TEST -
3
TITLE: Softening
point test
OBJECTIVE:
To find the Softening Point of
bitumen by Ring and Ball test.
APPARATUS
REQUIRED:
This
practical is performed by Ring and Ball method. It consists of the following
apparatus.
i) Steel
balls - 2nos. having 9.5 mm Æ and
2.5±0.05 g
weight.
ii) Brass
Rings - there are two rings of the following dimension:
Depth - 6.4 mm
Inside Æ at
bottom - 15.9 mm
Inside Æ at top -
17.5 mm
Outside Æ - 20.6
mm
Brass rings are placed with ball guides.
iii)
Metallic support-for placing the pair of spring. The upper surface of the ring
is adjusted to 50mm below the surface of water or liquid. The spacing of 25mm is
kept between bottom of the ring and top surface of bottom
plate.
iv)
THEORY:
The Softening Point is the temperature at which the substance attains particular degree of softening under specified condition of test. For bitumen, Softening point is usually determined by Ring and Ball test. A brass ring containing the test sample of bitumen is suspended in liquid like water or glycerine at a given temperature. In Ring and Ball test, the softening point is the temperature at which the bitumen just touches the bottom plate. Harder grade bitumen possesses higher softening point than softer grade bitumen.
PROCEDURE:
A mass ring containing the
test sample of bitumen was suspended in liquid like water or glycerin at a given
temperature. A steel ball was then placed upon the bitumen and liquid medium was
heated at 50ºC per minute. The temperature at which the softened bitumen touches
the metal plate placed at a specified distance below the ring was recorded as
the softening point of the bitumen.
OBSERVATIONS:
i)Bitumen
grade
= 80/100
ii) Approximate softening point
= 85 ºC ~ 100
oC
iii) Liquid used in the bath
= water
iv) Period of air cooling
= 30 min.
v) Period of cooling in water bath = 15
min.
The
initial temperature is 5ºC and
increased @ 5ºC
/ min. up
to the softening point is not achieved.
Observation
Table:
|
|
Ball
no (i)
(ii) |
Mean | |
|
Temperature(oc)
at which sample touches bottom plate |
40 |
42 |
41 |
RESULTS
& CONCLUSION:
Hence the
softening point of the given bitumen is found to be 41ºC.
According to ISI this type of bitumen having softening point 41ºC lies in
35 to 50 which is the range of A 90& S 90 .So the
bitumen grade is 80/100. Which is as given in the
table.
TEST-2
TITLE:
Ductility test
OBJECTIVE:
To find
the ductility value of given bitumen.
APPARATUS
REQUIRED:
i)
Briquette mould
ii)
Ductility machine
THEORY:
In the flexible pavement construction where bitumen binders are used, it is of significant importance that the binders form ductile thin films around the aggregates. This serves as a satisfactory binder in improving the physical interlocking of aggregates. The binder material which doesn't possess sufficient ductility would crack and thus provide pervious pavement surface. This in turn results in damaging effect. But sometime this statement may be incorrect. It may hence be mentioned that Bitumen may satisfy the penetration value but may fails to satisfy the ductility requirements.
The ductility is expressed in as the distance in cm to which a standard briquette of bitumen can be stretched before the thread breaks. The test is conducted at 27oC ± 0.50C and a rate of pull of 50 ± 2.5 mm per minute.
PROCEDURE:
The
ductility machine functions as constant temperature water bath with a pulling
device at pre-calibrated rate. Two clips are thus pulled apart horizontally at a
uniform rate of 50 mm per minute.
The bitumen sample was
heated and poured in the mould assembly placed on the plate. The samples along
with mould were cooled in air and then in water bath maintained at
270C. The excess bitumen in the mould was cut and the surface leveled
with a hot knife. The mould assembly was then arranged in water bath of the
ductility test machine for 85 to 90 minutes. The sides of the mould were
removed, the clips hooked on the machine and the pointer was set to zero. The
machine was the turned on such that the hooks were pulled apart in horizontal
direction mechanically.
The distance up to which the bitumen thread breaks was measured in
centimeters as ductility value.
OBSERVATION:
i) Grade of bitumen
= 80/100
ii) Pouring temperature
= 75oc
_ 100 oc
iii) Test temperature
= 26.5oc
iv) Periods of cooling
(a) in air = 30 mints to 40
min.
(b) In water bath before trimming= 30 min
(c) In water bath after trimming =
85min-95 min
Observation
and calculation table:
|
Test
property |
Briquette
| |
|
(1) |
(2) | |
|
1.
Ductility value (cm) |
100+ |
100+ |
RESULTS
& CONCLUSION:
Hence the ductile value of 80/100 grade bitumen is found above 100 cm. That is the bitumen for grade A90&S90 according to ISI. The results may be affected by pouring temp. , rate of pulling test temp. &dimension of briquette.
