Carbon-Trapping Concrete

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.

2018

Each year, more than 4 billion tonnes of cement are produced, accounting for around 8 per cent of global CO2 emissions Making Concrete Change: Innovation in Low-carbon Cement and Concrete Executive Summary vi | #ConcreteChange all will need to be deployed at scale to meet the decarbonization challenge. Some of these solutions are well recognized and common to other sectors: for instance, the energy efficiency of cement plants can be increased, fossil fuels can be replaced with alternatives, and CO2 emitted can be captured and stored. The main focus of this report, however, is on those emissions mitigation solutions that require the transformation of cement and concrete and are thus unique to the sector. More than 50 per cent of cement sector emissions are intrinsically linked to the process for producing clinker, one of the main ingredients in cement. As the by-product of a chemical reaction, such emissions cannot be reduced simply by changing fuel sources or increasing the efficiency of cement plants. This report therefore focuses on the potential to blend clinker with alternative materials, and on the use of 'novel cements'-two levers that can reduce the need for clinker itself by lowering the proportion of clinker required in particular cement mixtures. Despite widespread acceptance among experts that these are critical, they have received far less policy focus. Well-known barriers stand in the way of deep decarbonization of cement. The sector is dominated by a handful of major producers, which are cautious about pioneering new products that challenge their existing business models. In the absence of a strong carbon-pricing signal, there is little short-term economic incentive to make changes. Alternative materials are often not readily available at the scale required. Meanwhile, architects, engineers, contractors and clients are understandably cautious about novel building materials. Implementing new practices also implies a critical role for millions of workers involved in using concrete across the urban landscape. Low expectations around the prospects for a radical breakthrough in cement production are reflected in the limited attention given to the sector in key assessments of low-carbon pathways in recent years. 5 As one recent report notes, 'When cement emissions are mentioned at all in public debate, it is typically to note that little can be done about them.' 6 There is, however, a growing sense not only of the urgency of the need to decarbonize cement production, but also of the expanding range of technological and policy solutions. The range of major organizations now working on relevant strategies includes the UN Environment Programme (UNEP), the International Energy Agency (IEA)-working with the industry-led Cement Sustainability Initiative (CSI)-and the Energy Transitions Commission, an initiative involving high-level energy experts and stakeholders aimed at accelerating the transition to low-carbon energy systems. For decision-makers, more insight is needed into the potential for scalable, sustainable alternatives to traditional carbon-intensive cement and concrete. For this report Chatham House worked with CambridgeIP, an innovation and intellectual 5 The New Climate Economy's Seizing the Global Opportunity report mentions energy-intensive sectors such as cement, chemicals and iron and steel 'where emissions are large and significant reduction poses undeniable challenges', without spelling out a potential pathway for reduction of those emissions.

Materials and Structures, 2013

Because of its low cost, its ease of use and relative robustness to misuse, its versatility, and its local availability, concrete is by far the most widely used building material in the world today. Intrinsically, concrete has a very low energy and carbon footprint compared to most other materials. However, the volume of Portland cement required for concrete construction makes the cement industry a large emitter of CO 2. The International Energy Agency recently proposed a global CO 2 reduction plan. This plan has three main elements: long term CO 2 targets, a sectorial approach based on the lowest cost to society, and technology roadmaps that demonstrate the means to achieve the CO 2 reductions. For the cement industry, this plan calls for a reduction in CO 2 emissions from 2 Gt in 2007 to 1.55 Gt in 2050, while over the same period cement production is projected to increase by about 50 %. The authors of the cement industry roadmap point out that the extrapolation of existing technologies (fuel efficiency, alternative fuels and biomass, and clinker substitution) will only take us half the way towards these goals. According to the roadmap, the industry will have to rely on costly and unproven carbon capture and storage technologies for the other half of the required reduction. This will result in significant additional costs for society. Most of the CO 2 footprint of cement is due to the decarbonation of limestone during the clinkering process. Designing new clinkers that require less limestone is one means to significantly reduce the CO 2 footprint of cement and concrete. A new class of clinkers described in this paper can reduce CO 2 emissions by 20 to 30 % when compared to the manufacture of traditional PC Clinker. Keywords Cement Á Carbon emissions Á Clinker chemistry 1 Introduction The link between climate change and human activity is no longer in question. As stated by the U.S. Global Change Research Program in its review 1 of the impacts of climate change in the United States [21]: ''Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil,

Academia Letters, 2021

Nature Reviews Earth & Environment, 2020

The use of concrete is under scrutiny as it appears as one of the few human activities where the transition toward a post-carbon society is not possible unless large investments in risky carbon capture and storage are made. With current urbanization, it is also a sector that is expected to continuously grow, leading to increased resource consumption and emissions. In this review, we aim to shed light on the available solutions that can be implemented in the short and long term to reduce greenhouse gas emissions. Rather than waiting for disruptive technologies that could transform a very slow moving and risk-averse construction sector, this review focuses on the small improvements that every stakeholder involved along the value chain of concrete production and use can achieve. We stress how significant the combined effect of these marginal gains can be. By balancing societal needs, environmental requirements, and technical feasibility, the intention of this review is to show credible pathways for a transition to sustainable use of concrete. Key points • Cement usage is so massive, more than 4 billion tonnes per year worldwide, that large-scale replacement by other materials within the next decade is not possible. • Environmental impact of cement and concrete is low per unit of material, but the amount used makes the impact of the sector highly significant. • Reductions in CO 2 emissions are possible through successive improvement all along the cement and concrete value chain: less clinker in cement, less cement in concrete, less concrete in structures, and less replacement of structures. • By engaging all stakeholders of the construction sector, immediate savings of the order of 50% can be reached without heavy investment in new industrial infrastructure or modification of standards. • Research and development need urgently to be conducted for post-2050 construction to meet future emissions reduction targets. Alternative cement and faster carbonation of concrete should be explored.

