低碱度水泥浆体中钙矾石通过液相形成的证据

前言钙矾石是硬化水泥浆体的重要组分之一,它对水泥石的结构和性能有重要影响。从钙矾石为基础的膨胀和自应力水泥、超硫酸盐水泥、硫铝酸盐早强水泥和低碱度水泥等都有相当数量的钙矾石,并且以它作为早强组分的新品种水泥正在不断增多。钙矾石的形成不仅是上述几种水泥水化中的一个重要反应,而且也是硅酸盐水泥早期水化和含硫酸盐的环境水与硬化浆体之间的一个重要反应。如水泥浆体的缓凝,膨胀水泥混凝土中自应力的发展以及混凝土的硫酸盐侵蚀等,都与钙矾石的形成有关。     

防腐阻锈剂对混凝土性能影响试验研究

将防腐阻锈剂按照不同比例等量取代普硅水泥配制混凝土,研究其对混凝土抗压强度、抗硫酸盐侵蚀系数、氯离子渗透系数、腐蚀电量等性能指标的影响,并通过SEM扫描电镜观察混凝土3 d、7 d、28 d的水泥水化产物形貌.研究结果表明:掺入防腐阻锈剂后,混凝土的工作性能、后期力学性能、抗硫酸盐侵蚀性能、氯离子渗透性能、抗氯盐侵蚀性能明显优于基准混凝土;防腐阻锈剂的掺入消耗了水泥中的C3A、水泥水化产生的Ca(OH)2,生成钙矾石和C-S-H凝胶,产生微膨胀效应使混凝土结构更加致密,提高了抗硫酸盐、氯盐侵蚀性能.     

利用FT-IR研究硫酸盐侵蚀后混凝土表层的胀裂

为了研究由硫酸盐侵蚀而导致的混凝土里表不同部位侵蚀的变化特征,利用傅里叶变换红外光谱定性地研究了在10％硫酸钠溶液中浸泡4年的混凝土试件内部的侵蚀产物分布规律.研究表明:在该类侵蚀介质的作用下,混凝土内主要侵蚀产物为石膏和钙矾石;在界面过渡区和水泥石基体中,石膏的含量沿着混凝士厚度方向减少,钙矾石增加;在同一厚度下,界面过渡区中钙矾石和氢氧化钙的含量高于水泥石基体中钙矾石和氢氧化钙的含量.     

合成条件对钙矾石形貌的影响

钙矾石是硫铝酸盐水泥水化的主要产物,决定着硫铝酸盐水泥的性能,而在硅酸盐水泥混凝土中影响也非常重要。钙矾石的形成条件决定了其形貌,其形成时间影响着水泥和混凝土的性能。采用化学合成方法合成钙矾石,研究了不同合成条件对钙矾石形成和形貌的影响。结果表明:不同原料合成的钙矾石形貌显著不同且长宽比差异显著;适当提高温度能够促进钙矾石的形成,80℃条件下反应可以形成钙矾石且形貌多样,100℃条件下反应钙矾石不能稳定存在;随着液相p H值的增加,钙矾石的长宽比逐渐减小;硼酸抑制钙矾石在(001)方向的生长。     

钙矾石相的形成、稳定和膨胀——记钙矾石学术讨论会

中国硅酸盐学会水泥专业委员会水泥化学和物化测试学组于1982年12月24～28日在杭州浙江大学的支持下,在杭州召开了钙矾石学术讨论会。16个高等院校、科研单位和工厂的39名从事钙矾石研究和对这项工作关心的科技工作者聚会在一起,宣读了22篇论文,并就钙矾石的形成、稳定和膨胀等三个问题,各抒己见,进行了充分的讨论。 钙矾石(C_3A·3CaSO_4·31H_2O),又称三硫酸盐型水化硫铝酸钙,是重要的水泥水化产物之一,它存在于各种硅酸盐水泥混凝土中,对其凝     

阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的研究

本文研究了石膏掺量对阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的影响,并与硅酸盐水泥进行了比较;利用XRD,SEM-EDS等测试方法对侵蚀后水泥水化产物的物相组成和形貌进行了分析.研究结果表明:阿利特-硫铝酸钡钙水泥具有良好的抗硫酸盐侵蚀性能.当石膏掺量为5%时,阿利特-硫铝酸钡钙水泥的抗蚀系数达1.31,而硅酸盐水泥的抗蚀系数仅为0.94.石膏对阿利特-硫铝酸钡钙水泥硬化浆体的致密性有较大影响,进而影响水泥的抗硫酸盐侵蚀性能.同时,对阿利特-硫铝酸钡钙水泥的抗侵蚀机理进行了初步分析.     

