Cement substitution with secondary materials can reduce annual global CO2 emissions by up to 1.3 gigatons

Abstract

Population and development megatrends will drive growth in cement production, which is already one of the most challenging-to-mitigate sources of CO2 emissions. However, availabilities of conventional secondary cementitious materials (CMs) like fly ash are declining. Here, we present detailed generation rates of secondary CMs worldwide between 2002 and 2018, showing the potential for 3.5 Gt to be generated in 2018. Maximal substitution of Portland cement clinker with these materials could have avoided up to 1.3 Gt CO2-eq. emissions (~44% of cement production and ~2.8% of anthropogenic CO2-eq. emissions) in 2018. We also show that nearly all of the highest cement producing nations can locally generate and use secondary CMs to substitute up to 50% domestic Portland cement clinker, with many countries able to potentially substitute 100% Portland cement clinker. Our results highlight the importance of pursuing regionally optimized CM mix designs and systemic approaches to decarbonizing the global CMs cycle.

Reducing Pb and Cl Mobility in Waste-to-Energy Fly Ashes via Chlorellestadite Formation

“…Correspondingly, the waste-to-energy (WTE) ashes produced from incineration require better management and upcycling, as opposed to the current practice of landfilling. These WTE ashes are a promising secondary reactive material containing development minerals that can partially substitute cement in concrete and reduce its carbon footprint . Unfortunately, the WTE ashes cannot be directly upcycled in concrete because they are concentrated in chlorides that are known to affect hydration kinetics and accelerate steel corrosion.…”

“…These WTE ashes are a promising secondary reactive material containing development minerals that can partially substitute cement in concrete and reduce its carbon footprint. 74 Unfortunately, the WTE ashes cannot be directly upcycled in concrete because they are concentrated in chlorides that are known to affect hydration kinetics and accelerate steel corrosion. This article demonstrated an ash treatment protocol for transforming the nonreadily removable chlorides in WTE ashes into chlorellestadite.…”

Thermodynamics of calcined clays used in cementitious binders: origin to service life considerations

“…To be able to predict and understand the behaviour of these complex materials when exposed to certain environments, we will start by discussing the different ideal minerals, to describe their (thermo)chemistry and compositional variability that would represent real-life clays that will be used in blended cement production, which may be either quite pure or relatively impure. It is noted that alkali-activation is another (potentially very attractive) pathway to the production of clay-based cementitious binders, [10][11][12] but is deemed to be beyond the scope of the current review, which is instead focused on blends with Portland cement. The review will include a description of calcination process modeling and the aspects that can be inuenced to control and optimise the process.…”

Elucidating the Size and Shape of Individual Clinker Phases via Raman Imaging: Impact on Cement Hydration

“…Although the finer cements are energy intensive due to the requirement of increased grinding, and the increased fineness also increases the water demand and the heat generated, the practical benefit of high early strength to modern, fast-paced construction schedules has necessitated the production and acceptance of increasingly finer cements. Increasing use of supplementary cementitious materials (SCMs) and blended cements, due to sustainability-driven interest in reducing the clinker factor, further necessitates the use of finer cements as finer PSDs have been shown to give higher early strengths . Nevertheless, grinding continues to be the biggest source of energy consumption in a typical cement plant where the PSD reduction accounts for roughly two-third of the electrical energy consumption for cement production (100 kW h/ton of cement) …”