Research on bond effect of high-performance emulsified asphalt for tack coat

1. Research on bond effect of high-performance emulsified asphalt for tack coat Wanyan Ren Ph.D. Candidate 10 July, 2018

2. Presentation outlines Preparation of high-performance emulsified asphalt Results and Discussion Materials and test method Introduction 1 2 3 4

3. Introduction • With the rapid growth of traffic, many roads can not meet the demand of traffic soon. This kind of distress has a great relationship with interlayer. • Early damage appears frequently, such as shear-slip. • In the heavy vehicle lane; • Steep slope; • High temperature and other adverse conditions. • Interlayer cohesion affects road early damage. • Insufficient adhesion • Unstable high-temperature performance

4. Materials and test method 1 New emulsified asphalt tack coat • Matrix asphalt: ESSO#90 asphalt. Tab.1 Technology indexes of matrix asphalt • Modifier：SBS latex was used as modifier • Tackifier：BB latex to improve the adhesive properties of the new modified asphalt. • Inorganic stabilizer: improve adhesion • Organic stabilizer: improve stability

5. Materials and test method 2 Test method （1）Sample preparation A composite board of 5cm cement concrete + tack coat material + 2cm ultra-thin friction course was selected. Fig.1 Sample structure of the composite slab

6. Materials and test method （2） Direct shear test • A direct shear instrument developed by Highway and Airport Pavement Research Center(HAPRC) of Chang'an University was used for the test. • The test considered the effect of vertical load and exerted vertical load through lever loading principle. • It was also equipped with a temperature control box to simulate road temperature. Fig.2 Direct shear instrument

7. Materials and test method （3）Pull-off test • A pull-off tester was developed by Highway School of Chang'an University was used for the test. The standard test conditions: test temperature 25℃, pulling-off rate 5mm/min. One side：fixed on the board with epoxy resin; The other side：a solid bond with pulling-off head. Fig.3 Pull-off tester

8. Preparation of the high-performance emulsified asphalt Fig.4 Preparation of emulsion The emulsion was poured into an emulsifying machine, and then the matrix asphalt was added for thorough stirring at 140℃ to 150℃.

9. Preparation of the high-performance emulsified asphalt 1 Emulsifier dosage • Effect of emulsifier dosage on the properties of emulsified asphalt Tab.2 Influences of emulsifier dosage on the properties of emulsified asphalt Notes: Sieve residue should be ≤0.1%. 5-day storage stability ≤5%.

10. Preparation of the high-performance emulsified asphalt • With the increase of emulsifier dosage： • The sieve residue decreased gradually • the 5-day storage stability improved continuously. • Emulsifier dosage was not less than 1.0%, the above indexes met the standard requirements. • When the emulsifier dosage reached 1.0%, the growth rate of ductility reached its peak. Emulsifier dosage: 1.0%

11. Preparation of the high-performance emulsified asphalt 2 Stabilizer dosage • The 5-day storage stability of emulsified asphalt with only a single type of stabilizers was tested respectively. Fig.5 Influences of stabilizer dosage on the 5-day storage stability of emulsified asphalt

12. Preparation of the high-performance emulsified asphalt • For inorganic stabilizer, suitable dosage is 0.2%, with regards to the 5-day storage stability • 5-day storage stability is improved gradually with increasing organic stabilizer dosage. • The index met the specification with dosage beyond 0.4%. When the dosage exceeded 0.4%, the improvement rate became smaller. Suitable dosage 0.2% for inorganic stabilizer. Suitable dosage0.4%for organic stabilizer.

