Grouting of Post-Tensioned Tendons

Grouting of post-tensioned tendons keeps the prestressing steel inside your structure protected for the long term. Freyssinet injects cementitious grout into post-tensioning ducts to fill voids and restore the corrosion protection that shields each strand and tendon from moisture. This preservation work extends the service life of bridges and parking structures without replacing the entire post-tensioning system.

Duct Grouting for Post-Tensioning Systems

Grouting of post-tensioned tendons is the injection of cementitious grout into the ducts that house the prestressing steel, encasing each strand and sealing any space that was never fully filled during original construction. A single tendon typically holds 4 to 37 strands, and the work protects internal and external tendons, their ducts, and the anchorages at each end. These post-tensioning systems carry far fewer strands than stay cables and follow a different load profile, so the grout specification matches their particular geometry and corrosion demands.

Once cured, the cement grout forms the permanent corrosion barrier that keeps the prestressing steel passive and shielded from moisture inside each duct. When that barrier breaks down, remediation restores it: the original grout is assessed, voids are re-injected, and the protective envelope around the tendon and its anchorages is rebuilt so the system regains the durability it was designed to deliver.

Why Does Grouting of Post-Tensioned Tendons Matter?

Grout is the primary line of corrosion protection for a post-tensioned structure, so its condition governs the durability and structural performance of the whole system. When grout is incomplete or has deteriorated, the prestressing steel loses that shield and becomes exposed to moisture, chloride, and the bleeding of trapped water, each of which drives corrosion, section loss, and a measurable loss of prestress force.

Catching that deterioration early is why a thorough post-tensioning inspection precedes any grout remediation, since it maps voids, corrosion, and force loss before they threaten load capacity. The findings tell us where grout has failed and which tendons need re-injection, turning reactive repair into planned, condition-based maintenance.

What Grout Voids and Incomplete Grouting Reveal

Voids form most often at the high points of the tendon profile, where cementitious grout was never fully filled during injection. A focused post-tensioning inspection locates these pockets early, before the strand components inside the duct sit exposed to air and moisture. Left unfound, that exposure drops prestress force and starts corrosion exactly where the grout should have sealed the void.

How Moisture and Bleed Water Compromise Grouted Ducts

Bleed water separates from the grout during curing and collects at high points inside the duct, and without proper sealing or drainage it sits directly against the steel. That trapped moisture, combined with ongoing bleeding, initiates corrosion that spreads along the tendon long before any surface signs appear.

Chloride Contamination and Strand Corrosion Risk

In coastal structures and decks exposed to de-icing salts, chloride ingress becomes the leading route to strand corrosion. Once chlorides reach the steel through unsealed anchor caps or poor waterproofing, they break down the protective film and attack the wires directly, cutting cross-section and shortening the durability of the entire tendon.

Our Approach to Grouting and Corrosion Protection of PT Tendons

Our approach to grouting begins with diagnosis, because effective corrosion protection depends on knowing exactly where grout has failed inside each tendon. Field and laboratory testing locate voids, moisture, and force loss, and that evidence sets the repair method and sequence for the structure.

From there, the process targets each defect directly: we vacuum re-inject voids with a qualified cementitious material, reinstate the watertightness of ducts and anchor caps, and remove poor-quality grout where access allows. This work sits within our broader program for the maintenance of post-tensioning tendons, so grout remediation is coordinated with inspection and long-term protection rather than treated in isolation.

Controlled injection pressure and post-injection verification confirm the grout fully encases the strands and that the restored barrier performs. Scheduling is built around your operations to keep the structural repair on time while these post-tensioning systems stay in service.

Why Choose Freyssinet for Grouting of Post-Tensioned Tendons?

01. Expert Diagnosis of Grout Condition and Voids

Our engineering teams bring decades of experience to the inspection and testing of grouted tendons, reading anchor caps and duct sections for early signs of trouble. That diagnosis pinpoints every void and confirms whether the prestressing steel still has the protection it needs.

02. Customized Re-Injection and Monitoring Programs

We design each re-injection and monitoring program around the specific requirements of your structure and its post-tensioning systems. Matching the method to the geometry and exposure of every tendon supports long-term durability.

03. Targeted Testing of Grout Fill and Tendon Force

Each test method we deploy, from duct testing to residual-force checks, measures how completely the grout fills the duct and how much force each strand still carries. This verification tells us exactly which tendon needs re-injection and which is sound.

04. Proven Grout Remediation and Corrosion Protection

When grout has broken down, our crews restore corrosion protection with proven remediation: they clear poor-quality grout, re-inject qualified material, and reseal the barrier that keeps the structural system safe. The result is a durable envelope that extends service life and stands up to the demands placed on the structure.

Our Post-Tensioning Grouting Process

Evaluation of Duct and Grout Conditions

• Review of construction records, tendon layout, and prior inspection findings
• Nondestructive testing to locate ducts, anchorages, and suspected voids
• Evaluation of duct condition to assess and rank tendons by exposure and corrosion risk

Location of Grout Voids and Deficiencies

• Endoscopy and borescope inspection at high points and anchorages
• X-ray, gamma radiography, and impact echo testing to map voids and soft grout
• Selection of the testing method used for each duct, with documentation of every void location

Vacuum Grout Re-Injection of Voids

• Vacuum evacuation of each void ahead of the re-injection process
• Hydraulic injection of qualified cementitious material until the duct is completely filled
• Controlled injection pressure to protect ducts and anchorages

Restoration of Duct and Anchorage Watertightness

• Sealing of injection and vent ports on the duct
• Reinstatement of anchorages and anchor cap watertightness with durable protective coatings
• Restoration of the continuous corrosion protection barrier across all components

Verification of Grout Fill and Tendon Protection

• Post-injection testing using a documented test method to confirm the duct is completely filled and the grout reaches design strength
• Verification of anchorage protection and duct integrity to confirm lasting durability
• Final documentation and long-term monitoring recommendations

Discover Our Projects

Our project experience spans bridges, parking structures, and landmark buildings across the US, where targeted grout remediation restored structural durability and corrosion protection.

Cumberland Street Parking Deck

At the Cumberland Street Parking Deck, our crews evaluated the post-tensioning tendons, located grout voids, and re-injected the affected ducts to reinstate a continuous corrosion barrier. The work extended the service life of the structure without disrupting daily parking operations.

Montgomery College Parking Garage

The Montgomery College Parking Garage required diagnosis of grouted tendons showing early signs of moisture intrusion. We restored watertightness at the anchorages and verified complete grout fill, giving the owner a new, durable layer of protection for the post-tensioning system.

Charleston Place Hotel

At Charleston Place Hotel, we assessed the prestressed structure, remediated poor-quality grout, and confirmed tendon protection through post-injection testing. The result preserved the structural integrity of the building for decades of continued use.

Contact Freyssinet Today!

Whatever the structural requirements of your post-tensioning system, our team is ready to support your grouting and corrosion protection goals.

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