The project identified changes in portland cement composition that occurred in recent years and developed, based on a limited investigation, tentative recommendations for modifying current cement specifications and related tests.

The chemical requirements and physical properties of portland cement are set forth in AASHTO M 85, Standard Specification for Portland Cement. However, many concrete bridge decks, pavements, and other highway structures, built with concrete mixtures incorporating portland cements meeting these requirements, have exhibited varying degrees of premature deterioration caused by factors such as freezing and thawing, internal and external sulfate attack, alkali-aggregate reaction, and reinforcing steel corrosion. There has been considerable debate about the contribution of cement to this deterioration, particularly in view of the adoption of cost-effective, energy-efficient, and environmentally beneficial cement production methods that seem to influence cement characteristics. Therefore, there is a need to assess the effects of cement characteristics on concrete durability; identify combinations of chemical, physical, and mineralogical requirements to ensure durability; and develop recommendations to help improve cement specifications.

The research included a review of literature relevant to the effects of cement and clinker characteristics on durability of portland cement concrete commonly used in the various types of highway construction, identified the changes in portland cement composition that occurred in recent years, conducted a laboratory investigation to determine the effects of cement characteristics on certain aspects of concrete durability, and developed tentative recommendations for changes to cement specifications and tests. The agency final report is summarized in NCHRP Research Results Digest 270.