Investigation of Emulsified Asphalts Properties by DSR to Evaluate their Performance

Transcription

1 Investigation of Emulsified Asphalts Properties by DSR to Evaluate their Performance Amir Golalipour, Ph.D. Anton Paar USA Delmar Salomon, Ph.D. Pavement Preservation Systems LLC Pacific Coast Conference on Asphalt Specifications March 24 th,

2 Outline 1. Introduction Motivation Overview Testing Emulsions 3. Tack test Experimental Set up Tack test Summary of Findings 2. Workability & Setting Test Experimental Set up Amplitude Sweep test Thixotropy test Summary of Findings

3 INTRODUCTION

4 Motivation Asphalt Emulsions The use of asphalt emulsions began in the early part of the 20th century. Today 5% to 10% of paving-grade asphalt is used in emulsified form, but the extent of emulsion usage varies widely between countries. The United States is the world s largest producer of asphalt emulsion. Standard bitumen (asphalt) emulsions are normally considered to be of the O/W type and contain from 40% to 75% bitumen, 0.1% to 2.5% emulsifier, 25% to 60% water plus some other minor components. With viscosities in the range Poise at 60 C, asphalt emulsion is of considerably lower viscosity than asphalt itself (100 4,000 Poise), allowing it to be use with these advantages: Lower temperature applications Reduce emissions Reduce energy consumption Avoid oxidation of the asphalt Less hazardous Cost effectiveness [1,2,3]

5 Asphalt Emulsions Overview An emulsion is a dispersion of small droplets of one liquid in another liquid. Typical examples include such everyday products as milk, butter, mayonnaise, and cosmetic creams. Emulsions are made by mixing hot asphalt binder with water containing emulsifying agents and applying mechanical energy sufficient to break up the bitumen into droplets. Other components & their functions: Calcium and Sodium Chloride -> to reduce the osmosis of water into the bitumen and minimize the changes in viscosity Adhesion Promoters -> have sufficient adhesion to aggregates Solvent -> to improve emulsification, to reduce settlement, improve curing rate at low temperatures Latex -> Polymer modification can improve the properties of bitumen in terms of cohesion, resistance to cracking at low temperatures [2, 4]

6 Testing Asphalt Emulsions Most test methods have been accepted as ASTM standards. The tests fall into three groups: 1. Test the handling properties of the emulsion, such as residue content, viscosity, and storage stability sieve residue 2. Those that classify the emulsion into rapid-, medium-, or slow-setting grades, such as demulsibility, cement mix test, and coating tests 3. Tests on the residue recovered by evaporation, such as penetration or ductility WHAT IS NEEDED FOR THE FUTURE? Probably the greatest need that exists is the method to evaluate rheological properties of fresh emulsions and residue because current purchase specifications use traditional and empirical viscosity, penetration and ductility test methods that are unrelated to their performance. The other great concern is the consistency of values achieved comparing those of a Saybolt type of viscometer to a paddle wheel or rotational spindle viscometers. [4,5,6]

7 PART I: EMULSION TESTING

8 EXPERIMENTAL SETUP

9 C-PTD170/AIR Cylinder - Peltier Temperature Device with Air Counter Cooling Temperature Range: 0 C to 180 C (0 C at 25 C room temperature)

10 Temperature Calibration C-PTD170/Air: Three point temperature calibration at 40 C, 65 C and 90 C With Calibration Sensor CC Asphalt and Digital Thermometer GMH 3710

11 C-PTD170/AIR Temperature Gradients Temperature Gradient Measurements: Top Middle close to bob Middle close to cup Bottom Temperature Gradient < 0.1 C Temperature distribution is as good as in a PP25/PE geometry!

12 Samples and Test Methods The following fresh asphalt emulsions were used: CRS-2: Rapid set cationic CRS-2L: Rapid set cationic with Latex SS-1: Slow set anionic SPMS: Medium set anionic Emulsions: Please Note: Emulsions were tested at their application temperatures, 50 C for cationic and 25 C for anionic based on manufacturer recommendation. Sample preparation was performed according to AASHTO T59 [7] For the measurements with CC27, the asphalt emulsion was directly poured into CC27/D/AL Asphalt cups New sample for each measurement

13 RESULTS AND DISCUSSION

14 Amplitude Sweep Tests

15 Test Parameters Measuring profile: This measuring profile was used for cylindrical (Bob & cup, CC27) measurements 15 min for temperature step to guarantee to reach thermal equilibrium. Amplitude Sweep test is intended to identify linear viscoelastic behavior. Also, cross over frequency can be determined with this test which shows the phase change in material. Automatic analysis in the software can be used to determine LVE range and cross over point.

