Larry Sutter, Ph.D., P.E., is the Principle of Sutter Engineering LLC. He is also Professor Emeritus and a Research Professor in Materials Science & Engineering at Michigan Technological University. His focus is concrete durability, the use of supplementary cementitious materials (SCMs), and the advancement of alternative cements and SCMs. He is a Fellow of the American Concrete Institute (ACI) and Chairman of Committee 321 Concrete Durability Code, Vice-Chairman of ACI Committee 232 Fly Ash and Secretary of ACI Committee 201 Concrete Durability. He is President of the Board for the ACI Center of Excellence for Carbon Neutral Concrete (NEU). He is also a Fellow of ASTM and a member of Committees C01 and C09, serving as Vice Chair of Committee C09 and Chairman of subcommittees C01.14 Non-Hydraulic Cements and C09.24 on Supplementary Cementitious Materials. He is a Registered Professional Engineer in Michigan.
Progress towards sustainability through performance-based standards and specifications
Historically, specifications for cement and concrete materials, as well as for concrete mixtures, have been largely prescriptive-based and evolved from local or national experience. Specific performance criteria such as strength requirements are obviously used, but performance requirements reflecting other properties, such as durability, are not common. Prescriptive limits such as water to cement (w/c) or water to cementitious materials (w/cm, or water to binder, w/b) ratios and minimum cement contents are largely based on experience with concrete performance using portland cements and were adopted prior to the widespread use of supplementary cementitious materials (SCMs), blended cements, and chemical admixtures. As an example, the durability of concrete in aggressive exposures is largely related to its resistance to the penetration of aggressive fluids, and concretes made with blended cements or SCMs have much better resistance than portland cement concretes made at the same w/cm. It would therefore be better (and more sustainable) to use a performance test to evaluate equivalent fluid penetration resistance for different concrete mixtures rather than to set a required w/c. The result is that prescriptive specifications often provide barriers to use of more sustainable materials combinations and as we work to attain specific sustainability goals, prescriptive specifications often are counter-productive to achieving those goals. To address these issues, standard tests and specifications are evolving and industry is moving towards performance specifications. For portland cement and blended cement concretes using conventional SCMs and admixtures, testing to support performance specifications has also evolved. Examples of these advancements will be discussed along with remaining challenges. Also, the use of alternative materials is increasing, leading to new and more complex concrete mixtures. With more complex mixtures, there is increased potential for unexpected interactions between new cement and SCM combinations when used together with a wide range of chemical admixtures, which can result in unexpected performance. For these new materials, specifications will be developed but it will not be sufficient to rely solely on those materials specifications without evaluating their performance in concrete mixtures. To address this, several ASTM tests have been developed to evaluate the performance of the entire cementitious plus admixture system in mortars or pastes. Some of these developments as well as future needs are discussed.