National Concrete Pavement Technology Center

Project description

Recent transportation industry studies have highlighted a growing uncertainty regarding the availability of Class F fly ash along with a trend towards incorporating alternative supplementary cementitious materials (SCMs) like raw or calcined natural pozzolans (e.g., calcined clay) and waste products (e.g., reclaimed/harvested coal ashes and ground ashes). Within the next 5 years, the industry is expected to face an urgent need for integrating these alternatives to produce sustainable and durable concrete for diverse highway applications. However, current standards may not allow the use of alternative SCMs or may not adequately evaluate their efficacy in mitigating durability issues such as alkali-silica reactivity (ASR), corrosion, freeze-thaw cycles, and oxychloride formation. Research under NCHRP Project 10-104, “Recommendations for Revision of AASHTO M 295 Standard Specification to Include Marginal and Unconventional Source Coal Fly Ashes,” proposed a research plan to enhance the AASHTO M 295 (ASTM C 618) specifications and to develop effective tests for measuring SCM reactivity, thus addressing issues related to unburned carbon, and ensuring uniformity. By improving the acceptance criteria, these efforts will promote the efficient utilization of traditional and alternative SCMs. However, the effects of alternative SCMs on vital concrete properties like workability, durability, and performance have not been comprehensively studied. To address these challenges, a comprehensive research approach is needed to help state departments of transportation (DOTs) and the transportation industry evaluate concrete mixtures containing alternative SCMs. The objective of this research is to develop a framework and complementary tools for state DOTs and the transportation industry to evaluate concrete mixtures containing alternative SCMs that provide a high probability of meeting specified requirements in highway applications. At a minimum, the research shall (1) investigate alternative SCMs' impact on concrete properties, (2) identify critical properties based on intended applications, and (3) propose appropriate test methods.