S08 Concrete

S:08 CONCRETE

Note: The term contractor is used interchangeably to describe both subcontractors & suppliers

1. Scope

1.1.  Refer to Structural Engineer’s drawings and specification which take precedence over:

  • architectural documents except for setout. Any set-out conflicts or conflicts between the Architectural drawings and structural drawings notify the Principal and under no circumstances scale drawings.

1.2.  Supply and install concrete and reinforcing steel for:

  • 1.2.1.  Strip and pad footings as well as piles and piers (over 2m depth) where shown
  • 1.2.2.  Slabs including downturns and stairs
  • 1.2.3.  Filled Retaining walls
  • 1.2.4.  Planters and hobs
  • 1.2.5.  Ramps and kerbs

2. Related Work

2.1. Close coordination is required with other sections as follows:

  • 2.1.1.  Excavation
  • 2.1.2.  Plumber
  • 2.1.3.  Sewerage, Drainage and Stormwater Detention
  • 2.1.4.  Electrical
  • 2.1.5.  Masonry
  • 2.1.6.  Damp-proof membranes
  • 2.1.7.  Floor Tiling
  • 2.1.8.  Structural Steel

3. Quality Assurance

3.1. Submit evidence of experience appropriate to the class of work required. Install under the direct supervision of a capable Foreman with a proven background in this trade.

4. References

4.1.  Comply with current relevant Australian Standards.

4.2.  Comply with the requirements of any Building Regulations applicable to the project.

5. Building Code of Australia

5.1.  Class of Building is 1a

5.2.  Construction shall be carried out in accordance with the “Deemed-to-Satisfy Provisions” of the Building Code of Australia. All internal and external stairways are to be designed and constructed in accordance with the Building Code of Australia.

6. Delivery and Handling

6.1.  Deliver all concrete materials to the site in ready-mix trucks in accordance with relevant current Australian Standard. Arrange and provide for concrete pumping equipment as needed.

6.2.  Avoid double handling at the site.

7. Warranty

7.1. Forward to the Principal a statement guaranteeing that the concrete complies with the approved mix design and that concrete has attained required strength at 28 days.

PART II MATERIALS

8. Formwork

8.1. Provide all formwork required to meet the requirements of both drawings and this specification.

8.2.  Comply with current relevant Australian Standard.

8.2.1.  Formwork Classes: Comply with current relevant Australian Standard.

8.2.2.  Class 2 Formwork for all concrete surfaces to be painted and all concrete surfaces that are exposed and critical to building appearance.

8.2.3.  Class 3 Formwork for carpark soffits and exposed non-finished work and works not otherwise specified or shown on the drawings.

8.2.4.  Class 4 Formwork for all concrete surfaces to be rendered, tiled or concealed by other finishes and all concrete surfaces permanently concealed in ducts, shafts and above false ceilings.

8.2.5.  Class 5 Formwork for all footings, concrete surfaces in the ground and rear surfaces of retaining walls, piers, etc.

8.2.6.  Formwork Materials: Approved timber, plywood or metal.

8.3.  Visually important surfaces

  • 8.3.1. General: For concrete of surface finish classes 1, 2 or 3, set out the formwork to give a regular arrangement of panels, joints, bolt holes, and similar visible elements in the formed surface.

8.4.  Allowances

8.5.  Allow for dimensional changes, deflections and cambers resulting from the following: Imposed actions.

8.6.  Concrete shrinkage and creep.

8.7.  Temperature changes.

8.8.  Design

8.9.  General: The design of the formwork other than profiled steel sheeting composite formwork is the contractor’s responsibility.

8.10.  Corners

  • 8.10.1.  Work above ground: Fillet at re-entrant angles, and chamfer at corners.
  • 8.10.2.  Face of bevel 25 mm unless noted otherwise for render or other final finish requirements.

9. Steel Reinforcement

9.1.  Provide all required steel reinforcement for concrete in accordance with drawings and details thereon. Refer all discrepancies to the Engineer for decision before proceeding with the work.

9.2.  Be solely responsible for the supply, fabrication and placing of all reinforcing steel. Remove reinforcement which does not comply with the requirements of this Specification and replace to the satisfaction of the Engineer.

