Testing Of Physical-mechanical Properties Of Coarse Aggregate, Used For .
TESTING OF PHYSICAL-MECHANICAL PROPERTIES OF COARSEAGGREGATE, USED FOR PRODUCING ASPHALT MIXTURES,AND ANALYSIS OF TEST RESULTSMatas Bulevičius1, Kazys Petkevičius2, Daiva Žilionienė3, Karina Drozdova41SE “Problematika”, Galves str. 2, LT-2028 Vilnius, Lithuania. E-mail: matas.bulevicius@vgtu.ltDept of Roads, Vilnius Gediminas technical university, Saulėtekio ave. 11, LT-10223 Vilnius, Lithuania.E-mails: 2kk@vgtu.lt; 3daizil@vgtu.lt4SJSC Latvian State Roads, Road laboratory, Gogola str. 3, LV-1050 Riga, Latvia. E-mail: karina@lvcelu.lv2, 3Abstract. In Lithuania investigation of various physical-mechanical properties of aggregate by using test methods ofEU standards was started already in 2004. A lot of tests were carried out for different type of aggregates of differentmanufacturers to determine resistance of aggregate to freezing and thawing (F value) according to EN 1367-1, resistance to fragmentation (SZ and LA values) according to EN 1097-2 and the polished stone value PSV according to EN1097-8. Taking into consideration aggregates, available in Lithuania and used in road building, the suitability testsand requirements for their properties were described. Based on the tests of rocks of the same origin and on the analysis of results obtained the relationship between F, LA, SZ and PSV physical and mechanical values was identified.When investigating aggregates used in road building the suitability of each test method was assessed for Lithuanianclimatic conditions. It was determined that the assessment of aggregate suitability by use of freezing and thawing testis not suitable to Lithuanian climatic conditions. Investigated aggregates are suitable not only for asphalt concretepavement and road pavement structure base layers, but can be used to transport construction, and building on thefoundations of watertight clay soils in place if there are of good filtration.Keywords: aggregates, physical properties, asphalt pavement, strength, asphalt mixtures, resistance to freezing andthawing, fragmentation, polished stone value.Introductiondependent on its mechanical and physical properties.Aggregate properties determine the mode of productionof asphalt mixture, the thickness of structural pavementlayers and other peculiarities of road pavement structure.Thus, when selecting aggregate the working conditions(loads, environment, operating requirements) of roadpavement structure shall be analyzed and the aggregateselected shall the best correspond to performance parameters. In each case selection of aggregate shall be economically justified. The selected aggregate shall be cheapand easily available. When a stronger aggregate is usedthe service life of road pavement structure is longer, thestructure is more reliable, the individual structural pavement layers are more thin, the costs of aggregate andother materials are lower, etc. Often the aggregate is selected not because of its better properties but because it ischeaper.Therefore, a special attention should be given to theselection of components of asphalt mixture, i.e. to carryout comprehensive investigations of all components ofasphalt mixture and the quality (suitability) control of theDefects of road pavement caused by the impact ofheavy vehicles influence functionality of road pavement,driving comfort and traffic safety. In order to improve theproperties of road pavement and the quality of traffic thescientists of Lithuania and various countries carry outinvestigations of structural pavement layers, analyze theeffect of their properties on pavement performance, mechanical and physical properties of asphalt mixtures usedfor structural pavement layers, etc. Aggregates (crushedstone, dolomite, gravel) differ in their size, shape andworking conditions of the material which depend on thesize and nature of loads, working temperature, environmental aggressiveness, etc. The aggregate can be affectedby static, dynamic, permanent, variable or cyclic loads.The temperature of working environment can be low orhigh, and the environment itself – neutral or agressive.Mechanical and physical properties of aggregate, used forproducing asphalt mixture, influence the quality indicesof pavement structure, i.e. functionality, reliability anddurability. Aggregate suitability to asphalt mixtures is1094
