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Accession Number PB2014-100565
Title Performance of High Performance Concrete (HPC) in Low pH and Sulfate Environment.
Publication Date May 2013
Media Count 188p
Personal Author N. Suksawang S. Zhang
Abstract The goal of this research is to determine the impact of low pH and sulfate environment on high-performance concrete (HPC) and if the current structural and materials specifications provide adequate protection for concrete structures to meet the 75-year design service life. In pursuit of this goal, a two pronged approach was proposed and conducted, which includes (1) field investigation and (2) laboratory experiment. The field investigation involved a review of the bridge environmental database, visual inspection of selected HPC bridges, and quantifying their deterioration. Considering that the concrete mixtures of the selected HPC bridges could not be obtained, laboratory experiments were conducted to evaluate the effect of pozzolanic and cementitious materials on concrete structures exposed to low pH and sulfate environment. Results indicated that bridges exposed to both low pH and moderate sulfate environment are prone to significant deterioration as compared to bridges with similar classification (moderately aggressive). In fact, corrosion was detected in the steel reinforcement on two bridges that had only been in service for less than 30 years. While similar classified bridges (moderately aggressive) that were only exposed to either moderately low pH (between 5.0 and 6.5) or moderate sulfate (between 150 and 1500 ppm) environment showed slight surface deterioration but not interior. The reason for this is because structures exposed to both environments will undergo exchange reaction between the acids present in the low pH environment that increase the concrete porosity allowing the sulfate to attack even at a moderate level. The expansion manifested by the sulfate attack causes cracks to form allowing aggressive water to penetrate the embedded steel reinforcement, which eventually leads to corrosion. Therefore, it is recommended that the Florida Department of Transportation review the environmental classification to include an exposure to both moderately low pH 'and' moderate sulfate as an 'extremely aggressive environment'.
Keywords Bridges
Cements
Corrosion
Cracks
Deterioration
Durability
Fumes
High performance concrete(HPC)
Laboratory tests
Prestressed concrete
Reinforcing steel
Silica
Slags
Sulfates
Visual inspection


 
Source Agency Department of Transportation Office of University Research
NTIS Subject Category 50C - Construction Equipment, Materials, & Supplies
50A - Highway Engineering
Corporate Author Florida International Univ., Miami. Dept. of Civil and Environmental Engineering.
Document Type Technical report
Title Note Final rept.
NTIS Issue Number 1403
Contract Number BDK80-977-16

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