151
Table 11-3: Minimum cover for unprotected main reinforcing steel (in. Situation Precast Reinforced Piles Noncorrosive Environments Corrosive Environments
Precast Prestressed Piles 2.0
Cast-in-Place Piles Noncorrosive Environments Corrosive Environments General
Protected Shells Auger cast,
tremie concrete, or slurry construction The cover required for transverse reinforcement maybe less than required for longitudinal bars by no more than 0.5 inch. Transverse reinforcement larger than inch diameter would thus necessitate greater cover than specified above for longitudinal bars. The above minimum concrete covers are for concrete with water-to-cementitious material ratios (W/CM) between 0.40 and 0.50. For W/CM ratios equal to or greater than 0.50, the cover requirements must be increased by a factor of 1.2. For W/CM ratios less than or equal to 0.40, the cover requirements maybe decreased by a factor of 0.8. The modification factors of 1.2 and 0.8 are in recognition of the changes in concrete permeability resulting from higher and lower values of W/CM ratio. However, low W/CM ratios can lead to constructability problems because the flow characteristics and ability of concrete to pass through the rebar cage generally decrease at low W/CM ratios. Centering devices must be used with drilled shaft and other drilled concrete foundation element construction to maintain alignment of the steel reinforcing cages and maintain the required minimum concrete cover. The centering devices are often plastic wheels installed around the transverse reinforcement. The wheels must be oriented such that they roll along the borehole wall without scraping into the soil.
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