marshall properties of dbm mix design - ijerst · specification as per morth table-500-18 test...

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Int. J. Engg. Res. & Sci. & Tech. 2016 Deepesh Kumar Singh Lodhi and R K Yadav, 2016

EFFECT OF GRADATION OF AGGREGATES ONMARSHALL PROPERTIES OF DBM MIX DESIGN

Bituminous mixes are most commonly used all over the world in flexible pavement construction.It consists of asphalt or bitumen used as a binder and mineral aggregate which are mixedtogether, laid down in layers and then compacted. Dense Bituminous Macadam (D.B.M.) usedfor air field or roadways to prepared bituminous bound surface. The thickness of a single layershall be 50 mm to 100 mm. The strength serviceability requirements of Bitumen mixes such asstability, flow, voids in mineral aggregate, voids filled with bitumen and air voids are highly dependon the physical properties of aggregate. Dense Bituminous Macadam (D.B.M.) mix having densegrading specification as per Ministry of Road Transport and Highways (MoRTH) has been usedas a bituminous course in a pavement structure to distribute stresses caused by heavily trafficloading and to protect underlying unbound layers from the effect of water. It is important toanalyze that how the variation in aggregate gradation within the specified limits can affect theessential mix design properties of Dense Bituminous Macadam (D.B.M.) mix. In order to studythis aspect five aggregate gradation for D.B.M. mixes were prepared at 4%, 4.5%, 5% bitumencontent. The gradation used correspond to Lower Grade (L.G.), Lower Middle Grade (L.M.G.),Middle Grade (M.G.), Higher Middle Grade (H.M.G.), Higher Grade (H.G.) of the gradation rangespecified by MoRTH. By evaluating the Marshall properties of the D.B.M. mixes with differentgradation result indicate that the performance of mixes made with middle gradation showshigher Marshall Stability value than other mixes and Optimum Bitumen Content (O.B.C.) is alsominimum at this gradation range. The Flow values obtained is maximum for the Lower MiddleGrade (L.M.G.) and Voids Filled with Bitumen (V.F.B.) is also maximum at Lower Middle Grade(L.M.G.).

Keywords: Aggregate gradation, Dense bituminous macadam, Marshall properties, MoRTH

INTRODUCTIONGrowth of good road infrastructure is thebackbone of the transportation system and is the1 Student, M.E. Geo-technical Engineering, Department of Civil Engineering, Jabalpur Engineering, College Jabalpur, India.2 Associate Professor, Department of Civil Engineering College Jabalpur, India.

Int. J. Engg. Res. & Sci. & Tech. 2016

ISSN 2319-5991 www.ijerst.comVol. 5, No. 2, May 2016

© 2016 IJERST. All Rights Reserved

Research Paper

key element of economy of country. About 98%of the paved roads in India have flexiblepavements. Coarse aggregate is prime material

Deepesh Kumar Singh Lodhi1* and R K Yadav2

*Corresponding Author: Deepesh Kumar Singh Lodhi [email protected]

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in pavement construction. Coarse and fineaggregate acts as the structural skeleton ofpavements while asphalt function as the gluefor the mixture. India has a road network of over4.69 million kilometers, second large roadwaysin the world. The bituminous mix design aimsto determine the proportion of bitumen, filler,fine aggregates, and coarse aggregates toproduce a mix which is workable, strong,durable and economical. An aggregate’sparticle size distribution, or gradation, is one ofits most influential characteristics. In hot-mixasphalt, gradation helps to determine almostevery important property including stiffness,stability, durability, permeability, workability,fatigue resistance, and resistance to moisturedamage. Gradation is usually measured by asieve analysis. D.B.M. mix is a heterogeneousmaterial that consists of aggregate, filler,bitumen binder, stone dust and air voids. Theparticle size distribution, or gradation, ofaggregates is most important factor that affectsthe whole performs of the pavement material.Gradation is one of most influence factors forMarshall Properties of DBM mix, so it requiredto select best aggregates gradation. The bestgradation is that gradation of aggregates whichgives the highest density. When fine particlesare properly packed between coarser particles,which reduces the voids space between to aspecified limit particles is called as Bestgradation. In the present study five gradationLower Grade (L.G.)., Lower Middle Grade(L.M.G.), Middle Grade (M.G.), Higher MiddleGrade (H.M.G.), Higher Grade (H.G.) were usedwithin the range specified by Ministry of RoadTransport and Highways (MoRTH) at 4%, 4.5%,5% bitumen content, Marshall mixes wereprepared and tested for its properties.

