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基于渡槽混凝土病害严重、耐老化性能差等问题,采用萘系和聚羧酸盐两种高效减水剂,根据不同水胶比、粉煤灰掺量、粉煤灰矿粉复掺配制出C50渡槽高性能混凝土,并测试混凝土的抗氯离子扩散系数、抗冻性和抗碳化性能等耐久性指标,分析水胶比、粉煤灰掺量、粉煤灰矿粉复掺对其耐久性的影响。结果显示:随着粉煤灰掺量增加,混凝土的抗氯离子渗透性能有所提高,但抗冻性能和抗碳化性能均呈下降趋势;粉煤灰矿粉复掺提高了混凝土的抗氯离子渗透性能和抗碳化性能,抗冻性略有降低。 相似文献
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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. 相似文献
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为提高掺石灰石粉混凝土在硫酸盐环境下的耐久性能,研究掺石灰石粉混凝土抗硫酸盐侵蚀性能以及粉煤灰/矿粉改善机理,通过混凝土硫酸盐干湿循环实验,得到试件外观及抗压强度变化,采用傅里叶红外光谱、XRD、SEM/EDS分析探究侵蚀产物物相组成.研究结果表明,硫酸钠结晶作用和生成的侵蚀产物石膏导致试件膨胀开裂,强度性能下降.石灰石粉的掺入增加了侵蚀产物中石膏的含量,从而引起混凝土试件抗侵蚀性能的下降,单掺25%和50%(质量分数)石灰石粉试件抗压强度耐蚀系数分别下降了23.1%和33.9%.粉煤灰/矿粉与石灰石粉互掺时表现出互补的协同效应,改善了掺石灰石粉混凝土抗硫酸盐干湿循环侵蚀的性能.矿粉的效果优于粉煤灰,胶凝材料采用66%水泥-17%石灰石粉-17%(质量分数)矿粉组成的混凝土表现出最优的抗侵蚀性能. 相似文献
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通过实验室模拟高岩温、低湿度施工环境,研究了高岩温对单掺粉煤灰和双掺粉煤灰与矿粉混凝土耐久性能的影响规律,并对不同养护温度下的混凝土试样进行了微观形貌分析,从微观角度探讨了不同养护温度对混凝土抗氯离子渗透性能和抗碳化性能的影响机理.结果表明:高温、低湿养护制度下获得的水化产物分布不均匀,水分蒸发过快,导致了混凝土内部结构疏松;单掺粉煤灰和双掺粉煤灰与矿粉的C30衬砌混凝土的抗氯离子渗透性能均随着养护温度的升高而降低,当养护温度低于80℃时,双掺粉煤灰与矿粉的混凝土电通量值低于单掺粉煤灰的混凝土,当养护温度达到80℃时,前者大于后者;养护温度升高增大了混凝土内部的孔隙率,降低了混凝土的密实度,混凝土抗碳化性能随着温度的升高逐级下降. 相似文献
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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。 相似文献
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碳化作用对混凝土强度及氯离子渗透性能的影响 总被引:1,自引:0,他引:1
试验研究了CO2对粉煤灰混凝土28d抗压强度和氯离子渗透性能的影响。结果表明:碳化作用提高了粉煤灰混凝土28d抗压强度,但随着粉煤灰掺量的增加,混凝土28d抗压强度逐渐减小;在标准养护条件下,粉煤灰对混凝土抗氯离子渗透性有改善作用,而碳化作用使混凝土抗氯离子渗透性能明显降低,且此时粉煤灰的掺人更加增强了对混凝土抗氯离子渗透性能的不利影响。 相似文献
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1 买方市场是赊销现象的主要社会经济原因我国从经济转型过程中,社会生产力迅速发展,许多商品从供不应求转变为供大于求。在供大于求的现实情况下,竞争的压力往往迫使许多企业会采用各种促销手段,向买方提供优惠的交易条件,以求开拓市场,增加销售收入。赊销就是行之有效的促销手段。 相似文献
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通过批试验,对砂岩对浸出铀的吸附解吸做了研究,研究了不同pH、不同液固比条件下,砂岩对浸出铀的吸附和解吸效果。结果表明,pH在1.5~2.0范围内,吸附量与pH成正相关,解吸量与p H成负相关;液固比2∶1和5∶1两种条件下,液固比越大,吸附量和解吸量都增大。 相似文献
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Translated from Steklo i Keramika, No. 5, pp. 15–16, May, 1988. 相似文献
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Influence of rubber on the curing kinetics of DGEBA epoxy and the effect on the morphology and hardness of the composites 总被引:1,自引:0,他引:1
Angel Romo-Uribe Jose Antonio Arcos-Casarrubias Araceli Flores Cintya Valerio-Cárdenas Agustin E. González 《Polymer Bulletin》2014,71(5):1241-1262
The influence of the end groups of two liquid rubbers on curing kinetics, morphology, and hardness behavior of diglycidyl ether of bisphenol-A based epoxy resin (DGEBA) has been studied. The rubbers are silyl-dihydroxy terminated (PDMS-co-DPS-OH) and silyl-diglycidyl ether terminated (PDMS-DGE). Crosslinking reactions, investigated by shear rheometry, ranged 90–110 °C, using a constant concentration (5 phr) of liquid rubbers and 1,2-Diamino cyclohexane (1,2-DCH) as hardener agent. The gel time, t gel, of the neat epoxy significantly decreased when adding the elastomers, more so for the silyl-dihydroxy terminated elastomer; at 110 °C the reaction was nearly complete before rheological test started. The results suggest that the elastomers induced a catalytic effect on the curing reaction. Scanning electron microscopy revealed phase separation of the elastomer during the curing reaction with rubber domains about 5 μm size. However, the DGEBA/dihydroxy terminated elastomer composite cured at 110 °C exhibited a homogenous morphology, that