Chapter 9

 High temperature stability  Low temperature crack resistance  Durability  Skid resistance  Construction workability Chapter 9 §9.3 Technical Property of Bituminous Mixture

 Definition ： High temperature stability refers that bituminous mixture can not form much plastic deformation under repeated loads at high temperature.  Influencing factors ： Bituminous cohesion, the mutual influence between bituminous and stone, the property of the stone. High Temperature Stability

TestMethod Wheel rut test Triaxial Shear test VB stability test Marshall test Back

Low Temperature Crack Resistance Low Temperature Crack Resistance  Definition ： Low temperature crack resistance refers that bituminous admixture material resists shrinkage deformation without cracks  Reasons of bituminous pavement cracks ① Repeated load → fatigue cracking ② Embrittlement at low temperature → low ability to deform → cracking ③ Shrinkage at low temperature ④ ① + ②

 Influencing factors includes: quality and quantity of bitumen and mineral material gradation  Test ： Pure draw test: → to test the stress, strain, tensile strength and limiting deformation of the cylinder specimen → to make out the stiffness modulus and the index of temperature shrinkage → to evaluate the breakage temperature of bituminous mixture. Low Temperature Crack Resistance

Durability  Definition:  Durability refers that bituminous mixture obtains the abilities to endure the influence of atmosphere for a long time with traveling load.  Influencing factors :  chemical properties of bituminous  the component of mineral material  the composite structure of bituminous mixture  the quantity of bitumen

For example: With reduction of 0.5% of bitumen, V v will increase and bituminous mixture ’ s life will shorten one year. Durability  Influencing factors  Measures of Improving Durability: Employing hard mineral material; Improving the density of bituminous mixture; Selecting bituminous mixture with fine particles and dense gradation; Increasing the quantity of bitumen

 Test ： Accelerated weathering test Marshall test  Index Durability can be evaluated by the index  available porosity  saturation degree bituminous interstitial rate  residual stability Durability

Skid Resistance  Influencing Factors ： Mineral material surface structure, gradation, composites of mixture and quantity of bitumen.  Improvement measures ： ① Selecting anti-friction stone with required rate of wearing and impact value. Notice: It is necessary to add some antistripping agent because the hard stone often belongs to the acid stone. ② Controlling the quantity of bitumen: the quantity of bitumen ↑→smoothness of the surface ↑→anti-slide ↓

Construction Workability Construction Feasibility Construction Feasibility is determined by: Mineral material’s gradation: It is not easy to occur isolation with appropriate gradation Cohesion and quantity of bitumen Temperature and construction condition