BACKGROUND LITERATUREChowdhury et al. (2001) reported that theperformance of a bituminous mixture dependson external and internal conditions; the externalconditions being traffic load and environmentaland the internal conditions being properties of thematerials, structure of the mixture, design of themixture, and process of the construction. BrijeshKumar (2013) conclude that “Marshall retainedstability of BC mix used in road construction byadding cellulose fiber.” He added cellulose fibreto bituminous concrete mix and evaluate thevarious mix properties like Marshall Stability, flowvalue, bulk density, void in the mix and VFB andthe result indicates that flexible pavement withhigh performance and durability can be obtainedwith 0.5% Cellulose fibre in Bituminous concrete.Coree and Hislop et al. (2000) reported thatBituminous mixture consists of bitumen binder,aggregates and air voids. The properties of abituminous mixture depend on the quality of itscomponents, the construction process, and themix design proportions. Roberts et al. (1996)suggested that gradation is perhaps the mostimportant property which affects almost all theimportant properties of a bituminous mixture,including stiffness, stability, durability, permeability,workability, fatigue resistance, frictionalresistance, and resistance to moisture damage.Fred et al. (1967) reported that aggregategradation appeared to have more influence thanaggregate type. He also concluded that thetemperature susceptibility characteristics of theasphalt appear to have more influence at longertime of loading.

MATERIALS USEDAggregatesThere are various types of mineral aggregates

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used to manufacture bituminous mixes can beobtained from different natural sources such asglacial deposits or mines and can be used withor without further processing. The aggregates canbe further processed and finished to achieve goodperformance characteristics. Industrial by-products such as steel slag, blast furnace slag,fly ash, etc., sometimes used by replacing naturalaggregates to enhance the performancecharacteristics of the mix. Aggregate contributesup to 90-95% of the mixture weight andcontributes to most of the load bearing andstrength characteristics of the mixture. Hence,the quality and physical properties of theaggregates should be controlled to ensure a goodpavement. Aggregates are of three types;

Coarse AggregatesThe aggregates retained on 4.75 mm sieve arecalled as coarse aggregates. Coarse aggregateshould be screened crushed rock, angular inshape, free from dust particles, clay, vegetationsand organic matters which offer compressive and

shear strength and shows good interlockingproperties. In present study, stone chips are usedas coarse aggregate with specific gravity 2.67-2.72 shown in Table 1.

Fine AggregatesFine aggregate should be lean screened quarrydusts and should be free from clay, loam,vegetation or organic matter. Fine aggregates,consisting of stone crusher dusts were collectedfrom a local crusher with fractions passing 4.75mm and retained on 0.075 mm IS sieve. It fillsthe voids in the coarse aggregate and stiffensthe binder. In this study, fine stones and slag areused as fine aggregate whose specific gravityhas been found to be 2.78 shown in Table 1.

FillerAggregate passing through 0.075 mm IS sieve iscalled as filler. In bitumen mixes there is differenttype of fillers were used like limestone dust,cement, stone dust, brick dust, silica fume ormarble dust cement, fly ash and Stone dust are

S. No. Description of TestSpecification as per MORTH

Table-500-18Test Method Test Result

1 Aggregate Crushing Value (%) Max 10-25 IS-2386 (P IV) 18.40%

2 Aggregate Impact Value (%) Max 24% IS-2386 (P IV) 19.50%

3 Loss Angles Abrasion (%) Max 30% IS-2386 (P IV) 24.20%

4 Water Absorption Max 2% IS-2386 (P III) 0.75%

Specific gravity

26.5 mm

10 mm 2.67

Dust 2.72

Lime 2.78

2.4

6 Stripping Min. retained coating 95% IS-6241-1971 96.50%

5 2.5-3.0 -

Table 1

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S. No. Description of TestSpecification as per IS: 73

