QPD Construction

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STEPS IN SLAB ON GRADE (SOG) PREPARATION 🔥

1. Subgrade Soil Condition
• Identify the type of soil (clay, sand, silt, gravel).
• Remove organic materials, roots, or soft soil.
• Replace weak soil with engineered fill or granular base.
• Expansive clay soils need stabilization (lime or cement treatment).
2. Moisture Content
• Soil must be at optimum moisture content (OMC) for proper compaction.
• Too dry → soil will not bind well.
• Too wet → soil becomes unstable or “pumping.”
• Water should be added or soil aerated before compaction.
3. Layer Thickness (Lift Thickness)
• Soil or gravel should be compacted in layers, not all at once.
• Typical lift thickness:
• 150–200 mm (6–8 inches) for soil
• 200–300 mm (8–12 inches) for granular fill
• Each layer must be compacted before adding the next.
4. Compaction Equipment
Choose equipment based on soil type:
Soil Type Recommended Equipment
Clay / cohesive soil Sheepsfoot roller
Sand / gravel Vibratory plate compactor or roller
Small areas Plate compactor or rammer
5. Compaction Standard
• Most building slabs require 95% compaction based on the Proctor Compaction Test.
• Field verification may use:
• Nuclear density test
• Sand cone test
6. Subbase or Base Course
Typical materials:
• Crushed gravel
• Crushed stone
• Base course
Functions:
• Improves drainage
• Distributes load
• Prevents capillary water rise.
Typical thickness: 100–150 mm (4–6 inches).
7. Drainage Considerations
• Ensure the site has proper slope and drainage.
• Standing water weakens compacted soil.
• Install perimeter drains or gravel layers if groundwater is high.
8. Proof Rolling
After compaction:
• A heavy roller or truck passes over the surface.
• If the soil deflects or pumps, it indicates weak spots that must be reworked.
9. V***r Barrier Installation
Before pouring concrete:
• Install polyethylene v***r barrier to prevent moisture from rising into the slab.
• Usually 6–10 mil plastic sheet.
10. Final Surface Leveling
• Ensure the base is level and well graded.
• No loose spots before placing reinforcement and concrete. TATAK QUALITY