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ASTM D558: Moisture-Density (Unit Weight) Relations of Soil-Cement Mixtures
The Proctor-style compaction curve for soil-cement and cement-treated base, giving the optimum moisture and maximum density that field compaction of stabilized layers is judged against.
| Designation | ASTM D558 |
| Setting | Laboratory |
| Service line | Construction Materials Testing |
Testing is performed to the current edition of ASTM D558 referenced by your project specification. This page is a plain-language overview, not a substitute for the published standard.
What the ASTM D558 test measures
ASTM D558 establishes the moisture-density relationship of a soil-cement mixture: the compaction curve that gives the optimum moisture content and maximum dry unit weight of a soil blended with a specified percentage of portland cement. It is the Proctor test for cement-treated base, cement-stabilized subgrade, and soil-cement slope protection and liners.
Field density of a stabilized layer is judged as a percentage of this maximum, so the curve must be run on the actual soil and cement content the contractor will place.
How the ASTM D558 test works, step by step
The soil is dried, processed, and mixed with the design cement content by dry mass. Water is added, the mixture is compacted in a 4-inch mold in three layers with a 5.5-pound rammer dropped 12 inches, and the wet unit weight and moisture content are measured. The process repeats at increasing moisture contents until the dry unit weight peaks and falls. Because cement begins hydrating immediately, the mixing and compaction window is limited and the timing is recorded.
What the numbers mean
Typical cement-treated base peaks around 115 to 135 pcf at 8 to 12 percent moisture, but the curve moves with the soil and the cement content. The result sets the field compaction target used with ASTM D6938 nuclear density tests during placement, and it is paired with unconfined compressive strength testing of cured specimens per ASTM D1633 to verify the design cement content.
What can throw the result off
Delays between adding water and compacting, which let hydration stiffen the mix; cement content measured by volume rather than mass; and reusing compacted material for later points all distort the curve. The method uses fresh material for every point.
Common questions about ASTM D558
Is this the same as a standard Proctor?
Same equipment and effort as ASTM D698, but run on the cement-treated mixture, with time limits that D698 does not have.
How is the design cement content chosen?
By a mix design program that runs D558 and D1633 at several cement percentages and picks the lowest content meeting the strength or durability requirement.
How we help with ASTM D558 testing
We run soil-cement mix designs and verification curves in our laboratory and support placement with field density testing on the treated layer, so the target and the field result come from the same source.
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