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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.

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The large volume o Rui He f the using of Portland cement makes the industry a large emitter of CO2 despite it has a relatively low carbon footprint compared to most other construction materials. The CO2 curing has been found to be an effective method to achieve carbon neutrality of cementitious materials. In this work, cementitious materials with the addition of nano-silica were cured by CO2. The carbon footprint of cementitious materials with and without the addition of nano-silica was calculated. The mechanical performance of cementitious materials cured by CO2 is tested. The chemical composition of cementitious materials cured by CO2 incorporated with various dosage of nano-silica is characterized by thermogravimetric analysis (TGA) and X-ray powder diffraction (XRD). The pH value change of cementitious materials after CO2 curing is measured. The pore structure of cementitious materials is characterized by mercury intrusion porosimetry (MIP) and 3D X-ray microscopy (Micro-CT) techniques. The morphology of CO2 curing products is also characterized by scanning electron microscope (SEM) analysis. The results indicates that the CO2 curing method can significantly reduce the car-bon footprint of cementitious materials. The addition of nano-silica can improve the mechanical performance and result in a dense microstructure of cementitious materials.

An important part of improving the embodied carbon of the built environment is reducing the carbon emissions associated with concrete. The beneficial use of carbon dioxide (CO2) in ready mixed concrete production has been developed and installed as a retrofit technology with industrial users. An optimum dose of CO2 added to concrete as an admixture leads to the in-situ formation of mineralized calcium carbonate (CaCO3) and can increase the concrete compressive strength. The improved performance can be leveraged to design concrete mixture proportions for a more efficient use of portland cement along with the use of CO2 to reduce the carbon footprint of concrete. The physicochemical aspects of CO2 mineralization, the fresh and hardened concrete performance, durability performance and life cycle impacts will be discussed.

High carbon emissions of cementitious materials are increasingly raising concerns under the grand goal of global carbon neutrality. This presentation will introduce an approach to achieve low-carbon cementitious materials and enhance the mechanical properties while retaining the desired constructability for cast-in-place and precast applications of civil infrastructure. The proposed approach utilizes CO2 to produce a CaCO3 suspension that is uniformly dispersed and used to prepare cement pastes. The mechanical properties were tested, and the results showed that the 28-day compressive strength was increased by up to 16%. Further research was conducted to understand the effects of CaCO3 suspension on cement hydration kinetics and microstructures of cement pastes through isothermal calorimetry, thermal gravimetry analysis, mercury intrusion porosimetry, dynamic light scattering analysis, and scanning electron microscopy. The results revealed that the CaCO3 suspension promoted cement hydration and densified the microstructures because of the nucleation effect caused by the high-level dispersion of CaCO3 particles. The proposed approach provides an alternative solution for CO2 utilization in the concrete industry with minimal modification of the manufacturing facility and offers a promising avenue for achieving low-carbon infrastructure.

Buildings are a significant source of greenhouse gas (GHG) emissions. Much has been done to lower operational carbon. However, GHG emissions from construction activities and embodied in the materials used to build buildings can, in certain circumstances, constitute a majority of the 10-15-year GHG footprint of a building. Decarbonization of construction materials is a viable and scalable opportunity for project teams and can contribute to achievement of LEED certification. This webinar will cover basics of GHG accounting and foot printing of construction materials, and introduce the EC3 tool as a viable means for owners, designers and contractors to reduce GHG emissions in their building projects.