Post-tension cable protection system, method for installing the system and method for remediation of a defective post-tension reinforcement system

Abstract

An improved method of creating a waterproof seal for post tension cable systems roughens and decontaminates the cable's stressing end pocket with a diamond bladed reaming tool and closes the newly formed cavity with epoxy resin and a precasted plug made of non-shrink grout. The method includes pouring a concrete slab around an anchor and a pocket former through which a cable passes and is held by wedges. After the pocket former is removed and the cable is stressed, the cable is cut and a grease cap is applied. The system ensures that the cable is properly cut, the grease cap is properly seated, the inside of the pocket is roughened, and the seal at the cable's stressing end is waterproof. Furthermore, the invention aids in removing previously grouted pockets when cable remediation is needed and closing the pocket with a precasted plug when cable remediation is completed.

Claims

1. A post-tension reinforcement system for building construction, the system comprising: a concrete slab having an edge and a pocket formed in said edge, said pocket having a reamed-out clean and rough surface; an anchor embedded in said slab; wedges disposed within said anchor; a cable passing through said slab, being held by said wedges and having an end within said pocket; and a prefabricated reinforcement plug formed of non-shrink grout, said reinforcement plug closing said pocket at said edge and being sealed to said reamed-out clean and rough surface of said pocket in a waterproof manner with an adhesive.

2. The system according to claim 1, which further comprises a grease cap covering said end of said cable in said pocket.

3. The system according to claim 1, wherein said adhesive is an epoxy adhesive.

4. The system according to claim 1, wherein said reinforcement plug is formed of high-strength, non-metallic grout.

5. The system according to claim 2, which further comprises grease disposed within said grease cap.

6. The system according to claim 2, wherein said reinforcement plug has an outer surface, and an accuracy of a location of said grease cap in said pocket is determined by a degree of alignment of said outer surface of said reinforcement plug with the edge of the slab.

7. A method for waterproofing a post-tension concrete reinforcement system for building construction, the method comprising the following steps: placing an anchor and a pocket former over a cable; pouring a concrete slab around the anchor and the pocket former disposed on the cable; removing the pocket former from an edge of the slab to form a pocket through which the cable extends; placing wedges on the cable within the anchor; stressing and elongating the cable at the edge while using the wedges to prevent the cable from retracting; cutting the cable within the pocket; reaming-out the pocket; closing the pocket with a prefabricated reinforcement plug formed of non-shrink grout; and sealing the reinforcement plug to the slab in a waterproof manner using an adhesive.

8. The method according to claim 7, which further comprises placing a grease cap on a cut edge of the cable within the pocket before closing the pocket.

9. The method according to claim 7, wherein the adhesive is an epoxy adhesive.

10. The method according to claim 7, wherein the reinforcement plug is formed of high-strength, non-shrink, non-metallic grout.

11. The method according to claim 8, which further comprises placing grease within the grease cap.

12. The method according to claim 7, which further comprises carrying out the step of reaming-out the pocket with a reaming tool providing a clean and roughened surface in the pocket before closing the pocket with the prefabricated plug.

13. The method according to claim 12, wherein the reaming tool has diamond sections.

14. The method according to claim 7, wherein the pocket former is formed of molded plastic.

15. The method according to claim 8, which further comprises determining an accuracy of a location of the grease cap in the pocket by observing a degree of alignment of an outer surface of the reinforcement plug with the edge of the slab.

16. The method according to claim 12, which further comprises placing a grease cap on a cut end of the cable within the pocket before closing the pocket, and providing a recess in the reaming tool for accommodating the grease cap and the cable end during reaming.

17. A method for remediating a conventional post-tension concrete reinforcement system for building construction, the method comprising the following steps: providing a conventional post-tension concrete reinforcement system including a concrete slab having an edge, a pocket formed in the edge, an anchor embedded in the slab, wedges disposed within the anchor, a cable passing through the slab, being held by the wedges and having an end within the pocket, and grout closing the pocket; removing the grout and exposing the end of the cable in the pocket; reaming-out the pocket to provide a clean and rough surface of the pocket; placing a prefabricated reinforcement plug formed of non-shrink grout against the reamed-out clean and rough surface of the pocket to close the pocket at the edge; and sealing the prefabricated reinforcement plug to the reamed-out clean and rough surface of the pocket in a waterproof manner with an adhesive.

