road materials testing lab manual by er. hamender singh shekhawat

Road Materials Testing Lab Manual List of Experiments:

1. Aggregate crushing value test.

2. Aggregate impact test.

3. To determine fineness modulus of a given sample of coarse aggregate.

4. Los angles abrasion test.

5. Angularity number test .

6. Specific gravity and water absorption test.

7. To determine the elongation index for given sample of aggregate.

8. To determine the flakiness index of given sample of aggregate.

9. Ductility test.

10. To determine the softening point for give sample of bitumen.

11. Marshall stability test.

12. Determine the percentage of free or surface moisture in both fine

and coarse aggregate.

Road Materials Testing Lab Govt. College of Engineering and Technology, Bikaner

1 Submitted by Er. Hamender Singh Shekhawat

Crushing Value The principal mechanical properties required in road stones are satisfactory

resistance to crushing Under the roller during construction and adequate resistance

to surface abrasion under traffic surface stresses under rigid tyre rims of heavily

loaded animal, drawn vehicles ate high enough to consider the crushing strength of

road aggregates as an essential requirement in India. Crushing strength of road

stones may be determined either on aggregates or on cylindrical specimen cut out of

rocks. These two tests are quite different in not only the approach but also in the

expression the results. Aggregates used in road construction, should be strong

enough to resist crushing under traffic wheel. loads If the aggregates are weak, the

stability of the pavement structure is likely to be adversely affected. The strength of

coarse aggregates is assessed by aggregates crushing test. The aggregate crushing

value provider. a relative measure of resistance to crushing under a gradually

applied compressive load. To achieve a high quality of pavement, aggregate

possessing low aggregate crushing value should be preferred.

Apparatus:- The apparatus for the standard aggregate crushing test consists of the

following:

1. Steel cylinder with open ends, and internal diameter 25.2 cm, square base

plate plunger having a piston of diameter 15cm with a hole provided across

the stem of the plunger So that a rod could be inserted for lifting or placing the

plunger in the cylinder.

2. Cylindrical measure having internal diameter of 11.5cm and height 18 cm.

3. Steel temping rod with one rounded end, having a diameter of 1.6 cm and

length 45 to 60 cm

4. Balance of capacity 3kg with accuracy up to 1g.

5. Compressions testing machine capable of applying load of 40 tones, at a

uniform rate of loading.



Procedure:- The aggregate passing 12.5 mm IS sieve and retained on10mm IS sieve is selected

for standard test. The aggregate should be in surface-dry condition before testing.

The aggregate may be dried by heating at a temperature 100°c to 110°C for a period

of 4 hours and is tested after being cooled to room temperature. The cylindrical

measure is filled by the test sample of aggregate in three layers of approximately

equal depth, each layer being tamped 25 times by the rounded end of the tamping

rod. After the third layer is tamped, the aggregates at the top of the cylindrical

measure are levelled off by using the tamping rod as a straight edge. About 6.5kg of

aggregate is required for preparing two test samples. The test sample thus taken is

then weighed. The same weight of the sample is taken in the repeat test. The

cylinder of the test apparatus is placed in position on the base plate; one third of the

test sample is placed in this cylinder and tamped 25 times by the tamping rod.

Similarly, the other two parts of the test specimen are added, each layer being

subjected to 25 blows. The total depth of the mater in the cylinder after tamping shall

however be 10 cm . The surface of the aggregates is levelled and the plunger

inserted so that it rests on this surface in level position. The cylinder with the test

sample and plunger in position is placed on compression testing machine. Load is

then applied through the plunger at a uniform rate of 4 tones per minute until the total

load is 40 tones, and then the load is released. Aggregates including the crushed

portion are removed from the cylinder and sieved on a 2 36 mm IS Sieve. The



hames

Typewritten Text

material which passes this sieve is collected. The above crushing test is repeated on

second sample of the same weight in accordance with above test procedure. Thus

two tests are made for the same specimen for taking an average value.

Calculation:- Total weight of dry sample taken = W1 g.

Weight of proportion of crushed material passing 2.6mm IS sieve =W2 g.

