Comparative carbon emission assessments of recycled and natural aggregate concrete: Environmental influence of cement content

IF 8.5 1区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Geoscience frontiers Pub Date : 2021-11-01 DOI:10.1016/j.gsf.2021.101235
Marian Sabău , Dan V. Bompa , Luis F.O. Silva
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引用次数: 36

Abstract

This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications. The environmental influence of cement content, aggregate production, transportation, and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region. To obtain a detailed insight into the optimum life cycle parameters, a sensitivity study is carried out in which supplementary cementitious materials, different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered. The results show that carbon emissions were between 323 and 332 kgCO2e per cubic metre of cement only natural aggregate concrete. These values can be reduced by up to 17% by replacing 25% of the cement with fly ash. By contrast, carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50% and 100%, and transportation is not included in analysis. However, the concrete with 50% recycled aggregate presented lower increase, only 0.3% and 3.4% for normal and high strength concrete, respectively. In some cases, the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%, and case-specific transportation distances were considered. In absolute values, the concrete mixes with 100% recycled aggregates and 25% fly ash had lower carbon emissions than concrete with cement and natural aggregates only. Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short (15–25 km) and the cement replacement by fly ash is equal or higher than 25%, considering that the mechanical properties are adequate for practical application. The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete, recommending them as an alternative to achieving global sustainability standards in construction.

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再生和天然骨料混凝土的碳排放比较评估:水泥含量对环境的影响
这项工作考察了再生骨料混凝土生产对环境和地球化学的影响,其性能代表了结构应用。水泥含量、骨料生产、运输和废物填埋的环境影响是通过进行生命周期评估和考虑主要针对该地区的生命周期清单来分析的。为了获得最佳生命周期参数的详细信息,进行了敏感性研究,其中考虑了补充胶凝材料,不同的天然与再生骨料含量比值和特定情况下的运输距离。结果表明,每立方米水泥纯天然骨料混凝土的碳排放量在323至332千克二氧化碳当量之间。如果用粉煤灰代替25%的水泥,这些数值最多可降低17%。相比之下,当天然粗骨料以50%和100%的比例被再生骨料替代时,碳排放量会增加,并且不包括运输。而掺加50%再生骨料的混凝土的增幅较低,普通混凝土和高强混凝土的增幅分别只有0.3%和3.4%。在某些情况下,当粉煤灰取代水泥的比例为25%时,运输对总碳排放的相对贡献增加,并且考虑了具体情况的运输距离。从绝对值上看,掺100%再生骨料和25%粉煤灰的混凝土比仅掺水泥和天然骨料的混凝土碳排放量更低。考虑到实际应用所需的力学性能,粉煤灰输送距离较短(15 ~ 25 km),粉煤灰水泥替代量等于或大于25%,可获得较高的环境效益。本文的观察结果表明,具有结构构件强度特征的再生骨料混凝土可以比传统混凝土具有更低的碳排放,建议将其作为实现建筑全球可持续性标准的替代方案。
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来源期刊
Geoscience frontiers
Geoscience frontiers Earth and Planetary Sciences-General Earth and Planetary Sciences
CiteScore
17.80
自引率
3.40%
发文量
147
审稿时长
35 days
期刊介绍: Geoscience Frontiers (GSF) is the Journal of China University of Geosciences (Beijing) and Peking University. It publishes peer-reviewed research articles and reviews in interdisciplinary fields of Earth and Planetary Sciences. GSF covers various research areas including petrology and geochemistry, lithospheric architecture and mantle dynamics, global tectonics, economic geology and fuel exploration, geophysics, stratigraphy and paleontology, environmental and engineering geology, astrogeology, and the nexus of resources-energy-emissions-climate under Sustainable Development Goals. The journal aims to bridge innovative, provocative, and challenging concepts and models in these fields, providing insights on correlations and evolution.
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