(2007)Test Method Test Result

1 Penetration Value of bitumen 50-70 mm IS-1203 56 mm

2 Ductility Min. 40 cm IS-1208 90 cm

3 Specific Gravity Min.0.99 IS-1202 1.025

4 Softening Point >47 °C IS-1205 52 °C

5 Viscosity at 135 °C Min.350 cSt IS-1206 360 cSt

Table 2

Grading 2

Nominal aggregates ize

25 mm

Layer Thickness 50-75 mm

IS Sieve (mm) Cumulative aggregate pass ing %

45 -

37.5 100

26.5 90-100

19 71-95

13.2 56-80

9.5 -

4.75 38-54

2.36 28-42

1.18 -

0.6 -

0.3 7-21

0.15 -

0.075 2-8

Bitumen content %by mass of total mix

Min 4.5

Bitumen grade (pen) 65 or 90

Table 3

used as filler. Function of filler is to fill up the voidsin the mixes. By using of Filler in the bitumenmixes can makes the bitumen more harder andstiffer. This will cause least possible of

deformation occurs due to the traffic load. Thefiller which used in design of bitumen mixesalways free from organic impurities. In this studylime is used as filler. The specific gravity of limefound out to be 2.4 shown in Table 1.

BitumenBitumen is defined as a tarlike mixture ofhydrocarbons derived from petroleum naturallyor by distillation and used for road surfacing androofing Bitumen is a, black and highly viscousliquid or semi-solid form of petroleum. It may befound in natural deposits or may be a refinedproduct. The primary use (70%) of asphalt/bitumen is in road construction, where it is usedas the glue or binder mixed with aggregateparticles to create asphalt concrete. Bituminousmaterials are very commonly used in highwayconstruction because of their binding and theirwater proofing properties. Viscosity gradebitumen VG 30 used as a binder in this researchfor preparation of mix, whose specific gravity was1.025. It’s important property as per Indianstandard code specification for paving bituminousIS:73 (2007) was used.

Aggregates GradationGradation of aggregates is a important factorwhich affecting permanent deformation of hot mixasphalt. Aggregate grading and binder content

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when tested in accordance with IS:2386 Part 1the combined grading of the coarse and fineaggregate and added filler shall fall within the limitsas shown in table. The combined gradation rangefor the different size of aggregates as specifiedin MoRTH for D.B.M. mix is present in Table 3.

SUMMARY OF MARSHALLTESTFor each gradation and aggregate type, Marshalltest specimens were prepared at 4%, 4.5%, 5%bitumen content to study the effect of aggregategradation on the Marshall properties of SDBCmix. The Optimum Bitumen Content (OBC),andother properties such as Stability, Bulk Density,Flow, Voids Filled with Bitumen (V.F.B.) and Airvoids obtained at OBC were plotted againstrespective gradations shown in Table 5 andFigures 7 to 12.

Sieve Size L.G L.M.G. M.G. H.M.G. H.G. MORTH Range

26.5 90 92.5 95 97.5 100 90-100

19 71 77 83 89 95 71-95

4.75 56 62 68 74 80 56-80

2.36 38 42 46 50 54 38-54

0.3 7 10.5 14 17.5 21 21-Jul

0.075 2 3.5 5 6.5 8 8-Feb

Table 4: D.B.M. Gradation

Properties L.G. L.M.G. M.G. H.M.G. H.G.

O.B.C. % 4.46 4.46 4.42 4.57 4.46

Stability 9.9 10.6 11.5 9.85 9.7

Flow 2.8 3.3 3 3.1 2.7

Density 2.346 2.348 2.356 2.336 2.342

V.F.B. 72 74.8 74 65 72.2

Air Voids Vv 3.84 3.86 3.62 4.2 3.88

Table 5: D.B.M. Marshall Properties

Figure 1: Gradation vs O.B.C. Variation

Figure 2: Gradation vs Stability Variation

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Figure 2 (Cont.)

