Chapter 9Chapter 9

Task and contentComposite design Optimum quantity of bitumen

Chapter 9Chapter 9

§9.6 Mix Design of Bituminous Mixture9.6 Mix Design of Bituminous Mixture

TaskTask ：： Deciding on the proper proportion of all

kinds of aggregate correctly, making the mixture meet the required technical index completely.

ContentContent ：： Mineral material composites design

The optimum quantity of bitumen

Task and Content

There are two methods for composite design: experimental calculation and diagrammatic methoddiagrammatic method

Experimental CalculationBasic Theory of Experimental Calculation

First, we suppose that some particle of certain diameter in the mixture is composed by a kind of aggregate, which is predominant in the particle diameter. Then we try to find out the general proportion of all kinds of aggregate and adjust the proportion as required

Composite design ofComposite design of mineral admixture material mineral admixture material

Aggregate A B C

Proportion（%） X Y Z ∑X+Y+Z=100

Content of I particle diameter

mai mbi mcimai X+ mbi Y+ mci Z=Mi

mai X+ mbi Y+ mci Z=Mi

Experimental Calculation Methodology

Put A 、 B 、 C kinds of aggregates into mineral material of grade (Tab.9.6.1):

Tab.9.6.1 Methodology of experimental calculation

Mi-the content of mixture M on grade I particle,

mai, mbi, mci-the content of A 、 B 、 C on the grade I particle.

Composite Design ofComposite Design of Mineral Admixture Material Mineral Admixture Material

X ： Picking out I, which aggregate A, is dominant, making mbi= mci=0, then X= Mi/ mai

Z: Picking out j, which aggregate C, is dominant, making mbi= mci=0, then X= Mi/ mai

Y: Y=100-X-Z Checking: Checking grade according to mai X+ mbiY+ mciZ=Mi

Adjusting the proportion of X 、 Y 、 Z as required gradation that the composed aggregate should be satisfied with the mixed mineral material.

Experimental CalculationMethodology

Diagrammatic MethodDiagrammatic Method

It is available to the design of mix proportion.Basic Theory: Dividing the required gradation into several

sections according to the range of the particle diameter, making the content of each aggregation(%) equal to the content of particle(%)required in each section

Composite Design ofComposite Design of Mineral Admixture Material Mineral Admixture Material

Known Condition ①Sieve analysis of each aggregate →

passing percentage of each aggregate → gradation curve

②The range of the synthetic gradation according to the technical requirements → the median of passing percentage of the synthetic gradation.

Diagrammatic MethodDiagrammatic Method

Process of Design

① Drawing Coordinate Draw a rectangle map boundary; make the

diagonal line as median of synthetic gradation, vertical coordinate as the passing percentage; draw parallel line from the vertical coordinate according to the passing percentage of the sieve opening required by the median of synthetic drawing vertical line from the point of the diagonal line with the parallel line. The point of the vertical line and the cross coordinate is the position of the correspondent sieve opening

② Drawing Gradation Curve Drawing gradation curves of the aggregate in

the coordinate ③ Ensure Relation of Gradation Curves

Overlapping of adjacent gradation curve （ A and B ）

Connection of adjacent gradation curve （ B and C ）

Separation of adjacent gradation curve （ C and D ） ④ ④ Ensuring Quantity of Aggregates (illuminated Ensuring Quantity of Aggregates (illuminated in the flash)in the flash)

Diagrammatic MethodDiagrammatic Method

Optimum Quantity of BitumenOptimum Quantity of Bitumen

It can be ascertained through the test. Marshall test is used in our country.

The process is: Preparing a group of Marshall specimen.

Each specimen is 0.5% greater than the former according to the regulated quantity range of bitumen.

Testing the technical index of each group specimen (Sm(0), f, Vv, Sm)

Draw curvilinear coordinates between the quantity of bitumen and the technical index

According to the standard, the range of quantity of the eligible bitumen will be decided. The median is the optimum quantity of bitumen optimum quantity of bitumen

The technical index and the test result of the The technical index and the test result of the granulated bitumen concrete in heavy trafficgranulated bitumen concrete in heavy traffic are listed in Tab.9.6.2 Tab.9.6.2

Optimum Quantity of BitumenOptimum Quantity of Bitumen

Tab.9.6.2 The technical index and the test result of the Tab.9.6.2 The technical index and the test result of the granulated bituminous concrete in heavy trafficgranulated bituminous concrete in heavy traffic

Technical indexTechnical indexTechnical Technical standard standard

Quantity of Quantity of bitumen bitumen

Optimum Optimum quantity of quantity of

bitumenbitumen

Stability (N)Stability (N) 50005000 4.5~6.74.5~6.7

5.3~5.85.3~5.8

Preferably 5.5Preferably 5.5

Flow value Flow value （（ 1/100cm1/100cm ）） 30~4030~40 5.3~6.35.3~6.3

VoidageVoidage（（%%）） 3~63~6 4.6~5.84.6~5.8

Residual stabilityResidual stability SSm(0)m(0) （（ %%）） ＞＞ 7575 5.3~7.05.3~7.0

4.5 5.0 7.06.56.05.5

5.0

4.0

8.0

7.0

6.0

(kN)ms

4.5 5.0 5.5 6.0 6.5 7.0

40

30

20

10

50

f

cm210

4.5 5.0 5.5 6.0 6.5 7.0

6

5

4

3

2

(%)

vV

4.5 5.0 5.5 6.0 6.5 7.0

80

70

60

50

40

(%)

)0(ms

4.5 5.0 7.06.56.05.5

5.0

4.0

8.0

7.0

6.0

(kN)ms

4.5 5.0 5.5 6.0 6.5 7.0

40

30

20

10

50

f

cm210

4.5 5.0 5.5 6.0 6.5 7.0

6

5

4

3

2

(%)

vV

4.5 5.0 5.5 6.0 6.5 7.0

80

70

60

50

40

(%)

)0(ms

Chapter 9