Title:
Concrete Q&A: Concrete Cover for Unbonded Tendons
Author(s):
Post-Tensioning Institute (PTI) staff
Publication:
Concrete International
Volume:
38
Issue:
1
Appears on pages(s):
72
Keywords:
DOI:
10.14359/51688716
Date:
1/1/2016
Abstract:
Q.I have a question regarding tolerances for concrete cover for unbonded tendons in post-tensioned concrete. Section 9.3.5.5.f of ACI 301-101 states: "Unless otherwise specified, concrete cover for the tendon end from the exterior edge of the concrete shall not be less than 3/4 in. for nonaggressive environments and 1 in. to the encapsulating device for aggressive environments." Section 9.3.6.2 of ACI 301-10 also states the following regarding tendon tolerances: "Place tendons and anchorages within the tolerances of ACI 117 for reinforcement placement, distance between reinforcement, and concrete cover." However, ACI 117-102 does not appear to include any tolerances for the concrete cover for tendon ends in unbonded post-tensioning systems. Are there any such tolerances? Is there a separate concrete cover requirement for unbonded post-tensioned tendon ends that are angled at 45 degrees to the horizontal? I’m afraid that the stressing pocket might hold water if the building cladding allows moisture to penetrate to the slab edge.
Related References:
1. ACI Committee 301, “Specification for Structural Concrete (ACI 301-10),” American Concrete Institute, Farmington Hills, MI, 2010, 77 pp.
2. ACI Committee 117, “Specification for Tolerances for Concrete Construction and Materials (ACI 117-10) and Commentary (ACI 117R-10), Reapproved 2015,” American Concrete Institute, Farmington Hills, MI, 2010, 76 pp.
3. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 2014, 519 pp.
4. PTI M10.2-00, “Specification for Unbonded Single Strand Tendons,” Post-Tensioning Institute, Farmington Hills, MI, 2000, 36 pp.
5. ACI Committee 423, “Specification for Unbonded Single-Strand Tendon Materials (ACI 423.7-14),” American Concrete Institute, Farmington Hills, MI, 2014, 8 pp.