黑龙江省渠首枢纽砼建筑物的病害与防治

论述了黑龙江省灌溉渠首枢纽砼建筑物的病害与防治措施。     

冷融技术对剩余污泥的调理研究

采用冷融技术对城市污水处理厂的剩余污泥进行了预处理,分析了剩余污泥在-18℃下冷冻不同时长并于室温下解冻后,污泥的沉降性能、脱水性能等的变化情况。试验结果表明剩余污泥经13 h的冷冻作用后,污泥的沉降性能和脱水性能都有很大程度的提高,而污泥完全冻结后继续延长冷冻时间至22 h时,污泥的沉降性能和脱水性能并没有进一步的改善。结果还表明,随着冷冻时间的增加,剩余污泥的pH下降而SCOD上升。     

普通混凝土在盐湖环境中的抗卤水冻蚀性与破坏机理研究

采用快冻法测定了普通混凝土在新疆、青海、内蒙古和西藏盐湖卤水环境中的抗卤水冻蚀性,提出了混凝土在盐湖卤水的物理化学腐蚀和冻融循环双重因素作用下的冻融破坏机理,定量研究了混凝土的冻融损伤叠加效应与交互作用。结果表明,普通混凝土在不同冻融介质中的耐久性顺序是:青海盐湖卤水>新疆盐湖卤水>水>西藏盐湖卤水>内蒙古盐湖卤水;其冻融破坏特征是盐结晶压导致混凝土膨胀开裂。盐湖卤水对于混凝土冻融的损伤效应,既有降低冰点、缓解冻融的损伤正效应,也有促进盐类结晶、导致混凝土膨胀开裂的损伤负效应,两者之间的大小决定了混凝土在盐湖卤水中冻融时的损伤规律。     

生长激素脂质体的研制

用冰冻熔融法制备脂质体 ,包封率可达 2 9% ,当n(卵磷脂 )∶n(胆固醇 ) =5∶2 ,超声时间 3min ,中性环境 ,冰冻 2 4h或 4℃贮藏 3d ,其稳定性良好 ,包封率 ( 2 9.1± 0 .4 ) % ,变化不显著     

Effects of Cyclic Loading,Freeze-Thaw and Temperature Changes on Shear Bond Strengths of Different Concrete Repair Systems

An experimental study was performed to evaluate the residual shear bond strengths between different cementitious and resinous repair materials and substrate concrete after being subjected to cyclic loading, freeze-thaw, and temperature changes. In this paper, techniques and results of test methods that induce shear along the repair/concrete interface are discussed. In addition to the effect of surface preparation on the strength of the old concrete surface, which proved the saw cut surface as the most suitable substrate concrete for shear bond strength assessment, by means of cylindrical shear and friction-transfer methods, the effects of cyclic loading, freeze-thaw, and temperature changes on the shear bond strengths of six different repair systems are illustrated. Analysis of the results indicated that: in order to avoid fatigue failure, the maximum safe stress level to be applied should be between 20 to 40% of the original shear bond strength of the repair system, and the critical stress level differs for different repair materials; 300 freeze-thaw cycles can reduce the shear bond strength of a resin mortar by up to about 80%; and 200 cycles, of temperature changes can reduce the original shear bond strength of a cementitious mortar by up to about 90%.     

Effects of alkali addition on the mechanical properties and durability of concrete

Increasing the concrete alkali content from 0.6% to 1.25% of Na₂O_e of the cement mass by adding NaOH to the mixture water has harmful effects on most mechanical properties (compressive, splitting, direct tensile, and flexure strengths) of concrete made with a water-to-cement (w/c) ratio of 0.41 and limestone aggregates not susceptible to alkali-silica reaction (ASR), however not on the elasticity modulus measured under compression or direct tension. Shrinkage tests at 50% RH and 23 °C started after 7 days at 100% RH and 23 °C show that the low-alkali concrete shrinks more than the high-alkali one, despite similar water losses. Freeze-thaw tests performed on air-entrained concretes show that the two concretes resist well to freezing and thawing while showing similar air-void systems. When examined under the scanning electron microscope (SEM), the hydrates in the two concretes present similar microstructure; however, the high-alkali concrete shows a more reticular and porous microtexture, which could explain the reduction in strength.     

预应力纤维布加固混凝土梁冻融特性试验

为了研究预应力碳纤维布对受冻融作用影响的混凝土梁的加固效果,从而进一步认识混凝土与碳纤维布共同工作的行为,研究了加固梁中碳纤维布和混凝土的各自力学性能以及碳纤维布加固混凝土梁的整体力学性能.结果表明,冻融后的试验梁开裂荷载和极限承载力有所下降;初始预应力水平越高,试验梁的开裂荷载和极限荷载下降速度越快;在冻融循环和预应力耦合作用下混凝土内部损伤严重,碳纤维布-混凝土界面的粘结力退化明显.     

Concentration of aqueous dye solution by freezing and thawing

The concentration phenomena during freezing and thawing were investigated to study the feasibility of freeze–thaw process as a concentration operation. An aqueous dye solution was employed as a model binary eutectic solution. The localised concentration in the frozen matrix was determined, and the concentration profile of the melting solution during thawing was examined. It was found that the solution obtained during thawing showed higher concentration than the original solution, and the concentration did not correspond to the amount of solute localised in the frozen matrix. It was suggested that the concentration phenomena during thawing would be governed by the melting droplet growth rate at the melting interface and by the diffusion rate of solute from eutectic phases to the droplet.     

冻土理论研究进展

为梳理冻土理论在工程领域的研究进展,在总结前人研究成果的基础上,系统地总结了冻土理论下的冻土力学研究进展,冻土在动力作用下性状的研究进展,冻土的冻融研究进展,冻土水、热、力耦合机理研究;其中冻土的冻融研究进展中着重总结梳理了土体冻胀、融沉以及冻融循环对土体物理力学性质影响的研究思路。针对冻土水、热、力耦合机理研究,深入探讨了冻土水迁移理论、冻土温度场以及冻土三场耦合研究现状。最后,结合前人的研究成果,给出了进一步研究的方向:将理论研究和试验研究相结合,反复模拟出最贴近真实情况的冻土破坏机理;研究冻融或反复冻融条件下工程地质灾害情况,考虑运用三场或多场耦合原理模拟地质灾害最不利工况,用以指导实践。研究所得结果为冻土理论的继续研究提供思路,为寒区工程设计和施工提供参考经验。     

冻融循环对植被混凝土养分及其固持能力的影响

由于植被混凝土基材在高寒地区应用效果较差且研究成果不多,为此开展了冻融循环试验,研究了植被混凝土基材三大类营养元素含量变化对冻融循环频次的响应,并对冻融循环后的基材进行淋溶试验,探究了冻融循环对基材养分固持能力的影响。利用Matlab软件对4种速效养分的淋失率进行主成分分析,对冻融循环后的基材养分淋失情况进行综合性评价。结果表明:冻融循环对植被混凝土基材养分含量及流失情况影响较大;随着冻融循环次数的增加,基材全氮含量先上升后下降,氨态氮、有效磷、有效钾含量逐渐上升,硝态氮含量逐渐下降;冻融循环作用提高了3种营养元素的淋出率,增加了基材养分淋溶流失的风险,降低了基材对速效养分的固持能力,这与主成分分析的结果相同。