MAKERERE UNIVERSITY
FACULTY OF TECHNOLOGY
DEPT. OF CIVIL ENGINEERING
NAME: KWESIGA IVAN
REG. NO: 07/U/9623/PS
STUDENT NO: 207014939
SIGNATURE:
COURSE UNIT: HIGHWAY ENGINEERING – LAB
PRACTICAL REPORTS
LECTURER: MR. MUKASA
DATE: 30-11-2009
SOIL TESTS
NATURAL MOISTURE CONTENT OF SOIL
Objective
To determine the amount of water present in fresh soil expressed as a percentage of the mass
of the dry soil.
Introduction
Moisture content of soil is the amount of water within the pore spaces in soil grains. Natural
moisture content is the amount of water in freshly obtained soil in its natural state. It is
determined by oven-drying the soil at a temperature not exceeding . Moisture content
greatly influences the behavior of soil.
Standard reference
BS 1377:1990
Apparatus
Soil sample
Weighing balance
Metal cans
Drying oven at temperature of - .
Procedure
Collect a fresh soil sample and divide into four parts by using a rifle box. This will provide
the soil from which the samples for the oven will be taken.
Clean and dry the moisture cans and weigh each, recording their respective weights.
Fill each moisture can with soil from each soil heap and weigh the cans again. Record their
weights.
Place the soils samples into the oven for a minimum of 12 hours. Remove the samples and
weigh them again. Record the results in a suitable table.
Treatment of results
sample A B C D E
Mass of soil + can (m1) 47 45 58 67 53.5
Mass of dry soil + can (m2) 42.5 41 53.5 62 48.5
Mass of can (m3) 1.5 1 1 1 1
Mass of water 4.5 4 4.5 5 5
Moisture content (%) 11 10 8.6 8.2 10.5
Calculation
Compute the moisture content W of the specimen as a percentage of the dry soil mass from
the equation:
Moisture content of the soil is 9.7%.
PARTICLE SIZE DISTRIBUTION
Particle size distribution is a necessary classification of soils because it shows the relative
distribution of particle sizes in a particular soil type. It makes it possible to determine whether
soils are predominantly gravel, sand, clay or silt which will also affect the engineering
properties of the soil.
Introduction
Wet sieving is performed in order to remove the clay and silt particles in the soils. The soil is
first washed on a 75µm sieve and the soil retained is oven-dried to obtain the soil that is
passed through the series of sieves to determine the distribution.
The results obtained are plotted on a graph with a logarithmic scale and the soil classified by
identifying the distribution as being gravel or sand.
Apparatus
Test sieves
Tray
Evaporating dish
Balance
Sieve brushes
Drying oven
Procedure
First prepare the test sample by air drying soil for over 12 hours. Take a representative
sample from the heap of about 2.5kg by rifling.
Sieve the sample through the 20mm sieve. This may be skipped since the rifle box apertures
are 20mm.
Take the sample and wash it through the 75µm sieve. This washes out the clay and silt
particles from the sample.
Transfer the retained material from the sieve to an evaporating dish which is placed in an
oven at for 24 hours to ensure complete drying of the sample. Weigh the dry sample.
Stack the sieves in decreasing in order of decreasing aperture size and then pass the soil
through the sieves either mechanically or manually. Weigh the mass of soil retained on each
sieve and then plot the particle sizes against percentage passing on a graph with a logarithmic
scale.
Treatment of results
Obtain the total mass on all the sieves. Find the difference between the original mass and the
retained sample mass.
Grade the soil from the results plotted on the graph.
Classification –gravelly sand
sieve weight retained % retained % passing
14.0mm 86 4.8 95.2
10.0mm 161.5 9.1 86.1
2.36mm 925 51.9 34.2
1.18mm 148 8.3 25.9
600µm 110 6.2 19.7
300µm 156.5 8.8 10.9
150µm 104.5 5.9 5
75µm 65.5 3.7 1.3
Pan 25 1.4 0
Total 1782 100
Discussion of results
18g of the soil was lost during the analysis. This is due to the particles that get stuck in the
sieve spaces and the others that fall out of the sieves during the sieving process and transfer
to the weighing pans.
