aiv vs protodyakonov method

8/10/2019 Aiv vs Protodyakonov Method

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IMPACT STRENGTH OF BRITTLEIMPACT STRENGTH OF BRITTLEMATERIALS (ROCKS)MATERIALS (ROCKS)

COMPARISONCOMPARISON OF THE PROTODYAKONOVOF THE PROTODYAKONOVANDAND AIVAIV ((AGGREGATE IMPACT VALUEAGGREGATE IMPACT VALUE))

METHODSMETHODS

Kostas Tsakalakis,Kostas Tsakalakis,

School of Mining & Metallurgical EngineeringSchool of Mining & Metallurgical Engineering

National Technical University of Athens, AthensNational Technical University of Athens, Athens--GreeceGreece

ee--mail:mail: [email protected]@metal.ntua.gr

Presented at the Meeting of the Refractory Experts MORE, heldPresented at the Meeting of the Refractory Experts MORE, heldin T.U. Freibergin T.U. Freiberg--Saxony, Germany, 4Saxony, Germany, 4--5 May 20065 May 2006


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AGGREGATESAGGREGATES--PROPERTIESPROPERTIES

They depend on the properties of the parent rock,They depend on the properties of the parent rock,which are:which are:

chemical and mineralogical compositionchemical and mineralogical composition

petrographicpetrographic originorigin

specific gravityspecific gravityhardnesshardness

strength and elasticitystrength and elasticity

physical and chemical stability (behavior)physical and chemical stability (behavior)particle shape and surface textureparticle shape and surface texture

porosity, absorption and permeability andporosity, absorption and permeability and

color.color.


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TESTINGTESTING MECHANICAL PROPERTIESMECHANICAL PROPERTIES OFOF

AGGREGATESAGGREGATESAggregatesAggregates are subjected toare subjected to variousvarious dynamic stressesdynamic stresses((impactimpact,, compressioncompression,, abrasionabrasion))..

It must be thoroughly tested for their mechanicalIt must be thoroughly tested for their mechanicalproperties and their performance.properties and their performance.

Standard methods have been adoptedStandard methods have been adopted ((AA..SS..TT..MM.,., BSBS,,

DD..II..NN.,., etcetc.).)..

In brittle fracture, the cracks run close to perpendicularIn brittle fracture, the cracks run close to perpendicularto the applied stress. This leaves a relatively flat surfaceto the applied stress. This leaves a relatively flat surface

at the break. Besides having a nearly flat fractureat the break. Besides having a nearly flat fracturesurface, brittle materials usually contain a pattern onsurface, brittle materials usually contain a pattern ontheir fracture surfaces. Some brittle materials have linestheir fracture surfaces. Some brittle materials have lines

and ridges beginning at the origin of the crack andand ridges beginning at the origin of the crack andspreading out across the crack surface.spreading out across the crack surface.


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Aggregates iAggregates impactmpact ttestingesting

IImpact testingmpact testing measures the energy required to break ameasures the energy required to break a

specimen by dynamically applying a load.specimen by dynamically applying a load. Impact strength is one of the most commonly tested andImpact strength is one of the most commonly tested and

reported properties ofreported properties of brittle materials in which thebrittle materials in which the

aggregates also belongaggregates also belong..

As theAs the cement and concretecement and concrete industry grows, so do theindustry grows, so do the

number of different methods for measuring impactnumber of different methods for measuring impactstrengthstrength of the aggregatesof the aggregates -- with each method having itswith each method having its

own inherent advantages and disadvantages.own inherent advantages and disadvantages.


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Fracture

Fracture: separation of a body into pieces due to

stress, at temperatures below the melting point.

Steps in fracture: crack formation

crack propagation

Depending on the ability of material to undergo

plastic deformation before fracture,two fracture modes can be defined

ductile or brittle


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Ductile & Brittle Fracture

Ductile fracture - most metals (not too cold):

Extensive plastic deformation ahead of crack

Crack is stable: resists further extension unless

applied stress is increased

Brittle fracture - ceramics, ice, cold metals,

brittle rocks:

Relatively little plastic deformation Crack is unstable: propagates rapidly without

increase in applied stress.