硫酸亚铁对铝酸盐水泥浆体性能及水化产物的影响

铁相对水泥混凝土耐久性具有显著的积极作用,为拓宽铁相来源,本文研究了铁盐对铝酸盐水泥性能及水化产物的影响。通过将铝酸盐水泥和硫酸盐(二水石膏和硫酸亚铁)复合,使铝酸盐水泥水化生成以钙矾石为主的产物,在此基础上,研究了硫酸盐中硫酸亚铁比例对铝酸盐水泥浆体凝结时间、抗压强度以及体积稳定性的影响规律,并采用XRD和SEM分析水化产物类型以及微观形貌,阐明硫酸亚铁对水泥浆体性能的影响机理。结果表明：适量的硫酸盐可提升铝酸盐水泥浆体的抗压强度;硫酸亚铁对铝酸盐水泥表现出轻微的促凝作用,对膨胀率具有显著的抑制作用;硫酸亚铁对钙矾石的形成具有明显的抑制作用,适量的硫酸亚铁使得所生成的钙矾石尺寸较小,且分布均匀,有利于提升硬化浆体的抗压强度。     

论水泥石的硫铝酸盐膨胀——兼论液相中CaO低于饱和浓度时硫铝酸钙膨胀的特点

本文回顾了膨胀和自应力水泥发展以及对水泥石的硫铝酸盐膨胀研究的历史。介绍了建材研究院水泥所物化室自六十年代初至最近关于水泥石硫铝酸盐膨胀的研究结果。认为:1.在水泥石硬化初期形成的钙矾石起强度骨架作用,在水泥石具有一定强度后,继续形成的钙矾石才起膨胀作用;不管形成钙矾石的Al_2O_3、CaO、SO_3的来源如何,不管液相中 CaO的浓度是饱和还是不饱和,所形成的钙矾石均能引起膨胀。2.水泥石的硫铝酸盐膨胀时产生的自应力值和水泥石结构与下述条件有关:钙矾石形态(取决于液相CaO浓度)、数量、形成钙矾石时的水泥石强度;与钙矾石同时生成的胶凝相的形成方式、数量、形态以及混凝土的限制条件。3.水泥石液相中CaO低于饱和浓度时,某些铝酸盐矿物形成了膨胀性较小的钙矾石并在同一反应中形成了水化氧化铝凝胶,得到的水泥石的显微结构致密,强度和膨胀协调发展,混凝土的自由膨胀率和限制膨胀率的比值较小,有利于获得高自应力值及高气密性的自应力水泥混凝土。用上述论点,讨论了与形成钙矾石有关的膨胀现象和理论,展望化学予应力逐步赶上机械予应力及大幅度提高水泥制品抗气渗性能的前景。     

硫酸盐侵蚀水泥砂浆动弹性模量的超声检测

用普通硅酸盐水泥,分别配制了水灰比在0．4～0．8范围内的水泥砂浆试件进行硫酸盐加速侵蚀实验。运用超声波技术测定了不同浓度硫酸盐侵蚀下不同水灰比水泥砂浆试件的动弹性模量值,分析了此实验条件下试件动弹性模量随侵蚀时间变化的规律,并对实验结果作了简要的机理分析。结果表明：在硫酸盐侵蚀条件下,水泥砂浆试件的动弹性模量随侵蚀时间首先增大至某一峰值,随后迅速降低或者逐渐缓慢降低。水灰比和硫酸根浓度对动弹性模量的影响只是反映在数值上;硫酸盐对水泥砂浆材料的侵蚀是由表及里的,动弹性模量的演化可以来反映试件整体平均强度的变化,而回弹法测定的抗压强度反映的是试件表面强度的变化。比较而言,动弹性模量的演化在时间上存在着滞后性。试件微观分析及宏观形貌表明：硫酸盐侵蚀条件下,砂浆试件动弹性模量的演化主要是膨胀产物钙矾石等的形成引起砂浆内部微观结构变化的缘故。     

高温环境下碳硫硅钙石-钙矾石固溶体的研究

由碳硫硅钙石引起的硫酸盐侵蚀破坏在许多国家都有相关工程案例.铝相可以加速碳硫硅钙石的生成,并能够与钙矾石形成固溶体,但铝相的作用机理目前尚无定论.在不同温度下合成了一系列固溶体,并利用XRD,SEM-EDS及红外对固溶体进行了测试分析,结果表明:40℃温度下亦可以生成碳硫硅钙石/固溶体;20℃与40℃均能够形成碳硫硅钙石型与钙矾石型两种形态固溶体;a轴固溶体间隙随温度升高而增大,20℃环境下固溶体间隙为1.1076～1.1182nm,40℃时固溶体间隙为1.1069～1.1189nm;随温度升高碳硫硅钙石-钙矾石固溶体晶体形貌更加细长.     

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。