General
The development of the CARES certification scheme for the supply and installation of post-tensioning systems and its acceptance by the post-tensioning industry played a key part in the Highways Agency lifting its moratorium on grouted post-tensioned bridges in September 1996. CARES certification enables companies to comply with the major specifiers' quality requirements and enable them to bid for major post-tensioning contracts.
Supply and or installation of post-tensioning systems:
PT 1. The Supply and Installation of Post-tensioning Systems in Concrete Structures, is for major structures with a high durability requirement such as The Concrete Society Technical Report 47 (TR47) type contracts and is for internal and external systems. Under this scheme an approved specialist contractor must supply and install, stress and grout (where required) the post-tensioning system.
Certification to this scheme is a requirement of the Highways Agency's Specification for Highway Works, 1700 Series.PT 2. The Supply and or Installation of Post-tensioning Systems in Concrete Structures (Excluding Highways Structures), is for general structures such as concrete frames, floor slabs and containment structures. This scheme allows an approved specialist producer to supply post-tensioning systems and another approved specialist to install, stress and grout (where required) the post-tensioning system.
PT 3. The Supply and or Installation of Bar Post-tensioning Systems in Concrete Structures. Under this scheme a specialist approved contractor/subcontractor must supply, install and stress the post-tensioning system and an approved specialist contractor must pressure grout (where required) the system.
Approval of post-tensioning kits:
PT 3. The Production and Supply of Prestressing Anchorages for Post-tensioning systems. This scheme requires an approved specialist producer to supply post-tensioning systems that comply with BS EN 13391 or ETAG013 as appropriate.
CARES is also an ETA issuing body and can issue European Technical Approvals (ETA) against ETAG013.
Remedial grouting
PT 5. Void grouting of Post-tensioning Systems in Concrete Structures. This scheme requires an approved specialist to investigate ducts with voids; locate voids and ascertain the void characteristics and disposition and regrout the voids in accordance with TR47 and/or contract requirements.
Prestressing bar, wire and strand:
PT 6. Feedstock rod for high tensile wire and strand.
PT 7. Prestressing bar which ensures high tensile steel prestressing bars comply with BS 4486.
PT 8. Wire and strand which ensures that highe tensile prestressing wire and strand comply with BS5896.
Training
PT 9. Training requirements for post-tensioning operatives and supervisors. CARES requires PT companies to provide the training for PT supervisors and operatives specified in PT9 and assess the efeectivemness of the trianing. Once personnel have reached a satisfactory level, evidnce of achievement is to be sent to CARES which will issue operative i.d. cards.
Grout
PT 10. Prebagged grout complying with the requirements of BS EN 445, 446 and 447.
Site Quality Requirements
The supplier must have a quality system that complies with CARES requirements and BS EN ISO 9001. The supplier's quality system must cover system production, key on-site and off-site activities as appropriate:
a) Office Activities: contract review, quality planning, resources, communications between off-site and on-site activities, product testing and compliance with national standards and contract specifications, quality records and training of site personnel. The supplier should be able to demonstrate that it has the necessary resources, skills and experience to carry out post-tensioning activities. b) Site Activities: grout trials, storage and receipt of materials, traceability of materials, duct installation, duct testing and identification, duct investigation, strand installation, stressing, anchoring, batching and mixing of grout, injection of grout, grout suitability testing, post-grout inspection and site records.
c) Product Requirements: The post-tensioning system components must comply with EN13391, wire and strand must be CARES approved and comply with BS5896, bar must be CARES approved and comply with BS4486 and grout must comply with BS EN 445, 6 and 7 and for PT2 must be prebagged. 
CARES Model Specification for Bonded and Unbonded Post-tensioned Flat Slabs
There are a number of documents that deal with various aspects of post-tensioning of flat slabs, however none comprehensively deals with the technical aspects of post-tensioning in building construction. CARES has produced a model specification as a guide to specification writers.
The model specification is freely available in hardcopy from CARES' office and available in PDF format from : Model specification for bonded and unbonded flat slabs.
How to specify CARES Approved Post-tensioning Contractors
The CARES certification scheme allows two stage certification as a concession to companies which do not have suitable post-tensioning contracts which could be assessed for certification purposes. This facility avoids the need for companies to wait until they have secured a contract before applying for certification and reduces the potential for disparate and anti-competitive bidding.
The suggested wording for inclusion in a specification for a post-tensioning contractor is:
"Only firms that have achieved full certification under the CARES Certification Scheme for the Supply and Installation of Post-tensioning Systems in Concrete Structures shall be permitted to bid for or undertake contracts to supply and install post-tensioning systems.
However, in exceptional circumstances, where through the lack of a suitable contract, full certification cannot be obtained, a firm will be required to have obtained the letter of pre-certification, in accordance with Section 4, paragraph 4.7 a) of the CARES Certification Scheme."
Note: Evidence of compliance with the above should be requested for submission with contract bids.
