A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Study of Early-Age Bridge Deck Cracking in Nevada and Wyoming
In late 2009, the Echo Wash and Valley of Fire bridge decks were constructed in the Lake Mead National Recreation area in Nevada. Within six months after installation, in early 2010, both decks exhibited considerable transverse cracking, with some cracks extending through the thickness of the deck. Similar cracking was observed in the Snake River bridge deck in Wyoming. This report details the results of a two-pronged approach to examining the causes of such cracking. First, for the Nevada bridge decks, materials similar to those used in the construction of these bridge decks were obtained and mortars were prepared and evaluated for chemical shrinkage, autogenous shrinkage, and drying shrinkage. Second, cores from all three bridge decks were obtained and analyzed using both optical microscopy and scanning electron microscopy to assess air contents, paste and aggregate volume fractions, and the overall nature of the concrete microstructure. In all three cases, the concrete mixtures had been reportedly batched at a considerably lower water-to-cementitious materials ratio (w/cm) than that in the approved concrete mixture proportions, with reductions from the specified w/cm of approximately 0.40 to w/cm of 0.35 (Snake River) to 0.31 or 0.32 (Nevada). In the laboratory mortars, w/cm was therefore varied between 0.30 and 0.40 to examine the influence of this variable on shrinkage and cracking. The observed effects of w/cm on shrinkage and cracking were small, while petrographic analysis revealed that the in place concrete cores exhibited a w/cm of 0.4 or slightly higher, consistent with the concretes having been retempered with additional water after being batched.
Study of Early-Age Bridge Deck Cracking in Nevada and Wyoming
In late 2009, the Echo Wash and Valley of Fire bridge decks were constructed in the Lake Mead National Recreation area in Nevada. Within six months after installation, in early 2010, both decks exhibited considerable transverse cracking, with some cracks extending through the thickness of the deck. Similar cracking was observed in the Snake River bridge deck in Wyoming. This report details the results of a two-pronged approach to examining the causes of such cracking. First, for the Nevada bridge decks, materials similar to those used in the construction of these bridge decks were obtained and mortars were prepared and evaluated for chemical shrinkage, autogenous shrinkage, and drying shrinkage. Second, cores from all three bridge decks were obtained and analyzed using both optical microscopy and scanning electron microscopy to assess air contents, paste and aggregate volume fractions, and the overall nature of the concrete microstructure. In all three cases, the concrete mixtures had been reportedly batched at a considerably lower water-to-cementitious materials ratio (w/cm) than that in the approved concrete mixture proportions, with reductions from the specified w/cm of approximately 0.40 to w/cm of 0.35 (Snake River) to 0.31 or 0.32 (Nevada). In the laboratory mortars, w/cm was therefore varied between 0.30 and 0.40 to examine the influence of this variable on shrinkage and cracking. The observed effects of w/cm on shrinkage and cracking were small, while petrographic analysis revealed that the in place concrete cores exhibited a w/cm of 0.4 or slightly higher, consistent with the concretes having been retempered with additional water after being batched.
Study of Early-Age Bridge Deck Cracking in Nevada and Wyoming
D. P. Bentz (author) / P. E. Stutzman (author) / A. R. Sakulich (author) / W. J. Weiss (author)
2012
63 pages
Report
No indication
English
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