Better Roads

August 2014

Better Roads Digital Magazine

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Better Roads August 2014 17 Email: ® 7H[W,1)2WRRUYLVLWZZZEHWWHUURDGVFRPLQIR 7H[W,1)2WRRUYLVLWZZZEHWWHUURDGVFRPLQIR elaborate steel framework is possible, which can reduce girder size and result in a stronger, more durable product. SCC mixes also contain less entrained air, so fewer bubbles and "bug holes" appear in the finished product to cre- ate a smoother, more aesthetically pleasing surface. The flowability of SCC is measured in terms of spread when using a modi- fied version of the slump test (ASTM C 143). The spread (slump flow) of SCC typically ranges from 18 to 32 inches depending on the requirements. Most SCC mixes require an increase in the proportion of fines and a reduc- tion of coarse aggregate compared to traditional concrete. This raises con- cerns that the materials' shear resistance may be adversely affected, and that stiffness may be compromised. Re- searchers hope that the results of testing on this bridge will prove the materials' merit and clear the way for the use of SCC on future transportation projects. The three-span Highway 50 bridge contains three sets of girders fabricated by County Materials' Bonne Terre, Mo., plant. The girders for the first span are made from a standard SCC mix. The second set of girders is manufactured with a high-strength SCC. This mix contains a higher percentage of cement for a stronger, more durable product with a compressive strength of up to 14 KSI. The third span is constructed with a standard Missouri DOT ap- proved concrete mix design and func- tions as the control in the experiment. Sensors embedded in the girders and bridge deck will allow researchers to monitor the materials' performance over time, and provide real-world data about their relative strength as well as detailed information on the bridge's internal stresses. He says using the high-strength self- consolidating mix allowed the span length to increase by 20 percent, and is expected to reduce maintenance costs over the life of the structure. "Most of the current bridges (in Mis- souri) have a service life of 25-50 years," Myers says. "We're hoping to double that." For more information on this project, go to a-prestress/item/s-t-bridge-project-in- missouri?category_id=201.

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