HPC Precast Sewer Pipe

Abstract

Recently, a major North American City replaced a large collector sewer which was deteriorated due to corrosion of the reinforcement. This replacement was well in advance of the life cycle estimate of the pipe. The deterioration was caused predominantly by the presence of chloride ion in the soils. As a part of this reconstruction, it was decided to design the concrete to resist the intrusion of chloride ion. Several proprietary admixtures were considered, as well as the use of silica fume, to produce this pipe. The contract was awarded to a conventional dry process pipe plant. Some modification of the mixture proportions was required. An interground silica fume cement was used to reduce the handling difficulties associated with silica fume. A preconstruction trial batch was evaluated for physical properties, including rapid chloride permeability and chloride ion diffusivity. The cost effectiveness of the modified cement and the relatively simple adjustments to the casting process resulted in a very minimal increase in the total construction cost. Design calculations and quality control methods are discussed.