This article makes a strong case that prescriptive specifications are an impediment to sustainability. Some of the least sustainable prescriptive requirements are the use of minimum cementitious contents, restrictions on types and dosages of SCMs, and the overuse of maximum w/cm. It is not feasible to adopt an optimized prescriptive specification. On the other hand, performance-based specifications allow for mixture optimization, which requires producers and contractors to be more knowledgeable about their materials. Performance-based specifications reward attaining lower variability, which promotes investment in better quality and improved technology practices. Optimized mixtures with a lower variability will result in mixtures that are more cost-effective and sustainable. The article concludes by making a case that sustainability is more than CO2 emissions from cement and concrete production only.

Today, the demand for high-performance building materials continues to grow along with the demand for "green" product manufacturing and sustainable building practices. Supplementary cementitious materials (SCMs) and blended cements offer sustainable and performance advantages for those who build and occupy structures of all kinds. The growing use of these environmentally friendly materials is due to several performance factors, including low permeability, resistance to chlorides and sulfates, mitigation of alkali silica reaction, greater strength, lower temperatures for mass concrete, and improved workability. The use of cementitious blends not only results in stronger, more durable, high-performance concretes but also helps reduce global climate impact by lowering energy consumption and greenhouse gas emissions. In fact, each ton of portland cement that is replaced by SCMs reduces CO2 emissions by approximately 0.8 ton (0.7 metric ton). Using cementitious blends also reduces solid waste disposal because SCMs are by-products from other industries. These environmental benefits are increasingly important to project developers and owners.

The transportation industry is viewed by some as less sustainable due to its lack of a green rating system similar to the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) system. However, many long-standing design considerations of the transportation market segment have embraced sustainable design criteria. This paper relates current bridge design and construction terminology to sustainable design concepts and the sustainable benefits of precast concrete. A case study of the Otay River Bridge illustrates some of these concepts in practice. Sustainable concepts discussed in the case study include material choices, minimizing site disturbance, community involvement, and wildlife preservation.

Concrete is the most widely used building material in the world. Fortunately, concrete, especially architectural and decorative concrete, is a very sustainable material. The constituent materials that make up concrete are readily available throughout most of the world and can be collected, processed, and manufactured in an environmentally sound manner. Concrete has low embodied energy and great thermal mass that can enhance buildings’ energy efficiency. All human activities have some greenhouse gas associated with them. The electrical power generation and transportation sectors of our economy generate over 60% of the greenhouse gas emissions in the United States. The greenhouse gas emissions associated with concrete and cement’s manufacture is only approximately 1% of the U.S. total. Durability and superior life cycle are solid benefits commonly associated with decorative and architectural concrete. When using Life-Cycle Assessments conforming to international standards, concrete outperforms other building products because it conserves resources by preventing premature replacement and excessive maintenance while delivering superior service life and smaller environmental impacts than other commonly used building products. Architectural concrete is sustainable because it combines form and function in a single material. Designers and industry professionals can improve the long-term viability of architectural finishes and decorative elements by anticipating maintenance needs and designing with the future in mind.

This CD-ROM consists of seven papers that were presented by ACI Committees 130 and 233 at the ACI Spring convention in San Antonio, TX, in 2009. Topics include Performance-Based Specifications for Concrete to Advance Sustainable Development, Supplementary Cementitious Materials for Sustainability, and Cementitious Blends and Their Impact on Sustainable Construction. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-269