AGGREGATES CIVIL WORKS FOR UNDERGROUND CABLE INSTALLATION
Aggregated Civil Works and Construction Materials Management in Cable Installation Site
The underground cable installation project is not a contemporary high-tech major aggregates civil work, but some special complaint and engineering practice should followed to keep the power cable safe and liveliness for long lifetime.
This article is introduced on the aggregated civil work for high voltage electrical power transmission underground cable installation project. The scope of civil works for such project as highlighted as below:
· Cable trench cutting, bedding, backfilling;
· Cable protection RCC slab;
· Pipe trench, bridge trench, road and canal crossing etc;
· Piling for bridge trench and terminal equipment structure;
· Cable joint and cable earthing or grounding RCC Bay construction;
· Concrete structure and foundation for outdoor steel structure, etc.
To ensure quality and follow engineering layout the aggregates for all concrete should be take approval of the Engineer. Un-reinforced mass cement may use first class broken brick, aggregate. Reinforced concrete should use only stone aggregate.
They must be hard, strong, durable, clean and free from adherent coatings and should be protected from contact with any deleterious mater whatsoever.
Delivery and Storage System
Sufficient quantities of each grade of aggregate should be kept on the site to ensure continuity of work. Aggregate of different sizes should be stored in different stacks and the arrangements for storage should be subject to the approval of the Engineer.
Aggregates for Reinforced Concrete
For reinforced concrete work the fine aggregate should consist of clean well graded Sunarganj, Jaladia or Savar sand.
The coarse aggregate for reinforced concrete should consist of well graded Sylhet shingles.
The fine and coarse aggregate should be kept well separated during storage on site and during mixing, measured separately and mixed in the proportions specified or permitted. The individual and combined grading should be to the satisfaction of the Engineer.
Aggregates for Mass Concrete
All brick aggregate should be tested periodically and as often as the Engineer should decide to be necessary, to ascertain the proportions of the sand contents. In such testing the following conditions should be observed:
o All material passing a 5mm square mesh should be defined as sand and the residue on such a sieve as coarse aggregate.
o The sand and coarse aggregate are to be separated by sifting a dry sample and the proportion of each ascertained.
o The proportions by volume in a shaken measure are to be approximately one part sand and two parts coarse aggregate.
Aggregate for cement Mortar
The aggregate for cement mortar should consist of natural sand as specified in British standard BS 1200; sands for mortar for plain and reinforced brickwork. Mortar for brickwork should generally consist of 1 part cement to 0.5 parts to 4 or 4.5 parts of sand as per BS 5628.
Water for Concrete
The size of aggregate effects on workability and strength of concrete and also influences the water demand for getting a certain work-strength and fine aggregate content required for achieving a unified mix.
Water for concrete, cement mortar and grout should be free from salt, oil, alkali, organic matter or other deleterious substances and the Engineer’s approval must be obtained prior to its use. Any tests required by the Engineer on the suitability of the water should be carried out in accordance with BS 3148.