Proctor Compaction Test (MDD & OMC) — Lab Manual

Objective & standard

Maximum dry density and optimum moisture content — the target for compaction on site.

Standard: ASTM D698 (standard) / D1557 (modified)

Apparatus

• Mould 944 cm³ with collar & base
• Rammer 2.5 kg (standard) or 4.5 kg (modified)
• Straight edge, balance, oven
• Sieve 4.75 mm

Procedure

1. Take about 3 kg of air-dry soil passing 4.75 mm and add water to about 4 % below OMC.
2. Compact in 3 layers × 25 blows (standard) or 5 layers × 25 blows (modified).
3. Trim, weigh the mould + soil and take a moisture sample from the middle.
4. Repeat with 2 % more water each time until the weight drops (5–6 points).
5. Plot dry density vs water content; the peak gives MDD and OMC.

Calculations

• γ = (W mould+soil − W mould) ÷ V
• γd = γ ÷ (1 + w)
• Zero air voids: γd = Gs·γw ÷ (1 + w·Gs)

Typical values: Sandy soils MDD 1.9–2.1 g/cc at OMC 8–12 %; clays 1.6–1.8 g/cc at 15–22 %.

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Data sheet (print this page)

Project: ____________________   Sample: __________   Date: __________   Tested by: __________

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