Published by department of transportation

46-2.02C(3) Corrugated Plastic Sheathing

PVC corrugated sheathing must have a nominal wall thickness of 40 mils.

HDPE corrugated sheathing with an outside diameter of 3 inches or greater must have a nominal wall thickness of 60 mils. HDPE corrugated sheathing with an outside diameter of less than 3 inches must have a nominal wall thickness of 40 mils.

46-2.02D Strand Coating and Encapsulation

Hot melt extrude or shop apply the sheath onto the strand using a method that ensures all spaces between the sheath, strand, and strand wires are filled with corrosion-inhibiting grease.

The corrosion-inhibiting grease must:

1. Fill all space between the strand wires

2. Encapsulate the strand, giving an encasement diameter at least 5 mils greater than the diameter of the bare strand

3. Provide a continuous, nonbrittle film of corrosion protection to the prestressing steel

4. Provide lubrication between the strand and the sheathing

5. Resist flow from the sheathing

6. Be chemically stable and nonreactive with the prestressing steel, sheathing material, and concrete

7. Be organic

8. Have appropriate polar, moisture-displacing, and corrosion-inhibiting additives

9. Have the physical properties shown in Table 1 of Specification for Unbonded Single Strand Tendons published by the Post-Tensioning Institute

46-2.02E Grout

For drilled holes 8 inches or larger in diameter, you may add fine aggregate to the grout used outside of the corrugated sheathing. The fine aggregate must comply with section 90-1.02C. Grout with fine aggregate must contain at least 845 pounds of cement per cubic yard.

46-2.03 CONSTRUCTION

46-2.03A General

Determine the bonded length necessary to comply with the specified acceptance criteria.

Sheathe the tendons in the unbonded length with smooth plastic sheathing that extends into the steel tube of the permanent anchorage assembly. Sheathe the tendons full length with corrugated plastic sheathing.

The transition between the corrugated plastic sheathing and the anchorage assembly must allow stressing to the maximum test load without evidence of distress in the corrugated plastic sheathing.

Select a ground anchor installation method that achieves the loadings specified.

Do not drill for ground anchors in a wall zone until any required stability testing is complete and the test results are authorized.

Drill the holes for ground anchors in the foundation material deep enough to provide the necessary bonded length beyond the minimum unbonded length shown.

If coring through concrete structures, core the holes using methods that do not shatter or damage the concrete adjacent to the hole.

The diameter of the drilled hole must be large enough to provide a minimum grout cover of 1 inch over the corrugated sheathing for the full length of the tendon.

Before installing a ground anchor, repair or replace any damaged portions of the sheathing.

Place centralizers at 10-foot maximum intervals for the full length of the tendon, with the uppermost centralizer located 2 feet from the end of the steel tube and the deepest centralizer located 2 feet from the end of the anchor.

Pregrout each tendon at least 48 hours before you place the tendon in the drilled hole.

At each grouting stage, inject the grout at the low end of the void to be filled. Place the grout using grout tubes. Do not place grout in the unbonded length under pressure. Record the quantity of grout and the grout pressures.

If hot weather conditions will contribute to quick stiffening of the grout, cool the grout by authorized methods as necessary to prevent blockages during pumping activities.

After initial grouting, the anchor must remain undisturbed until the grout is strong enough to provide anchorage during load testing.

Protect the anchorage assembly against rust, corrosion, and physical damage until the enclosure is grouted or the assembly is encased in concrete.

For ground anchors installed inside driven structural elements such as pipe, casing, shells, and pipe piles, construct the drilled hole in the foundation material as follows:

1. Use construction methods that do not reduce the compression or tension capacity of the driven element.

2. After the driven element is installed, advance the anchor hole with a drill casing using rotary methods to at least 10 feet beyond the tip of the driven element. Do not use percussion drilling until the casing is in place.

3. Do not extract the casing until the tendon is installed, and the portion of the initial grout outside the corrugated sheathing and within the bonded length has been placed.

46-2.03B Bar Tendons

Center the bar in the corrugated sheathing and pregrout the annular space between the bar and the sheathing before placing the tendon in the drilled hole.

You may place the initial grout in the drilled hole before or after inserting the bar tendon.

Stress the bars for multiple-bar tendons simultaneously.

46-2.03C Strand Tendons

1. Spaced at 5 feet maximum

2. Made of plastic

3. Strong enough to support the individual strands during construction activities

After inserting the strand tendon and before placing the initial grout in the hole, inject grout into the corrugated sheathing to the limits shown.

46-2.03D Lock-off

Secure the ends of strand tendons with a permanent-type anchorage system that:

1. Holds the prestressing steel at a force producing a stress of at least 95 percent of the specified ultimate tensile strength of the steel

2. Permanently secures the ends of the prestressing steel

1. Stress the tendon to the maximum test load.

2. Fully set the permanent wedges in the anchor head.

3. Remove the shims or use other appropriate means to achieve the lock-off load shown.

After lock-off, place grout to the secondary grout level shown. At least 24 hours after the secondary grout has set, fill the remaining void in the steel tube and bearing plate with grout. Maintain a minimum grout head of 2 feet until the grout has set.

If a grouted anchorage enclosure is shown, install the enclosure as follows:

1. Grout the steel tube.

2. Clean the bearing plate surface.

3. Place the sealant.

4. Bolt the anchorage enclosure in place.

5. Fill the void in the anchorage enclosure with grout.

6. Clean and seal any holes in the top of the anchorage enclosure used for grout placement. Use a nonsag polysulfide or polyurethane sealing compound that complies with ASTM C920.