The aggregate crushing value is defined as a ratio of to the total weight of the

sample expressed as a percentage decimal place the weight, of fines passing the

specified IS sieve .The value is usually recorded up to the first

=

Observation table:-.

Sample Number

Total weight of dry

Sample. W1 g

Weight of fines passing 2.36 mm IS

Sieve. W2 g

Aggregate crushing

value

Average aggregate

crushing value

1.

2. 3. 4. 5.

Results:- The mean of the crushing value obtained in the tests is reported as the aggregate

crushing value is______.



Impact Value

Toughness is the property of a material to resist impact. Due to traffic loads, the road stones

are subjected to the pounding action or impact and there is possibility of stones breaking into

smaller pieces. The road stones should therefore be tough enough to resist fracture

under impact. A test designed to evaluate the toughness of stones i.e., the resistance of the

stones to fracture under repeated impacts may be called an impact test for road stones.

Impact test may either be carried out on cylindrical stone specimens as in Page Impact

test or on stone aggregates as in Aggregate Impact test. The Page Impact test is not

carried out now-a-days and has also been omitted from the revised British Standards for

testing mineral aggregates. The Aggregate Impact test has been standardized by the British

Standards Institution and the Indian Standards Institution. The aggregate impact value

indicates a relative measure of the resistance of an aggregate to a sudden shock or an

impact, which in some aggregates differs from its resistance to a slow compressive load.

The method of test covers the procedure for determining the aggregate impact value of

coarse aggregates.

Type of pavement Material Aggregate impact value, maximum, % Water bound macadam (WBM), sub-base course 50 Cement concrete, base course (as per ISO 45 (i) WBM base course with bitumen surfacing 40 (ii) Built-up spray grout, base course 35 Bituminous macadam, base course 35 (ii) Built-up spray grout, surfacing course

(iii) Bituminous penetration

macadam (iv) Bituminous

macadam, binder course (v)

Bituminous surface dressing

30

Object : -

To determine the impact value of the aggregate .

Apparatus:-

The apparatus consists of an impact testing machine, a cylindrical measure, tamping rod,

IS



sieves, balance and oven.

1) Impact testing machine:- The machine consists of a metal base with a plane lower

surface supported well on a firm floor, without rocking. A detachable cylindrical steel

cup of internal diameter 10.2 cm and depth 5cm is rigidly fastened centrally to the

base plate. A metal hammer of weight between 13.5 and 14 kg having the lower end

cylindrical in shape, 10m in diameter and 5 cm long, with 2 mm chamfer at the lower

edge is capable of sliding freely between vertical guides, and fall concentric over the

cup. There is an arrangement for raising the hammer and allowing it to fall freely

between vertical guides from a height of 38 cm on the test sample in the cup, the height

of fall being adjustable up to 0.5 cm. A key is provided for supporting the hammer while

fastening or removing the cup.

2) Measure: A cylindrical metal measure having internal diameter 7.5 cm and depth

5cm for measuring aggregates.

3)Tamping rod: A straight metal tamping rod of circular cross section, 1cm in diameter

and 23cm long, rounded at one end.

4) Sieve: IS sieve of sizes 12.5mm, 10mm and 2.36mm for sieving the aggregates.

5) Balance: A balance of capacity not less than 500 g to weigh accurate up to 0.1 g.

6) Oven: A thermostatically controlled drying oven capable of maintaining constant

temperature between 100°C and 100°C.

Procedure:-

The test sample consists of aggregat.es passing ~m sieve and retained on 10 mm sieve

and dried in an oven for four hours at a temperature 100°C to 110°C and cooled. Test

aggregates are filled up to about One third full in the cylindrical measure and tamped, 25

times with rounded end of the tamping rod further quantity of aggregates, is then added

up to about two-third full in the cylinder and 25 strokes of the tamping rod are given. The

measure is now filled with the aggregates to over flow, tamped 25 times. The surplus

aggregates are struck off using the tamping rod as straight edge. The net weight of the

aggregates in the measure is determined to the nearest gram and this weight of the

aggregates is used for carrying out duplicate test on the same material. The impact

machine is placed with its bottom plate fiat on the floor so that the hammer guide columns

are vertical. The cup is fixed firmly in position on the base of the machine and the whole



of the test sample from the cylindrical measure is transferred to the cup and compacted by

tamping with 25 strokes.

