橡胶混凝土低温轴心抗压及抗折性能试验研究

橡胶混凝土在低温下的力学性能与常温相比有较大差异.为研究橡胶混凝土低温下的力学性能,使用粒径为5～ 10目的 橡胶颗粒等体积代替砂,配制了水胶比为0.35,0.40,0.45,橡胶掺量分别为0％,10％,20％,30％的橡胶混凝土.通过对比低温-30℃和常温20℃下橡胶混凝土力学性能的试验结果,分析低温-30℃下橡胶混...     

沥青路面常见高低温病害原因及维修

从气候、气温对沥青材料的影响分析了沥青路面常见高低温病害的原因,针对具体病害提出了防治与维修方法。     

高温下无黏结预应力混凝土受弯构件的非线性有限元分析

采用混凝土和钢筋的增量型温度-应力耦合本构模型,在充分考虑高温下无黏结预应力筋总变形协调条件和其对梁单元有限元列式影响的基础上,将无黏结预应力筋内力与未知结点位移共同作为待求列矢,推导高温下无黏结预应力混凝土受弯构件非线性有限元全过程分析的增量有限元格式,建立其高温下非线性有限元计算模型,并提出其非线性有限元平衡方程组的求解方法,编制NAUPCLF非线性有限元程序,并对进行的高温试验及有关试验资料完成实例计算。结果表明,计算数值基本能反映其高温下变形及预应力筋应力的变化规律,计算理论较充分地表现了无黏结预应力混凝土受弯构件的无黏结特性及高温受力特点,可为建立高温下无黏结预应力混凝土受弯构件的耐火极限计算方法、进一步深入研究预应力混凝土结构的抗火性能和完善其基于抗火特性的设计方法提供手段和参考。     

低温合成煤矸石水泥

介绍低温合成煤矸石水泥的生产工艺流程及其工艺参数,研究了水泥中矿物形成机理和主要性质,并对其性能特点进行了分析。研究表明,低温合成煤矸石水泥等级可达32.5级普通硅酸盐水泥的指标,并具有早强特性,且长期强度稳定。对其原料及配料要求不苛刻,煤矸石用量可达70%以上,是煤矸石综合利用的一项有效途径。     

Strengths of compacted soils at Novosibirsk

Soil Mechanics and Foundation Engineering -     

严寒对煤矸石页岩烧结砖生产的影响及应对措施

详细论述了严寒季节低温和冷风对原料破碎、坯体成型、干燥和窑炉焙烧产生的不利影响,并提出了相应的解决方法。     

用弯曲应变能评价沥青混合料低温抗裂性

采用低温弯曲破坏试验评价Superpave沥青混合料的低温抗裂性,并通过弯曲破坏试验的应力应变曲线求算应变能,结果表明用弯曲应变能作为评价指标可以很好表征沥青混合料的低温性能。     

Fatigue of asphalt binder,mastic and mixture at low temperature

The fatigue damage is one of the most common distresses observed on the asphalt concrete pavement. To thoroughly understand the fatigue of asphalt concrete, the behaviors of the major components of asphalt concrete under cyclic loading are investigated respectively in this study. A new experiment method is developed to evaluate the performances of asphalt binder, mastic and fine aggregates mixture under cyclic tensile loading. The fatigue test results of asphalt binder show that the fatigue performance of asphalt binder is closely related with loading magnitude, temperature and loading rate. Mastic specimens with different filler content are tested and the results indicate that mastic specimens with 30% filler content show better fatigue resistance and higher permanent strain. The micro-structure analysis of mastic and mixture indicates that the fatigue resistance is closely related with the air void content of specimen. 3D digital specimens are developed to model the fatigue of the asphalt binder, mastic and mixture specimens based on the finite element method (FEM). Fatigue damage of asphalt concrete is simplified by a damage model. With proper selection of damage parameters, the simulation results agree well with laboratory test results and can be used as a basis for future fatigue research.     

Application of response surface methodology to optimize nitrate removal at low temperature by aerobic denitrificator Pseudomonas strain An‐1

Response surface methodology (RSM) was applied to optimize the conditions of nitrate removal by Pseudomonas strain AN‐1 at low temperature, which was isolated from aniline‐contaminated groundwater. A three‐factor, three‐level Box–Behnken experimental design and analysis of variance were combined with the obtained second‐order polynomial equation and applied for RSM optimization. By solving the second‐order polynomial equation and analysing the 3D response surface, a ‐N concentration of 65.29 mg/L, an initial pH of 6.65, and an initial DO of 7.53 were identified as the optimized conditions. These conditions achieved a removal percentage of 53.7485% after 48 h at 10°C, which was in good agreement with the predicted 53.8085%. This study showed the excellent ability of the Pseudomonas strain AN‐1 to degrade nitrate at low temperatures, which provided a solid foundation for the further application of this microorganism in the treatment of nitrate‐contaminated groundwater.     

