Lab Report #3: Standard Proctor Test for Soils
Abstract
Soil Compaction is the process in which stress is applied to a soil which causes
densification as the voids are filled with solids. This plays a vital part in
construction for soils are mainly used as supports for a lot of infrastructures.
Compaction is greatly affected by soil type, moisture content, and compaction
effort and is usually test using ASTM D698. In this report it is concluded that
the soil sample reaches its highest compact state when the dry unit weight is as
its maximum value of 16kN/m3 and 15% moisture content.
Submitted by: Nur-Ranji Jajurie
Group Mates:
Prince Charlie Intal
Vanessa Gale Marie Natividad
Carl Joshua Rebutiaco
Xerxes Tupag
Date Performed: April 11, 2016
Date Submitted: April 29, 2016
1
I.
Objectives

To determine the optimal water content at which the soil sample can reach its
maximum dry density in accordance to ASTM D698: 12 Standard Test
Methods for Laboratory Compaction Characteristics of Soil Using Standard
Effort

To discuss the relevance of the results of the experiment in Civil Engineering
practices and to compare it with other soils that exhibit different compaction
property
II.
Materials

4-in. Mold Assembly

Manual Rammer

Balance

Drying Oven

Sieve no. 4

Containers and Mixing Apparatus
2
III.
Methodology
3
4
IV.
Data and Results
Table 1 shows the recorded mass and dimensions of the cylindrical mold that was
used for the computation for its volume as shown in Equation 1:
[Equation 1]
,
Measurements on the Mold
Mass
Diameter
Height
3.5145 kg
0.1016 m
0.1164 m
3
Volume 0.000943692 m
Table 1: Recorded masses and dimension of the mold used
The initial mass of the air dried soil sample that was used in the experiment was
5.002 kg in which 5% (or 0.25 kg) moisture was added and was used in the first trial.
For each of the succeeding trials, 2% (or 0.1 kg) moisture was added. Table 2 presents
the data on the masses of the mold after the addition and compaction of the soil as
indicated in Section III. Note that the mass of the empty mold is 3.5145 kg.
Trial
1
2
3
4
5
6
7
Mass of Mold +
Soil, kg
Mass of Soil,
kg
5.0945
5.1315
5.2215
5.274
5.327
5.314
5.293
1.58
1.617
1.707
1.7595
1.8125
1.7995
1.7785
Table 2: Mass of the Soil Sample inside the mold in each trial
The moisture content of the soil sample in each of the trials is determined using Equation 2:
,
In which
is the moisture content of the compacted soil sample in percent,
mass in kg, and
[Equation 2]
is its wet
is its mass after drying in kg. Table 3 presents the data used in order to
determine the moisture content of each trial using Equation 2.
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Trial
1
2
3
4
5
6
7
Mass of
Container,
kg
0.015
0.0115
0.012
0.012
0.0065
0.006
0.006
Mass of
Container
+ Soil
Sample
(wet), kg
0.1205
0.055
0.1495
0.1595
0.1135
0.0615
0.0715
Mass of
Container
+ Soil
Sample
(dry), kg
Mass of
Soil
Sample
(wet), kg
0.1055
0.0435
0.1375
0.1475
0.107
0.0555
0.0655
0.111
0.0505
0.1325
0.1395
0.097
0.0515
0.0582
Mass of
Soil
Sample
(dry), kg
Moisture
Content, %
0.096
0.039
0.1205
0.1275
0.0905
0.0455
0.0522
9.0047
10.3448
12.3636
13.5593
15.4206
18.018
20.3053
Table 3:.Moisture content of the compacted soil in each trial
Next is to present the moist (total) and dry density, and dry unit weight of the
compacted soil in each trial. First to calculate the total density, Equation 3 is used:
[Equation 3]
,
Where
is the moist density of the compacted specimen in kg/m3,
is the mass
of the moist compacted soil in kg, and V is the volume of the mold which is equal to
0.000943692 m3. Using trial 1 as a sample computation:
⁄
Moist density of all the trials is then presented in Table 4.
Trial
1
2
3
4
5
6
7
Mass of
Soil (kg)
1.58
1.617
1.707
1.7595
1.8125
1.7995
1.7785
Moist
Density
(kg/m3)
1674.275
1713.483
1808.853
1864.485
1920.648
1906.872
1884.619
Table 4: Moist Density of the Compacted Soils
The dry density of the compacted soil sample can be computed using Equation 4:
,
In which
is the dry density of the compacted soils in in kg/m3,
density of the compacted soil in kg/m3 shown in Table 4, and
[Equation 4]
is the moist
is the moisture
content of the soil in percent as shown in Table 3. Using trial 1 for sample
computation we then have:
6
⁄
Dry density of all the trials is presented in Table 5:
Trial
Moist
Density
(kg/m3)
Moisture
Content (%)
Dry Density
(kg/m3)
1
2
3
4
5
6
7
1674.275
1713.483
1808.853
1864.485
1920.648
1906.872
1884.619
9.004739
10.34483
12.36364
13.55932
15.42056
18.01802
20.30534
1535.965
1552.844
1609.821
1641.86
1664.043
1615.747
1566.53
Table 5: Dry Density of the Compacted Soils
Finally, the dry unit weight of the compacted soil sample can now be acquired using
Equation 5:
,
Where
is the dry unit weight of the compacted specimen in kN/m3, and
[Equation 5]
is the
dry density in kg/m3, computing the dry unit weight of trial 1:
Table 6 contains all the computed values for the computed dry unit weight of all the
trials.
Trial
Dry Density
(kg/m3)
Dry unit
weight
(kN/m3)
1
2
3
4
5
6
7
1535.965
1552.844
1609.821
1641.86
1664.043
1615.747
1566.53
15.0626
15.22812
15.78687
16.10107
16.3186
15.84498
15.36233
Table 6: Dry Unit Weight of the Compacted Soil
The compaction curve is then generated by plotting the dry unit weight versus the
moisture content graph as shown in Table 7.
7
Trial
Moisture
Content (%)
Dry unit
weight
(kN/m3)
1
2
3
4
5
6
7
9.004739
10.34483
12.36364
13.55932
15.42056
18.01802
20.30534
15.0626
15.22812
15.78687
16.10107
16.3186
15.84498
15.36233
Table 7: Points used in the Compaction Curve
16.4
Dry Unit Weigth (kN/m3)