The hammer is raised until its lower face is 38cm above the upper surface of the

aggregates in the cup, and allowed to fall freely on the aggregates. The test sample is

subjected to a total of15 such blow, each being delivered at an interval of not less than one

second. The crushed aggregate is then removed from the cup and the whole of it sieved

on the 2.36 mm sieve until no further significant amount passes. The fraction passing the

sieve is weighed accurate to 0.1gm. The fraction retained on the sieve is also weighed

and if the total weight of the fractions passing and retained on the sieve is added it

should not be less than the original weight of the specimen by more than one gram; if the

total weight is less than the original by over one gram, the result should be discarded and a

fresh test made.

Figure 7: Apparatus for Impact Value Test

Calculation:-

The aggregate impact value is expressed as the percentage of the fines formed in terms of

the total weight of the sample.



Let the original weight of the oven dry sample be W1 gm.

The weight of fraction passing 2.36 mm IS sieve be W2 gm.

Aggregate impact value= %.

Serial No. Detail Trail No. Average

1. Total weight of aggregate sample filling

the

2. Weight of aggregate passing 2.36 mm

sieve

3. Weight of aggregate retained on 2.36µ

sieve

4. Aggregate Impact value =percent fines

= %.

Results:-

The result is reported as the aggregate impact value of the specimen to the nearest

whole number

Aggregate impact value is to classify the stones in respect of their toughness property

as indicated below: Aggregate impact values

<10% exceptionally strong 10-30% satisfactorily for road surfacing

10-20% Strong >35% Weak for road surfacing



Fineness Modulous of Aggregate

Object :To determine fineness modulus of aggregate.

APPARATUS :

1) Set of : 80mm, 63mm, 40mm, 20mm, 12.5mm, 10mm, 6.3mm, 4.75mm

2) Weighing balance with weight box.

3) Tray

THEORY :

Fineness modulus of aggregate is an index number which gives an

idea about the coarseness or fineness of an aggregate It can be written

as FM. Fineness modulus. of an aggregate is approximate proportional

of the average size of particles in the aggregate. In another words

coarse particles of the aggregate having of Fineness modulus is

determined by adding the cumulative percentage of material retained

on each sieve and dividing the sum of cumulative percentage of

material retained on each sieve by100

In this method, the fineness modulus of coarse fine and com In this

method, the fineness modulus of coarse fine and communed aggregate

are determined separately.

The value of F.M. is higher for coarse aggregate (I e stone metals

etc.)Are as follows

For 20mm size = 6 to 6.9

40mm size= 6.9to7.5

For all in aggregate 20mm size = 4.8 to 5.1

25mm size = 5.1 to 5.5



PROCEDURE:

i) Take a suitable sample of aggregate

ii) Put the aggregate on the upper most sieves.

iii) Sieve it as per sieve analysis.

iv) Find out wt retained on each sieve.

v) From that value cumulative percentage of weight retained on each

was calculated.

OBSERVATION TABLE :

Weight of coarse aggregate =………kg

PRECAUTION :

i) The sieve should be in the proper sequence

ii) There should be no wastage of aggregate during sieving

iii) The weight of the aggregate retained on each sieve should measure

carefully.

RESULT : Fineness modulus of aggregate is found to be ….



Abrasion Value Object:- Determine the Abrasion vale of aggregate.

Theory:- Due to the movements of traffic, the road stones used in the surfacing course are

subjected to wearing action at the top. Resistance to wear or hardness is hence an

essential property for road aggregates, especially when used in wearing course.

Thus road stones should be hard enough to resist the abrasion due to the traffic.

When fast moving traffic fitted with pneumatic tyres move on the road, the soil

particles present between the wheel and road surface causes abrasion on the road

stone. Steel tyres of animal drawn vehicles which rub against the stones can cause

considerable abrasion of the stones on the road surface. Hence in order to test the

suitability of road stones to resist the abrading action due to traffic, tests are carried

out in the laboratory. Abrasion test on aggregates are generally carried out by

anyone of the following methods:

• Los Angeles abrasion test

• Deval abrasion test

• Dorry abrasion test

Los Angeles Abrasion Test:- The principle of Los Angeles abrasion test is to find the percentage wear due to the

relative rubbing and action between the aggregates and steel balls used as abrasive

charge; pounding action of these balls also exist while conducting the test. Some

investigators believe this test to be more dependable as rubbing and pounding action

simulate the field conditions where both abrasion and impact occur. Los Angeles

abrasion test has been standardized by the ASTM, AASHO and also by the ISI.

