Environmental and technical assessment to support sustainable strategies for limestone calcined clay cement production in Brazil
TL;DR: In this article, the authors analyzed the mechanical and environmental performance of an alternative low-carbon cement (Limestone Calcined Clay Cement, LC3) made from different Brazilian natural and waste clay-based materials.
Abstract: This study analyzed the mechanical and environmental performance of an alternative low-carbon cement (Limestone Calcined Clay Cement, LC3) made from different Brazilian natural and waste clay-based materials. Data from an extensive laboratory program to characterize the alternative materials have been utilized. A Life Cycle Assessment (LCA) based on a cradle-to-gate approach was also performed. The results give decision-makers and the cement industry a better understanding of environmental impact at regional, national, and local levels. Moreover, this study opens a new perspective on the natural and waste clay-based materials to further the production of eco-efficient cements in Brazil and other countries.
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TL;DR: In this article , the authors investigated the environmental impact of modified granulated copper slag (MGCS) utilization in blended cement production at a representative cement plant in China, and the life cycle impact assessment (LCIA) model was applied.
Abstract: This study aimed to investigate the environmental impact of modified granulated copper slag (MGCS) utilization in blended cement production at a representative cement plant in China. Sensitivity analysis was performed on the substance inputs, and the life cycle impact assessment (LCIA) model was applied. A detailed comparative analysis was conducted of the environmental impact of cement production in other studies, and ordinary Portland cement production at the same cement plant. Results showed that calcination has the largest contribution impact of all the impact categories, especially in causing global warming (93.67%), which was the most prominent impact category. The life cycle assessment (LCA) result of blended cement was sensitive to the chosen LCIA model and the depletion of limestone and energy. In this study, producing blended cement with MGCS effectively mitigated the environmental impact for all the selected impact categories. Results also show a reduction in abiotic depletion (46.50%) and a slight growth (6.52%) in human toxicity. The adoption of MGCS in blended cement would therefore generally decrease the comprehensive environmental impact of cement, which contributes to the development of sustainable building materials.
3 citations
TL;DR: In this paper , the current situation of the cement industry in Latin America and the Caribbean and the global opportunities and strategies to reduce the carbon footprint of cement and concrete and their adaptation to the regional conditions are discussed.
Abstract: Carbon neutrality to limit global warming is an increasing challenge for all industries, particularly for the cement industry, due to the chemical emission of the process. For decades, reducing the clinker factor has been one of the main strategies to reduce the carbon footprint. Additional cuttings in the clinker content of cements seem possible with the upsurge of novel supplementary cementitious materials. This potential contribution represents only a fraction of the required carbon reductions for achieving the goal of carbon neutrality in the coming decades. This paper describes the current situation of the cement industry in Latin America and the Caribbean and the global opportunities and strategies to reduce the carbon footprint of cement and concrete and their adaptation to the regional conditions. Besides describing emerging supplementary cementitious materials, the potential contributions of industrialization and quality control are discussed. Moreover, limitations related to geography and standardization are analyzed. Regional considerations are made given the specific prospects of human development.
2 citations
TL;DR: In this article , a methodology was performed from a circular economy perspective using the systematic Classification-Potentiality-Quantity and feasibility-application (CPQvA) criterion for identifying potential applications of these materials.
Abstract: Mineral coal reserves are distributed across all continents in more than 70 countries. The extraction and industrial processing of these reserves generate large amounts of tailings. These tailings are composed of three residual fractions: pyritic, clayey, and carbonaceous. In Brazil, approximately 49% of these generated materials is disposed of in controlled industrial landfills. In China, nearly 15% of the total run of mine (ROM) is discarded as waste. In this context, the present study analyzes the valorization potential of such wastes based on the technical–scientific information from recent literature and characterization of the waste generated in southern Santa Catarina, Brazil. This new methodology was performed from a circular economy perspective using the systematic Classification–Potentiality–Quantity and feasibility–Application (CPQvA) criterion for identifying potential applications of these materials. Based on the evaluation criteria, the waste was classified as environmentally nonhazardous and noninert (class II-A). The waste was primarily composed of silica, alumina, and iron oxide (52.43%, 21.35%, and 6.40%, respectively). This chemical characterization and the mineralogical characterization of the predominant phases—quartz, muscovite, and kaolinite—were similar to those of the raw materials used for manufacturing construction materials. The potential analysis of different fractions, based on circular economy principles, inferred that most residual fractions (approximately 60% of the total discarded material) had mineral characteristics and geographical availability. Therefore, coal tailings have great application potential in the construction sector. The separation of the generated waste into different fractions according to their origins and production characteristics will become one of the innovations in the search for cleaner production and a more circular economy.
2 citations
TL;DR: In this article , the synergistic effect of combining supplementary cementitious materials (SCMs) as partial substitutes for clinker improves cement properties and reduces its clinker factor and, hence, its carbon footprint.
Abstract: The synergistic effect of combining supplementary cementitious materials (SCMs) as partial substitutes for clinker improves cement properties and reduces its clinker factor and, hence, its carbon footprint. Limestone-calcined clay cement (LC3)—a family of clinker, calcined clay, and limestone filler mixes—is studied worldwide for its properties equivalent to those of Portland cement. Although slag and fly ash are no longer sufficient to keep up with current commercial blended cements, in the long run, these SCMs can support the development of optimized formulations for the future. By relating the environmental and the mechanical performances, the GHG emission intensity offers a broader assessment and selection perspective. In this article, 13 blended cements were evaluated: ternary, quaternary, and multi-admixture (i.e., OPC plus 4 SCMs) blends with clinker factor between 40 and 50%, composed of—in addition to calcined clay and limestone filler—blast furnace slag and fly ash. Compressive strength was measured at 3, 7, 28, 91, and 365 days. The greenhouse gas (GHG) emissions were estimated through life cycle assessment and related to the blends’ compressive strength unit. Quaternary and multi-addition cements consistently outperformed after 3 days of age, demonstrating the benefits of the synergistic effect between SCMs jointly on GHG emissions and compressive strength. Such an effect enables reducing not only the clinker factor and carbon footprint but also the GHG emission intensity, which relates both. This study showed that the formulated cements, particularly those composed of multi-additions (Series D), are potential alternatives for reducing the GHG emissions, whilst preserving mechanical performance demanded by construction market practices. From a multidisciplinary analysis standpoint, durability assessments are necessary to complement the reported findings, as low clinker contents can affect the pH of the concrete’s pore solution and carbonation which ultimately lead to deterioration.
