Detailed Specification for Providing and Laying Uncoursed Rubble Masonry for Earthen Dam
1. Scope of Work
This specification outlines the requirements for providing and laying uncoursed rubble masonry in cement and sand mortar for an earthen dam. The work includes:
- Mixing and laying of rubble masonry.
- Use of header and bond stones.
- Scaffolding and finishing to the required shape and batter.
- Racking out the joints and curing.
2. Materials
2.1 Stones
- Type: Stones should be clean, hard, durable, and free from cracks and organic impurities.
- Size: Stones should be of varying sizes to fit together without large voids. Larger stones should be used at the base and corners for stability.
2.2 Cement and Sand Mortar
- Cement: Ordinary Portland Cement (OPC) conforming to IS 269:2015 standards[1].
- Sand: Clean, well-graded sand free from silt, clay, and organic matter, conforming to IS 383:2016 standards[2].
- Mix Ratio: The cement and sand mortar should be mixed in a ratio of 1:6 by mass.
3. Construction Methodology
3.1 Preparation of Site
- Site Clearance: Clear the site of all vegetation, roots, and debris. Remove tree roots to a minimum depth of 1.20 meters below ground level.
- Excavation: Excavate to the required depth and dimensions as per the drawings. Over-excavation should be backfilled with compacted gravel or murrum.
3.2 Mixing of Mortar
- Machine Mixing: Use a mechanical mixer to ensure a uniform mix of cement and sand. Add water gradually to achieve the desired consistency.
- Mixing Time: Mix for at least 3 minutes to ensure thorough blending of materials[3].
3.3 Laying of Rubble Masonry
- Placement of Stones: Place larger stones at the base and corners. Hand-pack stones tightly together to minimize voids. Use smaller stones to fill gaps.
- Header and Bond Stones: Use header stones to tie the masonry together and bond stones to ensure stability. Place header stones at regular intervals.
- Mortar Application: Apply mortar to the bed and sides of each stone. Ensure full contact between stones and mortar to avoid voids.
3.4 Scaffolding and Finishing
- Scaffolding: Erect scaffolding as required to reach higher levels. Ensure scaffolding is stable and safe for workers.
- Finishing: Shape and batter the masonry to the required profile as per the drawings. Ensure a neat and uniform appearance.
3.5 Racking Out Joints
- Process: Rake out the mortar joints to a depth of 20 mm while the mortar is still green. This helps in achieving a better bond with the finishing mortar[4].
3.6 Curing
- Curing Method: Keep the masonry moist for at least 7 days to ensure proper curing. Use wet burlap or water spray to maintain moisture[5].
4. Quality Control
4.1 Material Testing
- Stones: Test stones for hardness, density, and durability.
- Mortar: Test mortar for compressive strength and consistency.
4.2 Inspection
- Site Inspection: Conduct regular inspections to ensure compliance with specifications.
- Final Inspection: Perform a final inspection upon completion to ensure all requirements are met.
5. Measurement and Payment
5.1 Measurement
- Measure the work in cubic meters of the finished masonry.
5.2 Payment
- Payment will be made at the unit rate per cubic meter as specified in the Bill of Quantities. The rate includes the cost of all materials, labor, equipment, and other incidental expenses required to complete the work as per the specifications.
References
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