谈混凝土工程的现场浇筑

对混凝土工程的现场浇筑工艺进行了介绍,分别阐述了混凝土的分类,组成材料及配合比要求,着重论述了混凝土的施工技术及缺陷处理方法,以指导实践。     

基础地下室混凝土施工的几点体会

分析了基础地下室混凝土产生裂缝的原因,对混凝土配合比设计、混凝土的测温与养护进行了论述,并总结了基础地下室混凝土施工的几点体会,对类似工程施工质量的提高具有一定指导意义。     

In situ fibre‐reinforced composite films of poly(lactic acid)/low‐density polyethylene blends: effects of composition on morphology,transport and mechanical properties

This study aimed to investigate the effects of blend composition on packaging‐related properties of poly(lactic acid) (PLA) and low density polyethylene (LDPE) blown films. Blend films with PLA contents of 5–20 wt% were produced and compared. Scanning electron micrographs of cross‐sectional cryofractured surfaces of the blend films revealed that in situ fibre‐reinforced composites were obtained. Viscosity ratio of the polymer components of ca 1 confirmed that fibre formation was favourable for this blend system. PLA microdomains were dispersed throughout the film in forms of long fibres (length‐to‐diameter ratio > 100) and ribbons. The number of fibres and ribbons increased with an increase of PLA content. Critical content of PLA was found to be 20 wt% for effective improvement of both moduli and gas barrier properties. Incorporation of poly[ethylene‐co‐(methyl acrylate)] compatibilizer showed minimal effect on PLA structure. However, it did improve moduli and O₂ barrier properties when sufficient amount (1.5 pph) was used in 10 wt% PLA/LDPE. In short, flow behaviour, ratio of polymer components and degree of compatibility together played intricate roles in the morphology and hence mechanical and transport properties of PLA/LDPE immiscible blends. © 2017 Society of Chemical Industry     

标准段预应力混凝土箱梁浇筑的控制方法

通过对武汉市黄浦大街-金桥大道快速通道工程在标准段预应力混凝土箱梁浇筑顺序、浇筑方法、人员配置等方面的经验总结,同时简要介绍了在标准段预应力箱梁在浇筑过程中应该注意的事项和措施,为今后类似桥梁工程预应力混凝土箱梁浇筑提供参考借鉴。     

现浇钢筋混凝土楼板裂缝控制措施及修复方法

对某工程钢筋混凝土楼板产生的几类裂缝进行了原因分析,阐明了裂缝对结构的危害性,提出了该工程相应的裂缝修复处理方法,并从施工方面提出了针对性的预防和控制措施,为解决相同类型的工程问题积累了经验。     

密封养护混凝土内部湿度与收缩的一体化试验与模拟研究分析

三种强度等级不同的混凝土在密封养护的条件下，获得了动态发展数据，同时进行试验，实验结果与预测模型数值吻合极好，这种模型可在不同的环境条件下对其自动干燥以及自动收缩程度进行分析和检验。     

Failure of reinforced concrete and tuff stone masonry buildings as consequence of hydrogen pipeline explosions

Pipelines are the most efficient method of transporting large quantities of hydrogen, and the low volumetric energy density of gaseous hydrogen requires that the gas must be compressed to extremely high pressure to be used as a transport fuel. The failure of high pressure hydrogen gas pipelines and subsequent explosion may induce heavy damage to buildings. In this paper, such an issue is addressed for existing reinforced concrete framed buildings and tuff stone masonry buildings. Physical features such as the gas jet release process, flammable cloud size, blast generation and propagation, and explosion effects on structural components of buildings are considered and evaluated through the SLAB integral model, Multi-Energy Method and pressure‒impulse diagrams. Damage to both types of structural components was evaluated and the maximum distance of blast damage was derived in several environmental conditions, contributing to land-use planning and performance-based design/assessment of pipelines and buildings.     

混凝土工程冬季施工注意事项

为了保证施工进度，进行了混凝土工程的冬季施工作业，将原材料，混凝土的拌制、运输、浇筑、养护和拆模逐一论述，旨在指导冬季施工中对各个环节的细节控制，减少病害。     

Influence of limestone filler and viscosity-modifying admixture on the porous structure of self-compacting concrete

The objective of this experimental work is to study porosity in self-compacting concrete (SCC) made without adding limestone filler, comparing the results with other SCC and with normally-vibrated concrete (NVC). Several types of concrete were made, keeping the w/c ratio constant. The results show that the air content in SCC depends on the flowability and viscosity of the material, putting a forward an expression to estimate the air content in accordance with these two parameters. SCC shows a finer and more tortuous porous structure than NVC, leading to lower permeability to water under pressure. Nevertheless, in the absence of pressure, when water penetrates by capillary action, the results obtained from the different types of concrete were very similar, with differences below 3.5%. This is due to the fact that the content of pores over 0.5 μm is practically the same in SCC and NVC, but for smaller pore sizes, which are therefore only accessed when water under pressure is applied, the differences in porosity between the different samples is more pronounced. On the other hand, it was observed that the use of more fluid mixtures permitted more impermeable concrete to be obtained. The use of viscosity-modifying admixture on SCC as a replacement for limestone filler does not affect the total volume of pores, but generates a slightly more coarse porous microstructure, thereby leading to concretes in which water penetration depth under pressure is a little higher (around 4 mm).     

Na2SO4对低硫水泥及其混凝土性能的影响

本文探讨了单掺Na2SO4对低硫水泥及其混凝土性能的影响。结果表明:少量的Na2SO4缩短了水泥凝结时间,有利于提高混凝土的坍落度、改善混凝土坍落度损失,而且在低温时可以明显改善混凝土的早期强度。