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2015WinterShotcreteEMag

encompassed the entire substructure including the wing walls, abutments, columns, and parapets. Each of the 36 bridges crossed two-lane streets, had three piers, and 15 columns. The trail also crossed five arterial streets, each with four lanes of traffic. At these locations there were four piers and 20 columns. At the longest bridge crossing, Humboldt Park Boulevard, it crossed six lanes of traffic, and there were 11 piers and 33 columns (Fig. 2). Challenges Upon commencement of the project, ACR realized that the bridges were in far worse condi- tion than shown on the plans. Quantities imme- diately began increasing, as did the depths of the repairs, due to the fact that these walls were Fig. 1: Repair areas were found to be not only much larger in the field but constructed with 1 in. (25 mm) unwashed river also deeper than was called out on the plans and also lacking any rock aggregate and without reinforcing steel. It reinforcing bar was imperative to maintain excellent communica- tion with the general contractor and the owner’s engineers to verify work to be done and any additional repair steps to be taken, such as the addition of reinforcing bar, shoring, and identi- fying areas of complete deterioration requiring full replacement. Because all the bridges are in close proximity to residences, schools, daycare centers, parks, dog parks, small businesses, and main thorough- fares, some special precautions had to be taken to protect private property and also to protect the heavy pedestrian and motor traffic that trav- elled through these areas. Along this 2.67 mile (4.29 km) jobsite, ACR encountered numerous neighborhoods encompassing various demo- graphics. Many work zones were located adjacent to schools, requiring ACR to use extreme caution when conducting repairs and moving machinery in close proximity to young children who are Fig. 2: Repaired 11 piers spanning 250 ft (76.2 m) over six lanes of traffic often unaware of their surroundings and the dangers of a construction zone. Due to the congestion of the work area and the proximity to neighboring homes, parks, and schools, ACR sandblasted with water to keep dust to a minimum. ACR also cleaned up their work area at the end of every day to prework conditions, thus leaving the neighborhood safe for pedestrians and vehicle traffic (Fig. 3). As the bridges provided the only means of travel for residents from one side of the trail to the other, ACR had to phase its work at the bridge locations, keeping one lane of traffic and one sidewalk open at all times. ACR encountered both winter and summer conditions during the course of the project. This change in environment called for different approaches to quality control. When starting the project in late October, the cold temperatures of the infamous 2013-2014 Chicago winter were Fig. 3: ACI Certified Nozzleman shotcreting newly-reinforced repair areas Shotcrete • Winter 2015 31


2015WinterShotcreteEMag
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