With the concern of cement production as a major contributor of CO2 emissions, alternate materials have ramped up anti-cement development and marketing. The wood industry, for example, is pushing hard to promote expanded use of its products as renewable materials in tall structures. However, even timber, unquestioned as the sustainable preference, has its issues and escapes reporting its substantial impacts. While renewability is a great single attribute, reality is in the whole.
In such a holistic view, concrete holds up well, and concrete masonry is even more attractive as it utilizes far less cement than poured-in-place concrete. (See Concrete Masonry: An Optimized Low Carbon Wall.) For concrete masonry, the bulk of cement is contained in masonry grout that fills the cells of cmu, and by volume is the greater component in the wall. The good news is much work has been done to vet alternatives to Portland cement in masonry grout mix design. (See also CarbonKind Low Carbon CMU.)
Below are downloads related to research conducted in supplemental cementitious material (SCM) replacement of Portland cement in masonry grout, and an article on the minimal use of cement in concrete masonry structures compared to solid concrete walls.
Replacement of Portland Cement with Supplemental Cementitious Materials in Masonry Grout, Fonseca, Fernando S., Ph.D., S.E., and Siggard, Kurt, Director, Concrete Masonry Association of California and Nevada. Presented to 15th International Brick and Block Masonry Conference, Florianópolis, Brazil, 2012
High Supplemental Cementitious Material (SCM) Grout Phase 2 and 3 Research, Masonry Chronicles Winter 2010-11, Maribeth S. Bradfield, P.E., LEED AP.
High Volume Fly Ash Masonry Grout, Fernando S. Fonseca, Ph.D., S.E., and Kurt Siggard, Structure Magazine, May 2012.
There's More to Concrete Masonry
The inherent benefits of CMU are substantial, yet Angelus Block has lowered the CMU-related CO2 even further with CarbonKind™ Low Carbon CMU.
The tremendous improvements offered with CarbonKind CMU provide a potent element to an optimized concrete masonry wall utilizing high SCM masonry grout. They're a powerful carbon-cutting combo. See Concrete Masonry: An Optimized Low Carbon Wall.
And after its manufacture, CMU have exceptional carbon uptake potential, absorbing atmospheric CO2 at notable rates. See Carbon Uptake of Concrete Masonry