To determine the moisture-density relationship by Standard Proctor Test.

OBJECT :To determine the moisture-density relationship by Standard Proctor Test.

OBJECTIVE AND SCOPE

Determination of the relationship between the moisture content and density of soils compacted in a mold of a given size with a 5 lb rammer dropped from a height of 12 inches. The results obtained from this test will be helpful in increasing the bearing capacity of foundations, decreasing the undesirable settlement of structures, controlling undesirable volume changes, reduction of hydraulic conductivity, increasing the stability of slopes and so on.

STANDARDS

AASHTO T99-86

ASTM D698-91

BIS1377:part 4; clause 3

EQUIPMENTS

1. Proctor Mold
   
2. Collar
   
3. Containers
   
4. Mixing Tools & Tray
   
5. Rammer of 5 lb (2.5 kg) weight & having fall of 12 inches.
   
6. Sensitive weight balance.
   

THEORY

In Geotechnical Engineering, soil compaction is the process in which a stress is applied to a soil which causes densification as air is displaced from the pores between the soil grains. It is an instantaneous process and always takes place in partially saturated soil (three phase system). The Proctor compaction test is a laboratory method of experimentally determining the optimum moisture content at which a given soil type will become most dense and achieve its maximum dry density.

PROCEDURE

1. Take a representative oven-dried sample thoroughly mix the sample with sufficient water to dampen it with assumed water content. Start the assumption initially with 3% moisture content.
   
2. Weigh the proctor mold with base plate and without collar. Fix the collar and base plate. Place the soil in the Proctor mold and compact it in 3 layers giving 25 blows per layer with the 2.5 kg rammer falling through. The blows shall be distributed uniformly over the surface of each layer.
   
3. Remove the collar, trim the compacted soil even with the top of mold using a straight edge and weigh.
   
4. Divide the weight of the compacted specimen by volume of the mold and record the result as the bulk density·
   
5. Remove the sample from Mold and slice vertically through and obtain a small sample for water content.
   
6. Thoroughly break up the remainder of the material and shift it into a new container and find the water content of the Soil sample. Add water in sufficient amount to increase the moisture content of the soil sample by one or two percentage points and repeat the above procedure for each increment of water added. Continue this series of determination until there is either a decrease or no change in the wet weight of the compacted soil.
   

OBSERVATION

Diameter of mold = ______________(cm)

Height of mold = ______________(cm)

Volume of mold = ______________(cm³)

Water Content (w):

Dry Density (ϒ_dry):

Result

Optimum Moisture Content (OMC) = _____________ %

Maximum Dry Density = ___________(gm)

Fig. 1: SOIL COMPACTION CURVE Fig. 2: STANDARD PROCTAR TEST APPRATUS

Review Questions

1. What are the effects of compaction on the physical structure of soil sample?
   
2. What are the effects of compaction on the composition of soil?
   

How we can determine the OMC of a Sandy Soil