mixtures. At present, in Lithuania the aggregates of asphalt mixtures are selected according to the requirementsof TRA MIN 07:2007 „Description of technical requirements for the aggregates of motor roads“.A wearing course of asphalt pavement has a directcontact with vehicle wheel tyre, and the laid asphalt mixture is directly affected by traffic loads. Therefore, inorder to ensure a proper service of asphalt pavement under certain climatic conditions and mechanical impactswhen producing asphalt mixtures it is necessary to useaggregates with especially good mechanical and physicalproperties. Resistance of rock to the climatic and mechanical impacts and rock durability are assessed by thetests according to LST EN 1367-1:2007 „Tests for thermal and weathering properties of aggregates– Part 1:Determination of resistance to freezing and thawing“,LST EN 1097-2:2001 “Tests for mechanical and physicalproperties of aggregates – Part 2: Methods for the determination of resistance to fragmentation“, LST EN1097-8:2009 „Tests for mechanical and physical properties of aggregates – Part 8: Determination of the polishedstone value“ and LST EN 1097-2:2001 test by two methods: Los Angeles Test and Impact Test.Since there is no sufficient number of investigationsof coarse aggregate suitability for asphalt mixtures thisarticle gives the analysis of investigations of physical andmechanical properties of coarse aggregate that were performed in Lithuania.Fig 1. Freezertests of 79 specimens of different type of rock (granite,dolomite and gravel) were carried out. When analyzingand assessing the obtained coarse aggregate test results F1and F2 category for asphalt mixtures was selected, forexample, F1 when the mass loss is 1%. The percentagemass loss F is determined by the following formula:Tests of physical and mechanical properties of coarseaggregatesF One of physical and mechanical properties of coarseaggregate used for a wearing course of asphalt pavementis the resistance to repeated freezing and thawing cycles(in Lithuania 40–70 cycles). When the temperature dropsbelow zero the ice crystals, having formed in micro-poresof coarse aggregate of asphalt mixture, destroy the rock,therefore, asphalt pavement loses its strength properties.Resistance of coarse aggregate to freezing and thawingwas determined using water immersion test with 31.5/63mm size fraction material, and the coarsest grain of material that was used for asphalt mixture was 31.5 mm.During the resistance to freezing and thawing test three8/16 mm fraction test portions were subjected to investigation. The mass of each test portion– 2000 g 0.2 g.Specimens were stored at atmospheric pressure for(24 1) h in the cans at (20 5) C, in distilled water.After immersion the cans with water and samples wereplaced in the freezer (Fig 1) to conduct a series of 10freeze – thaw cycles. The obtained test result shows apercentage mass loss of the specimen after the test and isexpressed in categories. According TRA MIN 07:2007result of the freeze – thaw test is indicated by F1, F2 andF4 where the values are whole numbers representing themass loss in percent after the test.10 freezing-thawing cycles were performed according to the LST EN 1367-1:2007 test method at the varyingtemperature from 20 C to – 17.5 C. In order to determine this physical property of coarse aggregate theM1 M 2 100,M1(1)where M1 – the initial dry total mass of the three testspecimens, in grams, M2 – the final dry total mass of thethree test specimens that is retained on the specified sieve, in grams, F – the percentage loss in mass of the threetest specimens after freeze – thaw cycling.Fig 2. Results of tests to determine resistance to freezing and thawing (F value)Fig 2 gives the results of test to determine resistanceto freezing and thawing grouped by the type of rock(granite, dolomite, gravel), and the permissible mass lossis represented by the limits of corresponding categories1095
(limit F1 value and limit F2 value) selected according tothe use of coarse aggregate in asphalt pavement layers.The results of resistance to freezing and thawing ofthe tested coarse aggregate specimens are very good and100 % meet the requirements of F1 and F2 for asphaltpavement. 91 % of crushed granite results do not exceed1/10, 80 % of crushed dolomite results do not exceed 1/5F1. All the results of crushed gravel tests get between F1and F2.One of the most accurate tests to determine coarseaggregate strength is the test of resistance to fragmentation in accordance with LST EN 1097-2:2001. The mainmethod of this test lies in the determination of resistanceto crushing by use of the Los Angeles Test method, however, in Lithuania the most frequently used is the alternative Impact Test method. In order to comprehensivelydetermine the strength of coarse aggregate and to find outa relationship between the methods of this test the specimens were tested by both methods. LA and SZ valuesshow the same property of the material being tested butthe methods of tests are different. In the Los Angeles testmethod of coarse aggregate, 10/14 mm size fraction(5000 5) g specimen together with ten steel balls, eachØ 45–49 mm in diameter and weighing in total 