Conclusion
A complete substitute to cement does not yet exist on a commercial level—replacing concrete as a building technology is not practicable. It is strong and versatile. This has made it the most widely used building material in the world after water. It is relatively inexpensive to manufacture, and construction is relatively easy to teach as well. The concrete market is expected to grow to more than USD 480 billion by 2029,22 just 21 years ahead of the 2050 goals of the Paris Agreement and the over simple answer of simply removing cement, as with the bounty on snakes, is not going to work.
The industry’s priority today must be to not only curb embodied carbon, but also build good concrete. This means a diversification of supply sources, which include cellulose fibres, nano infused cements not only helping to reduce cement content, but aid in maximizing the benefits to be had with slag, fly ash, PLC, and grasping a new reality of high alkalinity concrete that did not exist just a few years ago.
Similar to the cobras of colonial India, increasing the sustainability of concrete is a complex problem and requires complex solutions. While a simple solution of removing cement and replacing with other materials seems simple, these material changes to concrete bring with it additional problems which must be addressed for the solution to work. Changing the material nature of concrete requires a similar change of approach to curing it. This ensures builders avoid inadvertently creating other problems in the concrete market, not least of which is lesser performing concrete with perhaps an even higher carbon footprint than first realized. This is all too often the case with simplistic solutions to complex problems. However, by digging a little deeper, and approaching a complex problem, such as reducing embodied carbon with more complex solutions, including updating curing methods, utilizing other types of SCMs, the industry cannot only reduce embodied carbon, but also make incredibly resilient, long life cycle concrete in much shorter schedules than ever before.
Notes
1 Read Alkali-silica reaction in concrete, published by Understanding Cement, https://www.understanding-cement.com/alkali-silica.html.
2 Read What Happens if Concrete is Not Cured Properly, published by The Constructor, https://theconstructor.org/concrete/inadequate-concrete-curing/30895/.
3 Refer to UK Concrete, published by Mineral Products Association, https://www.mineralproducts.org/Campaigns/UK-Concrete.aspx.
4 See H.F.W Taylor’s Cement Chemistry (2nd edition, vol.2), published in 1997 by Thomas Telford, for more on Locher’s 1966 work.
5 See Properties of Cements and Concrete Containing Fly Ash, by R.E. Davis et al, as published by the American Concrete Institute (ACI) in 1937.
6 See Composition and Microstructure of 20-year old Ordinary Portland and Cement-ground Granulated Blast-furnace Slag blends Containing 0 to 100% Slag, published in Cement and Concrete Research, 2010.
7 Consult Supplementary Cementitious Materials, published by Euclid Chemicals, https://www.nahb.org/-/media/NAHB/nahb-community/docs/councils/bsc/supplementary-cementitious-materials.pdf).
8 See Portland-Limestone Cement and Sustainability, published by PCA, https://www.cement.org/sustainability/portland-limestone-cement.
9 Refer to Factors Affecting the Rate of Evaporation, published by Byju’s, https://byjus.com/chemistry/factors-affecting-rate-of-evaporation/
10 Consult Legislative and Regulatory Timeline for Cement Kiln Dust Waste, published by United States Environmental Protection Agency (EPA), https://www.epa.gov/hw/legislative-and-regulatory-timeline-cement-kiln-dust-waste.
11 Consult Cement Kiln Dust Waste, published by EPA, https://archive.epa.gov/epawaste/nonhaz/industrial/special/web/html/index-2.html#:~:text=to%20learn%20more.-,Introduction,back%20into%20the%20production%20process.
12 See Soluble Silicates in Industry, by James G. Vail, published by Journal of the Society of Chemical Industry, https://onlinelibrary.wiley.com/doi/abs/10.1002/jctb.5000480211.
13 Watch Comparing Curing Methods for Concrete, by Tyler Ley, https://www.youtube.com/watch?v=1siLxrpm_PE.
14 Consult Chloride Penetration—Remedial Measures, published by Penn State College of Engineering (PSU), https://www.engr.psu.edu/ce/courses/ce584/concrete/library/chemical/clrem.html.
15 Consult Logistics Market by Mode of Transport, published by Allied Market Research, https://www.alliedmarketresearch.com/logistics-market.
16 Refer to Marin County Code Chapter 19.07, https://www.marincounty.org/-/media/files/departments/cd/planning/sustainability/low-carbon-concrete/12172019-update/low-carbon-concrete-code.pdf?la=en.
17 See What is the Paris Agreement?, published by the United Nations, https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement.
18 See Amazon Sustainability Goals and Progress, published by Amazon, https://sustainability.aboutamazon.com/our-approach/goals-and-progress.
19 See Changing the Language of Concrete, by Chris Bennett et al., https://prezi.com/conferences/construct/
20 See Effect of Nanoporuous thin silica films on interface microstructure and bond strength of cementitious grouts, by Jose F. Muñoz et al., published by Construction and Building Materials, https://www.researchgate.net/publication/349953198_Effect_of_nanoporous_thin_silica_films_on_interface_microstructure_and_bond_strength_of_cementitious_grouts
21 Watch Internal Curing Effect of Concrete Containing Colloidal Nano Silica (CNS), by the American Concrete Institute (ACI), https://www.youtube.com/watch?v=MEeowhp3IwQ
22 See NCCS, https://www.linkedin.com/feed/update/urn:li:activity:6740623195524726784/.
23 Consult Guide to External Curing of Concrete, by ACI Committee 308, published by ACI, https://www.concrete.org/portals/0/files/pdf/previews/308r_16_preview.pdf.
24 Read Cement Market Size, Share & Covid-19 Impact Analysis, published by Fortune Business Insights, https://www.fortunebusinessinsights.com/industry-reports/cement-market-101825.
Authors
Chris Bennett is the founder and CEO of Bennett Build, an industry-recognized leader in concrete consulting. His portfolio includes the longest history of helping project teams in commercial internal curing in North America. His firm enjoys a diverse cliental of global developer and design teams and a wide variety of project types. Bennett has also helped improve continuing education in concrete by facilitating such programs as The National Concrete and Corrosion Symposium, Concrete North, and various hands-on reality labs with institutions such as University of Alberta, the University of Akron National Center for Education and Research on Corrosion and Materials Performance (NCERCAMP), the Construction Specifications Institute (CSI), and the International Society for Construction Sciences (iSCS). His work has been featured at Dreamforce, Construct, Praxis!, World of Concrete, and more. He can be reached at chris@bennettbuild.us.
Rae Taylor, Ph.D., holds a doctorate in civil engineering and materials science from the University of Leeds, and a postgraduate certificate in technology management from the Open University. Her research includes a focus on the effect of cement replacement materials and additives on cement microstructure. She can be reached at raemorristaylor@gmail.com.
Keith Robinson, RSW, FCSC, FCSI, is an associate at Dialog in Edmonton, Alberta. Robinson also instructs courses for the University of Alberta, acts as an advisor to several construction groups, and sits
on many standards review committees for ASTM and the National Fire Protection Association (NFPA). He can be reached at krobinson@dialogdesign.ca.
Ken Hercenberg is a senior specifier at Corgan with more than 40 years of experience in design and construction services. Hercenberg specializes in project manual production, building envelope design, code reviews, quality and constructability reviews, keynoting, and sustainability.
what is being done to reduce carbon?