 Composite structure Composite structure  Strength theory Strength theory  Factors in affecting φ and C Factors in affecting φ and C § 9.2 Composite Structure and Strength Theory of Bituminous Mixture Theory of Bituminous Mixture Chapter 9

 Theory:  Surface Theory ： (Tradition Theory) Coarse, fine aggregate and filler –Mineral framework with compact gradation –Scattered distribution –Bituminous mixture  Adhesive Cement Theory ： (Modern Theory)  High consistent bitumen is added to breeze and produce adhesive cement-micro dispersion system.  Fine aggregate is added to adhesive cement to produce bituminous mortar-fine dispersion system.  Coarse aggregate is added to bituminous mortar to produce bituminous mixture-coarse dispersion system. Composite Structure

Coarse dispersion system Fine dispersion system Micro dispersion system Bituminous mixture Bituminous mortar Adhesive cement High consistent bitumen Breeze Fine aggregate Coarse aggregate Characteristics: / High consistent bitumen/Great consumption of bitumen/ Discontinuous gradation

Types of Bituminous Mixture : Types of Bituminous Mixture Fig Types of Bituminous Mixture a-Dense-suspended Type b- Framework-interstice Type c- Dense-framework Type Types of bituminous mixture Types and characteristics of bituminous mixture in in Fig and Tab.9.2.1

Tab.9.2.1: Types and Characteristics of Bituminous Mixture Types Sketch Map Characteristics Names of Admixture Material Dense-suspendedaV V midst, Φ small Continuous Dense Grading Framework- interstice b C small, V V large, Φ midst Continuous Open-Graded Dense-frameworkc C large, V V small, Φ large Discontinuous Dense Grading V V － Porosity of specimen Φ － Angle of internal friction C － Cohesion

normal and higher temperature respectively In Coulomb theory, insufficient cohesion cause distortion; at low temperature insufficient shear resistance and insufficient tensile strength cause destruction. There are two forms of destruction in pavement structure at normal and higher temperature respectively In Coulomb theory, insufficient cohesion cause distortion; at low temperature insufficient shear resistance and insufficient tensile strength cause destruction. Strength Theory Destruction Distortion Destruction Normal and higher temperature temperature Lowtemperature Insufficientcohesion Insufficient shear resistance Insufficient tensile strength tensile strength Coulombtheory

Method: Triaxial Shear Test τ—shear resistance C —cohesion σ—shear normal pressure stress φ —angle of internal friction Conclusion ： Shear resistance of bituminous mixture is determined by cohesion and angle of internal friction Strength Theory

 The influences of bituminous properties in cohesion is that: Viscosity ↑ →Cohesion ↑→Shear resistance τ↑  Reciprocity of bituminous and mineral material Breeze has adsorption to the peripheral bituminous molecule. The viscosity closer to the boundary surface increases and form diffused solvent film (10um) (Fig.9.2.2) Factors of Influencing φ and C Factors of Influencing φ and C

Fig Reciprocity of bituminous and mineral material Internal film-structural bituminous → strong cohesion C External film-free bituminous → weak cohesion C

Influences of Mineral Material ’ s Specific Area and Quantity of Bitumen  Influences of mineral material’s specific area: the quantity of bitumen is certain  the greater mineral material’s specific area, the more structural bituminous, the stronger C  Influences of quantity of bituminous, when bituminous and mineral material are certain  the quantity of bituminous (q)= the quality of bituminous / that of mineral material

The Relevant Curve Between q-C and q-φ Quantity of bitumen (q)(%) C φ Fig The Relevant Curve Between q-C and q-φ

Influences of Mineral Material Chemical Property Mineral Material Mineral Material Chemistry Property Alkalinity SiO 2 ＜ 52% Indifference SiO 2 =52%-65% Acidity SiO 2 ＞ 65% The change of mineral material chemistry property plays an important role on the property of bituminous mixture(Tab.9.2.2).

Name of mine admixture material Dry compressive strength (KN) Compressive strength after inundation （ KN ） Strength reduction after inundation （ % ） Limestone Quartz stone Influences of Mineral Material Chemical Property Tab Influences of Mineral Material Chemical Property

Alkaline stone can have chemical absorption with bituminous acid anhydrides → the absorption of solvent film which they produced grows perfectly → strong C→ high strength of the mixture; the film formed by acid stone and bitumen grows imperfectly → low C → poor strength of the mixture Influences of Mineral Material Chemical Property

Influences of Mineral Gradation, Particle Diameter, Characteristics of Surface Shape  Gradation: Continuous gradation, low cohesion C and angle of internal friction discontinuous gradation, strong cohesion C and angle of internal friction  Particle diameter: The bigger particle diameter, the bigger angle of internal friction

 Grain shape and roughness: Particles are close to square and have edge angles → C strong and φ big → τbig.  Conclusion: Coarse and even aggregate should be chosen. Influences of Mineral Gradation, Particle Diameter, Characteristics of Surface Shape

Others Others The higher the temperature→the lower C The slower the speed of distortion → the lower C →low influences on φ.