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Fundamental Interpretations of FractureFundamental Interpretations of Fracture

StrainStrain energy approach to fractureenergy approach to fractureThe work (The work (WW) done by a force) done by a force (e.g. falling hammer)(e.g. falling hammer) acting on aacting on asurface (e.g. mass of rock particles)surface (e.g. mass of rock particles) is converted intois converted into::

recoverable elastic energy (recoverable elastic energy (UU) and) and energy which is used for the creation of new surfaces through crenergy which is used for the creation of new surfaces through crackack

propagation, i.e.propagation, i.e.

However, unstable crack growth responsible for brittle fractureHowever, unstable crack growth responsible for brittle fracture resultsresultswhen the incremental change in the difference between the workwhen the incremental change in the difference between the workdone and the elastic energy exceeds the energy requirements fordone and the elastic energy exceeds the energy requirements for thethecreation of a new surface (crack):creation of a new surface (crack):

wherewhere is the surface energy per unit areais the surface energy per unit area ((AA)) andand aa is half theis half the

length of a crack.length of a crack.


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Brittle vs. Ductile Fracture

Ductile materials - extensive plastic deformationand energy absorption (toughness) before

fracture

Brittle materials - little plastic deformation and

low energy absorption before fracture.


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METHODS USED FOR AGGREGATESMETHODS USED FOR AGGREGATES

IMPACT TESTINGIMPACT TESTING Three basic factors contribute to a brittleThree basic factors contribute to a brittle--cleavage type ofcleavage type of

fracture. (fracture. (a)a) triaxialtriaxialstate of stressstate of stress, (, (bb)) a low temperaturea low temperature, and, and

((cc)) a high strain rate or rapid rate of loading (ea high strain rate or rapid rate of loading (e.g. impact.g. impactstress).stress).

All three of these factors do not have to be present at the sameAll three of these factors do not have to be present at the sametime to produce brittle fracture. Atime to produce brittle fracture. A triaxialtriaxial state of stress, suchstate of stress, such

as exists at a notch, and low temperature are responsible foras exists at a notch, and low temperature are responsible formost service failures of the brittle type. However, since thesemost service failures of the brittle type. However, since theseeffects are accentuated at a high rate of loading, many typeseffects are accentuated at a high rate of loading, many typesof impact tests have been used to determine the susceptibilityof impact tests have been used to determine the susceptibilityof materials to brittle behavior.of materials to brittle behavior.

Standard testsStandard tests evaluated hereevaluated here are theare the ProtodyakonovsProtodyakonovs test andtest andthe AIVthe AIV testtest ((Aggregate Impact ValueAggregate Impact Value)) used for theused for thedetermination of the strength of brittle materials (rocks) indetermination of the strength of brittle materials (rocks) in

impact and compression stresses.impact and compression stresses. The materials, whoseThe materials, whoseimpact strength is tested, are limestone, emery and quartzite.impact strength is tested, are limestone, emery and quartzite.


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Operating conditions of the variousOperating conditions of the various

impact test proceduresimpact test procedures

4040

(2 particles)(2 particles)

135135

640640

13501350

Mass of theMass of the

specimen, gspecimen, g

(e.g. 2.7 g/cm(e.g. 2.7 g/cm33))

VaryingVarying0.640.642.42.4ProtodyakonovProtodyakonov

10100.4120.4121515TRETONTRETON

15150.380.3813.513.5--14.014.0AggregateAggregate

impact valueimpact value

(AIV)(AIV)

10100.370.375050SchlagversuchSchlagversuch

Number ofNumber of

blows, Nblows, N

Height ofHeight of

fall, mfall, m

FallingFalling

mass, kgmass, kgMETHODMETHOD


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PROTODYAKONOVSPROTODYAKONOVS

rock strengthrock strength drop testerdrop tester


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ProtodyakonovProtodyakonovs tests test

For the prediction of theFor the prediction of the ProtodyakonovProtodyakonov rockrockstrengthstrengthcoefficientcoefficient FFNN, by the modified from the U, by the modified from the U..SS.. BureauBureauof Minesof Mines methodmethod,, a sample of total weighta sample of total weight ((gg)) equal toequal to

7575 timestimes of theof the specific gravity of the rockspecific gravity of the rock ((gg//cmcm33)) isissuitably preparedsuitably prepared..

