LAB CODE L4:
TITLE: DETERMINATION of DRY DENSITY / MOISTURE CONCEPT – Proctor Test
10 THEORY
The Proctor test is a test that is used in geotechnical engineering to find out the maximum density that can be practically achieved for a soil or similar substance. The Proctor soil compaction test is performed by measuring the density, or dry unit weight, of the soil being tested at different moisture content points. The aim of the soil test is usually to determine the optimum moisture content for the soil.
Soil testing equipment used for the Proctor test usually consists of a mold of a standard shape and size, and a device, such as a hammer, for compacting the soil into the mold. When soil testing machines are used, they must be able to measure how much force is applied to the soil in the mold. The hammer or other compacting tool is used to compact the soil in the mold. In this scenario, compacting the soil means increasing its density by forcing air out of the soil.
By compacting the soil at different moisture contents, an engineer can determine what is the optimum moisture content and compaction level of the soil for a specific use in a particular engineering or construction project. An example of where the Proctor test may be used in a construction project might be in the selection of which aggregate to use in the foundation of a building.
20 OBJECTIVE
The objective of the test is to determine the relationship between the moisture content and the dry density of soil.
30 PROCEDURE
1. 4 to 5 kg (nominal mass) of air dry soil is taken, the soil is pulverize sufficiently to run through the No.4 sieve, and then initial amount of water is mixed. This water is mixed into the soil carefully.
2. The compaction mould is weighted using calipers to determine its volume. 3. Either the standard or modified compaction method is used as specified by
the instructor, a cylinder of soil in 3 layers is compacted and with 25 blows per layer.
4. Both the top and the base of the compacted cylinder of soil is carefully strike off with the steel straightedge.
N o t e: If the last compacted layer in the mould is not above the collar joint,
do not add soil to make up the deficiency - redo this test point. You can avoid this unpleasant situation by carefully watching and if, after about 10 blows on the last layer, the soil is below the collar joint, add enough
material to fill above the collar joint and then continue with the remainder of the blows. On the other hand, you should try not to have more than 6mm of the soil above the collar joint. If you have much more than this amount of excess and are not careful, you will remove the last layer of compacted soil cake when remove the collar. If you do this, redo the test, since you can never replace the soil cake properly.
5. The mould and cylinder of soil are weight and the mass is recorded. 6. The cylinder of soil is extruded from the mould, then is split, and three
water- content samples are taken - one near the top, one on the middle and the other near the bottom - of as much as the moisture cups will hold (60 to 80 g).
7. Next more water is added on the original sample mass of 3 or 4 kg. Remix carefully and Steps 3 through 6 until, based on wet masses is repeated.
40 RESULT
4.1 Test Method
Mould Type
: Proctor
Rammer (kg)
: 2.5
Drop of Rammer
(mm)
: 300
No. Layers
: 3
NO. Blows of Layer
: 25
Test Sample
: SINGLE
Mould’s Diameter
(cm)
: 11
Mould’s Height (cm) : 11.5
Mould’s Volume
(cm )
3: 1092.881
Total Mass of Sample
Table 1: Test Compaction Result EST NO. 1 2 3 4 5 dded (ml) 350 350 350 350 350 + Soil (g) 5892.5 6058.5 6184.5 6250.5 6152.0 (g) 4402 4402 4402 4402 4402 cted Soil (g) 1490.5 1656.5 1782.5 1848.5 1750.0 olume (cm )3 1092.882 1092.882 1092.882 1092.882 1092.882 nsity, 3) 1.364 1.516 1.631 1.691 1.601 it Weight, γwet ) 13.377 14.867 15.995 16.584 15.701 ity, ρ (Mg/m )d 3 1.329 1.473 1.579 1.631 1.485 it Weight, γd ) 13.034 14.446 15.485 15.995 14.563 er No. 1a 1b 1c 2a 2b 2c 3a 3b 3c 4a 4b 4c 5a 5b il + Container 83. 5 102.0 89.5 95.0 76.5 76.5 93.0 92.0 78.5 60.5 113.5 70.5 116.5 139.5 l + Container 76. 0 91.5 80.0 72.5 74.0 70.5 77.5 87.0 64.5 53.5 90.5 61.5 89.5 106.5 er (g) 23. 0 20.5 28.5 40.0 20.5 27.5 26.5 28.0 18.5 41.5 21.0 23.0 20.0 21.0 re Loss (g) 7.5 10.5 9.5 22.5 2.5 6.0 15.5 5.0 14.0 7.0 23.0 9.0 27.0 32.5 l (g) 53. 0 71.0 51.5 32.5 53.5 43.0 51.0 59.0 46.0 12 69.5 38.5 69.5 85.5 RE CONTENT 2.1 4 3.00 2.71 6.43 0.71 1.71 4.43 1.43 4.00 2.00 6.57 2.57 7.71 9.29 E MC (%) , w 2.62 2.95 3.29 3.71 7.81
Graph of dry unit weight versus moisture content
The maximum dry density is 15.995 kN/m and the optimum moisture content is3 3.71%.