Revista Principia - Divulgação Científica e Tecnológica do IFPB, 2021

Life Cycle Assessment (LCA) quantifies the environmental impacts associated with products throughout their life cycle. LCA also assists in the interpretation of impact assessment results, enabling improvements in a product or process. This paper applied the LCA methodology to quantify and compare the greenhouse gas emissions associated with different types of concrete: with a traditional binder (Portland cement) and with alkali-activated materials (Metakaolin, Lateritic Soil, and Lateritic Concretion) as precursors. The environmental impact was evaluated by means of greenhouse gas emissions (kg CO2-eq/m³), considering 1m³ of each binder and resistance of approximately 30 MPa, obtained by a recommended mix ratio. The main objective is to evaluate whether alkali-activated binders present lower emissions than Portland cement. The results demonstrated that Portland cement is responsible for over 92% of the environmental impacts of traditional concrete production. The use of alternative materials in civil construction, such as laterite soil, reduces carbon dioxide emissions by 79% compared to Portland cement concrete emissions. Keywords: Life Cycle Assessment. Carbon Footprint. Concrete. Portland cement. Alkali-activated materials. Resumo A Avaliação de Ciclo de Vida é um método que permite quantificar os impactos ambientais de um produto ou processo ao longo do seu ciclo de vida. Ele também auxilia na interpretação dos resultados, com a finalidade de permitir melhorias no produto ou processo. Este artigo aplicou a metodologia em questão para comparar o processo de obtenção do concreto com o ligante tradicional, o cimento Portland, e os materiais alcalinamente ativados tendo como precursores o Metacaulim, o Solo Laterítico e a Concreção Laterítica. O impacto ambiental foi avaliado por meio das emissões de carbono (kg CO 2 /m 3) considerando 1m 3 de cada aglomerante, em função do traço recomendado para se obter concreto com resistência de aproximadamente 30 MPa. O objetivo principal desse trabalho foi avaliar se os aglomerantes alcalinamente ativados são mais sustentáveis do que o cimento Portland. Os resultados obtidos nesse trabalho mostraram que, na construção civil, a utilização de materiais alternativos como o solo lateritico torna possível uma redução de 79% das emissões de dióxido de carbono, quando comparado com as emissões do concreto de cimento Portland. O cimento Portland é responsável por pouco mais de 92% dos impactos ambientais ocasionados na produção do concreto tradicional.

2020

Carbon dioxide, CO2 accounts for most of the emission from all the types of greenhouse gasses in the world. The ability of CO2 to remain longer than other greenhouse gases and the convenience of producing CO2 has resulted in its high projection in a yearly manner. The prime factor for the emission of CO2 are from the actions of human beings. One such human act is the concrete industry. Total emissions from the concrete industry could therefore contribute as much as 8% of global CO2 emissions. Sequestered CO2 in concrete can provide an impact on reducing the carbon footprint and is also able to improve the compressive strength of concrete. During this process, the sequestered carbon dioxide chemically reacts with cement to produce a mineral, trapping carbon dioxide gas in the concrete. Hence, sequestering carbon dioxide gas in concrete does not only on a bigger scale reduces carbon footprint, but it also reduces the impact the construction industry has on the environment. This paper ...

Cement and Concrete Research, 2018

This paper, which is a contribution to the UNEP series on Eco-Efficient Cements, examines the role of materialbased solutions to reducing CO 2 emissions from cement production considering factors that could influence implementation. Global urbanization has led to an increase in demand for cement and cement-based materials. With its growth in consumption, the associated CO 2 emissions from its production are raising concern. However, the role of mitigation strategies in a global context that account for regional material availability and degree of market adoption have yet to be considered. This work shows that the 2°C scenario targets for 2050 can be met through increased use of calcined clay and engineered filler with dispersants. The introduction of new Portland clinker-based cement alternatives, use of alkali-activated materials, and improvement of efficiency of cement use could further contribute to reduction goals. There are currently-available technologies for reduction that could be rapidly implemented.

PNAS Nexus

Addressing the existing gap between currently available mitigation strategies for greenhouse gas emissions associated with ordinary Portland cement production and the 2050 carbon neutrality goal represents a significant challenge. In order to bridge this gap, one potential option is the direct gaseous sequestration and storage of anthropogenic CO2 in concrete through forced carbonate mineralization in both the cementing minerals and their aggregates. To better clarify the potential strategic benefits of these processes, here, we apply an integrated correlative time- and space-resolved Raman microscopy and indentation approach to investigate the underlying mechanisms and chemomechanics of cement carbonation over time scales ranging from the first few hours to several days using bicarbonate-substituted alite as a model system. In these reactions, the carbonation of transient disordered calcium hydroxide particles at the hydration site leads to the formation of a series of calcium carb...

MRS Bulletin, 2012