2 citations
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TL;DR: The main conclusions of an analysis of low-CO2, eco-efficient cement-based materials, carried out by a multi-stakeholder working group initiated by the United Nations Environment Program Sustainable Building and Climate Initiative (UNEP-SBCI) are presented, based on the white papers published in this special issue as discussed by the authors.
Abstract: The main conclusions of an analysis of low-CO2, eco-efficient cement-based materials, carried out by a multi-stakeholder working group initiated by the United Nations Environment Program Sustainable Building and Climate Initiative (UNEP-SBCI) are presented, based on the white papers published in this special issue. We believe that Portland-based cement approaches will dominate in the near future due to economies of scale, levels of process optimisation, availability of raw materials and market confidence. Two product-based approaches can deliver substantial additional reductions in their global CO2 emissions, reducing the need for costly investment in carbon capture and storage (CCS) over the next 20–30 years: 1. Increased use of low-CO2 supplements (SCMs) as partial replacements for Portland cement clinker. 2. More efficient use of Portland cement clinker in mortars and concretes. However, other emerging technologies could also play an important role in emissions mitigation in the longer term, and thus merit further investigation.
1,268 citations
TL;DR: In this paper, the authors present a review of coal fly ash at the global level, focusing on its current and potential applications, including use in the soil amelioration, construction industry, ceramic industry, catalysis, depth separation, zeolite synthesis, etc.
Abstract: Coal fly ash, an industrial by-product, is derived from coal combustion in thermal power plants. It is one of the most complex anthropogenic materials, and its improper disposal has become an environmental concern and resulted in a waste of recoverable resources. There is a pressing and ongoing need to develop new recycling methods for coal fly ash. The present review first describes the generation, physicochemical properties and hazards of coal fly ash at the global level, and then focuses on its current and potential applications, including use in the soil amelioration, construction industry, ceramic industry, catalysis, depth separation, zeolite synthesis, etc. Finally, the advantages and disadvantages of these applications, the mode of fly ash utilization worldwide and directions for future research are considered.
1,167 citations
TL;DR: The use of metakaolin (MK) as a pozzolanic material for mortar and concrete has received considerable attention in recent years as mentioned in this paper, which is part of the widely spread attention directed towards the utilisation of wastes and industrial by-products in order to minimise Portland cement consumption, the manufacture of which being environmentally damaging.
Abstract: The utilisation of calcined clay, in the form of metakaolin (MK), as a pozzolanic material for mortar and concrete has received considerable attention in recent years. This interest is part of the widely spread attention directed towards the utilisation of wastes and industrial by-products in order to minimise Portland cement (PC) consumption, the manufacture of which being environmentally damaging. Another reason is that mortar and concrete, which contain pozzolanic materials, exhibit considerable enhancement in durability properties. This paper reviews work carried out on the use of MK as a partial pozzolanic replacement for cement in mortar and concrete and in the containment of hazardous wastes. The literature demonstrates that MK is an effective pozzolan which causes great improvement in the pore structure and hence the resistance of the concrete to the action of harmful solutions.
1,077 citations
TL;DR: According to the International Energy Agency, the main levers for cement producers are the increase in energy efficiency and the use of alternative materials, be it as fuel or raw materials as mentioned in this paper, and therefore, the cement industry worldwide is facing growing challenges in conserving material and energy resources, as well as reducing its CO 2 emissions.
Abstract: Cement will remain the key material to satisfy global housing and modern infrastructure needs. As a consequence, the cement industry worldwide is facing growing challenges in conserving material and energy resources, as well as reducing its CO 2 emissions. According to the International Energy Agency, the main levers for cement producers are the increase in energy efficiency and the use of alternative materials, be it as fuel or raw materials. Accordingly, the use of alternative fuels has already increased significantly in recent years, but potential for further increases still exists. In cement, the reduction of the clinker factor remains a key priority: tremendous progress has already been made. Nevertheless, appropriate materials are limited in their regional availability. New materials might be able to play a role as cement constituents in the future. It remains to be seen to what extent they could substitute Portland cement clinker to a significant degree.
1,075 citations
TL;DR: In this paper, a brief discussion of the class of cementing materials known as "alkali-activated binders" is provided, which are identified to have potential for utilization as a key component of a sustainable future global construction materials industry.
Abstract: This paper, which forms part of the UNEP White Papers series on Eco-Efficient Cements, provides a brief discussion of the class of cementing materials known as ‘alkali-activated binders’, which are identified to have potential for utilization as a key component of a sustainable future global construction materials industry. These cements are not expected to offer a like-for-like replacement of Portland cement across its full range of applications, for reasons related to supply chain limitations, practical challenges in some modes of application, and the need for careful control of formulation and curing. However, when produced using locally-available raw materials, with well-formulated mix designs (including in particular consideration of the environmental footprint of the alkaline activator) and production under adequate levels of quality control, alkali-activated binders are potentially an important and cost-effective component of the future toolkit of sustainable construction materials.
1,052 citations