Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/307110
14 May 2014 Better Roads Bridge Improvement Program – a pro- gram that involved improvements to 802 of Missouri's worst bridges over the course of five years and is the larg- est bridge improvement project in the state's history. During the reconstruction of the bridge, seven precast, prestressed concrete slabs were installed. High- strength grout was needed to bond structural members and ensure load transfer. The high-strength, non- shrinking, fast-setting grout was used to fill the keyways between the cored slab and box beam girders and in the holes where dowels connect the beams to the piers and abutments. It was also used to fill the 2- to 3-inch keyways to allow the individual cored slabs to operate as one unit. Because the pour occurred in hot weather, Rapid Set Control additive was added to increase the working time for an additional 5 to 10 minutes. FLOW Control was also used to pro- duce a flowable mix, which eliminated voids within the keyway. Using fast- setting grout on the Highway J Bridge project achieved the strength required within the necessary time frame and helped keep the project on schedule; tests showed it reached between 7,000 to 10,000 psi within 18 to 24 hours. Lewis and Clark Bridge In the summer of 2005, after 18 months of partial closures, the Lewis and Clark bridge connecting Rainier, Oregon, to Longview, Washington, re- opened – six months ahead of sched- ule. The only bridge over the Colum- bia River for many miles, its closure time was restricted to late night and weekend hours and a financial bonus was awarded by the Washington State Department of Transportation (WS- DOT) for using a minimal number of full-weekend closures. To help meet these demands, rapid- setting cement, with a final set time of 35 minutes, was used for areas of the bridge that could be repaired by apply- ing a new concrete overlay: 450 cubic yards of the cement were used for the 1,575 foot length of overlay, and the work was performed during one weekend. The overlay achieved a com- pressive strength of 4,000 psi in four hours. Using this cement saved at least nine days compared to a slower-setting concrete overlay. San Francisco-Oakland Bay Bridge Seismic upgrades to the San-Francisco- Oakland Bay Bridge began in 2002. The west span (San Francisco side) was able to be retrofitted through rein- forcement, but the east span (Oakland side) needed to be replaced entirely, with its new design including the world's longest self-anchored suspen- sion span (SAS). The project took more than 10 years to compete and was one of the largest public works projects in U.S. history. Because of the variety of materials being used to afford seismic safety, typical cement set times of 28 days were not practical. The steel suspen- sion bridge can experience rapid ex- pansion and contraction, so cement used at joints on the bridge needed to set within a four-hour window of time. Quick-setting cement was used at the seismic joints on either side of the SAS so the concrete was able to set and achieve sufficient strength before bridge movement had time to oc- cur. After construction was complete, concrete compression tests were per- formed at joint segments in time inter- vals of one, seven and 56 days. All of the test results proved that the concrete strengths, measured in PSI, exceeded performance requirements and did so in a shorter time frame than was specified. A joint venture between American Bridge/Fluor was the bridge and highway contractor on this project. Walkway over the Hudson Once touted as the world's longest bridge, the historic 6,768-foot-long Poughkeepsie-Highland Railroad Bridge in New York is again claim- ing distinction, this time as the world's longest pedestrian bridge.