Clean production and properties of geopolymer concrete; A review

A review of waste products utilized as supplements to Portland cement in concrete

Carbon dioxide reduction potential in the global cement industry by 2050

Concrete is one of the most widely used building materials with a global consumption rate approaching 25 gigatonnes per year. Consequentially, its environmental burden is significant in terms of resource use and environmental emissions. There is a diverse audience of decision makers and manufacturers who are interested in understanding and lowering the environmental impact of concrete and other buildings materials, which requires a life-cycle assessment (LCA) approach. A critical first step in any LCA is the compilation of a credible life-cycle inventory (LCI), upon which subsequent life-cycle impact assessment (LCIA) can be based. This article reviews the strengths and weaknesses of concrete LCIs to date, and offers a research roadmap to improve the quality of future cement and concrete LCIs and meet the needs of major LCA users.

Life-cycle inventory analysis of concrete production: A critical review

Due to its prevalence in modern infrastructure, concrete is experiencing the most rapid increase in consumption among globally common structural materials; however, the production of concrete results in approximately 8.6% of all anthropogenic CO2 emissions. Many methods have been developed to reduce the greenhouse gas emissions associated with the production of concrete. These methods range from the replacement of inefficient manufacturing equipment to alternative binders and the use of breakthrough technologies; nevertheless, many of these methods have barriers to implementation. In this research, we examine the extent to which the increased use of several currently implemented methods can reduce the greenhouse gas emissions in concrete material production without requiring new technologies, changes in production, or novel material use. This research shows that, through increased use of common supplementary cementitious materials, appropriate selection of proportions for cement replacement, and increased concrete design age, 24% of greenhouse gas emissions from global concrete production or 650 million tonnes (Mt) CO2-eq can be eliminated annually.

https://iopscience.iop.org/article/10.1088/1748-9326/11/7/074029/pdf

Readily implementable techniques can cut annual CO 2 emissions from the production of concrete by over 20

A life-cycle approach to environmental, mechanical, and durability properties of “green” concrete mixes with rice husk ash

Impact of Singapore's importers on life-cycle assessment of concrete

Aggregate consumption rates have now exceeded natural renewal rates, signaling shortages both locally and globally. Even more concerning is that the worldwide markets for construction aggregates are projected to grow at an annual rate of 5.2% in the near future. This increase is attributed to rapid population growth coupled with the economic development worldwide. In terms of material availability, one of the most vulnerable regions is the Asia-Pacific region specifically, Singapore, where there is higher demand but limited availability of natural sand and gravel for use as aggregates in concrete construction projects. This paper focuses mainly on the environmental impacts of fine aggregate alternatives used in high-strength concrete applications in Singapore, which is one of the major global importers of natural sand following China. Singapore has been experiencing political and environmental challenges linked to the shortage of natural sand use as aggregates, even while the demand is increasing in the construction sector. Copper slag, a readily available waste material from shipyards in Singapore, is a possible replacement material for a portion of the natural sand in concrete mixtures, thus sustaining the projected growth in the region. A life-cycle assessment approach is applied to investigate the environmental impacts of copper slag and its alternative use as natural sand in high-strength concrete applications in Singapore. The system boundary consists of the major production processes of concrete constituents (including Portland cement and fine and coarse aggregates, with CS considered as fine aggregate) from a cradle-to-gate perspective, consisting of relevant life-cycle phases of raw materials extraction, transportation, and production processes at the relevant facility where the production occurs. Output from the assessment is provided in terms of embodied energy use and air emissions of concrete mixes with varying percentages of copper slag as fine aggregate. Results show that environmental impacts of aggregates decrease with the increasing substitution rate of natural sand with copper slag when calculated on the basis per unit volume of the concrete mix. For example, 40% and 100% sand replacements with copper slag result in a reduction of 8% and 40% in embodied energy, 12% and 30% in global warming potential, 8% and 41% in acidification, and 7% and 35% in particulate matter formation, respectively. Normalized impacts (i.e., normalized with respect to compressive strength) are observed to remain at almost similar levels for concrete mixes with up to 40% natural sand having been replaced with copper slag. Therefore, it is recommended that replacement of fine aggregates by 40–50% of copper slag (by weight) will produce concrete mixtures with comparable environmental impacts while maintaining feasible durability and strength properties.

/pdf/life-cycle-assessment-of-high-strength-concrete-mixtures-50briiribe.pdf

Life-Cycle Assessment of High-Strength Concrete Mixtures with Copper Slag as Sand Replacement

