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Civil - Soil Mechanics - Soil Classification And Compaction

Standard Proctor Compaction Test

   Posted On :  10.07.2016 09:47 pm
Standard Proctor Compaction Test

The standard was originall y developed to simulate field compaction in the lab

Standard Proctor Compaction Test


The standard was originall y developed to simulate field compaction in the lab




Find the optimum moisture content at which the maximum dry unit weig ht is attained ASTM D 698




Standard Proctor; 1/30 ft3 mold 5.5 lb hammer; 12' drop

3 layers of soil; 25 blows / l ayer


Compaction Effort is calc ulated with the following parameters


Mold volume = 1/30 cubic foot Compact in 3 layers




5.5 lb hammer 12" drop




1. Obtain 10 lbs of soil pass ing No. 4 sieve


2.  Record the weight of the Proctor mold without the base and the (c ollar) extension, the volume of which is 1/30 ft3.


3. Assemble the compactio n apparatus.


4. Place the soil in the mold in 3 layers and compact using 25 well dist ributed blows of the Proctor hammer.


5. Detach the collar without disturbing the soil inside the mold


6. Remove the base and determine the weight of the mold and compacte d soil.


7. Remove the compacted soil from the mold and take a sample (20-30 grams) of soil and find the moisture content


Place the remainder of th e molded soil into the pan, break it down, and thoroughly remix it with the other soil, plus 100 additional grams of water.

Zero-air-void unit weight:


At certain water content, w hat is the unit weight to let no air in the voids

It is clear that in the above equation, specific gravity of the solid and thewater density are constant, the zero-air-void density is inversely proportional to water content w. For a given soil and water content the best possible compaction is represented by the zero-air-voids curve. The actual compaction curve will always be below. For dry soils the unit weight increases as water is added to the soil because the water lubricates t he particles making compaction easier. As moree water is added and the water content is larg er than the optimum value, the void spaces be come filled with water so further compac tion is not possible because water is a kind like incompressible fluid. This is illustrated by t he shape of the zero-air-voids curve which decre ases as water content increases.


Compaction Curve


Compaction curve plotted ?d vs. w.The peak of the curve is the Maxim um Compaction (?d max) at Optimum Moisture Content (wopt )




Plot of dry unit weight vs m oisture content


Find ?d (max) and w and Plot Zero-Air-Void unit weight (only S=100% )



Tags : Civil - Soil Mechanics - Soil Classification And Compaction
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