Every sample consists of ten (10) irregularly shapedEvery sample consists of ten (10) irregularly shaped

particles weighing aboutparticles weighing about 2020 gg each, depending on theeach, depending on thespecific gravity of the material testedspecific gravity of the material tested..

For every test, two particles (For every test, two particles (40 g)40 g) are put on theare put on thebottom of thebottom of the Rock strength drop testerRock strength drop tester and areand arecrushed by a specific number N of hammer drops. Thecrushed by a specific number N of hammer drops. Theparticles suffer strains and fatigue like those of brittleparticles suffer strains and fatigue like those of brittlematerialsmaterials..


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ProtodyakonovProtodyakonovs test (contd)s test (contd)

The strength of each specimen (2 particles) isThe strength of each specimen (2 particles) istested by using, progressively, an increasingtested by using, progressively, an increasingnumber of drops (e.g. 5, 10, 15, 20, 25). Eachnumber of drops (e.g. 5, 10, 15, 20, 25). Eachcrushed sample is sieved through a U.S.crushed sample is sieved through a U.S.series No. 35 mesh (0.5 mm) sieve and theseries No. 35 mesh (0.5 mm) sieve and the

mass of themass of the --0.5 mm material produced is0.5 mm material produced isdetermined.determined.

he solid volume (Vhe solid volume (VNN) of the undersize) of the undersize

material is determined from the ratio of thematerial is determined from the ratio of themass (mass (WWNN) and the specific gravity () and the specific gravity () of the) of thematerial.material. ((VV

== WW

/ )./ ).


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The number of drops (N), used to produce the certain volumeThe number of drops (N), used to produce the certain volume

(V(VNN) of) of --0.5 mm material, divided by the volume V0.5 mm material, divided by the volume VNN gives thegives the

value of the impact rock strength coefficient (value of the impact rock strength coefficient (FFNN) for this) for this

particular number of drops.particular number of drops.

Thus, theThus, the ProtodyakonovsProtodyakonovs impact strength coefficientimpact strength coefficientFF

,, forfor

a specific numbera specific number of the hammer falls, is given byof the hammer falls, is given by::

FF

= /= / VV

Where:Where:

is the number of the free fallsis the number of the free falls

andand VV is the mean solid volumeis the mean solid volume of theof the00..55 mmmm material producedmaterial produced

afterafter hammer drops.hammer drops.


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After completing the test procedure for all specimens, a graphAfter completing the test procedure for all specimens, a graph((FF

,, ) is constructed.) is constructed.

The rock strength coefficientThe rock strength coefficient FFNN is graphically determinedis graphically determinedfrom the curve (from the curve (FF

,, ) and corresponds to the minimum) and corresponds to the minimum

value of the curve.value of the curve. This minimum value ofThis minimum value of FFNN is, by definition, the impact rockis, by definition, the impact rock

strength coefficient (strength coefficient (FFNN), as representing the optimum), as representing the optimumspecific crushing energy (minimum impact energy per unitspecific crushing energy (minimum impact energy per unit

volume ofvolume of --0.5 mm material).0.5 mm material).FFNN has dimensions cmhas dimensions cm--33..

It has been previously proved that it correlates with relativeIt has been previously proved that it correlates with relativeaccuracy with the mechanical properties of the rock, such as:accuracy with the mechanical properties of the rock, such as:

ToughnessToughness Modulus of resilienceModulus of resilience

UniaxialUniaxial compressive strengthcompressive strength

Shore hardness andShore hardness and

DriDri

lllabilitylability

of the rockof the rock



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ProtodyakonovProtodyakonovs test (modification)s test (modification)

Here, aHere, a modified proceduremodified procedure is proposed for theis proposed for thedetermination of thedetermination of the ProtodyakonovsProtodyakonovs rock strengthrock strength

coefficientcoefficient FFNN..

