Mix Design Levers and Decision Points-Lower-Carbon Precast Concrete - Webinar 3

Lower-Carbon Precast Concrete - Webinar 3 - Mix Design Levers and Decision Points

Pdf Summary

The PCI Lower-Carbon Precast Concrete Webinar #3, held on August 28, 2025, focused on mix design strategies and innovations to reduce the embodied carbon in precast concrete while maintaining or improving performance. The series aims to educate precast producers on sustainability, covering foundational sustainability principles, low carbon cement materials, and mix design levers.<br /><br />Dr. Charles Nmai of Master Builders Solutions, an expert with over 38 years in concrete technology and sustainability, presented the webinar. He detailed the global construction industry's increasing drive towards low-carbon concrete, influenced by environmental regulations, green building demands, and corporate sustainability goals. Concrete producers face growing requirements to reduce Global Warming Potential (GWP) by 20-30% through 2025, 30-60% toward 2030, and ultimately achieve net-zero emissions by 2050.<br /><br />Key challenges for low-embodied-carbon concrete (LECC) include increased water demand, mix stickiness, finishing difficulties, and slower strength development impacting production schedules. Dr. Nmai emphasized the importance of conducting trials to evaluate low-carbon cements and SCMs (supplementary cementitious materials) to identify operational impacts.<br /><br />Innovative admixture technologies provide solutions: <br />1. C-S-H (calcium silicate hydrate) nanoparticle-based strength-enhancing admixtures accelerate hydration, boost early and late strength, and enable reduced Portland cement content.<br />2. Rheology-modifying water-reducing admixtures improve workability, reduce mix viscosity, enhance pumping and finishing traits, and decrease defects like bugholes.<br /><br />Case studies showed how these admixtures support achieving strength targets with lower cement content or alternative cements such as Portland-Limestone Cement (PLC), while also reducing GWP. Mixing optimization and admixture use helped overcome stickiness and curing delays typical of some low-carbon mixes.<br /><br />In summary, producers must stay informed, plan ahead, test mixes thoroughly, and leverage available admixture technologies to meet sustainability specifications. These commercially ready solutions allow precast concrete producers to reduce environmental impact without compromising quality or productivity.<br /><br />PCI encourages members to utilize their sustainability resources and participate in ongoing educational efforts to advance low-carbon concrete practices.

Keywords

low-carbon precast concrete

embodied carbon reduction

mix design strategies

supplementary cementitious materials

C-S-H nanoparticle admixtures

rheology-modifying admixtures

Portland-Limestone Cement

global warming potential reduction

concrete sustainability

precast concrete production challenges