Concretor

CONCRETOR

Note: These are general specification clauses and should be adjusted to suit individual projects.

SECTION UNDER CONSTRUCTION

General

All work is to be supplied and installed to Standard.
Advise when the site and footings are excavated and formwork is in place. Also advise at the following stages so an inspection may be made: reinforcing placed ready for pouring concrete; plastic membranes and damp proof barriers in place; blockouts installed; concrete being poured; and prior to the concealment of any part of the structure or materials.
Provide details of curing of the concrete and protection in cold or wet weather.

Materials

Under the plastic membrane provide a compacted sand or compacted blue metal gravel base.
Plastic membrane is to be provided over compacted subbase and under concrete slabs with sealed joins, lapped 250mm, with sealed penetrations and punctures. Plastic membrane is to be taken up vertical concrete surfaces to the underside of damp proof courses.
Provide delivery dockets of concrete showing the strength, additives, time and date, and type of concrete used.
Use ready mixed concrete throughout apart from small areas less than 0.5m3 batches of concrete.
Cement is to be Blue Circle brand, or equal, fresh and less than 5 months old. Cement is to be free of admixtures unless specified.
Do not rewet ready mixed concrete and do not pour in cold or hot weather (>32degC and <10degC). Deliver concrete in rotating agitator containers fixed to trucks.
Provide fixings and embedded items  as detailed with greased threads to bolts. Cover and protect against damage any embedded items. Place embedded items securely but so as not to damage reinforcement or the structure of the concrete. Ensure water does not track from the fixing to the reinforcement. Fixings are to be placed in the correct position with no necessity to relocate structural elements to be fixed.
Concrete for smaller batches shall be mixed from 6 parts sharp aggregate, 2 parts sand and 1 part cement.

Placement of Concrete

Place concrete carefully into formwork and final locations. Do not drop concrete and do not drop from a height greater than 1350mm. Remove air pockets and fully vibrate the concrete for a homogenous setting. Do not over vibrate and cause segregation of materials. Use hoses, pumps, conveyors, buckets, wheelbarrows to transport the concrete. Avoid segregation of the mix. Protect the concrete from the rain and frost while mixing, pouring and setting.
Pour concrete in homogenous sequence so bonding occurs between layers.
Provide details of concrete including strength, batch number, time, date, slump, volume, company details.
Provide concrete tests if required (nominate) and take from the middle of concrete batches. Tests are to be undertaken by an independent testing authority approved by the architect. Provide test results to the architect.
Cover drying concrete for 28 days or wet after the initial set for 28 days and ensure proper hardening and hydrating.

Reinforcing

Provide steel reinforcing within the concrete for a complete structural system. Reinforcing is to be to a true line and shaped to profiles required. Lap and tie reinforcing. Reinforcing is to be free of rust, grease or clay. Galvanized for all balcony reinforcing closer than 1km of breaking surf. Support reinforcing on plastic supports capable of supporting the reinforcing in the correct location during pouring and setting of concrete. Protect plastic membranes and DPC from puncture by the use of plastic plates under reinforcing supports.
Embed the unpainted end of dowels first.
Provide plastic caps to protect workers on site from starter bars and other embedded reinforcing during construction.
Maintain adequate tolerance of reinforcing from surrounding surfaces. Cover to reinforcing steel shall be as follows: footings: 50 mm; slabs - external: 35 mm; slabs - Internal: 25 mm.
Chemical anchors are to be installed in accordance with manufacturers specifications. Minimum embedment 110mm or as shown.

Formwork
Construct formwork to achieve the shapes required. Adequately brace, support and fix formwork to ensure the wet concrete does not break the formwork. Support formwork until the concrete has reached design strength. Build in fillets, drip moulds, blockouts, as required. Provide release agents to provide a clean removal of the formwork for the desired finish. Formwork is to be (nominate smooth, rough textured, planked) for the required finish. Maintain formwork under suspended slabs until the concrete has reached its nominated strength.

Finish
For vinyl finish provide a maximum deviation of 3mm in 3m with no further deviation within the 3m. For carpet and tile finish provide a maximum deviation of 6mm in 3m with no further deviation within the 3m. Further flatness tests to Standard. Any areas that require smoothing are to be ground down and/or filled with a levelling compound equal to Ardit. Floor finishes are to be approved by the floor finisher prior to laying finish and any repairs to the floor required are to be provided by the contractor responsible for laying the floor substrate.
Exposed Aggregate - Surface and formwork is to be removed while the concrete is green. Remove the surface with a stiff fibre or wire brush. Use water to clean the surface and remove the same amount of concrete off the top of the aggregate uniformly across the surface. The type of aggregate is to be (nominate brown, grey, yellow, etc 10-15mm, etc.) 
Other surfaces (eg polished, hammered, rubbed, etc nominate)

Precast Concrete
Provide precast concrete to the sizes nominated. Provide shop drawings of the panels with fixing, surface details, anchors, lifting points, concrete mix and strength, and sealing details. Support panels on frames and with appropriate fixings. Seal panels to exclude water from entering the assembly or building.
Do not lift the panels until the concrete has reached its required strength. Lift carefully so as not to damage the panels, structure or persons.
Provide a smooth even finish to the panels with no holes, bumps or blemishes. Fix any defects in the panels with a suitable compound or by grinding. The surface finisher is to approve the surface of the panels prior to the application of the finish and any repairs required done by the panel manufacturer promptly.