Implementation of a Testing Protocol for Approving Alternative Supplementary Cementitious Materials (SCMs): Natural Minerals and Reclaimed and Remediated Fly Ashes
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2018-02-02
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TRIS Online Accession Number:01663378
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance
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Abstract:Supplementary cementitious materials (SCMs) provide many benefits to concrete mixtures in terms of cost, long term strength, and durability. Class F fly ash is the most widely used SCM in Texas, but its availability is dwindling while demand is increasing. Given the importance of Class F fly ash as a means to improve concrete durability, it is important to find alternative materials that can maintain the high quality and durability of concrete required in Texas. TxDOT Project 0-6717: Investigation of Alternative Supplementary Cementing Materials (SCMs), completed in August 2014, identified sources of Class F fly ash alternatives that can be used in Texas concrete and developed best practices for testing these materials. Lower cost sources of materials have been identified since the completion of that project and may present better opportunities for Class F fly ash replacement than those initially tested. These materials include natural mineral byproducts of other industries, reclaimed fly ashes, and remediated fly ashes. The experimental protocols developed in Project 0-6717 were performed on these new sources of materials to determine their suitability for use in Texas concrete. The materials were chemically and physically characterized, and their performance in cement paste, mortar, and concrete mixtures was tested. It was determined that some of the natural minerals were inert; thus, they are not recommended for use in concrete. Natural pumicite performed well as an SCM, including a pumicite that is quarry overburden and could be procured at a relatively low cost. This overburden pumice, however, did not perform as well as expected in testing for sulfate resistance and merits further investigation. It is possible that the overburden pumicite would perform better if used as at a higher replacement level of cement. The reclaimed and remediated fly ashes performed very well, proving their ability to be used as substitutes for “production” Class F fly ash based on the criteria established in this project. In the cases where reduced performance was seen in fly ashes, the problems should be easily managed through the addition of chemical admixtures.
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