The soil is gravelly sand because more than 70% of the particles lie in the region of gravel
and the remaining percentage is sand.
Conclusion
From the results of the particle size distribution it can be concluded that the soil is suitable for
use as highway sub-base.
LIQUID LIMIT- CONE PENETROMETER METHOD
Objective
The liquid limit is the moisture content at which soil passes from the liquid to plastic state.
The liquid limit provides a method of classifying fine grained soils since the smallest 10%
fines determine the properties of the soil such as the shear strength.
Introduction
The cone penetrometer test involves determining the liquid limit of a soil sample in its natural
state. The soil used is passed through a 425µm sieve. The soil is penetrated using a standard
cone and the penetration measured.
Apparatus
425µm sieve
Flat glass plate
Spatulas
Cone penetrometer
An airtight container
Metal cup
Wash bottle containing clean water
Procedure-sample preparation
Pass the soil sample through 425µm sieve until about 400g of sample are collected. This is
sufficient for the plastic limit, liquid limit and linear shrinkage tests.
Place the sample on the glass plate and mix it with water from the wash bottle. Using the
spatula, mix the sample into a paste.
Store the sample in an air tight container for 16-24hours to allow the water to completely
permeate the soil.
Liquid limit
Take the sample from the airtight container and place it on a glass plate where it is mixed
using palette knives for a few minutes. Add water to a portion of the sample and mix it again
until uniformity is attained.
Put some of the soil into a container using the palette knife ensuring no air is trapped by
tapping it on a hard surface. Smoothen the surface with a straight edge.
Place the container directly below the cone and lower it until it just touches the surface of
the soil. Slight movement of the container should mark the soil surface. Lower the dial
gauge to touch the cone and adjust the reading to zero.
Release the cone for 5±1 seconds record the reading on the dial gauge to the nearest 0.1mm.
Lift out the cone out clean it.
Repeat the procedure for different amounts of water added to the soil. The difference
between successive readings should not exceed 1mm for the same amount of water added.
Carry out the procedure for about four different amounts of water (15-25mm penetration
range) added to the soil and record the values obtained in a suitable table. Each time the
sample is penetrated clean the container and wash it before performing another penetration.
Take samples from each can for moisture content determination.
Treatment of results
Obtain the moisture content of the soil samples.
Plot a graph of penetration against moisture content and draw a line of best fit through the
points. The liquid limit is the moisture content that produces a penetration of 20mm to the
nearest whole number.
Table of results
Tin no. BR C A 2A 2B 2C 3A 3B 3C 4A 4B 4C
Weight of tin + wet
soil 40 47.5 46.5 24.5 23.5 22 22 24 24.5 23 25 22.5
weight of tin + dry soil 32.5 39.5 39 17 16.5 15.5 15 16 16.5 15.5 16.5 15.5
Weight of tin 15 21.5 20 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0 0
Moisture content 42.9 44.4 39.5 45.5 43.8 43.3 48.3 51.6 50.0 50.0 51.5 45.2
Average moisture
content 42.3 44.2 50 48.9
Average penetration 17.05 20.03 21.2 23.9
Moisture content at 20mm penetration = 45.5%
Liquid limit = 46%
COMPACTION TEST
Objective
The objective of the test is to get the relationship between the moisture content and the dry
density of compacted soil for a given compaction effort. These are used in specification in
works involving compacting of soil.
Main principles
The dry density of any given soil depends on the moisture content and the compactive effort
used. Compaction is the process of increasing the dry density of a soil by parking the soils
more closely. This can be done by vibrating, static load compaction, tampering or kneading.
Dry density of a soil increases with the increase in the mechanical effort. However for
moisture content, it increases up to a maximum value and then drops. The moisture content at
which the maximum dry density is achieved is the optimum moisture content.