Standard specification of Los Angeles abrasion values is also available for various

types of pavement constructions.



Serial No. Types of pavement layer Los Angeles abrasion value, maximum %

1. Water Bound Macadam (WBM), sub-base course 60

2. (i) WBM base course with bituminous surfacing (ii) Bituminous Macadam base course (iii) Built-up spray grount base course

50

3. (i) WBM surfacing course (ii) Bituminous Macadam binder course (iii) Bituminous penetration Macadam (iv) Buil-up spray grout binder course

40

4. (i) Bituminous carpet surface course (ii) Bituminous surface dressing, single or two coats (Hi) Bituminous surface dressing, using precoated aggregates (iv) Cement concrete surface course (as per IRe)

35

5. (i) Bituminous! Asphaltic concrete surface course (ii) Cement concrete pavement surface course (as per ISI)

30

Apparatus:- Los Angeles abrasion machine and sieve.

An opening is provided in the cylinder for the introduction of the test sample. A

removable cover of the opening is provided in such a way that when closed and fixed

by bolts and nut, it is dust tight and the interior surface is perfectly cylindrical. A

removable steel shelf projecting radially 8.8 cm into the cylinder and extending to the

full length of it, is mounted on the interior surface of the cylinder rigidly, parallel to the

axis The shelf is fixed at a distance of 125 cm from the opening Measured along the

circumference in the direction of rotation. Abrasive charge, consisting of cast iron

spheres approximately 4.8 cm in diameter and 390 to 445 g in weight are used. The

weight of the sphere used as the abrasive charge and the number of spheres to be

used are specified depending on the gradation of the aggregates tested. The

aggregate grading have been standardized as A. B. C, D. E, F, and G for this test

and the IS specifications for the grading and abrasive charge to be used are given

in IS sieve with l. 70 mm opening is used for separating the fines after the abrasion

test.

Procedure:- Clean aggregates dried in an oven at 105-110°C to constant weight Conforming to

anyone of the grading A, to G, as per is used for the test. The grading or grading



used in the test should be nearest to the grading to be used in the construction.

Aggregates weighing 5 kg for grading A. B, C or D and 10 kg for grading E, For G

may be taken as test specimen and placed in the cylinder. The abrasive charge is

also chosen in accordance depending on the grading of the aggregate and is placed

in the cylinder of the machine. The cover is then fixed dust tight. The machine is

rotated at a speed of 30 to 33 revolutions per minute. The machine is rotated for 500

revolutions for grading A. B, C and D. for grading E F and G, it shall be rotated for

1,000 revolutions the machine should be balanced and driven in such a way as to

maintain uniform peripheral speed. After the desired number of revolutions, the

machine is stopped and the material is discharged from the machine taking care to

take out entire stone dust. Using a sieve of size larger than I. 70 mm IS sieve, the

material is first separated into two parts and the finer position is taken out and sieved

further on a 1.7 mm IS sieve. The portion of material coarser than 1.7 rom size is

washed and dried in an oven at 105 to 110°C to constant weight and weighed

correct to one gram

.



Calculations:- The difference between the original and final weights of the sample is expressed as

a percentage of the original weight of the sample is reported as the percentage wear.

Let the original weight of aggregate =W1g = g

Weight of aggregate retained on1.70mm IS sieve after the test =W2 g = g

Loss in weight due to wear= (W1-W2) g = g

Los Angeles abrasion value= = %

Result:- The result of the Los Angeles abrasion test is expressed as a percentage wear and

the average value of two tests may be adopted as the Los Angeles abrasion value.



Determination of Angularity Number for the given aggregate sample.