4690–4860 g, was rotated for 500 revolutions at a constantspeed of 31–33 min-1 in a closed drum. In the Impact Testmethod 8/12.5 mm size fraction specimen was crushed 10times by a weight falling from 370 mm height. After thetests the percentage mass loss of material, having passedthe control sieve, was calculated. Using the Los AngelesTest method it is allowed by the standard to test alsoother aggregate fractions alternative to the standard 10/14mm size, whereas, the Impact Test method allows to testonly one 8/12.5 mm size course aggregate fraction.Therefore, when using the Los Angeles Test method a10/14 mm size fraction of coarse aggregate was selected,and when using SZ method – 8/12.5 mm coarse aggregatefraction. The test results were assessed according to theirconformity to the categories. The coefficients are respectively indicated as LA20, LA25, LA30, LA40 and LA50 wherethe indices 20, 25, 30, 40 or 50 show the percentage massloss after the test, for example, LA20 when the mass loss is 20%, and SZ18, SZ22, SZ26, SZ32, and SZ35 where theindices 18, 22, 26, 32 or 35 show the percentage massloss of material having passed 5 control sieves, for example, SZ18 when the mass loss is 18 %. The Los AngelesCoefficient LA is calculated by the formula:5000 mLA ,50(2)where m – retained mass on a 1,6 mm sieve, g.Schlagversuch Impact Test value SZ is calculated as:SZ M5 %,(3)where M – the sum of percentage mass passing 5 testsieves.In course of this test 238 specimens of the same rock(granite, dolomite and gravel) were tested. By the LosAngeles Test method 49 tests were carried out, and by theImpact Test method – 189 tests.Figs 3 and 4 give the results of test to determine resistance to fragmentation grouped by the type of rock(granite, dolomite, gravel), and the permissible mass lossis represented by the limits of corresponding categories(limit LA values and limit SZ values), selected accordingto the use of coarse aggregate in asphalt pavement layers.Fig 3. Results of tests to determine resistance to fragmentation by the Los Angeles Test methodFig 4. Results of tests to determine resistance to fragmentation by the Impact Test method100 % meet the requirements of F1 and F2 for asphalt pavement. 91 % of crushed granite results do notexceed 1/10, 80 % of crushed dolomite results do notexceed 1/5 F1. All the results of crushed gravel tests getbetween F1 and F294 % of coarse aggregate specimens, tested by theLA method, meet the requirements of LA20 for asphaltpavement. 88 % of the results of crushed dolomite specimens get between LA20 and LA25. The limit of LA30 requirements is exceeded by 33% of all crushed gravelspecimens. The requirements for asphalt pavement aresatisfied by 69 % of all the coarse aggregate specimenstested by the Impact Test method. The limit of SZ18 isexceeded by 27 % of the tested crushed granite speci-1096
mens, the limit of SZ22 is exceeded by 36 % of the testedcrushed dolomite specimens, and the limit of SZ26 is exceeded by 23 % of the crushed gravel specimens.The Polished Stone Value (PSV) Test is one of thenewest tests of coarse aggregate strength that is carriedout in Lithuania. The aim of this test was to determine thesuitability of material used in asphalt mixtures of pavement wearing course and enabled to determine stoneresistance to the wear-out under the action of the roadvehicle tyre. In course of this test 18 specimens wereplaced in the conditions similar to those occurring onasphalt pavement under the action of vehicle tyres. PSV isindicated by: PSV44 and PSV50 where indices 44 and 50represent the obtained PSV value exceeding the numberof index, for example, PSV50 when PSV value is 50.Determination of the PSV was carried out for thespecimens formed from 7/10 mm size fraction of crushedstone and glued into a mould of (90.6 0.5) mm lengthand (44.5 0.5) mm width, with the radius of 203 1.5 mm (Figs 5, 6).Fig 7. PSV mechanismAfter polishing cycles which lasted for 6 h thespecimens were taken out from the testing wheel and thesurface roughness of specimens was measured by use ofpendulum (Fig 8).Fig 5. SpecimenFig 8. PendulumThe results obtained were compared to the readingsof control PSV stone. The PSV was calculated to thenearest whole number by the following equation:Fig 6. MouldPSV S (52.5) C, (4)Then, the specimens were polished by a rubber(200 3) mm diameter “road wheel” under the load of(725 10) N. During the test the specimens were coveredwith corn emery, later with emery flour and water(Fig 7.).where S – the mean value for the four aggregate testspecimens, C – the mean value for the four PSV controlstone specimens.Since in most cases only the crushed granite (in rarecases crushed dolomite) is used for the wearing course,1097