Thus with the relationship between the dry density and the moisture content for a given
compaction effort, the optimum moisture content can be determined which is used in the
field.
Reference
BS 1377: part 4
Craig’s Soil Mechanics – R.F. Craig
Method
BS heavy – using a 4.5 kg rammer
Equipment used
Cylindrical compaction mould
Metal rammer 4.5 kg heavy
Balance
Moisture cans
Large metal tray
Measuring cylinder
Oven – for determining moisture content
Spatulas
Sample preparation
Sample was passed through a 20mm sieve and the particles larger than 20mm were removed.
The sample was then dived into five representative smaller samples. Each sample was mixed
with a different amount of water to give a range of moisture contents. The initial amount
water for the first sample was assumed to be 8%, amount of water to be added was computed
from the following equation;
Water was measured by a measuring cylinder. The each sample is mixed with water
thoroughly until uniform colour is reached. Each sample is further divided into five parts.
Each sample is compacted in five layers with each part of every sample receiving 27 blows
Procedure
The weight of the mould and the base plate were weighed and weight recorded. W1.The moist
soil was placed in the mould and compacted in five layers, each layer receiving 27 blows of a
4.5 kg rammer.
The rammer is dropped from a distance of about 450mm.A collar was fixed when the mould
filled up before the final layer compaction.
After compaction the collar was removed and the soil trimmed till the level of the mould
opening.
Weight of compacted soil and mould was measured and recorded. W2
Representative samples from top and bottom of the compacted soil were taken to determine
the moisture contents.
This procedure is carried out for all the five samples with different moisture contents.
Analysis
Moisture content of each soil is calculated using the average of the top and bottom moisture
contents.
Calculate the bulk density;
Dry density was computed using the wet (bulk) density and moisture content using the
formula;
Dry densities calculated where plotted as ordinates and the moisture contents as abscissas.
The line of best fit is drawn and the maximum point was identified and the corresponding dry
density and moisture content read off and recorded. This is the optimum moisture content.
On the same graph the 0%, 5% and 10% air void lines were plotted using the following
equation.
Results;
Weight of mould
+soil(g)
6400 6550 6640 6640 6540
Weight of mould(g) 5440 5440 5440 5440 5440
weight of soil(g) 960 1110 1200 1170 1100
volume of
mould(cm3)
1000 1000 1000 1000 1000
bulk density(kgm-3) 0.96 1.11 1.2 1.17 1.1
Dry density(kgm-3) 0.869 0.995 1.060 1.016 0.944
Moisture content can 1A 1B 2A 2B 3A 3B 4A 4B 5A 5B
Mass of can +
soil(g)
28.5 30.5 21.5 20.5 29.5 19.5 33.5 29.5 29 50
Mass of can + dry
soil(g)
27 26.5 19.8 18 25.8 17.5 30 25 23 47
Mass of can(g) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Mass water(g) 1.5 4 1.7 2.5 3.7 2 3.5 4.5 6 3
Mass of dry soil(g) 26.5 26 19.3 17.5 25.3 17 29.5 24.5 22.5 46.5
Moisture content (w
%)
5.66 15.38 8.81 14.29 14.62 11.76 11.86 18.37 26.67 6.45
Average w% 10.5 11.5 13.2 15.1 16.6
Optimum moisture content = 13.2%
Maximum dry density = 1.060gcm-3
= 1060 kgm-3
PLASTIC LIMIT
Introduction
Plastic limit is defined as the moisture content at which the soil becomes plastic on addition
of water.
Plastic limit and liquid limits are used to determine the plasticity index which is the
difference between the plastic limit and the liquid limit. It is proved that the finer the soil the
higher the plasticity index.
Sample preparation
The sample used for the determination of the plasticity index is the soil that passes through
the 425µm sieve. About 40g of sample are required for the experiment and the sample is
prepared in a similar way to the liquid limit.
