Project Details
RESEARCHERS
Craig Newtson
SPONSORS
Office of the Assistant Secretary for Research and Technology
KEYWORDS
Alkali silica reactions, Cement, Concrete, Durability, Fly ash, Literature reviews, Mix design, Pozzolan
Project description
New Mexico contains several aggregate sources that are extremely susceptible to alkali-silica reaction (ASR). To mediate ASR, the New Mexico Department of Transportation (NMDOT) requires a minimum of 20% class F fly ash (by mass of cement) in nearly all concrete produced for their projects. However, class F fly ash has become difficult for concrete producers to procure, and future availability is uncertain. Consequently, NMDOT is considering adopting alternative supplementary cementitious materials (SCMs) that could be used in place of class F fly ash. The purpose of this research project is to assess one of the alternative SCMs being considered for potential acceptance by NMDOT. The SCM to be studied is a natural pozzolan mined from a pumicite deposit near Espanola, NM. Natural pozzolans are a class of siliceous or siliceous and aluminous materials that possess little or no cementitious value by themselves, but can react chemically with calcium hydroxide and water at ordinary temperatures to form compounds possessing cementitious properties that can improve concrete strength and durability. NMDOT has little data for mixture proportions and durability properties of concrete produced with this material, so they are not able to confidently accept the material for use in concrete produced for NMDOT projects, even if class F fly ash is not available. This research project consists of a comprehensive literature review to identify the most important properties and characteristics of SCMs, and especially natural pozzolans, in terms of their influence on concrete durability. For the experimental work to be conducted in this study, a suite of concrete mixtures, similar to currently accepted NMDOT mixtures, will be proportioned using the natural pozzolan to replace different percentages of fly ash. Concrete produced from these mixtures will be tested for slump, air content, compressive strength, and flexural strength to ensure that the mixtures provide adequate workability and strength. Then, the durability of the concrete mixtures will be tested by assessing their chloride permeability, resistance to freezing and thawing, susceptibility to ASR, and their shrinkage characteristics. Results from mixtures containing the natural pozzolan will be compared to control mixtures produced using NMDOT concrete mixtures containing only class F fly ash. The implementation phase of the project includes documenting and disseminating the results of the research. Dissemination of the results will include the final report for the project, publication of journal papers, publication of conference papers, and presentations at conferences. The New Mexico State University (NMSU) research team is led by the PI, Professor Craig Newtson, who has over 20 years of concrete related research experience on projects totaling more than $2,300,000 in funding. The team also includes Associate Professor Brad Weldon as a Co-PI. Dr. Weldon has supervised more than $1,300,000 in funded research projects and has received national recognition for his research.