TEST –
1
TITLE:
Penetration test
OBJECTIVE:
To find
the grade of bitumen by Penetrometer.
To know
the softness & hardness of bitumen at the specified
temperature.
APPARATUS
REQUIRED:
|
i) Container
ii) Needle
iii) Water - bath
iv) Penetrometer
v) Transfer tray |
|
THEORY:
Penetration
test determines the consistency of the bitumen for the purpose of grading them,
by measuring the depth to which a standard needle will penetrate vertically
under specified condition of standard load, duration and temperature. Thus , the
penetration test is the measurement of the penetration(in unit of one-tenth of
mm) of a standard needle in a bitumen sample maintained at 25oC for a
period of one hour during 5 seconds release of the total weight of 100gm.The softer the
bitumen, the greater will be the penetration. The bitumen grade is specified in
terms of penetration value. 80-100 or 80/100 grade bitumen means that the
penetration value of the bitumen is in the range 80 to 100 at standard test
condition. The penetration values of various types of bitumen used in pavement
are ranged between 20 to 225. 30/40, 60/70 and 80/100 grade bitumen are more
commonly used, depending on construction type and climatic condition. In hot
climates, lower penetration grade bitumen like 30/40 bitumen is
preferred.
PROCEDURE:
The bitumen was softened to
a pouring consistency, stirred thoroughly and the poured into containers to a
depth at least 15mm in excess to the expected penetration. These sample
containers were then placed in a temperature controlled water bath
at
250C for an hour. The sample
was then taken out and set up in the Penetrometer apparatus. The needle of
Penetrometer was arranged such that it just touches the bitumen surface in the
container. The dial was then set to zero or the reading was
taken.
The needle was, then
released for 5 seconds and the final reading was taken on the dial gauge. At
least three penetration tests were made on the sample by testing at distances at
least 10mm apart. The depth of penetration is recorded in 1/10th of
millimeter. The mean value of the penetration readings is calculated which
represents the penetration value.
OBSERVATIONS:
i)
Pouring temperature
= 75oC_ 100 oC
ii) Period of cooling in atmosphere = 30
min
iii) Room temperature
= 26.3 oC
iv) Period of cooling in water bath = 1
hr.
v) Actual test temperature
= 25 oC
OBSERVATION
TABLES:
|
Test
1 |
Test 2 |
Test3 |
Test
4 |
Mean |
|
Initial
|
0 |
0 |
0 |
0 |
0 |
|
Final
|
85 |
83 |
90 |
95 |
88.25 |
|
Penetration
value |
85 |
83 |
90 |
95 |
88.25 |
Mean
Penetration value:
88.25
Standard
Deviation:
5.4
RESULTS
& COMMENTS
:
Hence the
penetration value of the given bitumen was obtained as 88.25 with standard
deviation 5.4. So the given bitumen lies between 80 to
100. The grade of bitumen is 80/100 or A90 & S90 (according to Indian
standard). This grade of bitumen can be used in regions with normal atmospheric
conditions, for bituminous macadam and penetration macadam as referred by
ISA.
It may be
noted that the penetration value is largely influence by any inaccuracy as
regards;
a)
Pouring temperature
b) Size
of needle
c) Weight
placed on the needle
d) Test
temperature
TEST NO -
4
TITLE:
Viscosity test
OBJECTIVE:
To find
the viscosity of given grade of Tar.
APPARATUS
REQuiredD:
|
Ten millimeter Orifice Viscometer is specified for testing road tar and is called tar viscometer 4.0 mm orifice is used to test cutback grades 0 and 1 and 10 mm orifice to test all other grades. The apparatus consists of main parts like cup, valve, water bath, sleeves, stirrer, receiver and thermometers, etc. |
|
THEORY:
Viscosity is defined as the inverse of fluidity. Viscosity thus defines the fluid property of bituminous material. Viscosity is the resistance to flow. It defines the consistency of the fluid. Viscosity defines the property of fluid to spread, penetrate into the voids and also coats the aggregates and hence affects the strength characteristics of the resulting paving mixes. The degree of fluidity at the application temperature greatly influences the ability of bituminous material to spread, penetrate into the voids and also coat the. High or low viscosity during mixing and compaction results in lower stability values. An optimum value of viscosity is assigned for each aggregate gradation of the mix and bitumen grade. At low viscosity, the bituminous binder simply lubricates the aggregate particles instead of providing a uniform for binding action. At higher viscosity, aggregates resist the compaction and the resulting mix is heterogeneous in character exhibiting low stability values.
One of the methods by which viscosity is measured by determining the time taken by 50 cc of the material to flow from a cup through specified orifice at a given temperature. This method is called Orifice viscosity test. Orifice viscosity test gives an indirect measure of viscosity of tars and cutbacks in seconds. Higher the duration, more viscous is the material.