Equipment
2 flat glass plates
2 palette knives or spatulas
Clean water
Moisture content apparatus
3mm diameter rod
Standard reference
BS 1377: part 2: 1990
Procedure
From the sample of 40g divide out 2 portions of 20g each and mould them into balls on the
glass plates until they are dry enough to crack on the surface.
Take a sample of soil from each ball for separate plastic limit determination. Mould the
samples into threads of about 6mm and then knead them between the thumb and the first
finger into threads of 3mm diameter. Compare the thread to the rod to ensure it is
approximately 3mm.
Roll the thread until it starts to crack and shear longitudinally. Remould the sample and then
repeat the procedure until the thread shears.
Transfer the samples to separate moisture cans to determine the moisture content of the two
samples.
The moisture content of the two samples should not differ by more than 0.5%, otherwise the
experiment is repeated.
The plastic limit of the sample is the average of the two moisture contents.
Treatment of results
Tin no. 3T A2
Weight of tin (g) 6.5 6
Tin + sample (g) 10.5 10
Tin + dry sample (g) 10 9.49
Moisture content (%) 12.5 12.8
Calculations
Conclusion
Plastic limit of the soil is 12.7% and the plasticity index is 33.3%.
CALIFORNIA BEARING RATIO (CBR)
The load bearing capacity of the sub grade is the main factor in determining the required
thickness of a flexible pavement for roads and airfields. The strength of the sub grade, sub
base, and base course materials are expressed in terms of their California Bearing Ratio
(CBR) value.
The California Bearing Ratio is the ratio of test load corresponding to chosen penetration to
the standard load for the same penetration.
One point CBR
The one point CBR method was used to determine the wet and dry CBR values of the soil
samples obtained.
Objective
The CBR value is a requirement in the design of pavements of natural gravel. This test is
performed to determine the bearing ratio of a given soil sample under a given applied
loading. The bearing ratio is obtained by the relationship between force on the plunger and
penetration of the plunger, when the cylindrical plunger penetrates the soil at a given rate.
The CBR value is used in the design of flexible pavements, granular base courses, rigid
pavements, air field runways. This value is also used to determine suitable thicknesses for the
different layers of pavements, which will withstand the anticipated traffic conditions in terms
of axial loadings and traffic frequency and to design the life span of the pavement.
Equipment
BS 20mm sieve
CBR mold
CBR penetrating machine
Weighing balance
Filter paper and surcharge discs
Sample preparation
A representative sample was obtained using the riffling method. The soil was sieved on a
20mm sieve and the material passing collected onto a large tray.6 kg of the soil was collected
onto a small tray.
The soil was mixed with a volume of water that would cause it to reach its optimum moisture
content (OMC %) obtained from the BS Heavy compaction test of this soil.
The soil was sealed in a polythene bag and stored for 24 hours before compacting into the
CBR mould fitted to a perforated base plate.
Compaction in the CBR mould was done in five equal layers with each layer receiving 62
blows being uniformly distributed over the surface using the 4.5kg rammer.
The collar on the mould was removed and the soil flush trimmed to the top of the mould. The
weight of the soil in the mould together with its base plate was measured and recorded.
Moisture content samples were taken and placed in the drying oven at c to determine the
moisture content (w %).
The procedure was repeated for the second mould.
Procedure for soaking
A filter paper was placed on the top surface of the soil in one of the moulds. Annular
surcharge discs were placed on top of the filter paper in the mould to provide a water tight
joint.
The mould assembly was placed in the soaking tank with the perforated base plate at the
bottom for four days after which it was removed and left to allow for draining for 15 minutes.
Testing of the specimen
After four days, the mould containing the specimen was removed from the soaking tank and
the annular surcharge discs removed.
The mould was placed in position, with the perforated base plate resting on the testing
machine.
The plunger on the testing machine was brought into contact with the surface of the soil and
the readings on the force and penetration dial gauges set to zero.
