3.1.1Tenderer to Allow in Tender for All Clauses Herein Applicable to This Contract

PART 3.

STANDARD PREAMBLES TO TRADES.

3.1GENERAL NOTES.

3.1.1Tenderer to allow in tender for all clauses herein applicable to this contract.

Only those clauses, or portions of clauses, in this “Standard Preambles to all Trades” which are applicable to the works in this contract as indicated on the drawings and/or described in the supplementary specification and/or included in any detail drawings, orders or instructions issued to the Contractor during the progress of the works, shall be considered as applying to the performance of this contract.

Unless inconsistent with the text, preambles for any one trade apply to other trades also.

No headings or sub—headings shall limit the application of the clause.

3.1.2Materials and workmanship.

All materials and workmanship are to be the best of their respective kinds. Materials are to be free of defect and subject to the approval of the architect. Unless stated to the contrary only new and unused materials are to be incorporated into the Works. Material used for temporary purposes in the construction process may not be incorporated into the Works. Where possible all materials used in this contract shall be of South African origin or manufacture. This clause applies to all the works in the contract and will not necessarily be repeated hereinafter. The Contractor undertakes to take care in the use of materials and in the preparatory work before and during the performance of all trades.

3.1.3Brands and manufacturers.

All materials incorporated into the Works shall be stored, used, applied, fixed, etc. in strict accordance with the manufacturers’ printed or written instructions. Where required by the manufacturer approved specialist Sub Contractors are to be employed for specified work. The representative of any firm whose goods are specified or may be subsequently specified, shall at all times have access to the works as required for the purpose of inspecting or taking samples.

The Contractor’s tender must include for the goods, materials, etc., as specified in the tender documents.

Should the architect subsequently sanction the use of alternative materials then any necessary adjustment to the prices will be made.

3.1.4SABS specification.

All items of labour and/or material specified or described in this standard specification and/or supplementary specification which are covered by a code of practice and/or specification prepared by the South African Bureau of Standards, shall comply with the current relevant codes and/or specifications. Where practicable materials shall bear the mark of the SABS

3.2 EXCAVATOR.

3.2.1Excavations.

Excavations in “earth” shall mean excavating in all kinds of material met with other than “brickwork or mass concrete”, “reinforced concrete”, “soft rock” or “hard rock” as hereinafter defined, and shall include boulders, rubble, etc. with a volume not exceeding .03 cubic metres per piece

The term “brickwork or mass concrete” shall mean any brickwork or mass concrete structure or form met with such as footings, manholes, etc.

The term “reinforced concrete” shall mean any reinforced concrete structure or form met with such as column bases, footings, columns, walls, beams, etc.

The ‘term “soft rock” shall mean hard material which, in the opinion of the Architect, requires the use of mechanical plant for its removal and includes hard shale, ferricite, ouklip and materials of a similar degree of hardness:

The ‘term “hard rock” shall mean granite, quartzitic sandstone, or other rock of similar hardness which, in the opinion of the Architect, requires drilling, wedging and splitting or the use of explosives or similar materials.

If the Contractor considers that any of the excavation warrants payment on the basis other than that of “earth”, he must immediately notify the architect in writing. Failing such notification, the excavation shall be deemed to be in “earth”.

Blasting will not be permitted without the written authority of the Architect. Where blasting is permitted the Contractor is to take all necessary precautions against injury to persons and animals and against damage to property. The Contractor will be liable for payment of compensation for any injury or damage resulting from blasting operations.

If the Contractor considers that any of the excavation warrants payment on the basis other than that of “earth”, he must immediately notify the architect in writing. Failing such notification, the excavation shall be deemed to be in “earth”.

Any excavation made larger or deeper than indicated on the drawings or subsequent dimensions given in writing by the architect, notwithstanding the fact that such excess excavation may unavoidably occur due to blasting or through other causes, will not be paid for, and the filling of the extra excavation shall be done by the Contractor at his own expense with 10Mpa cement concrete.

Excavation in trenches, bases, etc., shall only be regarded as such after the Contractor has completed all bulk excavations.

No soil shall be carted away until sufficient suitable earth has been deposited on the site to provide for the made up levels as indicated.

Selected surplus material is to be wheeled or carted within 50 metres of the building perimeter to a position on the site directed by the architect, deposited, leveled and rolled, All other surplus material is to be removed from the site.

3.2.2Planking and strutting, shoring, etc.

The Contractor shall provide all necessary planking, strutting, shoring, etc., as require to prevent the falling in of earth and/or the collapse of the sides of excavations and as required to ensure the safety of the building works, adjoining properties, streets, etc., the workmen and anything else whatsoever connected with the contract.

Responsibility for the adequacy of the above mentioned precautions and the consequences involved in the event of any collapse of the faces of the excavations, etc., shall be entirely at the Contractor’s risk

3.2.3Completion of trenches.