CRC＋AC复合式路面温度场分析

在既定路面结构层和材料选取的基础上,定性分析了CRC＋AC路面CRC层内的温度与CRCP路面的不同,认为AC层的设置会对CRCP温度分布产生明显的影响,并指出针对各区域不同材料的CRC＋AC层的路面温度场分析有待进一步研究。     

矸石仓低温滑模施工技术

结合工程实例,介绍了矸石仓低温滑模施工保温系统的设计,探讨了超低温气候下矸石仓滑模采取的施工工艺,并提出了施工中的安全措施,为超低温滑模施工积累了经验,可供同类工程参考借鉴。     

低温烧结轻质高强黏土瓦

在砖瓦用黏土中掺入适量钙与镁质的配合料,有助于提高瓦的强度,降低黏土瓦的密度和烧成温度,利于节能。     

Inactivation of Cryptosporidium parvum oocysts with ozone and monochloramine at low temperature

The rate of Cryptosporidium parvum inactivation decreased with decreasing temperature (1-20 degrees C) for ozone and for monochloramine applied alone as well as after pre-treatment with ozone. Synergy was observed at all temperatures studied for the ozone/monochloramine sequential disinfection scheme. The synergistic effect was found to increase with decreasing temperature. The inactivation rate with monochloramine after ozone pre-treatment was 5 times faster at 20 degrees C and 22 times faster at 1 degree C than the corresponding post-lag phase rates of inactivation with monochloramine at these temperatures when no ozone pre-treatment was applied. The CT required for achieving 2-logs of inactivation ranged from 11,400 mg min l-1 at 20 degrees C to 64,600 mg min l-1 at 1 degree C when monochloramine was applied alone. In contrast, the CT required for an overall sequential inactivation of 2-logs ranged from 721 mg min l-1 at 20 degrees C to 1350 mg min l-1 at 1 degree C when applying monochloramine after ozone pre-treatment. The presence of excess ammonia in the monochloramine solutions was not responsible for the synergy observed in ozone/monochloramine sequential disinfection.     

Degradation of chlorophenols in soil, sediment and water at low temperature

Chlorophenol degradation was studied under aerobic conditions in soil, sediment and water. Ortho-chlorophenol, p-chlorophenol and 2,4-dichlorophenol were degraded by soil and sediment microorganisms at 0°C and 4°C. Metachlorophenol and pentachlorophenol were also degraded, but to a lesser extent. Stream-water microorganisms were only able to degrade 2,4-dichlorophenol at 20°C. None of the other chlorophenols examined were degraded by stream-water microorganisms at 0 or 20°C. The addition of some chlorophenols stimulated aerobic, and to a lesser extent, anaerobic microbial growth in sediment incubated at 0°C. A decrease in the concentration of some chlorophenols was noted in both sterile and non-sterile stream water at 0 and 20°C; which could not be explained by microbial contamination, photodecomposition or volatilization.     

超低温环境混凝土研究与应用综述

应用于液化天然气(LNG)低温储藏的混凝土在超低温环境下的性能与常温状态时的性能存在较大差异。基于此原因,本综述总结了国内外超低温环境下和低温冻融后的混凝土各种性能研究,论述了混凝土在超低温环境下和低温冻融后性能变化机理,并指出含水量和环境温度对混凝土在超低温下的性能至关重要。阐述并指出了目前超低温环境混凝土的应用进展和急需解决的问题。     

Flexural and Split Cylinder Strengths of HSC at Elevated Temperatures

This paper investigates the effect of elevated temperature on the flexural strength (FS) and split cylinder strength (SCS) of high strength concrete (HSC). Four concrete mixes of 50, 90, 110, and 130 MPa grade were prepared and subjected to elevated temperature exposure of 200°C and 400°C, and cooled under slow and quick cooling conditions. In addition, 130 MPa grade concrete specimens were also subjected to 100°C and 600°C exposure temperatures to compare FS and SCS under elevated temperatures. It was observed that with the increase in the elevated temperature, the FS and SCS experienced significant losses. The loss was found to be higher for richer concretes. FS was observed to experience a sharp loss at low temperatures that became gradual later at high temperatures. SCS, however, experienced a gradual loss, though sharper than FS, with the increase in temperature. The results indicated that cooling had a significant effect on the residual values and quick cooling caused greater loss in FS and SCS, than slow cooling at elevated temperatures. The quick cooling was noted to produce maximum loss over slow cooling at temperatures around 400°C.     

关于沥青路面在低温时初始开裂的思考

针对沥青混凝土路面低温开裂进行了分析,阐述了开裂机理,通过建立模拟路面在寒潮时的受力状况的简化模型,分析了初始裂缝产生原因,并对路面抗裂措施提出建议,以期指导实践。     

低应变法和超声波法在Sofoline立交桥中的应用

介绍了低应变反射波法和超声波检测的基本方法及其在加纳Sofoline立交桥桩基础检测中的应用,并将这两种方法进行了对比,对个别桩的完整性进行了分析判别,以期为类似工程桩基检测积累经验。     

Effects of strain hardening of reinforcement on flexural strength and ductility of reinforced concrete columns

In the evaluation of flexural strength of reinforced concrete (RC) columns, the elastic–perfectly plastic constitutive model is generally used for steel reinforcement, which ignores the strain hardening effect. While some engineers believe that the flexural strength so obtained is on the safe side, others are concerned that underestimation of member strength could lead to inaccurate prediction of overall structural behaviour especially under extreme events. In any case, better understanding of the possible over‐strength and its effects on flexural ductility and failure mechanism is necessary. In this paper, the effects of strain hardening of reinforcement on the flexural strength and ductility of reinforced normal‐ and high‐strength concrete columns are studied based on rigorous full‐range moment–curvature analysis. The study has identified if and how various parameters affect the strain hardening effect, which include axial load ratio, concrete strength, confining stress, reinforcement ratio and the tensile‐strength‐to‐yield‐stress ratio of steel. The effects of strain hardening can be quite significant for RC columns under relatively low axial load and relatively high confining stress. Copyright © 2009 John Wiley & Sons, Ltd.