新型抑温抗裂防水剂效果测试及其在抽水蓄能电站隧洞工程中的应用

温度变化引起的混凝土开裂是大体积混凝土施工质量控制的难点,而在抽水蓄能电站中对于混凝土开裂有着严格要求。将掺量2.5%的JX-IIIWD新型抑温抗裂防水剂配入混凝土与空白对照组进行对比试验,测试混凝土凝结时间、抗压强度、半绝热温升、抗渗性能及早期抗裂性能。结果表明,使用JX-IIIWD新型抑温抗裂防水剂可显著降低混凝土半绝热温升、提高混凝土抗裂及抗渗性能,且凝结时间和抗压强度均能满足现场施工需求;抽水蓄能电站隧洞中应用实践也证明了其效果。     

水化热调控剂与氧化镁复掺对混凝土抗裂行为的影响

为了研究氧化镁膨胀剂与水化热调控剂复掺对混凝土抗裂性能的影响,探讨水化热调控剂的作用机理,开展了单掺氧化镁及水化热调控剂与氧化镁复掺对混凝土水化热、绝热温升、限制膨胀率、体积变形、自收缩、弹性模量及微观结构的影响研究。结果表明:水化热调控剂可显著改变水泥水化放热历程,净浆抑温率可达31.2%,随入模温度升高,抑温效果增强;水化热调控剂可激发氧化镁的水化,促进膨胀能的释放,随养护温度提升,作用效果更显著;水化热调控剂可改变混凝土温升历程,特别是降低混凝土早期水化热释放速率;水化热调控剂与氧化镁复掺可降低混凝土自收缩,当水化热调控剂掺量为0.2%和0.4%(质量分数)时,混凝土收缩值分别减少了84 με和54 με;水化热调控剂会导致混凝土早龄期弹性模量降低,但对长龄期弹性模量影响不大;水化热调控剂对水泥水化历程、水化产物生成及微观结构密实程度的改变是提高混凝土抗裂性能的根本原因。     

地铁超长侧墙结构混凝土裂缝控制及工程应用

地铁停车场地下侧墙属超长大体积混凝土结构,混凝土施工时具有水化温升高、温降速率大等特点,且受底板和已浇筑侧墙的复杂约束作用,混凝土在降温过程中极易出现早期开裂现象。通过掺入抗裂剂配制具有低水化放热和补偿收缩的侧墙高性能抗裂C35混凝土,以绝热温升和自身体积形变表征混凝土抗裂性能,结果显示:掺入抗裂剂后胶凝材料水化集中放热大幅度缓解,混凝土绝热温升及其早期温升速率明显降低,且混凝土膨胀率增加,自收缩得到有效补偿;应用于地铁超长侧墙结构的混凝土中心温峰为55.8℃,最大温升为23.3℃,侧墙中心厚度方向最大膨胀变形为256×10-6,且拆模后无明显裂缝,为同类超长混凝土结构工程裂缝控制提供参考。     

基于温度-应力试验的粉煤灰混凝土抗裂性能

在混凝土中掺加粉煤灰是抑制大体积混凝土早期开裂的有效措施之一。以水胶比0.42,掺量分别为40%和50%的粉煤灰混凝土(FA40、FA50)为研究对象,利用温度-应力试验机,在绝热温升模式和100%约束度条件下研究粉煤灰混凝土的温升、约束应力、应变和徐变性能,并综合评价了两种混凝土的早期抗裂性能。结果发现:升温阶段,FA50的早期温度、应变和应力发展均高于FA40;在恒温阶段,2种混凝土均发生了明显的应力松弛;在降温阶段,试件处于拉伸应力作用下时,FA40的徐变高于FA50。基于试验结果对两种混凝土早期抗裂性能的综合评价表明:FA40早期抗裂性能优于FA50。     

抗裂防水剂对硅酸盐水泥的收缩变形及水化特征影响的研究

研究了掺入抗裂防水剂的硅酸盐水泥砂浆早期变形性能以及水化温升特征.试验选择用水灰比为0.35、0.40、0.45,抗裂防水剂掺量为6％、10％、14％.用膨胀收缩仪,测试在不同的养护条件下试件收缩变形;利用智能多点测温仪,测试硅酸盐水泥砂浆的水化升温特征.结果表明:除0.35水灰比,抗裂防水剂为14％的硅酸盐水泥砂浆以外,其余组硅酸盐水泥砂浆,14 d的膨胀值均达到最大值,14 d以后均产生收缩.0.4水灰比的胶砂,经过60℃、70℃、80℃等成熟度养护再转常温养护后,表现为先膨胀后收缩,且膨胀值随抗裂防水剂掺量的增加而增大.当抗裂防水剂掺量为6％时,硅酸盐水泥砂浆的早期水化温升变化相差不大,抗裂防水剂掺量为10％、14％时,硅酸盐水泥砂浆的早期水化温升差别较大.     

