Role of conductive spreader layer in reducing surface temperature of HMA pavements

Rutting is a common type of shear failure-related deformation in asphalt (hot mix asphalt, HMA) pavements. It occurs over time as a result of slow, repeated heavy loads from vehicles moving along the wheel path. This problem is most noticeable when the pavement is at a high temperature and its stiffness is the lowest. Previous investigations have concluded that flowing water in pipes embedded in the pavement leads to a reduction in surface temperature, and consequently rutting. However, the thermophysical properties of HMA limit the cooling effect to a small region immediately around the pipe. It is proposed that the area of cooling be enhanced by adding a highly conductive spreader layer below the pavement in conjunction with the pipe. A theoretical design optimisation has been carried out by exploring different aspects of the spreader layer–pipe spacing (W), depth of the pipe–spreader (D), spreader thickness (t _s), thermal conductivity (k _s) and variation in the boundary conditions. Finite element modelling predicts that a properly designed, highly conductive spreader layer will lead to a significant reduction in surface temperature with a minimal piping network leading to an extended functional life of the HMA pavement.     

Development and analysis of high-performance green concrete in the urban infrastructure

Cement production accounts for approximately 5% of total global CO₂ emissions from all human activities. In addition, the consumption of virgin aggregates for concrete infrastructure has created virgin material scarcity issues in many areas of the USA. High-performance green concrete (HPGC) with fly ash and recycled aggregates can help reduce the demand for material inputs and reduce pollution outputs associated with bulk material flow of urban concrete. Structural and durability tests showed that HPGC containing fly ash and 50% recycled aggregate (100% of the coarse aggregate fraction) performed equally or better than 100% ordinary Portland cement concrete with the same cementitious content. Durability improvements were more significant with Class F than Class C fly ash. For both Class F and Class C fly ash, greater per cent replacement of Portland cement with fly ash led to slower and lower strength gain, but still within acceptable strength criteria for Colorado Department of Transportation Class B concrete. This paper quantifies the sustainability of HPGC in urban infrastructure by addressing structural performance, environmental, economic and resource depletion impacts.     

Life Cycle Assessment as Part of Sustainability Assessment for Chemicals (5 pp)

Background LCA is the only internationally standardized environmental assessment tool (ISO 14040-43) for product systems, including services and processes. The analysis is done ‘from cradle-to-grave’, i.e. over the whole life cycle. LCA is essentially a comparative method: different systems fulfilling the same function (serving the same purpose) are compared on the basis of a ‘functional unit’ - a quantitative measure of this function or purpose. It is often believed that LCA can be used for judging the (relative) sustainability of product systems. This is only partly true, however, since LCA is restricted to the environmental part of the triad ‘environment/ecology - economy - social aspects (including intergenerational fairness)’ which constitutes sustainability. Standardized assessment tools for the second and the third part are still lacking, but Life Cycle Costing (LCC) seems to be a promising candidate for the economic part. Social Life Cycle Assessment still has to be developed on the basis of known social indicators.Method and Limitations LCA is most frequently used for the comparative assessment or optimization analysis of final products. Materials and chemicals are difficult to analyse from cradle-to-grave, since they are used in many, often innumerable product systems, which all would have to be studied in detail to give a complete LCA of a particular material or substance! This complete analysis of a material or chemical is evidently only possible in such cases where one main application exists. But even if one main application does exist, e.g. in the case of surfactants (chemicals) and detergents (final products), the latter may exist in a great abundance of compositions. Therefore, chemicals and materials are better analysed ‘from cradle-to-factory gate’, leaving the analysis of the final product(s), the use phase and the ‘end-of-life’ phases to specific, full LCAs.Conclusion A comparative assessment of production processes is possible, if the chemicals (the same is true for materials) produced by different methods have exactly the same properties. In this case, the downstream phases may be considered as a ‘black box’ and left out of the assessment. Such truncated LCAs can be used for environmental comparisons, but less so for the (environmental) optimization analysis of a specific chemical: the phases considered as ‘black box’ and left out may actually be the dominant ones. A sustainability assessment should be performed at the product level and contain the results of LCC and social assessments. Equal and consistent system boundaries will have to be used for these life cycle tools which only together can fulfil the aim of assessing the sustainability of product systems.     

