CONSTRUCTIONAL CIVIL WORKS FOR UNDERGROUND CABLING
The Constructional Civil Works Required In Underground Cable Installation Project
The proposed batching of cement shall be submitted to the Engineer for approval.
The concrete shall be mixed in approved mixing machines. The time allowed for mixing (after all the ingredients have been placed in the machine) shall be as ordered by the Engineer but shall not be less than two minutes. Mixers shall be maintained in first class condition throughout the Contract and shall be cleaned before fresh concrete in mixed if the drum has been out to use for more than 30 minutes.
As the work proceeds test cubes shall be made by the Contractor as directed by the Engineer for each batch of concrete mixed. Six test cubes shall be taken three shall be tested at 7 days and three at 28 days if required. These cubes shall be composed of concrete taken from the actual mixes for the work. Cubes so tested shall comply with relative standard of this Specification which shall be approved by the Engineer, The failure of any one cube of a particular mix to satisfy the requirements shall render that mix unfit and it shall be condemned.
Those cubes made on the Site of the Works in advance of the pouring of permanent works and using materials which the Contractor proposes to use for the permanent works shall comply with the strength requirements for ‘Works Tests’.
Transport and placing
During the transport and depositing, mixing concrete shall be protected from contamination by rain, spray, dust and dirt, etc. and every precaution shall be taken to avoid the segregation of the constituent materials.
Concreting of any unit or section shall be carried out in one continuous operation and no interruption allowed except with the Engineer’s approval.
Concrete is to be worked up hard against every surface that it adjoins. The through compaction of the concrete is essential to ensure that it is in immediate contact throughout with ground, form and embedded stub anchors; therefore the method of carrying out this word and the number and type of punners, vibrators, etc., to be employed on any particular section of the work are to be to the entire satisfaction of the Engineer.
The compacting is not to be confined to the upper surface of the layer deposited, but the whole must be thoroughly well punned and vibrated and brought up in layers so as to become consolidated, with the mass, assuming a jelly-like consistency and the water just appearing on the surface.
No concreting shall be commenced in any portion of the Works until the preparations have been approved and permission granted by the Engineer.
Protection and Curing
During windy weather efficient protection shall be provided to prevent, cement from being blown away during the process of batching and mixing.
During wet weather adequate precautions shall be taken to protect the cement and to ensure proper mixing.
No concreting shall be commenced during periods of heavy rain.
All concrete shall be protected during hardening from the harmful effects of sunshine, moisture, drying winds and cold.
All exposed surface of concrete shall be kept continuously moist for a period of not less than 10 days after pouring by means approved by the Engineer.
Concrete Placing and Finishing During Hot Weather
Concrete placing and finishing operations during hot weather shall be done as quickly as possible. Ample personnel shall be available to handle and place the concrete immediately after its mixing and shall be placed in layers thin enough to ensure complete bond and union of adjacent layers and thus prevent “cold joints”. Concrete shall not be placed when temperature of the mix exceeds
or when above 250C
and subjected to hot drying winds.
The quantity of cement used in the approved concrete design mix shall be increased when and as necessary to maintain the specified maximum water-cement ratio in all case where additional water is added to compensate for loss of slump during handling or placing.
All exposed surfaces of concrete shall be kept continuously moist for a period of not less than 10 days after pouring by means approved by the Engineer.
Ducts and Holes
Ducts and holes shall be molded in the concrete as may be required.
No reconstruction or repairs to faulty works shall be done without the permission of the Engineer and then only in such manner as he may direct or approve.
All concrete surfaces shall be reasonably true and smooth. Any fines which may occur between boards or panels shall be removed and air holes filled with 1:1 mortar. Any area requiring treatment after stripping, as outlined above, shall afterwards be worked smooth with a wooden float and washed perfectly clean.
On completion of final surfaces treatment, as outlined above, all surface exposed to backfill shall be treated with an approved asphaltic emulsion in not less than 2 coats applied at a minimum of 24 hours between coats. Emulsified asphaltic coating shall be of a make similar to ‘Texacoat’ or ‘Flintokote,’ must resist attack by acids and shall be applied cold with a brush.
These shall be of 230mm wide buck worth internally rendered with 12mm cement lime mortar and externally rendered with 3mm spatter dash, 12mm cement lime mortar and two coats of broomstick paint.