Globally, construction and operation of the built environment is recognized as a significant source of greenhouse gas emissions (GHG). About 40% of anthropogenic GHG and 40% of raw materials use are assigned to buildings. Concrete, the most widely used man-made material, is used in buildings because of its flexibility and adaptability, its low maintenance requirements during the service life of the structures, and the economic and widespread accessibility of its constituents. The substantial production and consumption of global concrete manufacturing accounts for more than five percent of the human-related carbon dioxide emissions annually, mostly attributable to the production of cement clinker. However, environmental impacts are not limited to only GHG emissions. The analysis and quantification of the overall environmental impacts of concrete manufacturing and its application in building projects requires a holistic approach that is known as life-cycle assessment (LCA). In this dissertation, a new process-based LCA tool (GreenConcrete LCA) was developed for the purpose of evaluating the environmental impacts of concrete from extraction of its raw materials to the end-of-life stage. The GreenConcrete LCA has MS Excel and web versions, both of which have the capability of calculating and comparing the LCA of different concrete mixtures designed for specific project purposes. In the tool, not only the direct but also the supply-chain impacts of manufacturing processes of concrete and its materials are evaluated. The integration of regional variations and technological alternatives within the tool offers a wide range of applicability and flexibility for users in the U.S. and worldwide. The new tool will ultimately allow policy makers, researchers, architects, civil engineers, and government agencies to assess the environmental sustainability of concrete in various building construction projects. With the help of the tool, sensitivity analysis was conducted. GWP reduced significantly with the replacement of ordinary portland cement with supplementary cementitious materials (SCMs) such as fly ash and slag in concrete. Additionally, it was shown that environmentally and structurally advantageous concrete mixtures could be made with high-volumes of fly ash and limestone. A wide range of early and long term strengths were attainable depending on the selected mixture proportion. GHG emissions and criteria air pollutants were also successfully reduced and were in all cases similar to or lower than for ordinary portland cement concrete.The concrete and steel frame versions of a dormitory building in Istanbul were also analyzed. Results from the case study showed that the operation phase dominated in GWP and energy consumption, which is consistent with literature results. Finally, Turkish cement and concrete sector case study scenario analysis show that reductions in CO2-eq emissions can be achieved through, strategic choice of locations for cement and concrete plants for local and international distribution of products by less carbon-intensive modes of transportation, i.e., rail and water; switching to lower-carbon fuels in cement kilns, and expanding the use of biofuels and electric vehicles in delivery of cement and concrete products; Improvements in energy efficiency by installation of existing best available technologies for new plants and replacing older technologies for existing plants, switching to less carbon-intensive energy sources for electricity generation, integration of waste heat recovery systems in cement plants for off-grid electricity generation and using more energy efficient equipment in cement and concrete plants, use of alternative raw materials as sustainable waste management and GHG emission reduction options. Although these strategies can have great potential to abate CO2-eq emissions in cement and concrete industry both in Turkey and globally, technical, regulatory, and economic challenges are still considered obstacles against implementation of new approaches.

Life-Cycle Assessment of Concrete: Decision-Support Tool and Case Study Application

For countries like Singapore that is highly dependent on imported goods, it is essential to consider the consequences of consumption of imported cement and other concrete constituents for a fair carbon trading at global and regional levels. Recently, as a result of reduction in trade barriers and costs of materials and fuels, Singapore does not have much incentive in reducing environmental impacts of these imported goods. However, Singapore has set high environmental targets nationally to reduce impacts from building and construction. In addition to its national efforts, Singapore also needs to take action in trade-related consequences of importing energy-intensive products like cement and aggregates to Singapore. The purpose of this study is to quantify and suggest alternatives for reducing the embodied energy and life-cycle impacts of concrete consumption in Singapore on the basis of current trading volumes of these materials from Singapore’s importers. A detailed life-cycle assessment of concrete manufacturing in Singapore is performed to suggest possible ways to reduce the environmental impacts from importing cement and aggregates from Singapore’s trade partners based on an earlier life-cycle inventory developed for Singapore and its neighboring countries. Life-cycle impact assessment (LCIA) impact characterization factors are based on a midpoint-oriented and hierarchist approach as defined by ReCiPe method. Following the LCIA, a scenario analysis is conducted to select the best combination of cement and aggregate importers of Singapore based on their environmental performance. Results from the scenario analysis show that overall impacts can be reduced by importing the materials from a nearer source with efficient production technologies and greener fuel mixes. About 10–34 % reduction is estimated in embodied energy, acidification, eutrophication, global warming potential, smog, and health impacts by importing from a closer and technologically greener source. Despite the limitations due to data and modeling uncertainties, this study constitutes a baseline/benchmark for addressing the current cement and aggregate markets and associated environmental impacts of concrete consumption in Singapore based on historical import quantities of cement and aggregates from neighboring countries of Singapore. In the near future, policy-related action would be influential in achieving Singapore’s national and global environmental targets in buildings and construction sector. Incorporation of an LCA approach into Green Mark Scheme (GMS) by the Building and Construction Authority (BCA) is recommended for Singapore to comply both with its national goals and with its new climate action plan to the UN Framework Convention on Climate Change.

Aysegul Petek Gursel

Papers

A life-cycle approach to environmental, mechanical, and durability properties of “green” concrete mixes with rice husk ash

Impact of Singapore's importers on life-cycle assessment of concrete

Life-Cycle Assessment of High-Strength Concrete Mixtures with Copper Slag as Sand Replacement

Life-Cycle Assessment of Concrete: Decision-Support Tool and Case Study Application

Comparative life-cycle impact assessment of concrete manufacturing in Singapore