AS NZS 2425:2015 pdf free download.Bar chairs in reinforced concrete- Product requirements and test methods.
3 DEFINITIONS
For the purposes of this Standard the definitions below apply.
3.1 Bar chair
The embedded items within reinforced concrete elements, which are used to maintain the position and cover of steel reinforcement during construction to ensure durability, strength and serviceability of the as-built elements, in accordance with the design specification.
NOTE: Bar chairs may be singular or continuous.
3.2 Batch
A quantity of product produced from materials of the same specification, using the same
process and equipment in a continuous production run.
3.3 Continuous bar chair
The bar chair that is used to support reinforcing in a continuous line of support, which includes soffit-supported as well as middle deck chairs supported from a lower layer of reinforcement.
3.4 Cover
The distance between the outside of the reinforcement and the nearest permanent surface of the element excluding any external finish.
NOTES:
1 Cover is typically specified by the structural designer on the structural design drawings.
2 Unless otherwise noted, the tolerance on position of reinforcement and tendons given in the relevant design Standard will apply.
3.5 Durability
Ability of a structure and its component members to perform the functions for which they have been designed, over a specified period of time, when exposed to their environment.
3.6 Height of chair
The distance from the underside of the reinforcement to the base surface of the concrete,
when placed in the supporting surface of the bar chair.
3.7 Singular bar chair
The bar chairs that are used to support reinforcing at a single location.
3.8 Spacer
A non-vertical loadbearing chair used to maintain the position and cover of steel reinforcement during construction to ensure durability, strength and serviceability of the asbuilt elements, in accordance with the design specification.
3.9 Unit of manufacture (pack)
A quantity of product (typically 50 or 100) of the same nominal geometry and strength characteristics, which is typically in the form as delivered to the customer.
4 PRODUCT REQUIREMENTS
4.1 General requirements
When sampled and tested in accordance with Clause 6, batches shall be deemed to comply with the requirements of this Standard, provided all samples meet the requirements of Table 1.
4.2 Protective-tipped wire bar chairs
Protective-tipped wire bar chairs shall be examined after cessation of load test. The bar chair shall not exhibit evidence of penetration of wire end through the protective plastic coating or sleeve under the tip of the wire legs.
4.3 Plastic chairs
The chair design shall allow a nominal 20 mm aggregate concrete to readily penetrate the chair openings to minimize the risk of voids occurring in concrete placement.
4.4 Spacers
Spacers shall comply with the requirements of strength grade 60.
4.5 Concrete bar chairs
Concrete bar chairs shall have a minimum concrete compressive strength of 60 MPa.
When type tested in accordance with ASTM C1202, with specimens prepared and results adjusted in accordance with Appendix A, concrete bar chairs shall have a maximum RCPT (rapid chloride permeability test) expressed in coulombs, appropriate to the chloride permeability class set out in Table 2.
NOTE: See Note 1 of Table 1.The test procedure for ASTM C1202 shall be calibrated to either AASHTO T259 or NordTest NTBuild443 by means of a type test.
4.6 Continuous bar chairs
Continuous bar chairs shall comply with the requirements of nominated strength grade, measured by the application of pairs of the specified load at mid-node.
4.7 Product identification
All bar chair packaging shall clearly identify the strength grade of the chairs as set out in Table 1. Packaging for concrete chairs shall identify the permeability class as set out in Table 2. NOTE: A minimum load, as shown in Table 1, may be displayed on the pack or product.
5 TRACEABILITY/MARKING
The pack shall be traceable to the manufacturer and batch.
6 TEST REQUIREMENTS
6.1 General
Individual bar chairs shall be statically loaded in a calibrated test machine. NOTE: A typical test apparatus is shown in Figure 1.
The testing shall be carried out at a temperature of not less than 22°C. Plastic chairs and spacers shall be tested at a temperature of 30 ±2°C.AS NZS 2425 pdf download.