DURABLE PCCP REPAIRTECHNOLOGIES

REPAIR/STRENGTHENING

Problems Corrosion of the outer wire from chloride migration

Premature failure of prestressing wire due to hydrogen embrittlement

Corrosion of the liner initiating from inside the pipe

Leakage at joints due to construction defects and differential settlement

Research In 1999 Freyssinet was retained on an emergency basis after a major

PCCP burst and is still engaged in a continuous repair program with

an emphasis on long-term durability.

PCCP is a prestressed structure. As such, Freyssinet developed

specific methods to assess each structural deficiency and define

an appropriate technical repair strategy :

Durability PCCP have a minimum design life of 50 years

Low quality repair solutions have been implemented, usually under

emergency repair contracts

Well-designed repair solutions, specific to PCCP repairs were,

not commercially available.

Damaged or defective PCCP in aggressive soils, are subject to

accelerated deterioration.

To combat this, Freyssinet developed repair solutions with 50-year

design lives, even in severe environments.

Repair, a Cost Effective SolutionFreyssinet engineered PCCP repair solutions present the following advantages :

Savings of 60% to 75% in terms of global costs

Limited duration of intervention

Possibility to implement in-service PCCP repairs

Standardization of repair methods

Our philosophy

Monitoring

& Risk

Assessment

Analysis

of Causes

Finite

Element

Model

(Linear or

Non Linear)

DurableTechnology

Design

FullScale

Testing

Operations

Our solutions

External Repairs

DURALOOP : an External Durable Pre-Grouted PT SystemApplication of additional externally applied Post-Tensioning to compensate

the failing prestressing force is a natural idea. Freyssinets PCCP External

Durable Pre-grouted PT System, DURALOOP, is based on the use of Freyssinets

patented 2MX15 Anchorage and special indented strand centering external

HDPE/PP sheathing to achieve a fully encapsulated and durable post-tensioning

system. Pre-grouting of centralized strands prior to stressing provides uniform

support of the unbonded monostrands thus ensurign that the corrosion

protection systems remain intact.

Sand RecompactionAfter excavation and additional post-tensioning operations, the strengthened

area is backfilled below the pipe and the soil re-compacted to allow the

support of the PCCP load with no settlement. Freyssinets patented sand

re-compaction technique compresses the sand below the pipe to provide

uniform pressure and pipe support. It is the only known PCCP repair technique

that avoids pipe settlement and is applicable for repairs carried out with

dewatered or in-service pipes

Internal Repairs

Frey-CWrapFreyssinet has developed a unique technique using carbon fiber fabric

impregnated with a specifically designed resin for application onto surfaces of

PCCP. This system is designed to ensure there will be no risk of delamination

due to either internal or external pressure. The porosity of Frey-CWrap is such

that complete watertightness is guaranteed. Frey-CWrap has been approved by

NSF for use with PCCP carrying potable water and makes use of the Freyssinet

Carbon Fiber Techniques (TFC) used in more than 500 structures.

Frey-CWrap ReliningSpecific automated equipment has been designed to place Frey-CWrap with

a carefully controlled pitch, which may be varied to accommodate various

design criteria. The equipment is currently designed for pipes with diameters

between 1.5 m and 3 m. Details to treat special cases such as manholes and

valves are available.

Repair Solutions

Unique Technologies to Provide

Soft Joint Resealing SystemA special compound has been developed to reseal joints from the inside.

The compound adheres to the PCCP surface in wet or dry conditions and has

a tensile/shear strength of more than 2 MPa thus providing an adequate

surface for the relining process. The compound remains flexible and

accommodates local distortion, compressive and tensile stresses.

Monitoring and Risk Analysis

Freyssinet has developed strategic partnerships with Advitam and

Pure Technologies to provide monitoring and risk assessment capabilities.

The following techniques are available :

SmartBall is a leak detection system using an acoustic/electromagnetic

sensor placed in a ball (photograph 1).

SoundPrint is an acoustic monitoring system locating wire breaks

(photograph 2).

PWave is an electromagnetic system to inspect pipe from the inside and

quantify number of wire breaks (photograph 3).

ScanPrint is a GIS data management software capable to schedule

inspection and maintenance work in a cost-effective way (photograph 4).

A Special Risk Analysis Method has been developed and is integrated in

ScanPrint to calculate from soil and pipe construction data and monitoring

the expected life duration of pipes (photograph 5).

Durable Repair

1

2

3 4 5

Almost any pipecan be saved

Prestressed Concrete Cylinder Pipe (PCCP) has been widely used worldwide

for over 60 years. In 1939 Freyssinet manufactured and installed the first

PCCP in Algeria, which is still in service today !

The PCCP industry grew tremendously as it represented a very durable,

reliable and economical solution for large diameter pipelines.

However, due to various factors including material deficiencies and severe

environmental conditions, PCCP has encountered isolated problems,

especially in the past 10 years. These problems can lead to catastrophic

bursts resulting in huge financial losses to pipeline owners due to disruptions

in service, environmental impacts, as well as in unanticipated repair

and/or replacement costs.

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