BITUMINOUS MIX DESIGN BY MARSHALL METHOD (As per ASTM D 1559 – 62 T )

BITUMINOUS MIX DESIGN BY MARSHALL METHOD

(As per ASTM D 1559 – 62 T )

Introduction

One of the method of designing of bituminous mix is Marshall Method. Objective To determine the stability and flow properties of bituminous mixes and to design the mix at optimum bitumen content.

Apparatus used

i) I.S sieve

ii) Weighing machine

iii) Mixing tray with heating arrangement

iv) Moulds assembly including hammer, pedestal, sample extractor.

v) Marshall stability machine

Procedure

1) Grading of the aggregate to be used in the mix to be selected first.

2) The proportion of each aggregate is determined to achieve at desired grading within

limit specified in MoRT&H specification, 5th revisions.

3) The Sp. Gravity of each aggregate and the Sp. Gravity of Bitumen determined.

4) The quantity of each aggregate (in kg) as per desired proportion with respect to total quantity of 1200 gm dry aggregate is determined for preparation of each sample. The quantity of bitumen to be mixed is also determined in gm.

5) 2% filler (Lime, Cement etc.) material is added to aggregates and the mix heated to 150

to 170 °C and the bitumen (VG30) is heated to 150 to 165 °C , so that the difference in temperature should be maintained to 15 °C .

6) The aggregates and Bitumen is thoroughly mixed with trowel.

7) Mould assembly & rammer are preheated to a temp, of 100 to 145 °C.

8) Mixing temp. is maintained at 150-165° C for VG30 bitumen.

9) After mixing mixed materials is placed in the mould assembly and compacted by

rammer with 75 blows in each face.(Rammer weight = 4.50kg and height of drop=45.7 cm)

10) 2 such samples for each bitumen percentage are prepared.

11) At least four sets of such trial specimens are prepared generally with 0.25% increment

in bitumen content, so that total no of specimens to be prepared for testing is 2 x 4 = 8 nos.

12) The specimens are left in room temp. for cooling for at least 24 hours.

13) The weight, average thickness and diameter of each specimen is recorded. There is a

correction of volume, considering the height of specimen should be 63.5mm.

14) Theoretical Sp. Gravity & Bulk density of each sample determined

15) Air voids, VMA, VFB value are determined.

16) The samples to be tested fully immersed under water during 30 to 40 minutes in

controlled water bath so that temp. can be maintained 60±1 °C.

17) Finally the stability and flow value for each sample is observed by Marshall stability

testing machine.

18) Following graphs are plotted from the test results : i) Marshal stability vs. bitumen % ,

ii) Bulk density vs. bitumen %, iii) % Air void vs bitumen %, iv) Flow vs bitumen %, v) VMA vs bitumen %, vi) VFB vs bitumen %.

19) The optimization in bitumen design is obtained from first three curves ( against 4 % air void)

20) Prepare specimens (usually 3 sets) with the actual bitumen obtained from design and

check the value of density, flow, voids ,VMA, VFB, stability for confirmation with

MoRT&H’s specifications.

Calculations

Bulk Density by physical measurement method:

Marshall Stability & Flow test:

Gt = 100/(W1/G1+W2/G2+W3/G3+W4/G4)
where Gt=Theo. Sp. Gravity of mix, G1,G2,G3 are Sp. Gravity of coarse aggregate, fine
aggregate & filler respectively ,G4 is the Sp. Gravity of Bitumen. W1, W2, W3, W4 are the
percent by weight of aggregate.
Vol of voids = Vv = 100(Gt-Gb)/Gt , where Gb is the Bulk density calculated for the specimen
Volume of bitumen = Vb = Gb x W4/G4
Voids in mineral aggregate = VMA = Vv+Vb
Voids filled with bitumen = VFB = 100 Vb/VMA

Requirement of Dense graded Bituminous Mix as per IRC 111-2009

Correction factor for Stability value of bituminous mix specimen of nonstandard thicknesses are given in a tabular form in the next page.

Stability Co-relation Ratios table

(Source: Various Sources)

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