The Contractor shall give written notice to the architect when the trenches are ready to receive the concrete foundations, which shall not be poured until the trenches have been inspected by the architect and measured.

3.2.4 Filling, etc.

Filling is to be laid and compacted in layers not exceeding 230 mm thick, watered, leveled, graded or dressed to slopes and ramps as required. Backfilling to trenches and filling under solid floors is to be done immediately after the foundations are built. No pot clay is to be used for filling.

Suitable materials from the excavations may be used for filling. Borrow pits on site will not be permitted

Earth or sand filling is to be of clean, dry and hard material. Hardcore filling is to be of brick or stone broken to pass a 75mm ring and sand blinded on completion..

3.2.6Soil poisoning.

Where prescribed, ground shall be treated in accordance with SABS 0124. Insecticides shall comply with SABS 1165. Soil poisoning shall carry a written ten year guarantee.

3.2.7Dewatering and protection of excavations.

The Contractor shall protect the excavations which have been prepared for the subsequent operations and shall keep them continuously free from water, sand, silt, mud or any debris whatsoever and in a fit and proper state for subsequent operations.

If springs are encountered, they are to be traced to the source, piped and led clear of the site.

No building work is to commence or continue in trenches that are, or have been flooded, until permission has been obtained from the architect.

3.3CONCRETE, FORMWORK AND REINFORCEMENT

3.3.1Generally.

The engineer referred to hereafter shall mean the consulting structural engineer, appointed by the employer, who shall act as the agent of the architect, or of the employer.

Where services of a consulting structural engineer are not required the engineer referred to below shall mean the architect.

The whole of the concrete work shall be carried out in conformity with SABS 1200G except where this specification is in conflict therewith.

All structural reinforced concrete will be subject to strength testing by the engineer throughout the progress of the work. At the engineer’s discretion, structural concrete which does not comply with the results required by the tests will be removed and reconstructed or strengthened, entirely at the Contractor’s expense, including the replacement of steel reinforcement. In the work hereinafter described, concrete other than structural reinforced concrete is, where necessary, referred to as “mass concrete.

3.3.2Testing of materials.

Tests are to be carried out in accordance with the standard methods laid down in SABS 1200G and at the sole discretion of the engineer.

3.3.3 Cement.

Cement shall be a common cement complying with SANS 50197.

A manufacturer’s certificate of test shall be supplied on request for each consignment. Cement is to be measured by weight or by whole pockets: one 50kg sack of cement shall be taken to be 0.033m3. If it is imperative that a fraction of a pocket of cement must be employed such fractional pockets shall be measured by weighing out. Cement must be fresh and dry when used and no cement older than 3 months, or which has absorbed moisture to the extent that any portion becomes caked, shall be used. The cement must be stored in a weather-tight store with a floor at least 150 mm above the natural ground level.

Cement pockets must not be stored against the walls or higher than 12 pockets in height. Storage must be arranged in such a way that the cement may only be used in the order in which it has been delivered.

3.3.4 Aggregates.

Aggregates shall comply with the requirements of the SABS 1200G

Aggregates shall be stored in flat stockpiles in such a way that segregation of the sizes in any stockpile is avoided. Spillage of material from one stockpile to another shall be prevented by the provision of adequate bulkheads. The contamination of stockpiles by foreign matter shall be prevented by storing aggregates on clean hard surfaces. Sand must be stored in such a way that when used the moisture content shall be constant in the sand for at least one day’s use, or the moisture content of the sand shall be determined from time to time and due allowance made for its presence by adjusting the amount of mixing water added. The moisture content of the sand shall be determined daily and also whenever it is likely to have changed due to the delivery of additional material to the stockpile or due to the accidental or intentional addition of water to the stockpile from dampening—down or rain.

3.3.5Water.

Water must be clean and fresh, free from impurities or other material which may adversely affect the concrete and must be obtained wherever possible from the municipal water supply. The measurement of the quantity of the water for the various mixes of concrete shall be carried out in a graded container attached to the mixer or by means of a Flowmeter.

3.3.6Determination of concrete mix.

Readymix Concrete

Readymix concrete should be supplied by a SARMA (South African Readymix Association) member and be in compliance with the SANS 05878:2003 specification. Readymix concrete is a performance based specification and should be specified on a 28 day strength requirement. The mix determination to meet these criteria rests with the Readymix producer.

Site Mixed Concrete

Concrete mixes are to be formulated by an approved testing laboratory to provide the final design strengths specified. Together with fine and coarse aggregate samples, the Contractor must deliver one pocket of cement for each size of coarse aggregate that will be used to the test laboratory. Before the Contractor begins the work, he must present the engineer with the report of the laboratory in which the various concrete mixes complying with the design requirements are enumerated.

The mixes must be given in weight comparisons together with the recommended measurements of the proposed gauge boxes for fine and coarse aggregate if the Contractor intends to use volume batching of materials. The cube strength of the design mixes must be stated.

