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高贝利特水泥混凝土的断裂韧性 总被引:1,自引:0,他引:1
为研究高贝利特水泥混凝土的断裂性能,通过三点弯曲梁试验,比较了高贝利特水泥混凝土与硅酸盐混凝土的双K断裂参数。结合载荷–裂口张开位移曲线分析,探讨了高贝利特水泥混凝土的断裂能。结果表明:高贝利特水泥混凝土载荷–裂口张开位移曲线下覆盖的面积大于硅酸盐水泥混凝土,混凝土对载荷能量有较高的吸收能力,断裂能大,断裂韧度大;高贝利特水泥混凝土的起裂韧度和失稳韧度分别是硅酸盐水泥混凝土的1.17倍和1.24倍。高贝利特水泥混凝土的断裂性能优于硅酸盐水泥混凝土的。 相似文献
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通过现场试验,比较了普通硅酸盐水泥和高贝利特水泥混凝土与基岩的抗剪(断)性能。结果表明:高贝利特水泥混凝土的抗剪断和抗剪性能优于普通硅酸盐水泥。通过线性回归得出高贝利特水泥混凝土与基岩的抗剪断应力方程为τ=1.204δ+0.278(其中,δ为剪切面上的正应力),抗剪应力方程为τ′=1.119δ+0.150。普通硅酸盐水泥混凝土与基岩的抗剪断应力方程则为τ=0.790δ+0.257,抗剪应力方程为τ′=0.683δ+0.061。对高贝利特水泥改善混凝土–基岩的抗剪和抗剪断机理进行了探讨。 相似文献
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水泥水化热与比表面积和化学组成有关,但是相对于调整水泥的化学组成来说,通过减小水泥的比表面积来降低水泥水化热要容易得多。为了探索水泥比表面积与碾压混凝土抗裂性能的关系,采用相同熟料磨制了3种细度的水泥,研究了水泥细度对水化热、胶砂强度的影响,以及对混凝土的工作性、力学性能(抗压强度、抗拉强度和抗拉弹性模量)、极限拉伸值、绝热温升等性能的影响;同时,采用温度–应力试验机,评估了在100%约束和近似绝热条件下水泥细度对早龄期碾压混凝土综合抗裂性能的影响。结果表明:水化热与比表面积成线性关系,降低水泥比表面积是降低混凝土温升的有效、便捷的措施;粗磨水泥提高了碾压混凝土的工作性,降低了混凝土的抗压强度和弹性模量,但混凝土极限拉伸值没有明显变化;温度–应力试验表明,随着水泥比表面积的降低,混凝土第二零应力温度更低,粗磨水泥碾压混凝土综合抗裂风险更低。 相似文献
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通过研究经氯盐侵蚀的再生混凝土不同界面的显微硬度变化,确定不同强度等级再生混凝土不同界面过渡区的范围,研究氯盐侵蚀期对再生混凝土不同界面显微结构的影响规律,揭示了再生混凝土多重界面氯盐侵蚀的劣化机理。研究表明:随着氯盐侵蚀龄期的增长,同强度再生混凝土LG-XJ界面、LJ-XJ界面和LG-LJ界面的显微硬度逐渐降低,过渡区范围逐渐增加。侵蚀龄期为30 d时,C30再生混凝土的LJ-XJ界面过渡区范围几乎无变化;侵蚀龄期为90 d时,C60再生混凝土的LJ-XJ界面过渡区范围变化仍不明显。同强度再生混凝土界面抗氯盐侵蚀性能强弱关系:LJ-XJ界面抗氯盐侵蚀性能>LG-LJ界面抗氯盐侵蚀性能>LG-XJ界面抗氯盐侵蚀性性能。不同氯盐侵蚀龄期的再生混凝土,随着强度等级的提高,LG-XJ界面、LJ-XJ界面和LG-LJ界面的显微硬度与过渡区范围以及水泥浆体本身的显微硬度改变的幅度都有不同程度的降低。 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
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. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
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. 相似文献
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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. 相似文献
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Peter A. Edwards Grant Striemer Dean C. Webster 《Journal of Coatings Technology and Research》2005,2(7):517-527
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. 相似文献
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Dongjiang Yang Yao Xu Lei Zhang Shangru Zhai Dong Wu Yuhan Sun 《Journal of Coatings Technology and Research》2006,3(2):127-131
A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by 1H MAS NMR. For direct comparison purposes, an SiO2 coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N2 absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals. 相似文献