9.3.  Reinforcing steel shall comply with the current relevant Australian Standards.

9.4.  Ensure all reinforcing is free from loose mill scale, rust, mud, oil, grease or other non metallic coatings which would reduce the bond between the concrete and steel and is free from kinks or other defects, all at the time of placing concrete. When there is a delay between placing the reinforcement and pouring the concrete, the Engineer may require the reinforcement to be restored to a condition satisfactory to receive concrete.

10. Concrete

10.1. Cement: Comply with current relevant Australian Standard.

  • 10.1.1. Provide cement of one brand which has passed the standard tests not more than three months prior to use.
  • 10.1.2. If not delivered as a component of ready-mixed concrete, deliver cement to the site in branded and sealed bags stacked under protective covers to prevent deterioration, so stacked that each batch delivered may be identified.
  • 10.1.3. Remove from the site cement that does not comply with these standards or has been adversely affected in storage. Aggregate: Comply with the requirements of current relevant Australian Standard.
  • 10.1.4. Maximum Size of Coarse Aggregate : comply with current relevant Australian Standardand drawings.
  • 10.1.5. Water: Water shall comply with current relevant Australian Standard. Admixtures: None, except with prior approval of the Engineer in writing.10.1.6. If admixtures are used, comply with current relevant Australian Standard. Ready-Mixed Concrete: Grey ready-mixed concrete except areas as specified below, supplied by an approved manufacturer and mixed and delivered in accordance with the requirements of current relevant Australian Standard.
  • 10.1.7. Site Mixed Concrete: Subject to prior written approval of the Engineer.
  • 10.1.8. Concrete Strength: Comply with stated compressive strengths at 28 days as noted or scheduled on structural drawings for various locations.
  • 10.1.9. Testing: Comply with the requirements of current relevant Australian Standard.

11. Fabrication of Steel Reinforcement.

11.1.  Fabricate, bend and weld in accordance with the standards laid down in the current relevant Australian Standard, the drawings, the requirements of this Specification and to the satisfaction of the Engineer.

11.2.  Where possible, bend all steel prior to delivery.

11.3.  Do not bend or straighten in a manner which will damage the steel.

11.4.  Do not bend again a deformed bar of structural grade steel or cold work steel which has been bent and subsequently straightened or bent in the reverse direction within twenty (20) bar diameters of the previous bend.

11.5.  Supply all necessary support and spacer bar though not necessarily shown on the drawings, to the satisfaction of the Engineer.

11.6.  Paint ends of bars which are to be left projecting for longer than three days with a heavy coat of neat cement grout.

11.7.  Concrete cover to reinforcement as shown on the drawings to tolerances in accordance with current relevant Australian Standard. Ensure concrete cover to reinforcement is maintained at drip grooves in concrete soffits.

11.8.  Tie Wire: annealed iron wire not less than No. 16 gauge, or other approved fasteners, unless shown otherwise on the drawings.

11.9.  Welding (including spot welding) of hard grade bars is not permitted.

11.10.  Reinforcement from any section of concrete which has been demolished and removed may only be re-used after inspection and approval by the Engineer.

PART III EXECUTION

12.1.  Examination: Inspect the site and all relevant conditions before installing any work. Ensure all conditions are satisfactory for installation. Start of any work means total acceptance of all conditions.

12.2.  Preparation: Ensure that all preparatory work of other trades is complete, including site preparation, sub-base placement, plumbing and other fittings are in place and secured, membrane and other materials are secure and complete.

12.3.  Formwork: Place and secure all formwork complying with current relevant Australian Standard. Fix all supports so that all imposed loads will cause neither displacement of or unacceptable finishes to stripped concrete. Seal all joints on exposed surfaces. Allow drip mouldings to all exposed soffits.

12.4.  Polymeric film underlay

  • 12.4.1. Location
    • 12.4.1.1. General: Under slabs on ground including integral ground beams and footings, provide a vapour barrier or, in areas prone to rising damp or salt attack, a damp-proofing membrane.
  • 12.4.2. Installation
    • General: Lay over the base, lap joints at least 200 mm and seal the laps and penetrations with waterproof adhesive tape. Face the laps away from the direction of concrete pour. Take the underlay up vertical faces past the damp proof course where applicable, and tape fix at the top. Patch or seal punctures or tears before placing concrete. Cut back as required after concrete has gained strength and forms have been removed.
  • 12.4.3. Base preparation
    • General: According to base type, as follows:
      • Concrete working base: Remove projections above the plane surface, and loose material.
      • Graded prepared sub-grade: Blind with sufficient sand to create a smooth surface free from hard projections.
      • Wet the sand just before laying the underlay.
 12.5. Finished Levels
  • 12.5.1. Finished levels: Unless otherwise specified, provide set-downs as required to concrete surfaces to maintain finished floor levels without step or break at changes of floor finish, including carpet.

