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- High Tensile Steel :
High Tensile Steel in the form of strand shall conform to IS: 1735 Part I and IS: 6006 respectively. It shall be procured only from BUREAU OF INDIAN STANDARDS MANAGEMENT SYSTEMS CERTIFICATION (BIS) approved manufacturers who furnish proofs of approval by BIS. Each consignment of HTS accompanies test certificates showing the serial numbers of coils. Each coil carries a tag in accordance with Indian Standard Specifications.
Results of relaxation test are also furnished by the manufacturers once in six months. Separate tests as per BIS can be carried out if required by clients. The steel is used for production only after ascertaining that it meets the provisions for relevant specifications.
- Aggregates :
The aggregates shall conform to IS: 383 and is tested through an approved testing institute and results obtained in accordance with Appendix-A of IS:383 is submitted to the client for approval. The aggregates shall have an abrasion and impact value suitable for wearing surfaces. The flakiness index and elongation index does not exceed 30% when tested with IS: 2386 Part-I. Different sizes of aggregates are stacked in different stock piles.
Coarse aggregates used are crushed stone, angular in shape.
Fine aggregates being used are from the natural disintegration of rock and which has been deposited by streams or glacial agencies.
- Cement :
Cement used confirms to Indian Railways Specification No. T 40.
Each consignment of cement is covered by a test certificate issued by the cement manufacturers. Each consignment are being stacked separately, and tested at our plant laboratory for all relevant properties, immediately. In case the source of cement is changed, the mix-design is reviewed and modified by us, if necessary with subject to approval of client. The cement content of the mix shall not be less than 350 kg/cm and not more than 480 kg/cum.
- Control of Water :
Water to be used in making and for concrete shall be as per IS: 456.
The total water content per batch is regulated to confirm to ratio by weight of free water to cement required for the particular design mix as established by preliminary tests. The total water content of a batch includes :
- Absorbed water in the aggregates.
- Free water in the aggregates.
- Free water added to the mix.
The water to be mixed at the mixer has free water content required per batch, less the amount of free water in the aggregates, if wet or plus the amount of water the aggregates will absorb, if dry. Free moisture is determined at least once a day.
- Concrete :
The concrete is of controlled quality with the nominal maximum size of aggregates limited to 20 mm, and where wire spacing permits, aggregates up to 25 mm is used. The concrete mix-design along with the upper and lower limits of granulometric curves are approved by the clients. The granulometric curves are plotted on semi-log graph sheet once in a week and shall be between the approved limits.
- Minimum compressive strength of concrete (fc) 50 MPA.
- Maximum working compressive stress after all losses 0.4 X (fc).
- Maximum working tensile stress in concrete 0.04 X (fc).
- Minimum specified tensile strength of steel tendons (fu) 1720 MPA.
- Maximum tensioning stress in steel tendons 0.75 X (fu).
- Total initial tensioning load (IR Sleeper) 715 KN.
- Final tensioning load (IR Sleeper) 495 KN 80 cubes are cast, using materials proposed for regular manufacture, in ten batches of eight cubes each, four for steam curing and four for water curing.
All the forty cubes cured according to the proposed steam curing cycle shall attain specified release strength.
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