The mixes as designed must be of such a consistency and workability that they can be worked into the corners and edges of the formwork and around reinforcement without the materials becoming separated and without excess water accumulating on the upper surface.

Concrete is specified by its strength and maximum aggregate size incorporated in the mix, e.g. 30Mpa/19mm.

3.3.7Concrete proportions for mass concrete

The fine and coarse aggregates shall be measured separately. The proportions of cement to fine and coarse aggregates shall be such as to produce the following minimum crushing strengths for nominal mixes:

Class of concrete / Maximum size of coarse aggregate (mm) / Proportions of constituents by volume.
Cement Fine Coarse
Aggregate Aggregate / Estimated 28 day minimum Strength (MPa)
A
B
C / 38
20
20 / 1 4 8
1 3 5
1 2,5 3,5 / 7
15
20

3.3.9Site Mixing of concrete.

All concrete shall be mixed in a mechanical batch mixer. The quantity of material used at one time and loaded into the mixer must not exceed the prescribed quantity laid down by the manufacturer. The rotation speed of the drum must be in accordance with the manufacturer’s recommendation. The period of mixing must be two minutes. The drum must be emptied after mixing each batch before further materials are loaded. If the mixer has not been used for any lengthy period it must be washed before use.

3.3.11Placing of concrete.

No concrete may be placed if the air temperature is lower than five degrees Centigrade measured by a dropping mercury thermometer. Mixed concrete is to be handled and conveyed from the place of mixing to the place of final deposit by methods which shall prevent segregation or loss of the ingredients. Concrete not placed within one hour of the time of adding the mixing water may not be used.

A competent and experienced foreman, trained for reinforced concrete work, must maintain constant supervision of the mixing and placing of all concrete. The engineer must be advised of the Contractor’s intention to concrete before the work is commenced. No concrete may be placed before the engineer has approved the fixing of the steel. The foreman shall keep a record available at all times on the works of the time and date of placing concrete in each portion of the structure.

Surfaces which will be in contact with the fresh concrete as for example earth, old concrete, formwork, etc., must be wetted before the fresh concrete is placed thereon. Puddles must not be allowed to form.

Once begun, the placing of concrete must continue without break until the position of agreed construction joints has been reached.

Concrete must be worked into the corners and around the steel immediately after placing.

3.3.12 Construction joints.

Construction joints will only be allowed where shown or as agreed upon between the engineer and the Contractor. When concreting has to be resumed against a surface which has hardened, such surface shall be roughened by hacking and all laitance removed. The surface shall then be swept clean, wetted and covered with a 230 mm layer of freshly mixed mortar composed of cement and fine aggregate in the same ratio as the cement and fine aggregate in the concrete mix. Green concrete must be brushed and treated with a cement slurry.

3.3.13 Expansion joints.

Care shall be taken to consolidate concrete around rubber and other seals, angles, edges, etc., in expansion joints.

3.3.14Holes, sleeves, chases and lugs for embedding.

The cutting or forming of holes, chases, etc., which are not shown on the concrete drawings may not be done without the permission of the engineer. The placing of fixing blocks, lugs for embedding, pipes, ducts, channels, etc. in the concrete work may only be done in accordance with the instructions of the engineer. The minimum distance between pipes or between pipes and steel reinforcement, must be 40 mm or 1 1/4 greater than the largest size of stone used in the concrete, whichever is the greater.

3.3.15Vibration.

Tile type of vibrator used, and the time and method of vibration must be in accordance with the engineer’s instructions. Care must be taken not to vibrate the concrete excessively. The mixes herein—before given shall be suitably adjusted for the severity of vibration. Generally mixes subject to mild vibration shall not have a slump exceeding 50 mm and mixes for heavy vibration shall not have a slump exceeding 25 mm and the mixes shall be proportioned to minimise segregation.

3.3.16Protection and curing.

After concrete has been cast, the top surfaces are to be covered with planks, a 50 mm thick layer of sand, wet sacks, plastic sheeting or other material and kept wet for a minimum period of 7 days. Damage to concrete surfaces will not be permitted.

3.3.17Quality control and testing.

To ensure quality control of the concrete, the Contractor must carry out concrete strength tests at points in the structure to be decided upon in consultation with the engineer.

A strength test shall consist of taking at least three 150 x 150 x 150 mm test cubes in accordance with SABS 1200G, sending them to a test laboratory for testing at 7 and 28 days and delivering the test results to the engineer within 3 days after testing. The results must be accompanied by a sketch whereon the specific portion of the structure represented by the test cube is shown.

A minimum of one set of three test cubes must be made for each 50 cubic metres of concrete cast and for each of the following sections (a to d) of the reinforced concrete structure. The concrete for testing shall be taken from the point of deposit, the location of which shall be recorded for future reference.