Floor Junction Finish 

12.6.1. Location: Where changes of floor finish occur in doorways, make the junction directly beneath the closed door.

  • 12.6.1.1. Dividing Angle: Insert a dividing angle the full width of junctions between different floor finishes, with the top edge 40 x 5mm aluminium angle flush with both the finished floors.
    • 12.6.1.1.1. Dissimilar floor finishes must finish flush with one another in particular tiles in bathrooms to adjacent carpeted areas and the
  • 12.6.1.2. Fixing: Provide with fixings to sub-base so that angle is firm and top is level with floor finish.

12.7. Fixing Reinforcement

  1. 12.7.1.  Place and secure in correct location, all reinforcement in accordance with structural drawings.
  2. 12.7.2.  Unless otherwise shown on the drawings or directed by the Engineer, measurementsmade in placing the reinforcement are to be to the centre-lines of the reinforcement.
  3. 12.7.3.  Support and wire together reinforcement with a 0.5mm soft wire ties or clips toprevent displacement by construction loads.
  4. 12.7.4.  Use plastic-tipped metal chairs, metal hangers, metal spacers and other plastic, metalor concrete accessories as required for supporting reinforcement.
  5. 12.7.5.  Tie, clip or otherwise secure mesh reinforcement together by approved means atalternate intersections and at such other points as may be required.
  6. 12.7.6.  Splices on Reinforcement: Splice only at locations approved by the Engineer with minimum lap lengths as shown on the drawings.
  7. 12.7.7.  Cover to Reinforcement: Allow clear minimum cover to reinforcing as shown on theEngineer’s drawings. Maintain this cover during concreting. Ensure concrete cover to reinforcement is maintained at drip grooves in concrete soffits.

12.8. Build In

  • 12.8.1.  Install and build in all items required including:
  • 12.8.2.  Construction joints
  • 12.8.3.  Conduits and piping
  • 12.8.4.  Bolts, lugs and anchors
  • 12.8.5.  Waterstops and all other items so required.
  • 12.8.6.  Complying with structural and other trades requirements. Secure such items to prevent displacement during concrete pouring.

12.9. Pouring Concrete

  • 12.9.1.  Arrange for, with sufficient notice, inspection of all preparatory work by Engineer andCertifying Authority. No concrete may be poured until approval is received.
  • 12.9.2.  Ensure that all surfaces, trenches and formwork is both free of water and building debris and any material which may adversely affect concrete.
  • 12.9.3.  Transport concrete from the mixer to the place of final position without delay and by means that will prevent segregation and loss of materials. Where necessary, transport concrete on substantial gangways or barrow runs supported on stools clear of reinforcement. Remove hardened concrete and foreign materials from the inner surfaces of the conveying equipment.
  • 12.9.4.  Place concrete in accordance with current relevant Australian Standard.
  • 12.9.5.  During placement and prior to setting, do not expose concrete to rain. Should rain occur prior to setting, protect surface from damage by covering until hardened.

12.10. Compaction of Concrete

  • 12.10.1. Compact all concrete by mechanical vibration to the maximum practicable density, free of air or stone pockets. Any concrete not vibrated will be rejected.
  • 12.10.2. Vibrate concrete in layers not exceeding 450mm in thickness and avoid contact of the vibrating head with surfaces of the forms. Use of the vibrator to spread concrete is not permitted.

12.11. Curing Concrete

  • 12.11.1. Comply throughout with the requirements of current relevant Australian Standard.
  • 12.11.2. Protect freshly cast concrete from premature drying and excessively hot or cold temperatures.
  • 12.11.3. Maintain the concrete at a reasonably constant temperature with minimum moisture loss for the curing period.
  • 12.11.4. Period of Curing: Continue for seven days for normal Portland cement concrete.
  • 12.11.5. Prevent rapid drying out at the end of the curing period.

12.12. Completion

  • 12.12.1. Complete all contracted work in accordance with contract documents and written instructions issued by the Structural Engineer or Principal/Supervisor.

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