ACI Online Learning & Presentations

Portland cement is the most mass-produced human-made material on earth. Since the invention of Portland cement, it has become an indispensable material for building structures and social infrastructure, and it is now the cornerstone of modern society. The CO2 emitted by the cement industry is estimated to account for approximately 7% of the world's total emissions. From this background, the sector of concrete industry reacts against CO2 emissions. In this contribution, activities of government, societies, and each company in concrete sector of Japan are summarized and discuss the direction of the required research, activities, and pathway to collaboration.

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The last couple of decades have been characterized by a global awareness on rising greenhouse gas emissions, with the Intergovernmental Panel on Climate Change calling for 50-85% reductions in these emissions by 2050 to prevent threatening climate changes. The building and construction industries have been among the leading consumers of material by mass for almost 100 years, with approximately 5% of all anthropogenic global CO2 emissions being originated from Portland cement manufacture. With global population growth and rapid development of third world countries, it is very unlikely that advancements in the process efficiency of material manufacture will occur fast enough to meet emission reduction needs. Thus, new metrics that account for material performance and environmental impact concurrently during design and material selection stages is of great importance and represents a great opportunity for game-changing methods to reduce emissions. This study presents an innovative approach to design and characterize concrete materials with strengths up to UHPC levels, using a framework that allows one to efficiently design concrete mixtures considering multi-objective performance levels. A strategic framework of experimental data collection is coupled with machine learning models to generate performance and emission density diagrams (PDDs and EDDs, respectively). These diagrams intend to provide a flexible tool to evaluate performance, durability, and environmental impacts concurrently, without adding exhausting experimental campaigns. Addressing this issue is critical for public education and industry engagement on next-gen concrete materials such as UHPC, considering the very high cement content often required to achieve the outstanding properties of this material.

The concrete industry is one of the primary sources contributing to the world’s carbon dioxide (CO2) emissions. Therefore, the researcher and the industry are striving to improve sustainability and reduce the carbon footprint of cementitious materials. Enhancing the self-healing performance and mechanical properties of cementitious materials would positively benefit the life cycles and sustainability of concrete structures. In this study, colloidal nano silica (CNS) was incorporated in low carbon self-healing cementitious materials to investigate their mechanical properties and self-healing performance. The important mechanical behavior, including compressive, tensile, flexural properties, and bonding strength were assessed. The results indicated that the incorporation of CNS could effectively improve the mechanical properties of cementitious materials, particularly, the compressive strength would rise 13% to 27%, and flexural strength can increase 7% to 9% with the CNS additional ratio of less than 1% by weight of cementitious materials. Both non-destructive and destructive testing methods were implemented to monitor the medium-term self-healing performance of cementitious materials with various CNS incorporation rates. The samples were pre-cracked and placed under two different environmental conditions during the healing period. The thermal gravity analysis (TGA) and scanning electron microscope (SEM) were conducted to understand the hydration performance of each mixture. It is summarized that the CNS incorporation rate between 0.3% to 0.6% percent would be the optimal ratio for low carbon self-healing cementitious materials to have remarkable mechanical properties and self-healing performance.

Due to the increasing threat posed by climate change, there is a growing interest in reducing greenhouse gas (GHG) emissions throughout the economy. Considerable focus has been placed on the use of concrete, as Portland cement-based concrete is responsible for roughly 1.5% of the GHG emissions in the United States, with some estimating it is responsible for up to 8% of the world's anthropogenic GHG emissions. Concrete airfield pavements offer an opportunity for our industry to immediately reduce our GHG emissions through improved material selection and proportioning without compromising longevity or economic life cycle costs. Currently available strategies will be discussed as will emerging technologies that may offer additional savings. The presentation will conclude with a discussion on assessment and the need to use a standardized approach to quantify environmental impact as a means to ensure real improvement.

Commitment to reducing the environmental impact of concrete is of great importance nowadays. In case of self-consolidating concrete (SCC), this is of critical significance given the fact that the binder content of such concrete needed to ensure the required rheological properties is normally high. The present study aims to propose an appropriate design approach for producing SCC of low carbon footprint (Eco-SCC) for building applications. The presentation elaborates the step-by-step methodology to develop the Eco-SCC including packing density approach to optimize the volumetric proportions of sand and coarse aggregate to achieve an ideal particle gradation curve. The water content is adjusted to provide the necessary minimum paste volume to obtain self-consolidating properties. The powder composition is determined according to rheological optimizations of pastes to reduce the water demand while satisfying mechanical properties and durability considerations. Such design method is found to be effective for obtaining Eco-SCC. Mixtures with total powder content ranging from 280 to 310 kg/m3 are shown to exhibit satisfactory workability characteristics and 28-day compressive strengths in the range of 25 to 30 MPa and low drying shrinkage for building applications.

In most emerging economies of the World, such India, major construction is expected during this decade in both infrastructure and housing sectors. This presents a great opportunity for more efficient, responsible, and sustainable technologies to be implemented. This would require the consolidation and research, if needed, in the areas of waste processing, lean technologies, scaling-up and policy changes for large-scale adoption. Waste processing would go beyond fly ash, waste clay and slag, to consider construction and demolition waste, and non-recyclable plastics. Analytical tools, life estimation and demonstration of techniques such as 3D-printing need to be applied for lean philosophies to be applied at the site. Scaling-up would require test beds, simulation, visualization, and adoption management. Policy notes, road maps and influencing stakeholders will be needed for large-scale changes. Though the challenges may appear daunting, international collaboration and strengthening of local centres of excellence could provide the relevant solutions. IIT Madras has initiated a project along these lines with the participation of about 20 of its faculty members, 30 research scholars, and several collaborators from around the globe (https://civil.iitm.ac.in/pcoe/tlc/). The talk would present recent results, goals, and the potential collaboration with entities such as ACI and RILEM in this initiative.

This talk will discuss the demand for low-carbon cement and concrete by architects and owners to achieve more sustainable structures. Also addressed will be current and proposed legislative and executive measures that would require lower carbon materials for public and private projects.

Buildings alone account for 40% of the global greenhouse gas emissions. Two thirds of that total impact is from operational emissions while the remainder is from embodied emissions. Embodied emissions include all the emissions required to produce everything that goes into our buildings – the structure, enclosure and all the materials inside. Between now and 2050, half of the new construction emissions between now and then will be from embodied carbon. Therefore, the industry has begun to take action and groups like AIA 2030, Architecture 2030, SE2050, and USGBC have shifted their focus to include embodied carbon. In order to address this issue, we need to take steps to quantify and then reduce our impact. We can do this using a process called Whole Building Lifecycle Assessment (WBLCA). More and more project teams are using WBLCA as a design tool and are discussing decarbonizations strategies. As such, design professionals are actively and looking for low carbon material alternatives. Since cement is such a ubiquitous and carbon-intensive material, it is definitely at the center of these discussions. It’s important that the concrete industry be aware of what is being discussed in the market and how this will affect our industry in the future as this trend grows. This presentation will also look at examples of how this translates to the design documents, the specifications and ultimately the concrete mix designs.

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This presentation will discuss how slag cement and other supplementary cementitious materials (SCMs) can help reduce the carbon impact of concrete products and show attendees how to use industry wide documents and tools. Topics covered include: • Key terms and definitions commonly used when discussing the carbon impact of concrete; • How initiatives like the LEED point system, Architecture 2030, and the Carbon Leadership Forum are influencing the use of concrete materials; • How to reduce the carbon impact of concrete using SCMs like slag cement; and • How to use product specific information on slag cement including EPDs and LCA Calculator tools to show customers sustainable and durable options for concrete.

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