高性能阻裂抗渗外加剂的研制及其对混凝土性能影响的研究

采用将无机增强阻裂材料WJ和有机减水保塑憎水阻孔外加剂YJ进行分别研制并优化复合的技术路线研制了高性能阻裂抗渗外加剂KLFS.实验结果表明:以生明矾、硫铝酸盐水泥熟料、天然二水石膏和无机物质A作为主要成分的无机增强阻裂材料,膨胀性能稳定,膨胀率落差小,90d龄期仍有1.88×10-4的膨胀率,并有一定的增强作用;对高效减水剂引入憎水阻孔组分、保水组分进行改性研制成的有机减水保塑憎水阻孔外加剂YJ,可提高混凝土工作性,严格控制坍落度损失,并长期阻孔,同时降低混凝土早期水化温升,有效防止早期温度收缩裂缝的出现.混凝土中掺入KLFS后,2h后坍落度20cm,90d抗压强度比为128%,膨胀规律好,90d仍有1.12×10-4的限制膨胀率, 28d劈裂强度由基准混凝土的2.81MPa提高到3.28 MPa,碱含量低,无钢筋锈蚀,耐久性好.     

低热硅酸盐水泥应用于高寒地区混凝土坝的性能研究

为了改善高寒地区混凝土坝体内部因水化热引起的坝体开裂问题,以低热水泥为研究对象,对几种不同水泥的水化放热、绝热温升、胶砂力学性能、混凝土抗裂性能等进行了对比研究.结果表明:低热水泥可有效降低混凝土的水化放热,减小绝热温升,控制早期温度裂缝;C2 S反应较慢,使得低热水泥的早期力学强度远低于中热水泥,但C2 S较C3 S...     

粉煤灰品质及掺量对混凝土性能影响试验研究

粉煤灰能改善混凝土内部微观结构,对混凝土力学、热工及早期抗裂性能产生影响,本文通过改变粉煤灰的品质及掺量,Ⅰ级、Ⅱ级粉煤灰掺量分别设置0、10％、20％、30％、40％梯度试验组,对不同品质及掺量的粉煤灰型混凝土进行力学强度试验、平板热流计试验及早期抗裂试验,探究混凝土的抗压强度、保温蓄热性能及早期抗裂性能变化规律.结...     

KLJ型抗裂防渗复合材料对混凝土性能影响研究

本文阐述了KLJ型防裂抗渗复合材料对混凝土拌合物性能、力学、变形、早期抗裂及耐久性的影响规律,分析了复合材料对混凝土性能的影响机理。结果表明：KLJ型防裂抗渗复合材料能改善混凝土的各项性能,尤其混凝土力学性能显著提高,1 kg/m³掺量对混凝土性能改善效果最佳;掺量1 kg/m³,混凝土的干缩收缩率28 d、96 d分别降低42%、29%,早期开裂减少82%,平均渗水高度降低58%,碳化深度减少29%;KLJ型防裂抗渗复合材料中的粉体可以均匀填充混凝土内部孔隙,纤维能够阻止裂缝进一步扩大,进而改善混凝土各项性能。     

氧化镁膨胀剂对混凝土长期体积变化的影响

观察了外掺不同活性、不同剂量氧化镁膨胀剂混凝土的限制膨胀率曲线,并结合混凝土强度发展和绝热温升特性,补偿收缩胶砂试件的限制及自由膨胀率,分析了不同活性氧化镁膨胀剂的补偿收缩特性。结果表明:适量掺加氧化镁膨胀剂对于补偿收缩混凝土的强度发展基本没有影响,但导致混凝土的温升值较大,温升开始时间延迟。在氧化镁膨胀剂的常用掺量为6%~8%时,导致混凝土的绝热温升增加值约为3~4℃。氧化镁膨胀剂的活性越低,用其制备的补偿收缩混凝土的早期膨胀率越小,但最终膨胀量越大,膨胀稳定期出现越晚,采用"S"型膨胀剂时直到140 d膨胀仍未停止,因而容易造成混凝土结构的后期安定性不良。实际应用时应尽量选用高活性、大掺量的氧化镁膨胀剂,掺量宜控制在6%~8%。     

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。