The modification, applied to the procedure adopted byThe modification, applied to the procedure adopted by

the U.S. Bureau of Mines, is shown in thethe U.S. Bureau of Mines, is shown in the flowflow

diagramdiagram of the next slide.of the next slide.

From theFrom the FFNN values corresponding to each productvalues corresponding to each product

(undersize material), graphs ((undersize material), graphs (FFNN , N), similar to those, N), similar to those

shown in the following slides, are constructed.shown in the following slides, are constructed.

Then, the minimumThen, the minimum FFNN values are graphicallyvalues are graphically

determined.determined.


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SPECIMEN (2 Particles)

Mass 40 g

1st Test

(5 Hammer drops)

Classification in size

fractions

Recombination of the

size fractions

2nd Test

(10 Hammer drops)

Classification in sizefractions

Recombination of the

size fractions

Final Test (e.g. 45

Hammer drops)

Classification in sizefractions

Weighing &FNprediction

3rd Test etc.

Protodyakonovs Test (New modification)


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ProtodyakonovsProtodyakonovs

IMPACTIMPACT

STRENGTHSTRENGTH

COEFFICIENTCOEFFICIENT

of Limestoneof Limestone

0

0,20,4

0,6

0,8

11,2

1,4

1,6

1,8

2

2,2

2,4

2,6

2,8

3

5 10 15 20 25 30 35 40 45

Number of free falls (drops),

Protody

akonovimp

actstrength

coefficientF

(numberoffreefalls/cm

3)

2 1 0,5 0,25


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IMPACTIMPACT

STRENGTHSTRENGTHCOEFFICIENTCOEFFICIENT

of Emeryof Emery

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

5 10 15 20 25 30 35 40 45Number of free falls (drops), N

Protodyako

novimpacts

trengthcoeff

icientF(

number

offreefalls/cm

3)

2 1 0,5 0,25


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IMPACTIMPACT

STRENGTHSTRENGTH

COEFFICIENTCOEFFICIENT

of Quartziteof Quartzite

00,2

0,40,60,8

11,2

1,41,61,8

22,2

2,42,62,8

3

5 10 15 20 25 30 35 40 45

Number of free falls (drops), Protodyako

nov

im

pactstrength

coefficien

t

F

num

bero

ffree

falls

/cm

3

2 1 0,5 0,25


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PROTODYAKONOVSPROTODYAKONOVSImpact strengthImpact strength

((size fractionsize fraction --22

mm)mm)

Comparison ofComparison of

LimestoneLimestoneEmeryEmery

QuartziteQuartzite


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TestTest AIVAIV ((Aggregate Impact Value,Aggregate Impact Value,

SSSS19741974))

TheThe

AIVAIV

((Aggregate Impact ValueAggregate Impact Value

))

is ais a

standard test procedurestandard test procedureby which the impactby which the impact

strength of aggregates is testedstrength of aggregates is tested.. Just like inJust like in

ProtodyakonovsProtodyakonovs test, the material usedtest, the material usedconsists of irregularly shaped particles ofconsists of irregularly shaped particles of

thethe --1144 + 10+ 10 mm size fractionmm size fraction.. The weightThe weightof the specimen isof the specimen isAA..


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AIVAIV

ApparatusApparatus


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Aggregate impact value (AIV) testAggregate impact value (AIV) test

procedureprocedure

The two (2) specimens tested are subjected to 15The two (2) specimens tested are subjected to 15

blows of the hammer dropping 380 mm, at an intervalblows of the hammer dropping 380 mm, at an intervalnot less than one second.not less than one second.

