Proctor Compaction Test for Maximum Dry Density

1. Proctor Compaction Test for Maximum Dry Density

2. What Is Compaction? • Compaction is the process of increasing the bulk density of a soil or aggregate by driving out air. • For any soil, at a given compactive effort, the density obtained depends on the moisture content. • For any soil, an “optimum water content” exists at which it will achieve it’s maximum density.

3. Soils are compacted for the following reasons: • To increase strength and stability • To decrease permeability • To enhance resistance to erosion • Decrease compressibility under load and minimize settlement

4. Common Equipment Shown: • Sheepsfoot • Padfoot • Vibratory Roller • Grid Roller

5. Dynamic Compaction: Profile of Overlap

6. Definition: Maximum Dry Density • The peak dry unit weight is called the "maximum dry density”. • The Optimum Water Content, wopt, is the water content at the soil’s maximum dry density.

7. Achieving Maximum Compaction In The Field • Proctor Compaction Test determines the optimum water content and maximum dry density of for a soil. • A required range for moisture is often specified by the engineer: • Ie, 3% below and 2% above optimum. • For example, if optimum water content is 16%, the acceptable range would be from 13% to 18%. • Percent compaction is also specified: • Meaning “required percentage of max dry density” % Compaction = ρdry field /ρdry max

8. Dry Density Curve: Proctor Test

9. How Does A Contractor Modify Compaction in the Field? • Adjust Water Content • More Passes • Thinner Lifts • Bigger Rollers

10. How Do We Determine Actual Field Density? • Sand Cone Test • Nuclear Densometer

11. Getting Back To The Proctor Compaction Test • Test developed to help specify levels (%) compaction (1933). • Ralph R. Proctor first defined this standard compaction test in Engineering News Record

12. Proctor Compaction Procedure • Soil is air dried, pulverized & passed thru #4 sieve. • Separated into 4 to 6 samples. • Adjust the water content of each sample by adding water.

13. Proctor Compaction Procedure • Using the proctor mould (1/30th cubic foot) place & compact soil in 3 layers. • Each layer should receive 25 drops of the compaction hammer.

14. Proctor Compaction Procedure • After the last layer, use a straight edge to trim the excess soil leveling to the top of the mould.

15. Proctor Compaction Procedure • Determine the weight of the mould with the compacted moist soil. • Extrude from mould and collect a sample for water content determination. • Repeat for each sample over a range of moisture contents.

16. Proctor Compaction Procedure • After collecting all pertinent weights, calculate dry density and plot vs. water content

17. Typical Proctor Data

18. Graph from Proctor Data

19. Achieving Maximum Compaction • For any job requiring fill/compaction the engineer will specify the compaction requirements: ODOT Roadway Embankment Requirements:

20. Achieving Maximum Compaction • Since the maximum dry density is material specific, • AND • Since material being hauled in may change from truck to truck, • It is necessary to verify the maximum dry density number for the material being placed.

21. One-Point Proctor • Thus, the one-point proctor is used to verify the maximum dry density of soils in the field. • One proctor test is done to determine the wet density vs. moisture content. • Then a “family of curves” is used to determine the maximum dry density.

22. ODOT Family of Curves

23. Percent Compaction • Then, comparing the maximum dry density to the ACTUAL density being achieved (nuclear densometer), we can calculate % compaction. • % Compaction = ρdry field /ρdry max