This test is also carried out for determining shape of the aggregates. Based upon shape the aggregates may be classified as Rounded, Angular or Flaky. Angular particles possess well defined edges formed at the intersection of roughly planer faces and are commonly formed in aggregates prepared by crushing of rocks. Angularity in general is the absence of rounding of particles of an aggregate. This test is performed to determine the angularity number i.e. the absence of roundedness or the degree of angularity of the aggregate specimen. ANGULARITY It is the absence of roundness. An aggregate particle, which is more rounded, is less angular and vice versa. ANGULARITY NUMBER Angularity number of an aggregate is the amount (to the higher whole number) by which the percentage of voids in it after compacting in a prescribed manner exceeds 33. Where, “33” is the percentage of volume of voids, in a perfectly rounded aggregate. “67” is the percentage of volume of solids in a perfectly rounded aggregate. The value of angularity number generally lies between 0 & 11. In road construction angularity number of 7 – 10 is generally preferred. SIGNIFICANCE

• The degree of packing of particles of single sized aggregate depends upon the angularity of aggregate.

• The angularity of the aggregate can be estimated from the properties of voids in a sample of aggregate compacted in a specified manner.

• The angularity number ranges from 0 for a highly rounded grave to about 11 for freshly crushed angular aggregates.

• Higher the angularity number, more angular and less workable is the concrete mix.

• In cement concrete roads (rigid pavements) rounded aggregates are preferred because of better workability and higher strength.

• In bituminous or water bound macadam construction (like flexible pavements), angular aggregates with high angularity number are preferred because of high stability due to better interlocking and friction.

• Higher the angularity number, more angular and less workable is the concrete mix.

• In road construction, angularity number of 7 -10 is generally preferred.



APPARATUS

1 - A metal cylinder of about 3-liter capacity. 2 - Temping rod of circular cross-section, 16mm Φ, 60cm in length. Rounded

at one end. 3 - A metal scoop. 4 - A weighing balance.

PROCEDURE This procedure is for aggregate size ¾ to No.4. If aggregate is coarser than ¾, a cylinder of large capacity shall be required but amount of compactive effort or energy should be proportional to the volume of the cylinder. 10 Kg of the sample is taken for the test. The material should be oven dried. The aggregate is compacted in three layers, each layer being given 100 blows using the standard tamping rod at a rate of 2 blows/second by lifting the rod 5 cm above the surface of the aggregate and then allowing it to fall freely. The blows are uniformly distributed over the surface of the aggregate. After compacting the third layer, the cylinder is filled to overflowing and excess material is removed off with temping rod as a straight edge. The aggregate with cylinder is then weighed. Three separate determinations are made and mean weight of the aggregate in the cylinder is calculated. Calculations & Results Method – 1 Add measured quantity of water in the compacted aggregate till all the

voids are filled and water appears to the surface. Volume of water added is approximately equal to the volume of voids in the compacted aggregate.

Method – 2

where, W = mean weight of the aggregate filling cylinder. C = Weight/Volume of water that can completely fill the cylinder

(= 3 liters = 3000 ml – in our lab) Gs = Specific Gravity of the aggregate.

33100 −×=VolumeTotal

AddedWaterofVolumeNumberAngularity

sCGWNumberAngularity 10067 −=



Notes:

1- Method – 1 determines the angularity number from the solids point of view. 2- Method – 2 determines the angularity number from the voids point of view.

COMPUTATIONS & RESULTS Specific gravity of the aggregate = 2.67 Total volume of the cylinder = 3 liters = 3000 ml

WEIGHT (gm)

Volume of Water Added (ml)

Angularity Number

Empty Cylinder

Cylinder + Aggregate

Cylinder + Agg. + Water

Aggregate Method#1

Method#2

Result :



Specific gravity of Aggregate

Object: -

To determine the Specific gravity of Aggregate.

Apparatus:-

Figure 12: Apparatus Required for performing Specific Gravity Test for Aggregates

Theory:-

Apparent Specific Gravity: - It is defined as the ratio of the mass of a unit volume of the

impermeable portion of aggregate (does not include the permeable pores in aggregate) to the

mass of an equal volume of gas-free distilled water at the stated temperature.