Figure 3 Gradation vs Flow Variation

Figure 4: Gradation vs Density Variation

Figure 5: Gradation vs V.F.B. Variation

Figure 6: Gradation vs Air Voids Variation

Figure 6: Gradation vs Air Voids Variation

RESULTS AND DISCUSSIONThe variation of Marshall Parameters obtained asStability, Flow, Density, Air voids, Voids filled withbitumen (VFB) for Lower Grade (L.G.), LowerMiddle Grade (L.M.G.), Middle Grade (M.G.),Higher Middle Grade (H.M.G.), Higher Grade (H.G.)at 4%, 4.5%, 5% bitumen are shown in Figures 7to 11.

DensityIn this study it is observed that when bitumenpercent is increased Density is also increased atcertain point after increment of bitumen percentit again decreasing. The variation of compactedspecimen density obtained for various gradingsand different bitumen content are shown in Figure7. It is clear that the maximum density is obtained

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corresponding to M.G. gradation of aggregatesfor all bitumen content.

StabilityAccording to MoRTH table 500-11 minimumStability for Dense Bituminous Macadampavements is 9 KN at 60 °C. The stability valuesfor all five gradations are much higher that ofminimum value prescribed in guidelines. In thisstudy it is observed that when bitumen percentis increased stability is also increased at certainpoint after increment of bitumen percent it againdecreasing. The variation of Stability obtainedfor various grading and different bitumen contentare shown in Figure 8. It is clear that the

maximum density is obtained corresponding toM.G. gradation of aggregates for all bitumencontent.

AIR VOIDS, VvThe value of air voids in range of 3-6% is specifiedby MoRTH table 500-11. In this study for allgradations, the air voids percent are in this range.It is observed that at lower percent of bitumen airvoids is higher, due to increasing of percent ofbitumen the air voids percent are decreasing. Thevariation of compacted specimen densityobtained for various grading and different bitumencontent. are shown in Figure 9. It is clear that themaximum Air voids is obtained corresponding toH.M.G. gradation of aggregates for all bitumencontent.

Flow ValuesMoRTH specified the flow values in the range of2 to 4 mm for D.B.M. mix. In this study for allgradations, the flow values are in this range. It isobserved that due to increasing bitumen percentthe flow value is also increasing. The variation ofcompacted specimen density obtained for variousgradings and different bitumen content are shownin Figure 10. It is clear that the maximum density

Figure 7: Variation of Densityat Different Bitumen Content

Figure 8: Variation of Stability at DifferentBitumen Content

Figure 9: Variation of Air Voids at DifferentBitumen Content

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obtained for various gradings and differentbitumen content are shown in Figure 11. It is clearthat the maximum V.F.B. is obtainedcorresponding to M.G. gradation of aggregatesfor all bitumen content.

CONCLUSIONVarious laboratory tests on D.B.M. mixes resultsconcluded that Marshall values of Stability ismaximum in Middle Grade (M.G.) and OptimumBinder Content (O.B.C.) is also minimum inMiddle Grade (M.G.) which is more economicalfor design D.B.M. mix in this gradation. TheDensity value is maximum in Middle Grade (M.G.)and minimum at High Middle Grade (H.M.G.) Flowis highest in Middle Grade (L.M.G.) and minimumat Higher Middle Grade (H.G.). Air voids ismaximum in Higher Middle Grade (M.G.) andminimum at Middle Grade (M.G.). V.F.B. ismaximum in Lower Middle Grade (L.M.G.) andminimum at Higher Middle Grade (H.M.G.)Fromthe above points it can be concluded that in thedesign of D.B.M. mix most of the Marshallproperties are superior at Middle Gradation ofMoRTH specifications so D.B.M. mix is design atthis gradation.

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Figure 10: Variation of Flow at DifferentBitumen Content

Figure 11: Variation of V.F.B. at DifferentBitumen Content

Figure 11 (Cont.)

is obtained corresponding to L.M.G. gradation ofaggregates for all bitumen content.

Voids Filled With Bitumen (V.F.B.)MoRTH specified the Voids filled with bitumen(V.F.B.) values in the range of 65 to 75% for D.B.M.mix. The variation of compacted specimen density

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