粉煤灰对混杂纤维混凝土力学与耐久性能的影响分析

将粉煤灰加入混凝土中可以有效消耗工业固体废弃物，保护环境。基于此，制备了不同粉煤灰掺量的混杂纤维混凝土样品，开展了立方体抗压强度、劈裂抗拉强度、碳化深度以及冻融循环后的相对动弹性模量和质量损失率测试，分析了混凝土力学与耐久性能随粉煤灰掺量的变化规律。研究结果表明：养护龄期小于14 d时混杂纤维混凝土的抗压强度随粉煤灰掺量的增大而减小，养护龄期大于14 d时抗压强度随粉煤灰掺量的增大而增大；60 d养护龄期和12%粉煤灰掺量的混凝土抗拉强度最大；碳化深度随粉煤灰掺量的增大而先减小后增大；粉煤灰掺量小于12%时，掺入粉煤灰的混杂纤维混凝土的抗冻性能要略优于素混杂纤维混凝土。     

矿物掺合料再生混凝土力学性能研究

为探究矿物掺合料对再生混凝土(RAC)力学性能的提升作用,本试验采用预湿-二次搅拌法制备再生混凝土,系统开展单、复掺矿物掺合料再生混凝土力学性能研究.试验考虑再生混凝土强度等级、再生骨料取代率、矿物掺合料种类及取代率等因素,共设计23组试验配合比,研究再生混凝土立方体抗压强度和劈裂抗拉强度经时变化规律.结果 表明,再生混凝土力学性能随强度等级升高而提升,随再生骨料取代率增大而下降.与未掺矿物掺合料的再生混凝土相比,单掺粉煤灰对再生混凝土力学性能提升效果较弱,单掺矿渣、硅灰的再生混凝土力学性能提升效果显著.养护龄期90 d时,矿渣再生混凝土劈裂抗拉强度最高提升12.7％,硅灰再生混凝土立方体抗压强度最高提升21.3％.粉煤灰-矿渣复掺对再生混凝土立方体抗压强度无提升效果,20％粉煤灰-10％矿渣复掺抗压强度甚至下降18.8％,粉煤灰-矿渣复掺对再生混凝土劈裂抗拉强度略有提升,最高为5.9％.粉煤灰-硅灰复掺对再生混凝土力学性能提升效果较好,立方体抗压强度和劈裂抗拉强度最高分别提升9.7％和18.6％.     

喷射混凝土力学性能试验研究及预测模型建立

以喷射混凝土单层永久衬砌隧道为背景,采用干喷大板法,开展喷射混凝土力学性能试验.以宝鸡至兰州高速铁路麦积山隧道衬砌喷射混凝土配合比为基础,考虑水胶比、粉煤灰和钢纤维影响,研究喷射混凝土抗压强度和劈裂抗拉强度经时变化规律,建立相应的预测模型.结果表明:喷射混凝土早龄期强度较高.随着龄期增大,同配合比模筑混凝土强度增大并超过喷射混凝土,且二者差值逐渐增大.水胶比增大及钢纤维掺量减小,喷射混凝土强度减小;随粉煤灰掺量增大,强度先增大后减小.采用13组数据对抗压强度模型进行验证,其相对偏差的标准差为5.55,说明模型具有较好的适用性.喷射混凝土抗压强度和劈裂抗拉强度均呈正态分布,且二者之间呈指数关系.     

高活性矿物掺合料混凝土力学性能试验

利用正交试验的方法对高活性矿物掺合料混凝土(以下简称掺合料混凝土)的强度进行试验.研究偏高岭土掺量、超细粉煤灰掺量、硅灰掺量对掺合料混凝土7d、14 d、28 d抗压强度和劈裂抗拉强度的影响,并对数据结果进行系统分析.试验结果表明,偏高岭土对掺合料混凝土早期的力学性能影响最大,力学性能随着偏高岭土掺量的增加而增加.通过多元线性回归,建立不同因素对掺合料混凝土各龄期抗压强度、劈裂抗拉强度的数学表达式,得到偏高岭土和硅灰对掺合料混凝土均为正影响,而超细粉煤灰为负影响的结果.当偏高岭土的掺量为10％(质量分数),超细粉煤灰掺量为15％(质量分数),硅灰掺量为5％(质量分数)时,掺合料混凝土力学性能达到最佳.最后进行微观分析得出,矿物掺合料的复合化具有超叠加效应,能增强掺合料混凝土各龄期的力学性能.     