A penetrating force was applied on the plunger and the load at penetration of 0, 0.5, 1.0, 1.5,
2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0 and 7.5 of the needle recorded.
The mould was inverted and the perforated base plate at the bottom removed.
The testing procedure was repeated for the bottom surface of the soil.
The same procedure was carried out on the dry sample immediately after compacting and
therefore no filter paper was required.
Results
A force penetration curve is plotted from the following steps;
Calculate the force applied to the plunger from each reading of the loading ring observed
during the penetration test. Each value is plotted as ordinate against the corresponding
penetration and a smooth curve is drawn through the points.
If the curve is concave, a tangent is drawn at the point of the steepest slope to produce an
intercept at the abscissa. This is the corrected zero point.
Calculation of CBRPlunger value at 2.5mm and 5mm penetration are recorded from the force penetration curve.
CBR is calculated from the following equations;
The plunger force P, is in KN.
The higher value of the two is taken as the CBR value
Density calculations1. The internal volume of the mould is measured, Vm ( cm3)
2. Bulk density is calculated from the equation;
M3 – mass of the soil, mould and the base plate (g)
M2 – mass of mould and base plate (g)
3. Dry density is got from;
W is the moisture content.
4. If dry density for soaked is required, it is calculated from equation;
A is the area of the cross section of the mould (mm2)
X is the increase in sample height after swelling (mm)
ResultsDensity Determination
Mould No 1 2Mass of mould + soil g 10020 9870
Mass of mould g 4740 4740
Mass of soil g 5280 5130
Volume of the mould cm3 2305 2305
Moist density g/cm3 2.291 2.226
Dry density g/cm3 2.017 1.888
Wet CBR Dry CBR
Container 1TW 2TW Container T1 T2Mass of container(g)
0.5 0.5 Mass of container(g)
0.5 0.5
Mass of sample + container(g)
40.5 44.5 Mass of sample + container(g)
55.5 69.5
Mass of dry sample + container(g)
36.0 39.0 Mass of dry sample + container(g)
50.0 62.5
Mass of sample(g) 40.0 44.0 Mass of sample(g)
55.0 69.0
Mass of dry sample(g)
35.5 38.5 Mass of dry sample(g)
49.5 62.0
Mass of moisture(g)
4.5 5.5 Mass of moisture(g)
5.5 7.0
Moisture content (w %)
12.7% 14.3% Moisture content (w %)
11.0% 11.2%
Moisture content = (12.7% + 14.3%)/2 Moisture content = (11.0% + 11.2%)/2 = 14% = 11%
DRY CBR Wet CBR
Dial gauge reading Dial gauge reading
Penetration (mm) Top BottomPenetration (mm) Top Bottom
0.5 0.24 0.48 0.5 0.37 1.061 0.37 0.55 1 0.5 1.66
1.5 0.48 0.63 1.5 0.61 2.16 2 0.58 0.69 2 0.71 2.53
2.5 0.66 0.74 2.5 0.87 2.773 0.77 0.82 3 0.95 2.93
3.5 0.84 0.87 3.5 1.08 3.064 0.95 0.92 4 1.19 3.19
4.5 1.03 0.98 4.5 1.29 3.335 1.11 1.03 5 1.43 3.43
5.5 1.21 1.06 5.5 1.48 3.486 1.32 6 1.61 3.54
6.5 1.43 6.5 1.72 3.597 1.56 7 1.79 3.7
7.5 1.69 7.5 1.93 3.75
DRY CBR
. Force CBR
Average CBR. Top Bottom Top Bottom
2.5mm Penetration 0.66 0.77 5.0 6.0 5.5
5.0mm Penetration 1.11 1.03 6 5 5.5
WET CBR
. Force CBR
Average CBR. Top Bottom Top Bottom
2.5mm Penetration 0.87 2.77 7 21 14
5.0mm Penetration 1.43 3.43 7 17 12
Dry CBR is 5.5%.
Wet CBR is 14%.