3/ Graph Dry Density, d (Mg/m ) with Different Air Void against Moisturep 3 Content, w (%)
50 CALCULATION
5.1 Calculation for container 1a i. For Compacted Soil:
Compacted Soil= (Mould + Soil) – Mould = 5892.5- 4402
= 1490.5g
ii. For Bulk Density, :ρ
Bulk Density, ρ = Compacted SoilMould's Volume
= 1490.51092.882 = 1.364 g/cm3
iii. For Unit Weight, γ wet:
= 1.364 × 9.807 = 13.377 kN/m3
iv. For Dry Density, ρ d:
Dry Density, ρ d = 100100+w×ρw
= 100100+2.62×1.364 = 1.329 kN/m3
v. For Dry Unit Weight, d:
Dry Unit Weight, d= Dry Density × 9.807
= 1.329× 9.807 = 13.034 kN/m3
vi. For Moisture Loss:
Moisture Loss = (Wet Soil + Container) – (Dry Soil + Container)
= 83.5- 76.0 = 7.5 g
Dry Soil = (Dry Soil + Container) – Container = 76.0- 23.0
= 53.0 g
viii. For Moisture Content:
The Moisture Content = Moiture LossDry Soil×100%
= 7.553.0×100% = 2.14 %
x. For Average Moisture Content:
Average MC = container 1a+Container 1b+Container 1c3
= 2.14+3.00+2.713 = 2.62 %
5.2Calculation (Dry Density at 0%, 5%, 10% air Void);
i) For Dry Density at 0%:
Dry Density,ρ d = 1- Va 1001ρs + w 100ρw = 1-010012.65+2.62 100×1 = 2.477 Mg/m3 *assume the ρs = 2.65 kg/m3
ii) For Dry Density at 5%:
Dry Density,ρ d = 1- Va 1001ρs + w 100ρw = 1-510012.65+2.6210 0×1 = 2.354 Mg/m3 *assume the ρs = 2.65 kg/m3
iii) For Dry Density at 10%: Dry Density,ρ d = 1- Va 1001ρs + w 100ρw = 1-1010012.65+2.621 00×1 = 2.230 Mg/m3 *assume the ρs = 2.65 kg/m3
6.0 DISCUSSION
Compaction is the process of increasing the bulk density of a soil or aggregate by driving out air. For any soil, for a given amount of compactive effort, the density obtained depends on the moisture content. At very high moisture contents, the maximum dry density is achieved when the soil is compacted to nearly saturation, where (almost) all the air is driven out. At low moisture contents, the soil particles interfere with each other; addition of some moisture will allow greater bulk densities, with a peak density where this effect begins to be counteracted by the saturation of the soil.
In the experiment we found difficulties that cause the experiment to be conducted more than the given time. First is the equipment error where the mould we used was not fit and disturbing the compaction. Second, from the manual lab we were guided to compact three layers but while conducting the experiment we found that two layer is more suitable.
From the result, in the fifth sample the mass of compacted mould and mould is lower than the fourth. Then we stopped taking the sixth sample as we know that at the fifth sample that we get achieving the objective. The reason why the mass of the fifth sample is lower than the fourth could be the changing masses of soil to water that fulfil the mould.
7.0 CONCLUSION
From the graph that we plotted, we find that the relationship of moisture content between dry densities is, when the moisture contents at a lower value the dry density also in a lower value to. This because at the low value of water content most soil tends to stiff and difficult to compact. When the moisture content at the optimum (optimum water content), the maximum value of dry density will obtain. However, the dry density will decreases with the higher water content because an increasing proportion of the soil volume being occupied by water.
Reference
Craig, K.F (1997). Soil Mechanic (6 ed.).th London and New York : Spon Press Powrie William (1997). Soil Mechanic Concept and Application. London: E & FN Spon.
Conjecture Corporation (2003 – 2010). What Is the Proctor Test?. Retrieved
Appendix APPARATUS
Figure 1: Compaction mould with base plate and collar.
Figure 2 : Compaction rammer (24.5 N x 0.305 m drop or 44.5 N x 0.46 m drop) 10 to 12 moisture cans.