13. Preparation of the high-performance emulsified asphalt 3 SBS modifier dosage and tackifierdosage It was found that when the total dosage of SBS modifier and tackifier was 6%, the properties of emulsified asphalt was the better. Two kinds of ideal compound ratio were selected in the paper. Total dosage of SBS modifier and tackifier: 6%; Tab.3 Influences of composite modifier on the properties of emulsified asphalt SBS modifier: tackifierratio was4:1

14. Preparation of the high-performance emulsified asphalt 4 High-performance emulsified asphalt • The high-performance emulsified asphalt has the following formulation: 1.0% emulsifier + 0.2% inorganic stabilizer+ 0.4% organic stabilizer + 4.8% SBS modifier+ 1.2% tackifier. In order to evaluate the properties of the new emulsified asphalt, its properties are compared with the other two emulsified asphalt. Tab.4 Technical indexes of the 3 kinds of emulsified asphalt

15. Preparation of the high-performance emulsified asphalt • Compared with ORDINARY, the improvement : • SBS ductility: 36.4%; NEW ductility: 54.5% • SBS Softening point: 8.1%; NEW softening point: 11.9% • The high temperature performance and low temperature performance of the NEW and SBS were superior to ORDINARY. • Compared with SBS, the high temperature and low temperature performance of NEW emulsified asphalt improved and the viscosity increased. The storage stability of NEW decreased, but still met the specification.

16. Results and discussion 1 Optimal content of tack coat asphalt Too little tack coat asphalt will result in insufficient adhesion between pavement layers while too much tack coat asphalt will form a lubricating layer, resulting in interlayer slipping (shear-slip). Fig.6 Relationship between emulsified asphalt content and shear strength Optimal emulsified asphalt dosage: 0.8L / m2at 25 ℃; 0.6L / m2at 60 ℃

17. Results and discussion 2 Effect of test temperature on bonding effect between pavement layers • Emulsified asphalt dosage : 0.8L / m2 at 25 ℃, 0.6L / m2 at 60 ℃; • Shear strength and tensile strength With the increase of test temperature, the shear strength and tensile strength of the three kinds of emulsified asphalt decreased rapidly with temperature. Fig.7 Relationship between test temperature and shear strength

18. Results and discussion 3 Effect of water on bonding effect between pavement layers • The formed specimens were divided into two groups. One group was not immersed in water and the other group was immersed in water at room temperature for 48 hours. • The influence of water on the bonding effect between pavement layers was evaluated by the residual shear strength and the residual tensile strength. Tab.5 Effect of water on bonding effect between pavement layers • Water is unfavorable to the bonding effect between pavement layers.

19. Results and discussion • Table5 shows that the shear strength and tensile strength of the three kinds of emulsified asphalt decreases due to the immersion effect of water, which indicates that water is unfavorable to the bonding effect between pavement layers. • Figure 8 shows the residual shear strength and residual tensile strength of the three kinds of emulsified asphalt satisfy the rule: new emulsified asphalt> SBS modified emulsified asphalt> ordinary emulsified asphalt. Fig.8 Results of residual shear strength and residual tensile strength

20. Results and discussion 4 Effect of surface enhance on bonding effect between pavement layers Two groups of specimens were formed using new emulsified asphalt as tack coat material. One group of specimens were sprayed with surface enhancer on the surface of cement concrete slab and the other group was not treated. (a)Without surface enhancer (b)With surface enhancer Fig.9 Specimens in different interface conditions

21. Results and discussion Tab.6 Effect of surface enhancer on interlayer bonding performance From Table 6, it can be seen that the shear strength increased by 17.1% and the tensile strength increased by 23.9% by spraying surface enhancer on the surface of cement concrete, which showed that the surface enhancer could improve the bonding effect between pavement layers obviously.

22. Conclusions (1)The new emulsified asphalt formulation had better bonding properties when compared with SBS and ORDINARY emulsified asphalt. (2) With an increase of temperature, the shear strength and tensile strength showed a decreasing trend. No matter what temperature was adopted, the new emulsified asphalt showed good bond performance when compared with the other two kinds of tack coat materials. (3) The adverse effect of water on the bond performance was significant.While the new emulsified asphalt still showed the best bond performance among the three kinds of emulsified asphalt. (4) It was useful to improve the bond performance of tack coat by spraying interface enhancer on the surface of cement concrete.

23. Thank you！