is, the rapid reaction time would not allow for phase separation. Water contact angle tests evidenced either more hydrophilic (silyl-diglycidyl ether terminated rubber) or more hydrophobic (silyl-dihydroxy terminated rubber) behavior than the neat epoxy. The latter effect is attributed to the presence of aromatic rings in the backbone structure of PDMS-co-DPS-OH. Microindentation measurements show that the elastomers significantly reduced the hardness of the epoxy resin, the DGEBA/ether terminated composite exhibiting the lowest hardness values. Moreover, hardness increased as reaction temperature did, correlating with a reduction of microdomains size thus enabling the tuning of mechanical properties with reaction temperature. 相似文献
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以硝酸锌和氢氧化钠为主要原料,研究了120℃和180℃水热条件下,OH^-与Zn^2+物质的量比为8时,不同添加剂D-山梨醇、十六烷基三甲基溴化铵、十二烷基三甲基溴化铵对所得氧化锌形貌的影响。通过扫描电镜(SEM)观察,所有产品都表现为由棒状氧化锌组成的向外辐射的球状体。120℃时,所得氧化锌棒的直径大小较为均一,其中不加添加剂和添加D-山梨醇时所得捧状氧化锌末端为锥形,添加十二烷基三甲基溴化铵的氧化锌末端为针形,而添加十六烷基三甲基溴化铵的氧化锌长径比更大,直径也更为细小;180℃时,只有添加十六烷基三甲基溴化铵所得氧化锌较为均一,其它3种情况下所得氧化锌都表现为大小不等的球体。 相似文献
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D. S. Rutman T. V. Chusovitina S. Yu. Pliner Yu. S. Toropov 《Refractories and Industrial Ceramics》1985,26(3-4):183-186
Conclusions An increase to 4.5–5.5% in the concentration of anion vacancies in the lattice facilitates the transport processes in solid solutions. With a significant concentration of anion vacancies this process becomes difficult, as is indicated by the increase in the activation energy of conductivity.The stabilization of ZrO2 by oxides with a larger cation radius leads to a reduction in the level of conductivity of the solid solutions.The addition to the ZrO2 lattice of cations of stabilizing oxides with a charge close to that of Zr4+ facilitates the transport process of the oxygen ions.It is shown that, in principle, it is possible to predict the level of conductivity of solid solutions based on ZrO2 at 1200–1400°C.The use of a combined additive consisting of a mixture of rare-earth oxides to stabilize ZrO2 makes it possible to obtain solid electrolytes close in their electrophysical properties to the ZrO2-Sc2O3 electrolytes.Translated from Ogneupory, No. 4, pp. 15–18, April, 1985. 相似文献
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《国际聚合物材料杂志》2012,61(11):975-988
This study explores the photoelasticimetry as a means to investigate factors affecting the residual stresses, particularly the thermal stresses, in polymethyl methacrylate (PMMA). The aim was to study the effect of quenching temperature in three different media: air, water, and ethylene glycol, on the impact strength and thermal properties of PMMA. These temperatures varied from a fixed value of 120°C to various values below Tg and the fields of distribution of cooling stresses have been obtained using a charge-coupled device (CCD) camera. It was observed that the quenching in water at 20°C gives rise to an important density of tensile stresses. However, in the ethylene glycol at 110°C this density has a tendency to disappear. An approximate evaluation of these stresses in a point near the specimen center has been assessed, and it was found that the distribution profile of the fields of tensile stresses was much closer to a parabolic form. Notched Izod impact strength and heat deflection temperature (HDT) were measured, and were found to be particularly sensitive to thermal stresses. 相似文献