Methodology for Structural Concrete for Bridges and Culverts
Methodology for Structural Concrete for Bridges and Culverts 1. Scope The work shall consist of producing and placing concrete of grade M15 and higher by weigh batching in accordance with MoRTH Specifications, IRC:112, approved drawings, and contract specifications. 2. Reference Contract Agreement IRC: SP: 84-2014 MoRTH Specifications (5th Revision) IRC: 112 Relevant Drawings 3. Setting Out After completion of site preparation, alignment of the structure shall be marked on the ground using lime and string. Structural points such as abutment walls and wing walls shall be pegged accurately. Temporary Bench Marks (TBM) shall be established nearby for level reference and protected throughout construction activities. 4. Materials 4.1 Cement Cement conforming to IS:269 shall be used after ensuring the required design strength. Manufacturer Test Certificates (MTC) shall be submitted to the AE for every consignment. Independent testing shall also be conducted at approved laboratories. 4.2 Coarse Aggregate Coarse aggregates shall be obtained from approved quarries and shall consist of clean, hard, durable crushed stone conforming to Table 1700-7 of MoRTH Specifications / IS 383. 4.3 Fine Aggregate Fine aggregates shall be clean, durable, and free from deleterious materials. Gradation shall conform to Table 1000-2 of MoRTH Specifications / IS 383. 4.4 Water Water used for mixing and curing shall conform to IS 456 and Section 1010 of MoRTH Specifications. Water shall be free from harmful substances. Use of seawater shall not be permitted. 4.5 Reinforcement Steel Reinforcement steel shall conform to Section 1009.3 of MoRTH Specifications and IS 1786. TMT Fe-500 grade bars shall be used as per approved drawings. 4.6 Bending of Reinforcement Bar Bending Schedule (BBS) shall be prepared and submitted for approval before commencement of work. It shall include shape, number, cutting length, and weight of bars including auxiliary reinforcement. All materials shall be approved by the AE before use in construction. 5. Placing of Reinforcement Reinforcement shall be placed as per approved drawings and inspected by the AE before concreting. Bars shall be tied using 1 mm binding wire. Cover blocks of the same concrete grade shall be used. Spacer bars and chairs shall be provided to maintain spacing and cover. Horizontal reinforcement shall be adequately supported to avoid sagging. 6. Proportioning of Concrete Concrete shall be produced using approved design mix by weigh batching. Measuring equipment shall be maintained in proper condition and calibrated periodically. Water-cement ratio shall be maintained considering moisture content of aggregates and weather conditions. 7. Trial Mixes Trial mixes for all grades of concrete shall be carried out at the site laboratory before commencement of work using approved materials. Additional trial mixes shall be conducted whenever there is a change in source or proportion of materials. 8. Equipment Batching Plant Transit Mixer Concrete Pump Vibrators & Vibrator Needles Wheel Loader Excavator Shuttering Material Bar Bending & Cutting Machine 9. Transporting, Placing & Compaction of Concrete Concrete shall be transported using transit mixers or concrete pumps. The delivery pipeline shall have minimum bends. Concrete temperature during placing shall be between 5°C and 40°C. Concrete shall be compacted within 30 minutes of discharge. Concrete shall be placed in layers not exceeding 300 mm compacted thickness. Fresh concrete shall not be placed against concrete older than 30 minutes without proper construction joints. Concreting shall not be carried out when ambient temperature exceeds 40°C. 10. Formwork Formwork shall conform to Section 1500 of MoRTH Specifications and IRC:87. Only steel formwork shall be used. Formwork shall be rigid and true to shape. Damaged formwork shall not be used without repair. Steel tubes used as supports shall have minimum 4 mm wall thickness. 11. Construction Joints Construction joints shall be kept to a minimum and provided as per drawings. Laitance shall be removed and the concrete surface roughened before placing fresh concrete. 12. Curing Water curing shall be carried out using approved water conforming to MoRTH Specifications. Concrete surfaces shall be kept continuously wet. Wet hessian cloth, sacks, or canvas may be used. Curing shall continue for at least 14 days after concreting. 13. Finishing Finishing shall be carried out as per Clause 1713 of Section 1700 of MoRTH Specifications to achieve smooth and durable concrete surfaces.
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