16.2
16
15.8
15.6
15.4
15.2
15
14.8
0
5
10
15
20
25
Moisture Content (%)
Graph 1: Compaction Curve of the Soil Sample
The optimum water content and the maximum dry unit weight of the soil sample are
acquired through analyzing the curve and getting the coordinate values of the
maximum point, which is:
Optimum Moisture Content: 15%
Maximum Dry Unit Weight: 16.36 kN/m3
V.
Analysis and Discussion
The main purpose of compacting soils is to reduce subsequent settlement under
working loads. Compaction also increases the shear strength of the soil, reduces voids
ratio making it more difficult for water to flow through soil and prevent the buildup of
large water pressures that cause soil to liquefy during earthquakes. Thus it is essential
to identify the maximum unit weight of the soil in order to maximize the usages
mentioned above through identifying the quantities or qualities of the factors that
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affect compaction such as water content, the type of soil being compacted, and the
amount of compactive energy that was used.
To assess the degree of compaction, the dry unit weight is greatly attributed because
we are more interested on the weight of solid soil particles in a given volume than the
amount of solid, air, and water in a volume (in which is the bulk density). In order to
analyze the effect of dry unit weight in the compaction let’s analyze Equation 6.
[Equation 8]
Where
is the dry unit weight,
gravity of the soil solids, and
is the unit weight of water,
is the specific
is the ratio of voids. Rearranging this equation, we
yield:
[Equation 7]
Since
and
are both constant it can then be inferred that the dry unit weight and
void ratio are inversely proportional to each other, such that the higher the dry unit
weight and lesser the voids which means that it is more compacted.
Moisture content acts as the driving force in controlling the dry unit density such that
if water is added to a soil (at low moisture content) it becomes easier for the particles
to move past one another during the application of the compacting forces. As the soil
compacts the voids are reduced and this causes the dry unit weight to increase.
Initially then, as the moisture content increases so does the dry unit weight as what
can be seen in Graph 1. However, the increase cannot occur indefinitely because the
soil state approaches its saturation point which indicates that the voids are filled with
water and prohibits the solids to compact with each other.
Varying compactive effort also affects the compactibility of the soil such that
increasing it causes greater dry unit weights to be achieved. This is because of the
solid particles being forced to interlock with one another. Although that it should be
noted that for moisture contents greater than the optimum the use of heavier
compaction machinery will have only a small effect on increasing dry unit weights.
Thus, it is really important especially in construction sites to be able to control the
moisture content of the soil at its optimal value in order to ensure that the dry unit
weight is at its greatest. By analyzing again the Graph 1, we could infer that it is best
to achieve 15% moisture content in order to attain the highest compaction of soil
possible.
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Lastly, soil types affect compaction of the soil because of its particle sizes and
characteristics. Table 8 presents the typical values of maximum dry unit weight and
optimum moisture content for some common types of soils.
Typical Values
Type of Soil
Well graded sand
SW
Sandy clay
SC
Poorly graded sand SP
Low plasticity clay
CL
Non plastic silt
ML
High plasticity clay CH
Dry Unit Weight
(kN/m3)
Optimum Moisture
Content (%)
22
19
18
18
17
15
7
12
15
15
17
25
Table 8: Typical Values of Dry unit Weight and Moisture Content for Common Soils
Although Table 8 only presents only typical values which must not be used in design
because soils exhibits great variability, we can still compare the computed values of
maximum dry unit weight of 16.36 kN/m3, and optimum moisture content of 15% to
CL and ML type of soils as shown in Table 8. Looking back on the previous
laboratory report, the soil sample was described to be clay with low plasticity which
gives reliability to the results of the experiment and some typical values.
VI.
Conclusions and Recommendations
After performing ASTM D698, it has been concluded that the maximum dry unit
weight of 16.36 kN/m3 can be achieved using 15% moisture content and a standard
effort of 600 kN-m/m3. The values attained can be of great use in construction using
the test sample if maximum compaction is wanted in order to support the maximum
load possible.
There was no way in order to compute the error of the experiment and thus it is
recommended to perform the experiment more than once in order to provide more
precise and accurate data.
VII.
References
1. American Society for Testing and Materials. ASTM D698: 12 Standard Test Methods
for Laboratory Compaction Characteristics of Soil Using Standard Effort (12 400
ft-lbf/ft3 (600 kN-m/m3)). E-book.
2. Das, Braja M. Principles of Geotechnical Engineering. Published on 2002. Ebook.
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3. Intelligentcompaction.com. Fundamentals of Compaction . retrieved
www.intelligentcompaction.com/downloads/IC_RelatedDocs/SoilCmpct_Fundam
entals%20of%20Soil%20Compaction.pdf on April 27, 2016.
4. McCarthy, David F. Essentials of Soil Mechanics and Foundations. E-book.
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