AGGREGATE TESTS
AGGREGATE IMPACT VALUE (AIV)
Introduction
Aggregates used in road construction are required to be strong enough to resist crushing
under traffic loads.
Aggregate impact value (AIV) is one of the tests used to measure the strength of aggregates.
Aggregate Impact value is the relative measure of the resistance of aggregates to sudden
shock or impact.
Sample preparation
The test can be performed in dry or soaked condition. For the test performed, the dry
condition was used. The sample used in the test passed through the 14mm sieve and was
retained on the 10mm sieve.
Equipment
Test sieves (10mm and 14mm)
Metal cylinder (75mm diameter and 50mm depth) and known weight
Metal tray of known mass
Riffle box
Tamping rod
Brush with stiff bristles
Aggregate impact testing machine
Procedure
Obtain a sample for the test by sieving with a 14mm and 10mm sieve. The sample larger than
14mm and smaller than 10mm is discarded. What remains is used for the test. The sample
collected should be enough to fill the metal cylinder to the brim.
Fill the cylinder completely with the aggregate and then tamp the aggregate 25 times using
the tamping rod. Remove any excess aggregate by rolling the rod over the top of the cylinder
and add aggregate in any spaces in the cylinder.
Place the aggregate impact machine on a level surface and fix the cup in position in the
machine. Place the cylinder in the cup and tamp the sample 25 times again with the tamping
rod.
Raise the hammer so that its height is 380±5mm above the top of the aggregates. Release the
hammer to drop freely 15 times at intervals of not more than 1 second between each blow.
Remove the cylinder and weigh it with the sample. Empty the sample onto a tray ensuring the
cup is cleaned using a brush. Sieve the sample with a 2.36mm sieve until no significant
amount passes and record the mass retain and mass that passes through the sieve. If the total
mass exceeds the initial mass by more than 1g, repeat the test.
Results and calculations
Mass of cup = 2585g
Mass of sample and cup = 3280g
Mass of sample
Mass retained on sieve = 631.0g
Mass passing through sieve
AGGREGATE CRUSHING VALUE (ACV) AND TEN PERCENT FINES (TFV)
Introduction
Aggregates used for road paving should be strong enough to withstand the traffic wheel loads
without failing due to crushing. Aggregate crushing value test is used to measure the strength
of coarse aggregates.
Aggregate crushing value test (ACV) is used to measure the resistance of an aggregate to
gradually applied loads. It is determined by measuring the amount of material passing
through a specified sieve after crushing under a 400KN load.
It is preferred to carry out the 10% fines test simultaneously with the ACV test where the
samples are crushed at 50KN, 100KN, 150KN and 400KN respectively.
10% fines test is used to determine the resistance of the aggregates to crushing under
gradually applied loads.
Sample preparation
The sample used for the test is the material retained when the aggregate retained on the
14mm sieve and passing through the 10mm sieve is discarded.
References
BS 812: Part 110: 1990
Equipment
Tamping rod
Open ended steel cylinder
Compression testing machine
Rifle box
Metal tray
Brush with stiff bristles
Balance
Test sieves
Procedure
Obtain sufficient material after sieving using the 14mm and 10mm sieves. With the steel
cylinder placed on its base, fill it to a third of its volume with aggregates. Tamp the
aggregates 25 times with the tamping rod. Do this at two thirds and when the cylinder is
completely filled.
Level the surface using the tamping rod and fill any voids in the cylinder. Place the plunger
on top of the aggregate surface so that it is horizontal.
Place the cylinder and plunger in the crushing test machine. Apply the crushing force for
about 10minutes. Release the crushing force and remove the steel cylinder.
Empty the material from the cylinder onto a tray. Remove the remaining material using the
brush and then weigh the metal tray and crushed sample ( ). Record the weight obtained to
the nearest 1g.
Sieve the crushed material through a 2.36mm sieve and weigh the sample retained and
sample that passes through the sieve. Record the two masses. If the sum of material passing
through the sieve and the sample retained differs from the initial mass recorded by
more than 10g, discard the sample.