The crushed material is removed from the mould andThe crushed material is removed from the mould and

then it is sieved over a 2.36 mm sieve. The mass ofthen it is sieved over a 2.36 mm sieve. The mass ofthe material passing (the material passing (BB) and the retained fraction on) and the retained fraction on

the sieve (the sieve (CC) are weighed to the nearest 0.1 g.) are weighed to the nearest 0.1 g.

IfIfAA--((BB++CC)>1 g, the result is discarded and the test is)>1 g, the result is discarded and the test isrepeated with fresh material. The AIV value isrepeated with fresh material. The AIV value is

calculated from the average of the two tests:calculated from the average of the two tests:

(%)100)/( = ABAIV


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ConclusionsConclusions

Applying theApplying the ProtodyakonovsProtodyakonovs test proceduretest procedurefor the determination of the impact strength offor the determination of the impact strength of

the three rocks results in:the three rocks results in:

The impact rock strengthThe impact rock strength ((FF

)) of quartzite isof quartzite islower than that of limestone, for all sizelower than that of limestone, for all sizefractionsfractions testedtested.. This obviously happens,This obviously happens,

because the quartzite presents greater brittlenessbecause the quartzite presents greater brittlenessthan the limestone.than the limestone.

Emery, as it was expected, presents greaterEmery, as it was expected, presents greaterimpact strength than the other rocks examined.impact strength than the other rocks examined.


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ConclusionsConclusions ((contcontdd))

The rock impact strength, according to theThe rock impact strength, according to the

AIV method, shows the same tendency ofAIV method, shows the same tendency ofthat presented by thethat presented by the ProtodyakonovsProtodyakonovs

resultsresults..

The percentage % mass lossThe percentage % mass loss ((--2.362.36 mmmm))

calculated from the AIV method is: onlycalculated from the AIV method is: only

3.68%3.68% for thefor the emery andemery and 9.569.56,, 1313..6%6% forforthe limestone and the quartzite,the limestone and the quartzite,

respectively.respectively.


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COMPARISON OF THE TWOCOMPARISON OF THE TWO

METHODSMETHODS

9.5813.620.292.68Quartzite

12.549.560.512.65Limestone

56.73.684.313.48Emery

AIV,

2.36 mm

Protodyakonov,

2 mm

Bond workindex Wi ,

kWh/short ton

Impact strength for 15

hammer falls (drops)Specificgravity,

g/cm3Material


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The two methods use irregularly shapedThe two methods use irregularly shapedspecimens (particles).specimens (particles).

Thus, they present certain advantages over theThus, they present certain advantages over thealternative standard testsalternative standard tests ((compressioncompression tensiletensileteststests)) in which regularly shaped specimensin which regularly shaped specimens(cylinders, cubes)(cylinders, cubes) are required. The alternativeare required. The alternativemethods present increased cost and are timemethods present increased cost and are time--consuming for performing the tests.consuming for performing the tests.

TheThe ProtodyakonovsProtodyakonovs method can also be utilizedmethod can also be utilizedfor the determination of the impact strength offor the determination of the impact strength ofother brittle materials (ceramics, cold metals,other brittle materials (ceramics, cold metals,

etc.).etc.).


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TheThe AIV methodAIV method is preferableis preferable than that ofthan that of

ProtodyakonovProtodyakonov for afor a roughroughprediction of theprediction of the

impact strength of the rocks, becauseimpact strength of the rocks, because::

The AIVThe AIV method is simpler in its application than themethod is simpler in its application than the

ProtodyakonovsProtodyakonovs ((except sizing, no need for particleexcept sizing, no need for particlesize preparationsize preparation of the test sampleof the test sample isis requiredrequired))

TheThe AIV method can be ranked asAIV method can be ranked as more reliable duemore reliable dueto the greaterto the greater mass of the sample testedmass of the sample tested ((atat leastleast 1515

times that used intimes that used in ProtodyakonovsProtodyakonovs testtest))..


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Thank you very muchThank you very much

VielenVielen Dank aufDank auf ihreihre

AufmerksamkeitAufmerksamkeit

aiv vs protodyakonov method

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