Construction of a Dry Dock Using Tremie Superplasticized Concrete


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Title: Construction of a Dry Dock Using Tremie Superplasticized Concrete

Author(s): M. Collepardi, R. Khurana, and M. Valente

Publication: Special Publication

Volume: 119


Appears on pages(s): 471-492

Keywords: concrete construction; concrete slabs; drydocks; permeability; plasticizers; sulfate resistance; tremie concrete; workability; Materials Research

Date: 9/1/1989

Describes the construction of San Marco dry dock in Italy. Approximately 82,000 m3 of superplasticized concrete with a slump of 250 mm was placed, of which 40,000 m3 were underwater at a depth of 16 m using a tremie system. The concrete was mixed at a central plant and transported to the site where it was pumped for 250 m from a fixed station to the hopper of the tremie located on a floating barge. The presence of heavy reinforcement (steel trestles) made the positioning of the tremie pipe and inspection by divers very difficult. To limit the number of shiftings of the tremie pipe, concrete had to have a very high workability and had to be very cohesive to prevent washing by seawater. Moreover, the specification required an impermeable, sulfate-resistant concrete with a strength of 25 MPa. In the first stage, a slab of 4 m thickness was created by placing overlapping "pizzas" of 45 m3 volume and 15 m diameter. If the concrete was not superplasticized, then the size of the "pizzas" would have been much smaller (approximately 20 m3 volume and 3 to 4 m diameter). After dewatering, the slab was completed with a second pour of self-levelling concrete of 1 m thickness. The use of a superplasticizer helped the contractor complete the job 3 months ahead of schedule.