The American Concrete Institute is promoting a guide to alternative cements which, it says, “is intended as an introduction for engineers, architects, contractors, and owners who are interested in using an alternative cement on a project, but lack experience with these materials.”
The guide, says ACI, “assumes (that) the reader has experience with conventional concrete materials and construction, and is seeking knowledge on how these new cement technologies compare to Portland cement when used in concrete.”
According to the ACI guide, “Portland cement concrete (PCC) is unrivalled when it comes to versatility and durability and, as such, is the most widely used man-made material on Earth. Countless civil engineering and architectural structures use concrete in their construction, including roads, bridges, public water and sanitary systems, and buildings. Almost 200 years of experience has resulted in a solid, practical understanding of how PCC works, and with the correct mixture design and materials, practitioners can manipulate concrete to easily meet the needs of society.
As engineers, architects, and contractors continue to push the bounds of what is possible in design and construction, materials must evolve as well, which is where alternative cements come in. To serve as an alternative to Portland cement, a binder technology needs to offer demonstrable improvements when considering factors such as environmental impact, life-cycle cost (LCC), and performance.
The use of an alternative cement is motivated by one or more of three main drivers: reduced costs … both initial cost and LCC; reduced environmental impact; and the need for specific properties unattainable with PCC.”
ACI goes on to say that: “Improving the sustainability of construction is clearly one force driving the emergence of alternative cement concrete technologies. Increasingly, construction alternatives are being considered in terms of their LCC, in addition to or in place of initial cost. When it comes to LCC determination, the industry has considerable experience with PCC and can estimate the individual costs that contribute to the LCC. For some alternative cements, the industry still needs to develop that experience and establish life-cycle costs. A life-cycle cost is strongly intertwined with the material’s functional performance and is inextricably linked to its durability.”
But, “given their recent development, long-term durability data are not available for all alternative cements.”
As is the case with all manufacturing processes, Portland cement production has environmental impacts that represent a cost to society. Chief among these are: the energy-intensive nature of producing Portland cement; and the inherent release of greenhouse gas (GHG) emissions in the production process. A key advantage of alternative cement production is a significant reduction in environmental impact as compared to Portland cement.”
Research shows that alternative cements generate “anywhere from 44% to 84%” less CO2 during their manufacturing process.
“Another aspect of functional performance is constructability,” says the report. “To achieve the desired hardened properties, the concrete must be properly placed and cured in the field. This aspect limits the application of some alternative cements that require specific non-atmospheric curing regimes such as a CO2-rich curing environment, or elevated temperatures. For other alternative cements, rapid setting and rapid strength gain, as compared to PCC, are principal value-added aspects of their performance. Constructability also depends on the availability of knowledgeable people to both place and adjust the mixture designs to achieve the desired performance. Therefore, it is necessary to have a workforce that is trained and able to proportion, test, mix, place, and cure these new materials.”
This important guide covers both currently available and emerging alternative cements, says ACI, “and is intended to aid people interested in using alternative cements in a project. A brief summary of each of the alternative cement technologies is provided, as well as selected case studies and a guideline for use that addresses mixture design as well as construction and design properties.”
If you would like a copy of the Practitioner’s Guide for Alternative Cements, please contact the American Concrete Institute at: 38800 Country Club Drive, Farmington Hills, MI 48331. USA. Tel: 001 248 848 3700. Web: www.concrete.org