Chapter 9

 Task and content Task and content  Composite design Composite design  Optimum quantity of bitumen Optimum quantity of bitumen Chapter Mix Design of Bituminous Mixture §9.6 Mix Design of Bituminous Mixture

Task ： Deciding on the proper proportion of all kinds of aggregate correctly, making the mixture meet the required technical index completely. Content ： Mineral material composites design The optimum quantity of bitumen Task and Content

diagrammatic method  There are two methods for composite design: experimental calculation and diagrammatic method  Experimental Calculation  Basic 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 of mineral admixture material

AggregateABC Proportion （ % ） XYZ∑X+Y+Z=100 Content of I particle diameter m ai m bi m ci m ai X+ m bi Y+ m ci Z=M i  Experimental Calculation  Methodology Put A 、 B 、 C kinds of aggregates into mineral material of grade (Tab.9.6.1): Tab Methodology of experimental calculation M i -the content of mixture M on grade I particle, m ai, m bi, m ci -the content of A 、 B 、 C on the grade I particle. Composite Design of Mineral Admixture Material

X ： Picking out I, which aggregate A, is dominant, making m bi = m ci =0, then X= M i / m ai Z: Picking out j, which aggregate C, is dominant, making m bi = m ci =0, then X= Mi/ m ai Y: Y=100-X-Z Checking: Checking grade according to m ai X+ m bi Y+ m ci Z=M i Adjusting the proportion of X 、 Y 、 Z as required gradation that the composed aggregate should be satisfied with the mixed mineral material. Experimental Calculation Methodology

Diagrammatic Method  Diagrammatic 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 of Mineral Admixture Material

 Known Condition ① Sieve analysis of each aggregate → passing percentage of each aggregate → gradation curve ② The range of the synthetic gradation according to the technical requirements → the median of passing percentage of the synthetic gradation. Diagrammatic Method  Diagrammatic 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 Ensuring Quantity of Aggregates (illuminated in the flash) Diagrammatic Method  Diagrammatic Method

Optimum 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 (S m(0), f, V v, S m )  Draw curvilinear coordinates between the quantity of bitumen and the technical index optimum quantity of bitumen  According to the standard, the range of quantity of the eligible bitumen will be decided. The median is the optimum quantity of bitumen  The technical index and the test result of the granulated bitumen concrete in heavy traffic Tab  The technical index and the test result of the granulated bitumen concrete in heavy traffic are listed in Tab Optimum Quantity of Bitumen

Tab The technical index and the test result of the granulated bituminous concrete in heavy traffic Technical index Technical standard Quantity of bitumen Quantity of bitumen Optimum quantity of bitumen Stability (N) ~ ~5.8 Preferably 5.5 Flow value （ 1/100cm ） 30~405.3~6.3 Voidage （ % ） 3~64.6~5.8 Residual stability S m(0) （ % ） ＞ ~7.0

(kN)

f

(%)

(%)

(kN) f (%) (%)

Chapter 9