thus, the Polished Stone Value Test was carried out onlyfor the specimens of these rocks. 18 PSV tests were performed. For the analyses of the results obtained the suitable categories (PSV44 and PSV50) for asphalt mixtureswere selected used in asphalt pavement. The results oftests for the determination of the polished stone value aregiven in Fig 9. The results are grouped by the type ofrock (granite, dolomite), and the limit PSV value showsthe limits of these categories. The limits were selectedaccording to the use of coarse aggregate in the structuralroad pavement layers.limits of resistance to freezing and thawing categories orto use another alternative test method.The results of the mentioned tests showed that whentesting the same aggregate according to LST EN 10972:2001 by use of the Los Angeles Test and the ImpactTest methods, most often the obtained LA value is lower.This indicates that the physical property of rock of itsresistance to crushing in the Los Angeles Test method isstronger than in the Impact Test method. TRA MIN07:2007 indicates that for the same asphalt mixture theLA category is lower than the correspondent SZ category.This means that those categories has been nonrepresentively equated. When assessing the strength propertiesof aggregate used in Lithuania the Impact Test method ismore acceptable than the Los Angeles Test method.It was determined by the test according to LST EN1097-8:2009 that a more frequent use of crushed granitefor the wearing course of road pavement is a good solution. When the crushed dolomite gets moist it becomesespecially nondurable and the surface becomes weak.When using crushed dolomite in asphalt mixtures theroad pavement rapidly losses roughness, becomes evenand due to insufficient skid resistance causes danger totraffic.ReferencesFig 9. Results of tests to determine PSVThe largest part, i.e. 83 % of the specimens tested,meets the requirements for PSV50 and PSV44 of asphaltpavement. All the crushed granite specimens meet thehighest category of PSV50. 17 % of the tested crusheddolomite specimens exceed the limit PSV44 value.ConclusionsIn order to assess the suitability of physical properties of aggregates used in asphalt mixtures it is necessaryto determine their resistance to freezing and thawingcycles, resistance to fragmentation by the Los Angelesand the Impact Test methods and the polished stonevalue.The test according to LST EN 1367-1:2007 showedthat even weak rocks (dolomite, gravel) do not exceed thepermissible 2 % mass loss. Whereas, the other strengthindices of the same specimens LA, SZ and PSV do notmeet the requirements to coarse aggregate used in asphaltmixtures. Therefore, the LST EN 1367-1:2007 testmethod does not allow to properly determine the strengthof coarse aggregate. A number of 10 freezing and thawing cycles as specified in the test method is too small toassess the resistance of rock used under the aggressiveLithuanian weather conditions, and the limits of categories F1, F2 and F4 are too wide. In order to improve theassessment of this property it is necessary to revise theBhasin, A.; Castelo Branco, V. T. F.; Masad, E; Little, D. N.2009. Quantative comparison of energy methods to characterize fatigue in asphalt materials, Journal of MaterialsCivil Engineering 21(2): utkevičius, S.; Petkevičius, K.; Kamaitis, I.Z. 2007. Evaluation of flexible road pavement construction state using objective strength criteria, The Baltic Journal of Road andBridge Engineering 2(2): 61–66.Ceylan, H.; Schwartz, C.W.; Kim, S.; Gopalakrishuan, K. 2009.Accuracy of Predictive Models for dynamic Modulus ofhot Mix asphalt, Journal of Materials in Civil Engineering 21(6): 6)Petkevičius, E.; Laurinavičius, A.; Petkevičius, R.; Babickas, R.2009. Effect of components content on properties of hotmix asphalt mixture and concrete, The Baltic Journal ofRoad and Bridge Engineering 4(4): evičius, K.; Sivilevičius, H. 2008. Necessary measures forensuring the quality of hot mix asphalt in Lithuania, TheBaltic Journal of Road and Bridge Engineering 3(1): 29–37. doi:10.3846/1822-427X.2008.3.29-37Radziszewski, P. 2007. Modified asphalt mixtures resistance topermanent deformation, Journal of Civil Engineering andManagement 13(4):307–315.Vaitkus, A.; Čygas, D.; Laurinavičius, A.; Perveneckas, Z.2009. Analysis and evaluation of possibilities for the useof warm mix asphalt in Lithuania, The Baltic Journal ofRoad and Bridge Engineering 4(2): 80–86.doi:10.3846/1822-427X.2009.4.80-861098
1094 TESTING OF PHYSICAL-MECHANICAL PROPERTIES OF COARSE AGGREGATE, USED FOR PRODUCING ASPHALT MIXTURES, AND ANALYSIS OF TEST RESULTS Matas Bulevi ius1, Kazys Petkevi ius2, Daiva Žilionien 3, Karina Drozdova4 1SE "Problematika", Galves str. 2, LT-2028 Vilnius, Lithuania.E-mail: matas.bulevicius@vgtu.lt
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