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2015WinterShotcreteEMag

already setting in. ACR devised a comprehensive thermometers to confirm the temperature of the plan for dealing with the upcoming winter months substrate, water, pre-bagged material, and mixed to accommodate low temperatures of up to –40°F material stayed at or above the specified minimum (–40°C) wind chill temperatures. Each bridge was temperatures. The temperatures were recorded on wholly enclosed using heavy-duty, fire-retardant quality control checklists every hour to document tarps (Fig. 4 through 6). ACR also deployed large ACR’s ability to maintain a high-quality shotcrete propane heaters to ensure proper ambient and mixture. ACR’s plan succeeded in providing substrate temperatures. Where full road closures quality repairs while allowing the project to were necessary, ACR was allowed a maximum progress through the brutal Chicago winter. of 2 weeks to complete the work on the specific Upon the arrival of the hot summer months, bridge, including 7 days for curing, to satisfy the ACR had to pay special attention to make sure restrictions of the City of Chicago permits for the shotcrete mixture remained at satisfactory street closures. ACR also used heaters to keep the maximum temperatures. To maintain the tem- water warm for mixing and torpedo heaters to peratures required in the specifications, ACR warm the skids of pre-bagged material and the replaced the water supply midday with fresh cold staging area. ACR used both infrared and standard water or added ice to the water supply containers. When possible, ACR’s staging area along with the pre-bagged skids of material were set on the North side of the bridge next to the retaining wall to decrease the amount and duration of direct sun exposure. If this was not possible, canopies erected over the material and shotcrete pump provided shade to aid in temperature control. Similar to the winter months, ACR used infrared and standard thermometers to verify the tem- perature of the substrate, water, pre-bagged mate- rial, and mixed material to ensure they stayed below the specified maximum temperatures. The Fig. 4: Heated enclosures were installed on portions of bridge during winter months Fig. 5: Large propane heaters kept temperatures inside enclosure within Fig. 6: Shotcrete placement inside a heated specifications during cold winter months bridge enclosure 32 Shotcrete • Winter 2015


2015WinterShotcreteEMag
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