Yajing Wang

Bio: Yajing Wang is an academic researcher. The author has contributed to research in topics: Life-cycle assessment. The author has an hindex of 1, co-authored 1 publications receiving 32 citations.

Comparative study of cement manufacturing with different strength grades using the coupled LCA and partial LCC methods—A case study in China

Abstract: A life cycle assessment (LCA) and partial life cycle cost (LCC) were carried out to identify the environmental and economic burdens of six different strength grades of cement manufacturing in China. The comparative results show that the higher the strength grade of the cement, the greater the environmental impacts and the slightly better economic performance compared with cement with lower strength grade. Common cement has more environmental impacts and a higher economic cost than the early strength cement with the same strength grade. The mid-point LCA and partial LCC results indicated that high resource and energy consumption, direct emissions and the transport of raw materials during cement production are the main processes contributing to the majority of the environmental categories and the economic cost. The endpoint LCA results indicate that the impacts generated with respect to global warming and resource categories made dominant contributions to the overall environmental burdens. Effective approaches to reduce the environmental impacts and economic cost of the cement industry in China include promoting cement production technology, decreasing the consumption of limestone and energy and increasing the energy recovery rate, and optimizing the transport distance.

Characteristics and applications of fly ash as a sustainable construction material: A state-of-the-art review

Abstract: Due to their good performance and environmental friendliness, fly ash-based construction materials have great potential as alternatives to ordinary Portland cement. To realize sustainable development and beneficial use of fly ash in the construction industry, this paper presents a comprehensive review of relevant literature to evaluate the properties and performance of fly ash, with a particular focus on recent advances in characterization, compositional understanding, hydration mechanism, activation approaches, durability and sustainability of fly ash as a construction material. Several key aspects governing the performance of fly ash, including chemical composition, activator type and hydrates evolution in concrete, are highlighted. Finally, the important needs, pertinent to the optimal and broad utilization of fly ash as an integral part of sustainable construction materials, are identified for further research and development, where large-scale application studies, further classification of fly ash, advanced characterization tools and technology transfer to biomass fly ash are recommended.

The past and future of sustainable concrete: A critical review and new strategies on cement-based materials

Abstract: The negative impacts of cement-based material (CBM) production are way bigger than ever expected. To illustrate the scale of this phenomenon, all the forests in the world, regardless of the fact that they are disappearing at an alarming rate, are not enough to offset even half the environmental impact (EI) of global aggregates and cement production. Thus, it is necessary to promote scientific research and guide more researchers and professionals in the construction industry to investigate the undiscovered sustainability paths, namely for concrete before and after end-of-life. For that purpose, a global and extensive review is made here to provide an overall view of concrete sustainability in all possible paths. Then, each path is organized as follows: (i) brief introduction, (ii) presentation of non-traditional materials and techniques that can be used for the selected strategy, (iii) their limitations and (iv) future trends. The study also identifies what is already known to avoid putting valuable research resources into redundant scientific studies. The following paths of concrete production sustainability were identified: mix composition (e.g. reduce the EI and resources use of binders, aggregates, water and reinforcement), materials manufacturing (e.g. new production techniques of cement, aggregates and steel bars), concrete mixing (e.g. mixer type and mixing method), on-site application (e.g. regular casting and digital concrete/3D printing), and in-service performance (e.g. increase the durability of reinforced concrete and carbon capture and thermal conductivity). On most of these paths, many studies have been made on the same non-traditional materials and techniques and similar outputs were obtained. Yet, many other non-traditional materials and techniques have not been explored before, or are incomplete in terms of the characteristics analysed. More than providing definite solutions, this contribution intends to open the minds of the readers to the vastly unexplored world of “green concrete”.

Comparative LCA on using waste materials in the cement industry: A Hong Kong case study

Abstract: Cement is traditionally regarded as an energy and emission intensive construction material. The reduction of environmental impacts in the cement industry has gained increasing concern worldwide for environmental sustainability. As a resource-scarce city, cement production in Hong Kong is associated with high CO2 emissions, thus contributing significantly to the high environmental impacts in the construction industry. This study herein has been conducted to comprehensively assess the energy consumption and global warming potential impacts of different types of cement manufactured in Hong Kong using life cycle assessment (LCA) techniques. Two sustainable strategies for the reduction of energy consumption and greenhouse gases emission in the cement industry were then proposed. The LCA results showed that ordinary Portland cement production has high environmental impacts mainly due to the import of associated raw materials and burning of fossil fuel. The use of alternative material, such as fly ash would help to reduce the environmental impacts. Significant impacts reductions associated with cement production can be further achieved by strategies such as the use of glass powder from locally generated waste glass bottles as part of the raw materials, and the use of a bio-fuel produced from locally generated wood wastes as a co-fuel with coal. The assessment results indicated that about 12% of the total greenhouse gases emission and 15% of energy consumption can be reduced from the cement industry in Hong Kong by using waste materials to replace virgin materials (clinker/coal).

Evaluation of environmental impact distribution methods for supplementary cementitious materials

Abstract: As the world’s most widely used construction material, the production of concrete has been recognized to lead to major environmental impacts. To promote sustainability in the concrete industry, various kinds of supplementary cementitious materials (SCMs), such as fly ash, blast furnace slag and silica fume have been used to replace cement in concrete production. The nature of these SCMs has therefore been changed from wastes to co-products or by-products. Life cycle assessment (LCA) has been increasingly adopted in the concrete industry to assess environmental sustainability. However, the choice of an appropriate method for impact distribution in the LCA of concrete incorporating SCMs is a research challenge. This study aimed to present a comprehensive review of the impact allocation approaches for assessing the environmental impacts of SCMs-incorporated concrete. Furthermore, the use of the system expansion approach was compared with the conventional mass and economic allocation approaches. A case study of concrete production using SCMs in Hong Kong was conducted using the different approaches. The results were then analyzed and it was concluded that the system expansion approach is appropriate for the assessment of the environmental impacts of SCMs-incorporated concrete.

Finding an economic and environmental balance in value chains based on circular economy thinking: An eco-efficiency methodology applied to the fish canning industry

Abstract: The production of food that is environmentally friendly and presents a high economic return is one of the current concerns for the food industry. Eco-efficiency links the environmental performance of a product to its economic value. In this context, this study combines Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) to propose a two-step eco-efficiency methodology assessment for the fish canning industry. An eco-label rating system based on a descriptive weighting of environmental (Global Warming Potential, Acidification Potential, Eutrophication Potential and the ReCiPe Single Score Endpoint) and economic (Value Added) indicators was applied to the canned anchovy. Secondly, LCA-LCC results were coupled to linear programming (LP) tools in order to define a composite eco-efficiency index. This approach enables translation into economic terms of the environmental damage caused when a given alternative is chosen. In particular, different origins for anchovy species (South American vs. Cantabrian) and related waste management alternatives (landfill, incineration and valorization) were evaluated under this cradle to gate approach. Results indicated that substantial differences can be observed depending on the origin of the fish. Anchovies landed in Cantabria show a higher value added score at the expense of larger environmental impacts, mainly due to fuel use intensity. Moreover, its environmental scores are lowered when fish residues are valorized into marketable products, while increasing the value added. This study demonstrates the environmental and economic benefits of applying circular economy. According to this, it is possible to introduce the cradle-to-cradle concept in the fish canned industry. The methodology proposed is intended to be useful to decision-makers in the anchovy canning sector and can be applied to other regions and industrial sectors.