16 Repeatibility To confirm reproducibility of measurements, at least two replicates were tested for each emulsion type. Good temperature control increases the accuracy and decrease the variability.

17 Emulsion Type Effect SPMS (anionic) vs. CRS-2 (cationic) The stiffness of Cationic emulsion is lower at its application temperature, so better workability. Furthermore, the linear and nonlinear viscoelastic behavior is very different for these two emulsions.

18 Viscoelastic difference between same family SPMS (anionic) vs. SS-1 (anionic) Amplitude sweep testing shows distinct differences between the viscoelastic behavior of these emulsions. SS-1 depicts a cross over point at 0.05% strain level while SPMS is still in linear region.

19 Viscoelastic difference between same family CRS-2L (cationic) vs. CRS-2 (cationic) Similar behavior in linear viscoelastic range (LVE). CRS-2L shows breaking point at 3% strain whereas CRS-2 is exhibiting nonlinear behavior at that point..

20 Thixotropy test (setting and curing behavior)

21 Test Parameters Measuring profile: This measuring profile was used for cylindrical (Bob & cup, CC27) measurements 15 min for temperature step to guarantee to reach thermal equilibrium. Thixotropy testing is used to simulate spraying, setting and curing emulsions in one test. Test is conducted in three steps. I. First, the sample was subjected to a low shear rate to mimic normal storage condition of emulsions. II. III. Then, shear rate was increased significantly (spraying and/or pumping process). followed by monitoring the viscosity to investigate the recovery behavior.

22 Comparison between Anionic Emulsions SPMS (anionic) vs. SS-1 (anionic) SS-1 shows higher initial stiffness than SPMS but after shearing, it has lower viscosity meaning better workability. SPMS gains back 100% of its initial stiffness meanwhile SS-1 does not show full recovery. This test is used to evaluate the run off of emulsified asphalts after spraying, for example in a chip seal application.

23 Comparison between Cationic Emulsions CRS-2L (cationic) vs. CRS-2 (cationic) CRS-2 shows significant higher initial stiffness than CRS-2L but after shearing, this difference decreased significantly. CRS-2L does not show stable results during high shear and that is the indication of high shear susecptibility in the strcuture of this material.

24 SUMMARY OF FINDINGS

25 Summary, Conclusions and Further Development Area Cylindrical geometry (Bob & Cup) can be used successfully to characterize rheological behavior of asphalt emulsions. Temperature control of this system is accurate to maintain uniform sample temperature. Rheological properties can be a useful tool to characterize workability of emulsions: Predict the stability of emulsified asphalts and differentiate between the different family of emulsions Simulate emulsified field applications Understand the breaking and setting behavior of the different emulsified asphalt applications such as chips seals, fog seals, and microsurfacing Further Development Area Development of Standard test methods for different emulsion applications and properties

26 PART II: EMULSION RESIDUE TESTING

27 EXPERIMENTAL SETUP

28 SmartPave with PP25/PE Perfect temperature control Lowest thermal gradients due to the actively heated hood Designed for testing according to AASHTO T315 No water or gas flow necessary Automatic temperature calibration Measuring plates and insets 25 mm and 8 mm Temperature range -30 C to 120 C Certified temperature calibration sensor Toolmaster Quick Connect Highly dynamic EC-Motor Air bearing of extremely high stiffness Torque range: 0.1 µnm to 150 mnm Angle resolution: 0.01 µrad

29 Temperature Calibration SmartPave 102 with PP25/PE: Three point temperature calibration at 40 C, 65 C and 90 C With Calibration Sensor Asphalt (CSA) and GMH 3710

30 SmartPave with PP25/PE Accurate temperature control is crucial in asphalt testing Special tools to measure the temperature distribution 2 or 4 temperature sensors at various positions in the sample Measurement of horizontal and vertical temperature gradients Fast temperature equilibrium Stable temperature 5 minutes after temperature steps Small temperature gradients: < 0.1 C

31 Samples and Test Methods In this part of study, two unknown asphalt emulsions were provided for tack coat application: Slow Set (SS) emulsions Two different labels: 10min & 25min Sample preparation was performed as below: 1) Stir the sample with glass rod and direct pour on the 25mm plate 2) Cure the sample for defined time period at 80C 3) Trim the sample and bring to the testing gap of 1mm 4) Take the temperature to 25C and condition the sample for 5min 5) Run the Tack test Two different conditioning times were selected to investigate the effect of curing on asphalt emulsion tackiness behavior. 15min and 30min were chosen as curing times based on the sample labels to be able to distinguish between samples adhesiveness behavior New sample for each measurement

