GENERAL SPECIFICATIONS FOR CONSTRUCTION WORK

1. Framework and Material Standards

The procurement guidelines emphasize drafting precise, clear, and non-restrictive specifications to ensure competitive bidding, economy, and fairness.

All materials must be new and up to date, incorporating recent design improvements. International, national, or alternative authoritative standards that ensure equal or higher quality are acceptable subject to prior review.

The specifications are purposefully structured in an instructional form to assist contractors, user committees, and site engineers in a rural environment. Local materials must be inspected at the source prior to site delivery.

Ordinary Portland Cement must comply with NS, Indian, or British standards, be purchased from trusted distributors to verify its freshness, and be stored in weather-proof facilities with raised wooden floors.

Sand for slow sand filter media must satisfy rigorous technical criteria, including an effective size of 0.20 to 0.3 mm and a uniformity coefficient between 3 and 5.

Coarse aggregates must be durable and chemically inert, rejecting flaky or elongated particles. Timber must be premium Sal Wood, while reinforcement steel must conform to specific Indian Standards (IS).

2. Earthworks and Site Execution

Site preparation requires clearing all vegetation, roots, and rocks, with topsoil removed as instructed. Fillings under floors and in trenches must be laid in well-watered and rammed layers not exceeding 15 cm. For pipeline trenches, the first backfill layer must be 30 cm thick and stone-free to protect the pipe.

Embankments require stripping 20 cm of turf and topsoil before tipping commences, and finished slopes must be hand-covered with 30 cm square, 5 cm thick matured grass turf.

Barbed wire fencing must feature 12 SWG galvanized wire with four points every 75 mm. Structural steelwork requires detailed shop drawings and a shop-applied coat of red lead paint.

3. Concrete and Mortar Technicalities

Concrete is classified into four standard grades (M10, M15, M20, M25) based on 28-day compressive strength.

Controlled concrete relies on strict weight batching for cement and aggregates, whereas ordinary concrete permits volume batching using fixed mix proportions (e.g., 1:2:4 nominal mix for M15).

Water-cement ratios must not exceed specified limits (varying from 26 liters per 50 kg of cement for M25 to 34 liters for M10). Mechanical mixing must run for at least 1.5 minutes.

For consolidation, internal vibrators must not be immersed longer than 3 minutes, and withdrawal must not exceed 8 cm per second. Concrete must be continuously cured with water for at least 7 days.

Timber formwork must prevent liquid leakage, and stripping times are strictly mandated: 2 days for vertical faces/beams sides, 4 days for slab soffits, and 7 days for beam soffits.

4. Masonry, Pipelines, and Measurement

Brickwork requires wetting the bricks before laying and maintaining them wet for three days post-construction.

Random rubble masonry requires tough, sound quarry stones (stretching 150–250 mm high); round river boulders are prohibited unless broken down. Mortar joints must be 15 to 20 mm thick and cured for seven days.

Pipeline installation dictates that C.I./D.I. pipes be laid with socket ends facing uphill, featuring Tyton flexible joints verified by feeler gauges. HDPE pipes require butt-welding using electric or kerosene hot plates.

New pipelines must undergo hydrostatic testing and disinfection at the contractor's expense. Finally, all measurements follow strict dimensional or IS code limits, with payments executed by unit rates based on verified volumes (cubic meters) or surface areas (square meters).

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