OBSERVATION:
i) Material: Tar
ii) Grade: 80/100
iii) Specified test temperature: 250c
iv) Size of orifice: 4 mm
v) Actual test temperature: 280c
Time taken to flow 50cc of
tar is 85sec
Therefore the viscosity value is 85sec
COMMENTS
AND CONCLUSION:
By the
help of viscometer, the time taken to flow 50 cc of tar is found to be 85
sec.
TEST –
6
TITLE:
Marshal Stability test
OBJECTIVE:
To design
the required bitumen mix.
To find
the optimum bitumen content
APPARATUS
REQUIRED:
a) Mould
assembly:
Cylindrical moulds of 10 cm dia. and 7.5 cm height are required. It further consists of a base plate and collar extension. They are designed to be interchangeable with either end of cylindrical mould.
b) Sample
extractor:
For extruding the compacted specimen from the mould, an extractor suitably fitted with a jack or compression machine.
c)
Compaction Pedestal and hammer:
It consists of a wooden block capped with M.S. plate to hold the mould assembly in position during compaction. The compaction hammer consists of a flat circular tamping face 8.8 cm dia. and equipped with a 4.5 kg weight constructed to provide a free fall of 45.7 cm. And the no. of free fall is 50 blows on both sides of specimen. Mould holder is provided consisting of spring tension device designed to hold compaction mould in place on the compaction Pedestal.
d)
Breaking Head:
It consists of upper and lower cylindrical segments or test heads having an inside radius of curvature of 5 cm. The lower segment is mounted on a base having two vertical guide rods, which facilitate insertion in the holes of upper test head.
e)
Loading Machine:
The loading machine is provided with a gear system to lift the base in upward direction. On the upper end of the machine, a pre-calibrated proving ring of 5 ton capacity is fixed. In between the base and the proving ring, the specimen contained in test head is placed. The loading machine produces a movement at the rate of 5 cm per min. Machine is capable of reversing its movement downward also. This facilitates adequate space for placing test head system after one specimen has been tested.
f) Flow
meter:
One dial gauge fixed to the guide rods of a testing machine can serve the purpose. Least count of 0.25 mm is adequate. The flow value refers to the total vertical upward movement from the initial position at zero loads to a value at maximum load. The dial gauge for the flowmeter should be able to measure accurately the total vertical movement upward.
THEORY:
Bruce Marshal, a bituminous engineer formulated the method for determining the bitumen mixes. Generally, this stability test is applicable to hot mix design using bitumen and aggregates with maximum size of 25 mm.
The
Marshal stability of the mix is defined as a maximum load carried by a compacted
specimen at a standard test temperature at 60oc. The flow value is
the deformation the Marshal test specimen undergoes
during the loading upto the maximum load, in 0.25 mm units.In this test an
attempt is made to obtain optimum binder content for the type of aggregate mix
and traffic intensity. The proposed design steps for the design of bituminous
mix are as follows:
i) Select grading to be used.
ii)
Selects aggregates to be employed in the mix.
iii)
Determine the proportion of each aggregate required to produce the design
grading.
iv)
Determine the
specific gravity of the aggregate combination and of the asphalt
cement.
v) Make
up trial specimens with varying asphalt contents.
vi)
Determine the
specific gravity of each compacted specimens.
vii) Make
stability tests on the specimens.
viii) Calculate the percentage of voids, VMA and the percent voids filled with bitumen in each specimen.
ix)
Select the optimum bitumen content from the data obtained.
x) Check the values of Marshal Stability, Flow, Voids in total mix and Voids filled with Bitumen obtained the optimum bitumen content, with the design requirements. The design may be repeated if necessary after altering the gradation so as to fulfill the design requirements.
Specific
gravity and compacted Specimen:
The
specific gravity values of the different aggregates, filler and bitumen used are
determined first. The theoretical specific gravity Gt of
the mix is given by-
Gt = 100/(W1/G1
+ W2/G2 + W3/G3 +
W4/G4)
where,
W1 = % by weight of coarse aggregate.
W2 = % by weight of fine aggregate.
W3 = % by weight of filller.
W4 = % by weight of bitumen in total
mix.
G1, G2 and G3 are apparent specific
gravity values of the coarse aggregates, fine aggregates and filler respectively
and G4 is the specific gravity of bitumen.
Density
and Void Analysis:
Soon
after the compacted bituminous mix specimens have cooled to room temperature,
the weight, average thickness and dia. of specimen are noted. The specimens are
also weighed in air and then in water. The bulk density value Gb of the specimen is calculated from the weight
and volume. The voids analysis are made as given
below:
Vv, (%) = 100(Gt - Gb)/Gt
Vb, (%) = Gb*
W4/G4
VMA, (%) = Vv + Vb
VFB, (%) = 100Vb/VMA
where,
Vv = air voids in the mix in %
Vb
= vol. of bitumen.
