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§ 17

Degree of compression compared to Proctor

Is the bearing layer compressed enough to the requirement?

Answer: Compaction control measures the soil or gravel's wet density in the field (e.g. with isotope probe or sand replacement method) and water content. Wet density divided by (1 + water content) gives dry density, which is compared against the laboratory's maximum dry density from the Proctor test. The ratio is the degree of compression. The requirement is in the project description or standard working description (AAB), typically as a percentage of Standard or Modified Proctor.

Formula

Tørdensitet = våd densitet ÷ (1 + vandindhold ÷ 100)

Komprimeringsgrad = tørdensitet ÷ Proctor-maks × 100 %

Margin = komprimeringsgrad − krav

Use the Proctor variant the requirement names: Standard Proctor (SP) and Modified Proctor (MP) give different max densities for the same material

Symbols and units in the formula
SymbolMeaningUnit
vaadMeasured wet densityt/m³
vandWater content%
maksProctor: largest dry density (from the laboratory)t/m³
kravRequirement in description%
=Degree of compression%
=Dry densityt/m³
=Margin til kravet (negativ = ikke godkendt)%-point
=Dry density requirement requirest/m³

Validity and source

Source
DS/EN 13286-2 (Proctor) · requirements from project description, e.g. 98% Standard Proctor

Does not apply when

  • The requirement depends on the layer and material and is in the project description. Working descriptions use e.g. 98% SP for base gravel and 95% MP for stab gravel, often with a mean requirement and a lower requirement for individual values. If the water content is far from the Proctor test's optimal water content, it's hard to meet the requirement no matter how much you vibrate.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Measured wet density2.15 t/m³
  • Water content6 %
  • Proctor: largest dry density (from the laboratory)2.08 t/m³
  • Requirement in description98 %

Giver

  • Degree of compression97.5 %
  • Dry density2.028 t/m³
  • Margin til kravet (negativ = ikke godkendt)-0.5 %-point
  • Dry density requirement requires2.038 t/m³

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Sådan bruger du den

Komprimeringskontrollen viser, om et lag er komprimeret nok. Beregneren regner komprimeringsgraden og marginen til kravet.

Step by step

  1. Skriv den målte våde densitet.
  2. Skriv vandindholdet.
  3. Skriv Proctor-maks og kravet.
  4. Læs marginen.

Typical errors

  • At bruge våd densitet direkte.
  • At bruge den forkerte Proctor-variant.
  • At komprimere for tykke lag.

Examples from everyday life

Bundsikring under en vej

Isotopsonden måler 2,15 t/m³ og 6 % vand. Proctor-maks er 2,08, og kravet er 98 %.

Measured wet density
2.15 t/m³
Water content
6 %
Proctor: largest dry density (from the laboratory)
2.08 t/m³
Requirement in description
98 %

It means: Tørdensiteten er 2.028 t/m³, komprimeringsgraden er 97.5 %, og marginen er -0.5 %-point. Laget er ikke godkendt.

Stabilgrus

Målingen giver 2,21 t/m³ og 5,2 % vand. Proctor-maks er 2,12, og kravet er 95 %.

Measured wet density
2.21 t/m³
Water content
5.2 %
Proctor: largest dry density (from the laboratory)
2.12 t/m³
Requirement in description
95 %

It means: Komprimeringsgraden er 99.1 %, og marginen er 4.1 %-point. Laget er godkendt.

Rule of thumb

1 % vand mere giver ca. 1 % lavere tørdensitet.

How to check the answer

2,15 ÷ 1,06 ÷ 2,08 × 100 ≈ 97,5 %.