Treatment of results
Force (KN) 50 100 150 400
Mass of crushed specimen m1(g) 3580 3481 3575 3481
Mass of retained sample m3(g) 3440 3235 3170 2700
Mass passing m2(g) 140 243 402 735
Calculation of ACV
BITUMEN TESTS
PENETRATION TEST
Introduction
The penetration test is used to measure the consistency of a bituminous material expressed as
distance in tenths of a millimeter when a standard needle penetrates the material under known
loading conditions.
A needle of specified dimensions and loaded with a standard load is allowed to penetrate the
bitumen at a specified temperature. The distance the needle penetrates is called the
penetration value.
Standard reference
ASTM D 5-86: Penetration of bituminous materials
Equipment
Standard penetrometer
Penetration needle (2.5g)
Standard 50g load
Needle holder
Stop watch
Penetration tins
Sample preparation
Heated bitumen is poured into 3 penetration tins to a depth of 10mm higher than the expected
penetration depth.
Allow the samples to stand and cool at room temperature for 24 hours. Cover the samples
with foil or glass plates to protect them from dust. The test is performed at room temperature
(25 ) and the penetration is performed for 5 seconds.
Procedure
Set up the penetrometer ensuring it is level. Check that the needle holder can move freely
unobstructed.
Clean the needle with a solvent like toluene and then set the penetration tin containing the
sample below the needle. The needle is lowered until it just touches the surface of the
bitumen.
Adjust the dial gauge to the zero mark and then release the needle to penetrate the sample
material for 5 seconds. Record the reading on the dial gauge.
Repeat the test for the two other samples recording the penetration values in millimeters. The
penetration value of the bitumen is obtained by calculating the average of the penetration of
the 3 samples.
Treatment of results
Penetration tins Penetration(mm)
P1 10.5
P2 10.5
P3 10.6
Penetration of the bitumen is 11mm.
SOFTENING POINT TEST
Introduction
The softening point of bitumen is the temperature at which bitumen begins to show fluidity. It
is used to check the uniformity of different bituminous supplies and sources. The softening
point is also used to determine the temperature at which the bitumen will begin to flow during
service conditions.
The test is performed by raising the temperature of the sample at a constant rate and the
temperature read at the point where the bitumen undergoes a specified deformation.
A 3.5g steel ball is placed on the sample held in a brass ring in a water bath. Water is used for
samples with softening points below 80 and glycerin for softening points greater than 80 .
The temperature is raised at 5 per minute until the bitumen begins to deform and the ball
falls through the ring. The temperature is read when the bitumen and the steel ball touch the
base plate 25mm below.
Equipment
Boiled water with a heater
Water bath
2 brass rings
2 steel balls (3.5g)
Smooth glass plate
Thermometer
Spatula
Glass container
Sample preparation
Heat the sample to a temperature high enough to liquefy the bitumen. Pour the sample into
the brass rings which are placed on the smooth glass surface. Fill the rings with the bitumen.
Allow the bitumen to cool for 24 hours before performing the test. Cut the excess bitumen
with a heated spatula.
Procedure
Place the brass ring into the glass container with the ring holder. Fill the container with water
up to about 110mm depth.
Place the steel ball on the rings and maintain a constant temperature for about 15minutes until
a uniform temperature is attained. Transfer the glass container to the heating unit.
Heat the water unit a uniform temperature rise of 5 per minute is achieved. This is done by
recording the temperature every minute until the temperature is within ±0.5 of the desired
rate.
The water is heated until the bitumen softens allowing the steel ball to fall through the brass
ring and touch the bottom plate. The temperature at this instant is recorded.
The temperatures for the ring and ball for each sample are recorded and the difference
between the two should not exceed 1 .
Results
Sample number Temperature
1 45.5
2 46.5
Softening point is obtained by finding the average of the two temperatures
Softening point of the bitumen is
Recommended
