Prestressed Concrete Tanks

Since 1953, CROM has designed and built 4,400 prestressed concrete tanks (PCTs) with capacities ranging from 35,000 to over 30,000,000 gallons. CROM adheres to the highest standards of professional engineering and construction including AWWA Standard D110, ACI Report 372, and ACI Code 350. As long-term active and contributing members of both design committees, CROM remains a leader in the water and wastewater industry. All CROM design drawings and calculations are signed and sealed by one of our company’s full-time registered professional engineers. 

Please Note: All engineering services are performed by CROM, LLC.

TYPICAL PCT INSTALLATIONS

WATER STORAGE TANKS

Fire protection TANKS

Fire Protection TN2

WASTEWATER STORAGE TANKS

Daytona FL wastewater storage tanks.

OXIDATION/AERATION TANKS​

UNIQUE TANKS

PHASES OF NEW TANK CONSTRUCTION

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The floor of the prestressed tank is typically a heavily reinforced concrete membrane slab. Structural and ballast floor designs are also common depending on site condition requirements. This view illustrates placement of floor concrete, highly reinforced; a strong foundation.

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Galvanized steel shell diaphragm is erected on a system of formwork specially designed for this purpose. The steel shell extends the full height of the tank to ensure watertightness. Vertical joints in the steel shell are sealed watertight by epoxy injection.* U.S. Patent No. 5,150,551

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Exterior encasement of the steel shell is accomplished with shotcrete, which is pneumatically placed concrete. The core wall of the tank is constructed using successive layers of shotcrete until the required wall thickness is achieved.

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Vertical reinforcing bars are placed to design requirements and encased in shotcrete.

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After supporting formwork is removed from the tank interior, shotcrete is applied to encase the diaphragm and complete the interior core wall.

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Dome roof construction is made possible with the aid of a forming system that ensures accurate dome curvature. The height of the dome rise is commonly 1/10th of the tank diameter, but lower rise domes are possible if desired.

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Once the dome formwork is completed with an overlay of sheathing, reinforcement is placed.

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The free-span dome roof is constructed of cast-in-place concrete. This view shows dome concrete being placed by a concrete boom pump.

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Both the core wall and the free-span dome roof are circumferentially prestressed using high-strength steel wire wrapped around the tank in a continuous helix. Wall prestressing is designed to carry the tank's hydraulic load, while dome ring prestressing resists the horizontal forced of roof live and dead loads.

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To avoid over-stressing or under-stressing of the tank, the tension in the wire is measured by the use of a direct-reading electronic digital stressometer after it is applied to the tank wall.

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In order to provide protection for the prestressing elements, a shotcrete covercoat is applied to the exterior, which permanently bonds the wire to the tank wall. Whenever two or more layers of prestressing wire are required, a thin coat of shotcrete separates and protects each layer.

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The covercoat completes the concrete portion of the tank construction.

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The final stage of construction involves installation of accessories and if desired, application of exterior coatings for decorative purposes.

TIME LAPSE OF PRESTRESSED CONCRETE TANK CONSTRUCTION