Effective Specific Gravity: - Volume measurement includes the volume of the aggregate

particle plus the void volume that becomes filled with water during the test soak period

minus the volume of the voids that absorb asphalt. Effective specific gravity lies between

apparent and bulk specific gravity. It is formally defined as the ratio of the mass in air of a

unit volume of a permeable material (excluding voids permeable to asphalt) at a stated

temperature to the mass in air (of equal density) of an equal volume of gas-free distilled



water at a stated temperature. Effective specific gravity is determined by a different

procedure and is not covered in this section.

The volume measurement only includes the volume of the aggregate particle; it does not include

the volume of any water permeable voids. The mass measurement only includes the

aggregate particle. Apparent specific gravity is intended to only measure the specific gravity

of the solid volume; therefore it will be the highest of the aggregate specific gravities. It is

formally Specific gravities can vary widely depending upon aggregate type. Some light

weight shale can have specific gravities near 1.050, while other aggregate can have specific

gravities above 3.000. Typically Aggregate absorption can also vary widely depending upon

aggregate type.

Where :-

A= Mass of oven dry sample in air

B= Mass of wet sample in Air

C= Mass of wet sample in water

Procedure:-

1. Obtain a sample of coarse aggregate material retained on the No. 4 (4.75 mm) sieve

This sample size is based on nominal maximum aggregate size (NMAS). Sample

sizes range from 2000 g for a 0.5 inch (12.5 mm) NMAS to 5000 g for a 1.5 inch

(37.5 mm).

2. Wash the aggregate retained on the No. 4 (4.75 mm) sieve. This discards small

aggregate particles clinging to the retained large particles.



3. Dry the material until it maintains a constant mass. This indicates that all the water

has left the sample. Drying should occur in an oven regulated at 230°F (110°C).

4. Cool the aggregate to a comfortable handling temperature.

5. Immerse the aggregate in water at room temperature for a period of 15 to 19 hours

6. Dry the sample to a saturated surface dry condition. Rolling up the aggregate into

the towel and then shaking and rolling the aggregate from side to side is usually

effective in reducing the sample to a SSD condition .It may be necessary to wipe the

larger particles separately. Once there are no visible signs of water film on the

aggregate particle surfaces, determine the sample mass.

7. Place the entire sample in a basket and weigh it underwater. The basket should be

preconditioned to the water bath temperature. Shake the container to release any

entrapped air before weighing. The container overflow needs to work properly to

compensate for the water displaced by the sample.

8. Remove the aggregate from the water and dry it until it maintains a constant mass.

This indicates that all the water has left the sample. Drying should occur in an oven

regulated at 230°F (110°C).

9. Cool the aggregate in air at room temperature for 1 to 3 hours then determine the

mass.

Calculation:-



Result:-

Specific Gravity of Coarse Aggregate =

Specific Gravity of Fine Aggregate =



Elongation Index Object:- To determine the Elongation index

Apparatus:- The apparatus consists of the length gauge and sieves.

Theory:- The percentage by weight of particles whose long dimension is greater than 1.8

times the mean dimension measured with a standard gauge. The elongation, n, is

length divided by breadth and the elongation ratio is 1/n.

Procedure:- The sample is sieved through the IS sieves. A minimum of 200 pieces of each

fraction is taken and weighed. In order to separate elongated material, each fraction

is then gauged individually for length in a length gauge .The gauge lengths used

should be those specified. The pieces of aggregates from each fraction tested which

could not pass through the specified gauge length with its long side are elongated

particles and are collected separately to find the total weight of aggregates retained



on the length gauge from each fraction. The total amount of elongated material

retained by the length gauge are weighed to an accuracy of at least 0.1 percent of

the weight of the test sample.

Calculation and Result: - In order to calculate the elongation index of the entire sample of aggregates, the

weight aggregates which is retained on the specified gauge length from each fraction

is noted. As an example, let 200 pieces of the aggregate passing 40 mm sieve and

retained 25 mm sieve weight W1 g. Each piece of these are tried to be passed

through the specified gauge length of the length gauge,

With its longest side and those elongated pieces which do not pass the gauge are

separated and the total weight determined =W1 g. Similarly the weight of each

fraction of aggregate passing and retained on specified sieves sizes are found, W1,

W2, W3 ... and the total weight of sample determined W1+W2+W3+...= Wg. Also the

weight of material from each fraction retained on the specified gauge length is found

=x1, x2, x3 and the total weight retained determined =x1+x2+x3+ ...=Xg.

