、陶粒-水泥砂浆界面过渡区构成的三相复合材料,采用M-T均匀化理论,通过对比试验结果验证模型参数的准确性。同时,建立陶粒混凝土细观二维模型,进一步研究陶粒混凝土的破坏损伤机理及裂缝发展规律。结果表明,通过合理的陶粒混凝土配合比设计,在陶粒等体积取代碎石下配制出可以满足LC35强度等级的陶粒混凝土,且符合规范对于轻骨料混凝土的密度要求。通过对陶粒混凝土二维150 mm×150 mm的构件进行模拟,发现陶粒混凝土的抗压破坏是从界面过渡区开始产生裂缝,随后裂缝贯穿陶粒并进一步扩展直至陶粒混凝土达到极限荷载强度;通过对陶粒混凝土劈裂抗拉的数值模拟,陶粒混凝土的端部裂缝一部分贯穿骨料,一部分沿着骨料与砂浆的界面区域发展。     

冻融作用后塑钢纤维轻骨料混凝土力学性能试验研究

以圆球形粉煤灰陶粒为粗骨料,对塑钢纤维(0kg/m3、3kg/m3、6kg/m3、9kg/m3)轻骨料混凝土试件进行快速冻融(0次、50次、100次、150次)试验,研究冻融后试件的抗压性能、劈裂抗拉性能、抗折性能、抗冲击性能.结果表明:冻融循环作用下,适量的塑钢纤维掺入可以明显增强轻骨料混凝土的劈裂抗拉强度和抗折强度;提高轻骨料混凝土折压比,增强轻骨料混凝土抗裂性能;并能显著改善轻骨料混凝土的抗冲击性能.综合各项力学性能指标,冻融后轻骨料混凝土塑钢纤维最优掺量为6kg/m3.     

高强轻集料混凝土力学性能试验研究

本文采用页岩陶粒，掺入粉煤灰和高效减水剂配制高强轻集科混凝土，试验研究水胶比、砂率和粉煤灰取代率对轻集科混凝土力学性能和表观密度的影响，并得出了一个合理的轻集料混凝土配合比。结果表明：轻集料混凝土强度与水胶比成反比；而对于砂率和粉煤灰取代率，存在一个最优的砂率和粉煤灰取代率。     

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。