PRECASTCONCRETE
UNDERGROUNDUTILITY VAULTSOUTLINE• Purpose• Precast Advantage• Purpose of Utility Vaults• Uses of Utility Vaults• Applicable Standards• Structural Design• Materials• Production• Installation• NPCA Plant Certification

PURPOSE• Provide current and accurate
technical information as it relates tothe design, production andinstallation of precast concrete utilityvaults.

PRECAST ADVANTAGE
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Available nationwide
Environmentally friendly
Non-combustible
Long life span and durability
Delivered and set by manufacturerLess maintenance than CMU
Easily designed to withstand traffic or aircraft loading
Mass
Faster installation – large structures easily designed
Produced in a controlled environment
Cost effective

PURPOSE• Provide easy accessto equipment formaintenance.
• Provide structurallysound enclosure.
• Provide a secure
enclosure for costlyequipment.

PURPOSE of UTILITY VAULT• Protect vital underground connections and controls
for utility distribution.

APPLICATIONAPPLICATIONAPPLICATIONAPPLICATIONUSES of UTILITY VAULTS• Communications• Electricity• Gas• SteamAPPLICABLE STANDARDS• ASTM C 857
 Practice for Minimum Structural Design Loadingfor Underground Precast Concrete UtilityStructures• ASTM C 858
 Specification for Underground Precast Concrete
Utility Structures• ASTM C 891
 Practice for Installation of Underground Precast
Concrete Utility Structures

APPLICABLE STANDARDS• ASTM C 1037
 Practice for Inspection ofUnderground Precast
Concrete Utility Structures

APPLICABLE STANDARDS• ACI 318
 Building Code Requirements for StructuralConcrete• AASHTO Specification for Highway Bridges• Project Specific Requirements

REFERENCES• NPCA BestPractices Manual –Precast Concrete
Utility VaultManufacturing

REFERENCES• NPCA Quality
Control Manualfor Precast Plants• Local Codes andRegulations

STRUCTURAL DESIGN• Loading Conditions
 Surface surcharge
 Concentrated wheel loads
 Lateral loads
 Presumptive soil bearing capacity
 Buoyant forces Connections and penetrations
 Point loads
 Live loads
 Dead loads

STRUCTURAL DESIGN• Concrete Thickness
 Sufficient to meet minimum reinforcement cover andwithstand design loading conditions.

• Concrete Mix Design
 Concrete Compressive Strength – Minimum 4,000 psi
strength at 28 days.
 w/c < .45 (water/cementitious ratio).
 Quality materials using well-graded aggregates.
 Air entrained in accordance with ACI 318.

• Reinforcement Reinforcement design by structural calculations as requiredby code or as proven by testing.

MATERIALS• Cement
The majority of cement
used in the manufactured
concrete products industry
is governed by ASTM C 150“Standard Specification forPortland Cement.”

MATERIALS• Aggregates
Well-graded, sound,nonporous aggregate
conforming to ASTM
C 33, “StandardSpecification forConcrete Aggregates,”
is essential in theproduction of highquality precastconcrete.

MATERIALS• Water
Water for mixing high-quality
precast concrete shall meet
ASTM C1602, “Standard
Specification for Mixing Water
Used in the Production ofHydraulic Cement Concrete.”

MATERIALS• Admixtures & Supplementary
Cementitious Materials (SCMs)
Admixtures and SCMs allow the manufacturer to finetune and enhance the properties of the concrete mix.
 Air entraining admixtures per ASTM C 260 improve
freeze-thaw properties while SCMs per ASTM C595
and C618 have impacts upon the water content andcan lead to significant improvements in the physicalproperties of the concrete.

• Today, precast concrete is thehigh-tech material of choice.

MATERIALS• Reinforcement Reinforcement of concrete
is required and must beprovided and designed tomeet structural loading andhandling conditions of thestructure.

MATERIALS• Reinforcement Reinforcement types canvary from WWM toconventional rebar tofibers – all reinforcement
must comply withapplicable standards.

PRODUCTION• Pre-pour Inspection
 Trained and qualified plant personnel perform
inspection before each pour to verify form
cleanliness, proper amount of release agent, andreinforcing steel placement and configuration.

• Post-pour Inspection
 As an essential part of the production process, thepost-pour inspection verifies product conformance
to project specifications.

PRODUCTION• Final Inspection
 Validation of Quality

INSTALLATION• Proper installation is absolutely
critical for maintaining the inherent
quality of plant-manufactured
concrete utility structures, andconsiderations include: Proper connections
 Planning for site conditions
 Excavation and bedding

INSTALLATION Vault placement
 Proper sealing methods
 Installation of access risers and entry
 Penetrations
 Backfilling procedures

NPCA PLANT CERTIFICATION• Quality Control
Manual to ensure theproduction of quality
precast products• Plant Inspections
conducted by thirdparty consultants