生命周期评价在水泥企业清洁生产审核中的应用

利用生命周期评价工具对企业的生产过程进行全面分析与评价,做好企业清洁生产的审核工作具有重要理论研究价值和现实应用意义。运用生命周期评价方法对重庆小南海水泥厂普通硅酸盐水泥生产过程进行了初步评价,认识了普通硅酸盐水泥生产过程的环境协调性,为普通硅酸盐水泥进一步提高环境性能提供了理论依据。     

Environmental and Cost Assessment of a Polypropylene Nanocomposite

This paper describes a study on the use of a polypropylene (PP)/layered silicate nanocomposite as packaging film, agricultural film, and automotive panels. The study’s main question was “Are the environmental impacts and costs throughout the life cycle of nanocomposite products lower than those of products manufactured from conventional materials?” The conventional (benchmark) materials studied were pure polypropylene as packaging film, pure polyethylene as agricultural film, and glass fiber-reinforced polypropylene as automotive panels. In all three cases, the use of the PP nanocomposite resulted in a reduction of the amount of material used, while ensuring the same functionality. Material reduction was estimated using Ashby’s material indices and amounted to ?9% for packaging film, ?36.5% for agricultural film, and ?1.25% for automotive panels. It goes without saying that a product’s impact on the environment will decrease when less material is used. The production and incorporation of nanoparticles, however, may have additional impacts. We found clear environmental benefits throughout the entire life cycle when the PP nanocomposite is used in the manufacture of agricultural film. We noted some cost benefits when the nanocomposite is used in the production of agricultural film and automotive panels. If the price of nanoclay is at most €5,000 tonne then the cost of nanocomposite packaging film is also lower than that of the conventionally produced product.     

生命周期环境成本核算方法研究

生命周期环境成本以成本企业作为进行生态产品设计的重要手段,但生命周期环境成本至今没有国际标准方法。本文对环境成本的分类、研究主体和研究动因进行了分析。对两种不同类型的生命周期环境成本核算方法进行了比较,认为基于环境影响评价结果的生命周期环境成本核算方法在国内具有较好的应用前景。     

GEIA-STD-0009《系统设计、研制和制造可靠性大纲标准》分析

研究了GEIA-STD-0009《系统设计、研制和制造可靠性大纲标准》的制定背景,分析了该标准的制定过程,主要介绍了该标准4个可靠性目标及信息流,简述了每个目标的6个组成部分,详细阐述了13项规范性可靠性活动.     

工业园区水管理创新研究

随着工业化和城市化进程,中国的水环境和水安全问题凸显。工业园区在中国经济发展过程中贡献突出,但同时也是环境污染特别是水环境污染的重要来源之一。在日益趋严的绿色生态发展政策导向下,园区实施可持续水管理具有重要现实意义和理论价值。研究基于全生命周期思考和系统优化原则,提出园区水管理创新概念模型,包含供(取)水、用水、废水处理、排放、污水再生回用、污泥处理处置及资源化等与水管理相关的关键环节组成的全生命周期园区水管理体系,实现生命周期全过程管理,防范水风险,改善水环境质量。从多利益相关方的角度,协同园区、企业、周边流域三个层面,采用PDCA循环,设计包含水管理问题识别、成因分析、实施对策和绩效考核四部分的园区水管理创新概念、框架及基本流程,制定以园区管理机构和企业为实施主体的全方位园区水污染防治关键行动,以达到园区和企业水资源消耗总量与用水强度双向优化、周边流域源洁流清,实现可持续生态化绿色发展的长期目标。