Result:- Elongation Index = %



Flakiness Index

Object:-

To determine the flaky and elongated index of particles

Apparatus:-

The apparatus consists of a standard thickness gauge shown, IS sieves of sizes 63, 50, 40,

31.5, 25, 20, 16, 12.5, 10, and 6.3mm and a balance weight the sample.

Apparatus for Flaky Index

Theory:-

The particle shape of aggregates is determined by the percentages of flaky and elongated

particles contained in it. In the case of gravel it is determined by its angularity number. For

base course and construction of bituminous and cement concrete types, the presence of flaky

and elongated particles are considered undesirable as they may cause inherent weakness with

possibilities of breaking down under heavy loads. Rounded aggregates are preferred in

cement concrete road construction as the workability of concrete improves. Angular shape of

particles is desirable for granular base course due to increased stability derived from the



better interlocking. When the shape of aggregates deviates more from the spherical shape, as

in the case of angular, flaky and elongated aggregates, the void content in an aggregate of

any specified size increases and hence the grain size distribution of a graded aggregate has to

be suitably altered in order to obtain minimum voids in the dry mix or the highest dry

density. The angularity number denotes the void content of single sized aggregates in excess

of that obtained with spherical aggregates of the same size. Thus angularity number has

considerable importance in the graduation requirements of various types of mixes such as

bituminous concrete and soil-aggregate mixes.

Thus evaluation of shape of the particles, particularly with reference to flakiness,

elongation and angularity is necessary.

Flakiness Index: - The flakiness index of aggregates is the percentages by weight of

particles whose least dimension (thickness) is less than three-fifths (0.6) of their mean

dimension. The test is not applicable to sizes smaller than 6.3 mm.

Procedure:-

The sample is sieved with the sieves mentioned. A minimum of 200 pieces of each

fraction to be tested are taken and weighed =W1 g. In order to separate flaky materials,

each fraction is then gauged for thickness on a thickness gauge or in bulk on sieves having

elongated slots. The amount of flaky material passing the gauge is weighed to an

accuracy of at least

0.1 percent of the test sample.

Size of aggregate

Passing through

Size of aggregate

Retained on

(a) Thickness gauge (0.6

times the mean sieve),

(b) Length gauge (1.8

times the mean sieve),

63.0 50.0 33.90 - 50.0 40.0 27.00 1.0 40.0 31.5 19.50 58.5 31.5 25.0 16.95 - 25.0 200 13.50 0.5 20.0 16.0 10.80 324 16.0 12.5 8.55 25.6 12.5 10.0 675 20.2 10.0 6.3 489 14.7



Calculation:- In order to calculate the flakiness index of the entire sample of aggregates first the weight of

each fraction of aggregate passing and retained on the specified set of sieves is noted. As an

example let 200 pieces of the aggregate passing 50 mm sieve and retained on 50mm sieve be

=W1g. Each of the particles from this fraction of aggregate is tried to be passed through the

slot of the specified thickness of the thickness gauge; in this example the width of the

appropriate gauge of the thickness gauge is :

Let the weight of the flaky material passing this gauge be W1 g. Similarly the weights of the

sections passing and retained the specified sieves, W1, W2, W3 etc. are weighed and the total

weight " W1 + W2 +W3 + '"=W g is found. Also the weights of material passing each of the

specified thickness gauge are found =W1, W2, W3... and the total weight of material passing

the different thickness gauges, W1 + W2 + W3 + '" =W g is found. Then the flakiness index is

the total weight of the flaky material passing the various thickness gauges expressed as a

percentage of the total weight of the sample gauged.

Result:-

Flakiness Index of Aggregate = %



Determining the Ductility Of Bitumen

This test is done to determine the ductility of distillation residue of cutback bitumen, blown

type bitumen and other bituminous products as per IS: 1208 – 1978. The principle is : The

ductility of a bituminous material is measured by the distance in cm to which it will elongate

before breaking when a standard briquette specimen of the material is pulled apart at a

specified speed and a specified temperature.

