Project Details
RESEARCHERS
Momen Mousa, Craig Newtson
SPONSORS
Office of the Assistant Secretary of Research and Technology
KEYWORDS
Admixtures, Cement, Durability, Fly ash, Mix design, Pozzolan, Ultra high performance concrete (UHPC)
Project description
Ultra-high performance concrete (UHPC) is an advanced fiber reinforced composite material with compressive strengths greater than 17,000 psi (120 MPa), flexural strengths greater than 1450 psi (10 MPa), and exceptional durability properties. UHPC is produced with a high cementitious materials content, and silica fume and high-range water reducing admixtures are used to produce a dense microstructure that can result in compressive strengths greater than 29,000 psi (200 MPa). The superior durability and corrosion resistance provided by UHPC provides the potential to increase service life and lower repair costs in concrete structures. New Mexico State University (NMSU) research has shown that non-proprietary UHPC produced with local materials can cost less than proprietary mixtures, primarily by using class F fly ash to replace much of the more expensive silica fume that is used as a supplementary cementitious material (SCM). Non-proprietary UHPC produces slightly lower strengths than proprietary mixtures, but durability properties of non-proprietary mixtures have been comparable to those of proprietary mixtures. UHPC mixtures developed at NMSU have been specified by New Mexico Department of Transportation (NMDOT) for pre-cast, pre-stressed bridge girders and bridge deck overlays. Unfortunately, class F fly ash production has decreased sharply as the energy industry has reduced coal consumption and moved to renewable energy technologies to produce electricity. NMDOT expects that by as early as 2022 the supply of class F fly ash will be insufficient to meet their needs for concrete construction, so alternative SCMs are needed for all concrete mixtures including the non-proprietary UHPC mixtures. This research project will assess the potential for using alternative SCMs such as a natural pozzolan, metakaolin, and ground-granulated blast furnace slag in non-proprietary UHPC mixtures. The research project includes a comprehensive literature review to identify the most important characteristics of SCMs for use in UHPC and to expose critical concerns for UHPC mixtures produced with these materials. A suite of mixture proportions utilizing the SCMs considered in the project will then be developed. Each of the new UHPC mixtures will be evaluated for fresh and hardened properties including workability, compressive strength, and flexural strength. The most promising UHPC mixtures will then be tested for durability related properties including rapid chloride permeability, surface resistivity, shrinkage, and frost resistance. Results from the testing program will be compared to results from existing mixtures containing silica fume and class F fly ash in the final research report. The implementation phase of the project includes documenting and disseminating the results of the research in the final report for the project, publication of journal papers, publication of conference papers, and presentations at conferences. The NMSU research team is led by the PI, Professor Craig Newtson, who has over 25 years of concrete related research experience on projects totaling more than $2,300,000 in funding and has received national recognition for his research.