Thermal Analysis of Concrete Mixtures with Recycled EPS Aggregates

Reusing recycled waste materials in buildings is gaining more and more attention for what it offers economic,environmental,and energy benefits;and many researchers are nowadays working on producing new sustainable construction materials incorporating recycled wastes.In this scope,this work uses an experimental approach aiming at understanding the effect of incorporating Expanded Polystyrene(EPS)beads in concrete and proposing thermally improved concrete mixtures for the production of hollow blocks in Lebanese constructions by substituting fine aggregates with recycled products such as EPS in order to promote their insulating properties.Three different diameters of EPS beads(2 mm~3 mm,3 mm~4 mm and 4 mm~5 mm)are studied with different volumetric ratios(20%,40%,60%and 80%)in order to investigate the effect of EPS on the thermal properties of concrete.The results showed that the only the percentage of incorporated EPS beads impacted the thermal performance of the concrete mixtures while the EPS diameters have a negligible effect on the thermal properties of the concrete samples.

Impact of Global Warming on Intensity-Duration-Frequency (IDF) Relationship of Precipitation: A Case Study of Toronto, Canada

Annual maximum rainfall intensity for several duration and return periods has been analyzed according to the Gumbel distribution. The Intensity-Duration-Frequency (IDF) curves before and after 1980 have been computed and compared. For the city of Toronto, it is shown that the rainfall intensities after 1980 are lower than those from before this date. This is especially clear for those of short duration. Comparing our results with those of other authors, it appears that, for the moment, no general law on the impact of global warming on the curves intensity duration frequency cannot be made. It appears that the impact of global warming on rainfall varies with geographic location and that it is not possible to draw some general conclusions across the planet.

耦合修正分析Al−Fe−Ni合金蠕变机理

在引入阈值应力和载荷传递系数后,对Al−Fe−Ni合金的蠕变本构方程进行耦合修正,描述该合金在300和400℃下的位错蠕变。量化结果分析及显微组织表征表明,蠕变过程中位错与共晶相间复杂交互作用是阈值应力的起源。同时,共晶相与基体之间模量的差异引起共晶相分担应力作用。此外,温度对基体及共晶相模量产生的影响差异导致高温时合金阈值应力降低,而应力转移系数增大。这些现象通过有限元模型分析得到进一步的论证。总体而言,共晶合金位错蠕变的控制机理得到了更深层次的量化认识。

Effect of initial gravimetric water content and cyclic wetting-drying on soil-water characteristic curves of disintegrated carbonaceous mudstone

The soil-water characteristic curve(SWCC)is often used to estimate unsaturated soil properties(e.g.strength,permeability,volume change,solute and thermal diffusivity).The SWCC of soil samples is significantly affected by cyclic wetting-drying.To examine how water content and cyclic wetting-drying affect the SWCC of disintegrated carbonaceous mudstone(DCM),SWCC tests were implemented using a pressure-plate apparatus.In addition,SWCC models for DCM considering the initial gravimetric water content and cyclic wetting-drying were developed.The test results showed that the volumetric water content(θ)of the DCM first decreased rapidly and then became stable as matric suction(s)increased.The initial water content affected the SWCC by altering the pore structure of the DCM.For a given number of wetting-drying cycles,the higher the initial water content,the higher the stabilizedθ.At a given s value,θdecreased as the number of wetting-drying cycles increased,which suggests that cyclic wetting-drying reduces the water-holding capacity of DCM.The Gardner model for DCM was constructed considering initial water content and cyclic wetting-drying,and was effective at describing and predicting the SWCC model for DCM.

改良预崩解炭质泥岩的力学行为及微观机理研究

预崩解炭质泥岩在中国西南地区常用作路堤填料。为改善预崩解炭质泥岩力学特性,采用粉煤灰、水泥和红黏土对预崩解炭质泥岩进行处理,通过三轴试验分析改良土的应力-应变关系和抗剪强度指标,并利用扫描电镜和X射线衍射表征其微观结构和矿物成分。结果表明,经水泥改良后预崩解炭质泥岩的应力-应变关系曲线由应变硬化型转变为应变软化型,但粉煤灰和红黏土不改变其应力-应变关系类型。三种添加剂对预崩解炭质泥岩黏聚力影响的大小顺序为:水泥>红黏土>粉煤灰。未加水泥的预崩解炭质泥岩均表现为鼓胀破坏,而经水泥改良的预崩解炭质泥岩均表现为剪切破坏或鼓胀-剪切破坏。由于胶结物能将土颗粒紧密胶结成团,使微观结构更加致密、稳定,因此,改良后预崩解炭质泥岩的力学特性得到显著增强。研究结果可为炭质泥岩在路基工程中的应用提供参考。

基于微观结构的压实二元粉质黏土渗透与持水特性

粉质黏土路堤的耐久性在一定程度上受水分迁移控制,而后者取决于土的水力特性。本文研究了压实二元粉质黏土的水力特性。首先,按不同混合比和干密度制备了的二元粉质黏土试样,并利用扫描电镜和压汞仪分析了粉质黏土的微观结构。然后,通过变水头渗透试验和持水性试验,研究了粉质黏土的渗透性和持水性。结果表明,当黏土含量为100%时,压实后黏土颗粒分散性良好,并呈现定向排列特征。随着黏土含量降低,黏土颗粒的定向排列逐渐受到粉粒存在的干扰,导致粉粒周围形成许多大孔隙。但粉粒周围孔隙的数量随着干密度的增加明显减小。并且,随着黏土含量和干密度的增加,粉质黏土的渗透性降低而持水性增强。黏土含量和干密度越大,粉质黏土中的孔隙越少,对水体流动的阻碍越强。粉质黏土的渗透与持水特性均可通过孔径分布特征参数进行预测。