32 Teck Test Adhesiveness or tack is the property of materials to form a connection to a substrate when contact pressure is applied for a short time. A typical tack test consists of three intervals: i. Positioning: The measuring system is in contact with the sampler stops shortly before touching the sample. ii. For solid samples: Contact pressure with a constant normal force between FN = 0.01 and 50 N iii. Removal: The measuring system is moved upwards from the sample with constant or variable speed and the required forces measured. As analysis criteria usually the maximum force (or minimum force) and the surface area below (or above) the normal force curve are used. The maximum force is a measure of the cohesive behavior and the surface area in the force-displacement diagram is a measure of the energy required for separation or of the adhesive behavior.

33 RESULTS AND DISCUSSION

34 Adhesion Behavior of Material

35 Repeatibility ( Nf vs. Time) Failure Maximum Strength For these measurements the following three intervals were set: i. Interval 1: Driving to the measuring gap of d = 1 mm ii. Interval 2: Set a constant normal force of 10 N for 5 s iii. Interval 3: Moving up the measuring plate with the constant removal speed of v=2 mm/s

36 Repeatibility ( Nf vs. Gap) Results from replicates are matching almost perfectly. Software uses this figure to calculate the Total failure energy of adhesiveness

37 Tackinees for different emulsions 10min and 25min samples cured at 80C for 30min to determine the difference between their tackiness behaviors. Considering the start point of Normal Force, the 10min sample gives slightly higher Normal force before failure; however, the 25min sample shows more continuous viscoelastic behavior.

38 Type of Failure Cohesive If there is a steep fall in the curve and a deep spiked force minimum followed by a steep rise in the curve, then the sample is lowdeformable with a tendency to form cracks (10min sample). The surface and therefore the value of the energy required for separation is relatively small. Cohesive failure means the rupture failure occurs within the material.

39 Type of Failure Adhesive If there is a shallow fall in the curve and a shallower force minimum followed by a smooth rise in the curve, then the sample normally shows more pronounced stringing (25min sample). Adhesive failure proves that this sample has well cohesive behavior but losing the adhesion to other surfaces. In the real field application, this may cause moisture damage issue with this material.

40 Effect of Curing

41 Effect of Curing Time Influence of curing time on 10min sample The curing progresses at different times ( 15 min vs. 30 min) as indicted by different Normal Force minimum values. This confirms that this material needs more time to cure fully and gets its full strength.

42 Effect of Curing Time Influence of curing time on 25min sample 25min sample do not depict significant difference after different curing time. This can be related to the fact that this sample is more solid like and has more viscosity, so it needs less time to cure.

43 Total Failure Energy W (J) 15min Cond 30min Cond Rep 1 Rep 2 Rep 1 Rep 2 10 min sample min sample Energy required for separation for both asphalt emulsion samples. The surface area in the force-displacement diagram is a measure of the energy required for separation or of the adhesive behavior. The energy value calculated using the in-built software analysis. This depicts that 10min sample has kind of brittle behavior and shows a sudden rupture: so the energy value is significantly lower than the 25min sample: The energy value is significantly lower than the 25min sample

44 SUMMARY OF FINDINGS

45 Summary, Conclusions and Further Development Area Tack test is able to differentiate between different emulsion samples Effect of curing time on tackiness of emulsions was investigated Different type of failures can be identified through tack test Software built-in analysis can be used to calculate tack test parameters Further Development Area Measurement with different emulsion family types development of test standard

46 ACKNOWLEDGMENT ASSOCIATED/MARIANI ASPHALT

47 LITERATURE

48 Literature [1] OKUR Machinery Manufacturing and Construction [2] Pavement Interactive [3] Chemicalcolloid Laboratories Inc. [4] Asphalt Emulsion Technology, TRB circular 2006 [5] Huachun Zhai, Delmar Salomon and Eric Milliron, Using Rheological Properties to Evaluate Storage Stability and Setting Behaviors of Emulsified asphalts, ISAET, 2004 [6] H. Zhai, D. Salomon, E. Milliron, J.Corona, Rheological and Rotational Viscosity Behavior of Road Asphalt Emulsions, in Advances in Rheology and Its Applications (2005), pp 573, Science Press USA Inc. [7] AASHTO Designation: T59 - Standard Method of Test for Testing Emulsified Asphalts, American Association of State Highway and Transportation Officials

49 Thank you for your attention Questions???