Eco-friendly mortar with high-volume diatomite and fly ash: Performance and life-cycle assessment with regional variability

Replacing Portland cement with supplementary cementitious materials (SCMs) reduces the high environmental impacts of cement production. However, in western U.S., such reduction is limited by the shortage of local SCMs. The use of diatomite (DE), abundantly deposited in western U.S., into cementitious materials can mitigate this local shortage. In this study, up to 60% cement was replaced with DE, fly ash (FA), and limestone, for reduced environmental impacts of mortar production. The workability and compressive strength of mortars with high-volume SCMs were comparable to 100%-cement mortar at optimized mix proportions. The energy consumptions, global warming potential (GWP), and air pollutants emissions of the production of 13 mixes were evaluated with cradle-to-gate life-cycle assessment in a California-based scenario. For a more comprehensive understanding of the regionally-variable greenness of the mixes, scenarios of mortar mixing in 11 U.S. states were modeled to estimate the energy consumptions and GWP from different processes, under the consideration of source locations of cement, FA, and DE in 18 states/provinces in U.S. and Canada and the geographically-dependent electricity grids and transport distances. In all cases, the environmental impacts are proven greatly reduced with the green mixes. Through optimization of transportation modes and electricity grids at resource origins, environmental impacts of producing green cement-based materials are further reduced in SCMs-lacking regions. The combined use of DE and FA in blended cement is promising for both mechanical and environmental benefits even in regions without their local deposits. (C) 2020 Elsevier Ltd. All rights reserved.