低品质粉煤灰混凝土力学性能发展规律研究

进行了掺加不同品质和掺量粉煤灰、复掺矿渣粉混凝土的力学性能试验,分析了轴心抗压强度、劈裂抗拉强度、弹性模量、泊松比等力学参数随龄期的发展规律。结果表明,单掺粉煤灰混凝土早期强度发展较慢,后期强度增长较快,180d轴心抗压强度和劈裂抗拉强度分别为28d的1.83倍和1.68倍,仅凭28d强度对低品质粉煤灰混凝土进行设计偏于保守。低品质粉煤灰混凝土复掺矿渣粉后,28d强度与180d强度相差不大,且抗碳化性能显著改善,可用于混凝土设计。     

风积沙与粉煤灰掺量对混凝土力学性能的影响

为了研究风积沙和粉煤灰掺量对混凝土力学性能的影响规律,通过风积沙内掺替代相同质量的河砂,替代率为0％、10％、20％、30％和40％,内掺粉煤灰为10％、20％情况下配制混凝土.对风积沙混凝土立方体抗压强度和劈裂抗拉强度进行试验研究,并采用扫描电镜(SEM)对混凝土微观结构形貌进行分析.结果表明:风积沙的掺入可以提高混凝土的抗压强度与抗拉强度,尤其对混凝土早期强度的贡献比较大;粉煤灰在风积沙混凝土后期抗压强度中发挥重要作用,对28 d抗拉强度影响较大,因此要控制其掺量;风积沙替代率20％,粉煤灰掺量10％,混凝土的力学性能表现最优.最后,建立了风积沙混凝土抗拉强度与抗压强度之间的演化方程.     

粉煤灰对桥梁混凝土抗渗性能的影响规律研究

为研究粉煤灰对桥梁混凝土抗渗性能的影响,制备了不同粉煤灰掺量的混凝土样品,测试分析了桥梁混凝土抗压强度、孔隙结构、渗透高度和抗氯离子渗透性能随粉煤灰掺量和养护龄期的变化规律。研究结果表明:(1)当桥梁混凝土养护龄期为7d时,桥梁混凝土的抗压强度随着粉煤灰掺量的增多而逐渐降低;当混凝土龄期大于28d时,桥梁混凝土的抗压强度在粉煤灰掺量为30%左右时最大。(2)粉煤灰掺量为30%时,桥梁混凝土密实度达到最大,此时其内部小孔隙增大而大孔隙减小。(3)桥梁混凝土抗氯离子渗透系数随着粉煤灰掺量的增大先减小后增大,在粉煤灰掺量为30%时取得最小值。     

活性掺合料对混凝土抗碳化性能影响的研究

研究了强度等级(C30和C45)、龄期(28 d和120 d)、矿物掺和料(矿粉和粉煤灰)质量掺量对掺有脂肪族高效减水剂(SAF)的混凝土抗碳化性能的影响,并建立了C30/C45混凝土在28 d/120 d龄期的碳化深度与矿粉/粉煤灰掺量比例之间的回归模型。结果表明:水胶比的降低、养护龄期的延长都能提高水泥石的密实度,从而提高抗压强度和抗碳化性能;混凝土抗碳化性能随矿粉掺量的上升、粉煤灰掺量的下降而提高;当矿粉掺量占胶凝材料质量的37.5%时,C30混凝土的抗碳化性能最佳;当矿粉掺量占胶凝材料质量的31.9%时,C45混凝土的抗碳化性能最佳;当龄期增加时,粉煤灰掺量比例越大则碳化深度的下降幅度越大;矿粉和粉煤灰掺量的相对比例变化时,对低强度混凝土的影响程度要大于高强度混凝土。     

钢纤维改善混凝土力学性能和微观结构的研究

研究了水胶比为0.45,钢纤维掺量为0、0.5％、1.0％、1.5％和2.0％的五种混凝土的力学性能以及其水化28天后的微观形貌.结果表明:钢纤维对混凝土的抗压强度改善并不明显,当钢纤维掺量为1.5％时,混凝土的抗压强度仅比普通混凝土提高了7.4％;但钢纤维的掺入大大提高了混凝土的劈裂抗拉强度和抗折强度,当钢纤维掺量为1.5％时,混凝土劈裂抗拉强度提高了80％,当钢纤维掺量为2.0％时,混凝土抗拉强度提高了近一倍.混凝土的宏观力学性能特征与微观结构分析结果相吻合.     

喷射混凝土渗透性、孔结构和力学性能关系研究

以喷射混凝土衬砌隧道结构为研究背景,开展喷射混凝土渗透性、孔结构及力学性能试验,采用AutoClam、非稳态氯离子快速测定法(RCM)、直线导线-线性回归法(ASTM C457)、压汞测孔法等,对喷射混凝土渗透性(透气性、透水性和氯离子迁移)、孔结构(砂浆孔结构和表面孔结构)及力学性能(抗压强度和劈裂抗拉强度)进行测试,研究喷射混凝土配合比对喷射混凝土能性的影响以及三者之间的相互关系.结果表明,喷射混凝土水胶比、粉煤灰及钢纤维对其渗透性、孔结构参数和力学性能具有直接影响,低水胶比、高钢纤维掺量对喷射混凝土性能的提高有利,粉煤灰可促进喷射混凝土性能优化,但过高的掺量会造成性能劣化.通过分析喷射混凝土渗透性、孔结构和力学性能之间的关系,认为喷射混凝土孔结构组成决定其渗透性和力学性能,随着孔隙率的增大,喷射混凝土渗透性提升、力学性能下降,孔隙率与渗透性及抗压强度之间呈指数关系.     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

2008～2009年世界塑料工业进展

收集了2008年7月～2009年6月世界塑料工业的相关资料,介绍了2008～2009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、环氧树脂、不饱和聚酯树脂)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。     

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.