双掺粉煤灰及聚羧酸减水剂再生混凝土性能试验研究

通过测试混凝土立方体抗压强度、劈拉强度、轴心抗压强度、弹性模量、抗弯强度、渗透系数、碳化深度、相对动弹性模量及质量损失,研究了双掺粉煤灰及聚羧酸减水剂对再生骨料混凝土性能影响。同时分析了粉煤灰和聚羧酸减水剂对混凝土性能的作用机理。研究结果表明:当粉煤灰掺量为胶凝材料的30%、聚羧酸减水剂掺量为胶凝材料的1.2%时,相比普通混凝土,复掺粉煤灰及聚羧酸减水剂再生混凝土28d抗压强度提高了7.1%、劈拉强度提高了8.3%、轴心抗压强度提高了6.5%、弹性模量提高了4.5%、渗透系数降低81.0%、碳化深度降低34.4%,200次冻融循环后,相对动弹性模量提高16.7%、质量损失降低43.8%。双掺粉煤灰及聚羧酸减水剂适用于制备高性能再生混凝土。     

C60自密实混凝土氯离子渗透和抗冻性能研究

采用绝对体积法配制C60自密实混凝土,研究C60自密实混凝土工作性能、不同龄期立方体抗压强度、混凝土氯离子渗透和抗冻融循环性能.结果表明:新拌自密实混凝土流动性能满足二级自密实混凝土要求;28 d标准养护后,抗压强度达标;6 h电通量较低,抗氯离子渗透性能优良;200次冻融循环后动弹性模量损失率26.05%,低于标准规定上限,试件质量损失率1.86%,抗冻性能良好.研究结果为自密实混凝土的推广应用提供依据参考.     

聚羧酸系减水剂对活性粉末混凝土性能的影响

研究聚羧酸系减水剂掺量对活性粉末混凝土性能的影响.试验采用单因素对照试验的方法进行活性粉末混凝土(RPC)配合比设计,测定其坍落度、流动度等工作性能,且将其在标准养护条件下分别养护7、28 d,测定其抗压强度.结果发现:当水胶比为0.25,聚羧酸系减水剂的掺量为1.14％时,活性粉末混凝土的工作性能与力学性能最佳.     

聚羧酸减水剂及不同掺合料对混凝土耐久性的试验研究

研究不同粉煤灰(20％、30％、40％)、矿粉微渣掺量及聚羧酸减水剂掺量(0、0.6％、0.8％、1.0％、1.2％)等多因素对寒区水工混凝土力学性能、抗碳化能力及抗冻融耐久性的影响规律.试验结果表明:聚羧酸减水剂的掺入可以显著提高不同外掺料混凝土的力学性能、抗碳化性能和抗冻性能;在本文所考虑的减水剂掺量范围内,减水剂掺量为1.0％时,各组混凝土试样的抗压强度最高,抗碳化能力最强,抗冻融效果最好;采用幂函数形式得到的碳化深度随龄期的变化规律有较高的拟合精度和相关性,建立的函数关系可以很好的反映实际碳化试验结果;在聚羧酸高效减水剂掺量相同的情况下,随着粉煤灰用量的降低,矿粉掺量的逐渐增多,混凝土的抗碳化性能和抗冻性能得到明显改善.研究成果可为寒冷地区外掺料混凝土在冻融环境下的耐久性应用提供一定的试验依据和参考.     

用粉煤灰配制自密实混凝土的试验研究

采用大掺量粉煤灰及矿渣微粉复合掺合料和高效减水剂,配制出C30自密实混凝土。试验结果表明：所配制的自密实混凝土的坍落扩展度为680mm,扩展时间T500为2．3s,符合规范的相关技术指标,自密实性能良好;28d抗压强度比普通混凝土稍低,但56d抗压强度超过C30混凝土的配制强度,可满足设计强度的要求;混凝土的28d碳化深度小于20mm,抗碳化耐久性较好,符合技术要求。     

减水剂对C80PHC混凝土拉/压比的影响研究

以管桩生产配合比为基本参照,分别研究了萘系、聚羧酸、氨基磺酸盐和磺化丙酮等4种减水剂对C80PHC混凝土抗压强度、劈裂抗拉强度,拉/压比以及密实性的影响.研究结果表明:不同品种减水剂对混凝土力学强度以及密实性影响不同,其中,掺磺化丙酮混凝土脱模强度较高而聚羧酸较低,掺聚羧酸混凝土拉/压比较大而磺化丙酮较小,掺聚羧酸混凝...     

脱硝粉煤灰用于水泥和混凝土的应用技术研究

通过对比脱硝粉煤灰与普通粉煤灰应用于水泥、混凝土的性能差异及其与减水剂的相容性等,探索脱硝粉煤灰资源化利用于建材的应用技术。研究结果表明:萘系减水剂、聚羧酸减水剂均可用于掺脱硝粉煤灰的水泥-粉煤灰体系,且聚羧酸减水剂与该体系的相容性更好;掺脱硝粉煤灰的水泥比掺普通粉煤灰的水泥的凝结时间缩短20~25 min,3 d抗压强度下降3.2%~9.3%,3 d抗折强度下降1.5%~13.2%。掺脱硝粉煤灰的混凝土与掺普通粉煤灰的混凝土拌合物性能相近,其7 d、28 d抗压强度比掺普通粉煤灰的混凝土降低12.6%、6.1%。建议在实际工程应用中限制掺入量上限或结合现场验证试验后谨慎使用。     

大掺量粉煤灰对聚羧酸盐减水剂自密实混凝土性能的影响

本文主要研究在一定水灰比（0．36）条件下,不同掺量粉煤灰以及不同掺量的聚羧酸盐减水剂对自密实混凝土塌落扩展度、密度、抗压强度、吸附作用等指标的影响。试验结果说明：高掺量粉煤灰的自密实混凝土有足够的强度;随着粉煤灰的增加,其吸水率增大;聚羧酸盐减水剂的掺量为0．7％时,自密实混凝土可以得到更好的工作性和抗压强度。     

高掺量聚丙烯纤维自密实混凝土制备及其性能研究

为了有效提高高掺量聚丙烯纤维自密实混凝土的工作性能,将调整水胶比和砂率进行配制聚丙烯纤维体积掺量为0.5％的自密实混凝土并对其材料性能进行试验研究.研究表明:高掺量聚丙烯纤维的掺入对自密实混凝土的流动性有较大影响,适当调整水胶比和砂率可配制满足工作性能要求的高掺量聚丙烯纤维自密实混凝土;水胶比的增大提高了高掺量聚丙烯纤维自密实混凝土的扩展度,同时也提高了其离析的风险,降低了其抗压强度;砂率的增大对高掺量聚丙烯纤维自密实混凝土的抗压强度基本没有影响,但可提高其拌合物的粘聚性.     

造纸废液接枝改性减水剂对混凝土性能的影响

本文系统对比研究了一种造纸废液接枝萘磺酸盐单体制备的新型高效减水剂(LPCN)与传统木质素磺酸钙普通减水剂(CL)对C40混凝土多种性能的影响.结果表明,LPCN能够大幅改善混凝土拌合物的初始流动性,但泌水率较高,具有弱于木质素磺酸钙的引气和缓凝作用;可使混凝土28 d抗压强度和抗折强度提高15％,能抑制混凝土后期收缩,使其一维和二维碳化深度降低20％以上,并延缓了冻融循环过程中混凝土损伤劣化.     

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.     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.