Identifying Regulatory and Practical Challenges in Decarbonizing New England Cement-Based Infrastructure by Using Supplementary Cementitious Materials

Abstract

Solutions to lower the greenhouse gas (GHG) emissions associated with cement-based products include replacing high-emission Portland cement with low-emission materials derived from industrial by-products and waste streams, such as supplementary cementitious materials (SCMs). Despite their environmental and performance benefits, increasing SCM utilization in Department of Transportation (DOT) infrastructure faces regulatory and practical challenges. The objective of this study is to systematically identify these challenges as well as opportunities for more extensive use of SCMs. This investigation starts with reviewing DOT standard specifications and comparing DOT standard specifications with industry standard specifications for concrete. It concludes with estimating available conventional and alternative SCMs. In our review of DOT standard specifications across the New England region, we found that several applications call for 100% Portland cement. Precast and prestressed concrete applications allow for the widest range of cement types and replacement, whereas mortar and grout applications allow for the most limited range. Cement replacement in industry standard specifications tends to be higher than DOT standard specifications, with 10%, 45%, and 1% gaps for fly ash, slag, and silica fume, respectively. Using SCMs relies on having steady supplies of these materials. The availability of fly ash, slag, and silica fume amounted to 55% of Portland cement consumption in 2018, while the availability of other secondary materials including biochar, glass pozzolan, and copper tailings amounted to 320%. Even as we deplete conventional SCMs, large supplies of alternative SCMs will remain untapped.