The apparatus required for this test:

i) Standard mould

ii) Water bath

iii) Testing machine

iv) Thermometer – Range 0 to 44oC, Graduation 0.2oC

Procedure to determine the Ductility Of Bitumen

i) Completely melt the bituminous material to be tested by heating it to a temperature of 75 to

100oC above the approximate softening point until it becomes thoroughly fluid. Assemble the

mould on a brass plate and in order to prevent the material under test from sticking,

thoroughly coat the surface of the plate and the interior surfaces of the sides of the mould

with a mixture of equal parts of glycerine and dextrin. While filling, pour the material in a

thin stream back and forth from end to end of the mould until it is more than level full. Leave

it to cool at room temperature for 30 to 40 minutes and then place it in a water bath

maintained at the specified temperature for 30 minutes, after which cut off the excess

bitumen by means of a hot, straight-edged putty knife or spatula, so that the mould is just

level full. ii) Place the brass plate and mould with briquette specimen in the water bath and

keep it at the specified temperature for about 85 to 95 minutes. Remove the briquette from

the plate, detach the side pieces and the briquette immediately.

iii) Attach the rings at each end of the two clips to the pins or hooks in the testing machine

and pull the two clips apart horizontally at a uniform speed, as specified, until the briquette

ruptures. Measure the distance in cm through which the clips have been pulled to produce

rupture. While the test is being done, make sure that the water in the tank of the testing

machine covers the specimen both above and below by at least 25mm and the temperature is

maintained continuously within ± 0.5oC of the specified temperature.



REPORTING OF RESULTS

A normal test is one in which the material between the two clips pulls out to a point or to a

thread and rupture occurs where the cross-sectional area is minimum. Report the average of

three normal tests as the ductility of the sample, provided the three determinations be within

± 0.5 percent of their mean value.

If the values of the three determinations do not lie within ± 0.5 percent of their mean, but the

two higher values are within ± 0.5 percent of their mean, then record the mean of the two

higher values as the test result.



Free Moisture & Water Absorption Object: - Determine the percentage of free or surface moisture in both fine and coarse

aggregate.

Apparatus: - Balance, minimum capacity of 2000 g, accurate and readable to at least 0.5 g or

0.1% of the mass of the test sample, whichever is greater. Pycnometer, Towel or lint-

free cloth.

Theory: - Free (Surface) Moisture: - The moisture in excess of that required for saturated

surface dry (SSD) condition in aggregate.

Water Absorption: -Water Absorption is the percent of water necessary to add to the

aggregate to obtain saturated surface dry (SSD) condition.

Wet Aggregate: - Wet Aggregate refers to aggregate in the stockpile condition.



Note 1—free moisture and water absorption calculated percentages based upon the

original weight of the aggregate.

Procedure: - 1. Determine the SSD specific gravity.

2. Obtain approximately 1500 g of coarse aggregate, or 1200 g of fine aggregate, in

stockpile moisture condition. Weigh the wet aggregate and record the mass to the

nearest 0.5 gm.

3. Place the wet aggregate in the pycnometer and fill with water at the same

temperature as used to calibrate the pycnometer.

4. Remove all entrapped air from the pycnometer.

5. Dry the outside of the pycnometer and completely fill it with water.

6. Determine the weight of the pycnometer and contents and record the mass to the

nearest 0.5 gm.

Calculations:- Calculate the mass of the pycnometer, containing sample in SSD condition with

water to Fill (Z):- Z=Y+X-(X/G)

Calculate Percent of Free Moisture based on the wet mass of the sample (M):

M=[100*G(Z-Z)] / [X (1XG-1)]

Convert the wet mass to the SSD mass:

SSD Mass = X (100-M)/ 100

Where:

X = mass of the wet sample, g

Z1 = mass of the pycnometer containing wet sample and water,

G = saturated surface-dry specific gravity

Y = mass of pycnometer filled with water (calibration), g.

Result: - Percent of Free Moisture of Coarse Aggregate 0.5%.

Percent of Free Moisture of Fine Aggregate 1%.



road materials testing lab manual by er. hamender singh shekhawat

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