VMA = voids in mineral aggregates in %
VFB = voids filled with bitumen in %
Determination
of optimum Bitumen content:
Five
graphs are plotted with values of bitumen content against the values
of:
i) density, Gb in
gm/cm3
ii)
iii)
voids in total mix, Vv in
%.
iv) flow value, F(0.25 mm units)
v) voids filled with bitumen, VFB(%).
Let the
bitumen contents corresponding to maximum density be B1,
corresponding to the maximum stability be B2 and that corresponding
to the specified voids content Vv(4% in the
case of dense AC mix) be B3. Then the optimum bitumen content(OBC) for mix design is given
by;
B0 = (B1 + B2 +
b3)/3
The value
of flow and VFB are found from the graphs, corresponding to bitumen content
B0. All the designed values of
PROCEDURE:
Coarse aggregate, fine aggregate and filler materials were proportioned
and mixed to meet the specified requirement. From this mix, 1500gm of the sample
was taken and heated to the temperature of 1800C. The bitumen was
heater to 1300C. The compaction mould assembly and rammer were
cleaned and heated to temperature 1300C. First the bitumen (5% of
aggregate by weight) is added to the heated aggregate and thoroughly mixed by
hand mixing with trowel. The mix is placed in mould and compacted by rammer with
50 blows on either side. Then it was taken out from the mould and kept in water
bath at 600C for half an hour. Similarly specimen of 6% and 7% of bitumen were
also prepared.
OBSERVATIONS
AND CALCULATIONS:
Stability
and flow value determination:
i) Type of grading of aggregate= grade-I(given
below).
ii) Mixing temperature = 1540C
iii) No of blows on either side = 50
iv) Flow value dial, 1 div. = .025
mm
v) Grade of bitumen = 80/100
vi) Compacting temperature =
1000c
vii) Proving ring calibration factor = given in code by
manufacturer.
Density and void determination:
Grade of aggregate:
|
Sieve
opening |
Passing
on Sieve |
Retaining
on Sieve |
Weight
(gm) |
Sp.
Gravity |
|
25 |
100 |
|
|
|
|
19 |
75 |
25 |
300 |
|
|
12.5 |
60 |
15 |
180 |
|
|
9.5 |
45 |
15 |
180 |
|
|
4.75 |
35 |
10 |
120 |
|
|
0.075 |
0 |
35 |
420 |
|
Note: The amount of coarse, fine and sand particle should be so determined that the grade of aggregate should lie on the recommended grade given.
From
graph, we get.
OBC = (6 + 6.1 + 5)/3 = 5.7 %
COMMENTS
AND CONCLUSION:
The
OBC is found to be 5.7 % by the graph. Hence we can maintained the bitumen content in the road construction while
running the pavement construction by the contractor. So we cannot use other than
this value since the maximum and minimum value other than OBC is not favorable
for road construction. Hence this value should be specified in the
specification.
TEST
5
TITLE: SKID RESISTANCE
TEST
OBJECTIVE:
To determine the
skid resistance test on the road surface
To determine the skid value between road
and tyre in different weather condition.
APPATRATUS
REQUIRED:
|
(1)
British Pendulum
taster (2)
Slider |
|
THEORY:
The test consists of using
Pendulum type taster with a standard rubber-slider to determine the friction
properties of a test surface. Road surface is cleaned and thoroughly wetted
prior to testing. The pendulum slider is placed and positioned to barely come in
contact with that road surface. A drag-pointer indicates the British pendulum
number.
PROCEDURE:
-Road surface was cleaned
and was made wet.
-Pendulum machine is
leveled.
-The pendulum was adjusted
in such a way that it only touches the surface smoothly and a line was
drawn.
-From the center of line a
mark was marked 38mm on both sides.
-The pendulum was raised and
clamped.
-The pendulum was then released.
-The reading was taken for maximum swing.
-The temperature of road surface was taken by inserting a thermometer in a nailed hole filled by oil.
OBSERVATION:
|
S.NO. |
B.P.N.
VALUE |
REMARKS |
|
1 |
136 |
Road
surface |
|
2 |
139 |
Road
surface |
|
3 |
131 |
Road
surface |
|
4 |
104 |
Road surface with
water |
|
5 |
103 | |
|
6 |
105 |
Mean B.P.N. value for road
surface = 135.33
And 103 for wet
surface.
RESULT AND
CONCLUSION:
The skid resistance is found
to be 135.33 for dry surface and 103 for wet surface.
If the surface is smooth the
BPN value is lower. On the other hand if the surface is rough
,the BPN value is higher. This pendulum test can be done before or after
road construction. The observational value of the skid resistance in the road
may be affected due to following factors.
1)
Water
2)
Temperature
3)
Dust
present
4)
Oil and
Grease