18. The method according to claim 17, which further comprises placing a grease cap over the cable end, carrying out the reaming step by using a reaming tool, and providing a recess in the reaming tool for accommodating the grease cap and the cable end during reaming.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a fragmentary, diagrammatic, longitudinal-sectional view of a concrete slab having a completed post-tension reinforcement plug system disposed therein according to the invention;

(2) FIG. 2 is a cross-sectional view of a portion of the slab showing an adhesive bead therein around a plug;

(3) FIG. 3 is a bottom-plan view of a PT plug;

(4) FIG. 4 is a top-plan view of a grease cap;

(5) FIG. 5 is a vertical-sectional view of a reamed-out pocket in the slab;

(6) FIG. 6 is a top-plan view of the PT plug;

(7) FIG. 7 is a bottom-plan view of the grease cap;

(8) FIG. 8 is a vertical-sectional view of a portion of the slab showing the plug;

(9) FIG. 9 is a cross-sectional view of the slab in which the plug is disposed and the grease cap has been omitted for clarity;

(10) FIG. 10 is a perspective view of a reaming tool for reaming-out the pocket in the slab;

(11) FIG. 11 is an exploded, perspective view of a post-tension anchorage system; and

(12) FIGS. 12 and 13 are perspective views of a molded pocket former.

DETAILED DESCRIPTION OF THE INVENTION

(13) Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a completed post-tension reinforcement plug system according to the invention which is installed at the stressing end of a post-tensioned concrete slab 1. The system includes a post-tension or PT reinforcement and corrosion-inhibiting plug 2 and a post-tension tendon or cable 3 which is covered with a plastic sheathing 4 in which grease is provided between the sheathing 4 and the cable 3. The plug 2 is prefabricated from a high-strength, non-shrink, non-metallic grout that complies with industry standards. The plug 2 cannot be made of concrete due to industry standards and the relatively high shrinkage rate of concrete.

(14) According to the method of the invention, the sheathing 4 and a metal anchor or embed 5 are placed over the cable 3. A plastic pocket former 12 seen in FIGS. 12 and 13 is also placed over the cable 3 so that the cable passes through a hole 13 in the plastic pocket former 12.

(15) The concrete slab 1 is then poured in forms around the cable 3 having the sheathing 4, the anchor 5 and the plastic pocket former 12 so that after the concrete cures, the plastic pocket former 12 can be removed leaving a PT pocket 8 between the anchor 5 and an edge 7 of the slab 1. The other end of the cable remains stationary in the slab. The cable 3 then extends out of the pocket 8 about 12 inches to the left in FIG. 1. Wedges 6 shown in FIG. 11 are placed on the cable after the concrete is poured and cured (about 12-16 hours after pouring). The cable 1 is pulled to the left in FIG. 1 by a stressing machine which pulls the cable tight while keeping the wedges tight against the anchor so as to elongate and tension the cable. The cable 1, which is prevented from retracting by the wedges 6, is then cut or severed with a torch or other cutting device within the pocket 8 and covered with grease. A grease cap 9 is placed over the cut end of the cable, so that a length of the cable 3 of between and of an inch remains within the smaller diameter part of the grease cap 9. The grease cap 9 is shown separately in FIGS. 4 and 7.

(16) According to the invention, a surface 10 of the pocket 8 towards the edge 7 of the slab 1 is reamed out and roughened with a grinding tool or reamer 14 shown in FIG. 10. The reaming is dry reaming which is carried out without the aid of water or other fluids, in contrast to the prior art. The reamer 14, which preferably has diamond sections, provides a roughened, cleaned and decontaminated surface 10 of the pocket 8 as seen in FIG. 5. The reaming removes about 1/16- off the inner surface of the pocket, creating a shelf for the PT plug to rest in. The shelf creates a seat on which the PT plug can rest. The reaming tool has a 1.5 inch recess in the center of the tool for accommodating the grease cap and cable during the reaming process. It is important to avoid contact with the grease cap and the cable when roughening the surface, because any impact with the cable or grease cap could loosen the wedges and cause the cable to retract.

(17) Epoxy adhesive is applied both to the inner surface of the pocket 8 and to the outer surface of the reinforcement plug 2, which is seen separately in FIGS. 3 and 6. The reinforcement plug 2 is tapped into place with a rubber mallet so as to close the pocket 8 and cover the grease cap 9. The reinforcement plug 2 is generally either 2.75 or 3.00 in diameter, but it could have a different diameter as well. The reinforcement plug 2 has a thickness of 1.25 with a recess of in the middle to accommodate the grease cap. This recess is configured to provide a 1 minimum coverage needed in aggressive environments while also acting as a check to make sure that the grease cap is properly seated.

(18) It can be seen from FIG. 2 that a bead 11 of epoxy remains around the plug 2 in the pocket 8 and even when the slab is cut as shown in FIGS. 8 and 9, the plug 2 is nearly indistinguishable from the slab 1. The bead 11 of epoxy is also shown in FIG. 1 from which it can be seen that a space between the reinforcement plug 2 and the grease cap 9 around the end of the anchor 5 is empty. A completely waterproof pocket is thus formed.