Design Consideration of Asphalt Mixtures Containing RAS: Impact of Recycling Agents

Transcription

1 Design Consideration of Asphalt Mixtures Containing RAS: Impact of Recycling Agents Louay N. Mohammad Sam Cooper, Jr. Department of Civil and Environmental Engineering LA Transportation Research Center Louisiana State University William H. Daly Ioan Negulescu Sreelatha Balamurugan Department of Chemistry Louisiana State University Asphalt Binder Expert Task Group Baton Rouge, Louisiana September 16-17, 2014

2 Presentation Outline Background Objective/Scope Methodology Mix experiment Binder Experiment Results Summary/Conclusions

3 Sustainability in Flexible Pavement Conventional materials Asphalt Treated Mixtures Recycled materials RAP, CRM, RAS Industrial waste extender Sulfur Plant-based Bio-binder Bio-rejuvenator Pavement construction practice Warm Mix Asphalt Air-pollution reduction photocatalytic pavements

4 Asphalt binder Recycles Asphalt Shingles Post Consumer: 25 30% Manufacture waste: 18 22% Mineral matter 40 to 60% granules and fillers Fibers 8 to 12%

5 Recycles Asphalt Shingles Supply (US) 10M: Post Consumer 01M: Manufactures Waste Benefits Sustainability Partial aggregate and binder replacement Prevent landfilling of valuable resource Improved rut resistance Concerns Consistency of asphalt content Availability vs Credit of the asphalt binder Quantity vs Quality of the asphalt binder Performance Intermediate and low temperature

6 Typical Asphalt Mixture Design Volumetrics Voids in the Total Mix, VTM Voids in the Mineral Aggregate, VMA Voids Filled with Asphalt, VFA Densification Stages during lab compaction process VOLUME air asphalt MASS Total Volume aggregate aggregate Total Mass

7 Use of RAS in HMA/WMA? AASHTO MP AASHTO MP Use of RAS as an Additive in Hot Mix Asphalt (Asphalt) Provides Standard definitions for RAS Process RAS 100% passing 12.5-mm sieve Allows blending of RAS with fine aggregate Prevent agglomeration Addresses deleterious materials

8 How to incorporate RAS in HMA/WMA? AASHTO PP53 AASHTO PP Standard Practice for Design Considerations When Using RAS in Asphalt Mixtures Provides guidance on design considerations RAS size can affect the fraction of RAS binder that contribute to the final blended binder fibers in RAS may require additional virgin asphalt binder RAS asphalt availability factor is

9 Our Experiment Design mixture with no shingles Calculate OAC VMA, VTM Add shingles Calculate OAC VMA and VTM similar to mix with no shingles Binder credit Add shingles + Recycling Agents Calculate OAC VMA and VTM similar to mix with no shingles Binder credit

10 Objective / Scope Mixture Experiment Evaluate the intermediate and low temperatures laboratory performance conventional asphalt mixtures mixtures containing RAS Effect of recycling agents (RAs) Three 12.5mm Mixtures - NRA Mix 1: 70CO RAS = 0% PG 70-22M Mix 2: 70PG5M-B RAS = 5% Type: manufacturer waste shingles (MWS) PG 70-22M Mix 3: 70PG5P-B RAS = 5% Type: post-consumer waste shingles (PCWS) PG 70-22M Three 12.5mm Mixtures - RAs Mix 4: 52PG5P-RA 1-B RAS = 5% PCWS RA 1: PG Mix 5: 70PG5P-RA 2-B RAS = 5% PCWS RA 2 = 5% Mix 6: 70PG5P-RA 3-B RAS = 5% PCWS RA 3 = 12%

11 Objective / Scope Binder Experiment Correlate the molecular structure of asphalt binders to fracture property of asphalt mixtures Asphalt mixtures: Conventional Asphalt mixtures: RAS with and without RAs Gel Permeation Chromatography (GPC) Fourier Transform Infrared Spectroscopy (FTIR)

12 Design Consideration OAC=5.3% No Recycling Agent Asphalt Binder Content, % RAS Binder Virgin Binder % 100% 43% 100% CO (No RAS) Mix 1 Mixture Type Available RAS Binder = 26 * 5% RAS = 1.3

13 Design Consideration OAC=5.3% No Recycling Agent Asphalt Binder Content, % RAS Binder Virgin Binder % 100% 43% 100% CO (No RAS) Mix 1 70PG5M-B Mix 2 70PG5M-A Mix 2 Mixture Type Available MWS RAS Binder = 26 * 0.05 = 1.3 Available Binder Factor = (0.6/1.3)*100 46%

14 Design Consideration OAC=5.3% No Recycling Agent Virgin Binder ~ 90% Asphalt Binder Content, % % 100% 36% RAS Binder Virgin Binder % CO (No RAS) Mix 1 70PG5M-B Mix 2 70PG5M-A Mix 2 70PG5P-B Mix 3 70PG5P-A Mix 3 Available PCWS RAS Binder = 28% * 0.05 = 1.4% Mixture Type Available Binder Factor = (0.5/1.4)*100 36%

15 Mixture Design Concerns RAS Type Recycled binder Ratio (RBR) Recycled binder content / total binder content Design binder content Mix with No RAS 5.3% binder Scenario 1 (100% availability -- P) RBR = 1.40 / 5.3 = 0.26 Scenario 2 (< 100% availability -- P) RBR = 0.50 / 5.3 = 0.09 Increase the RBR Recycling Agents Softening Rejuvenators RBR = Ensuring structural performance + volumetrics high temperature intermediate temperature low temperature performance moisture damage resistance %RAS Total AC Content %RAS in Mix Design %RAS AC Binder Available PCWS

16 Mixture Design Concerns Classes of Recycling Agents REJUVENATING AGENTS RAS Type %RAS Total AC Content %RAS in Mix Design %RAS AC Binder Available PCWS SOFTENING AGENTS Lube Extracts Extender Oils (aromatic oils) Anti-Stripping Agent Naphthenic Oil Vegetable Derived Oils Lube Stock Lubricating or Crankcase Oil Slurry Oil Asphalt Flux Oils Soft Asphalt Binders Purpose of Recycling Agents Softening Agents lower the viscosity of the aged binder Rejuvenators help restore physical and chemical properties of aged binder contain a high proportion of maltene constituents

17 Mixture Design Concerns Classes of Recycling Agents REJUVENATING AGENTS Lube Extracts Extender Oils (aromatic oils) Anti-Stripping Agent Naphthenic Oil RA 3 Purpose of Recycling Agents Softening Agents lower the viscosity of the aged binder Rejuvenators RAS Type %RAS Total AC Content help restore physical and chemical properties of aged binder contain a high proportion of maltene constituents %RAS in Mix Design %RAS AC Binder Available PCWS SOFTENING AGENTS Lube Stock Lubricating or Crankcase Oil Slurry Oil Asphalt Flux Oils Vegetable Derived Oils RA 2 Soft Asphalt Binders -- RA 1

18 Design Consideration OAC=5.3% Recycling Agent (RA) 6.0 Asphalt Binder Content, % CO (No RAS) Mix 1 Mixture Type Available RAS Binder = 28 * 5% RAS = 1.4%

19 Design Consideration OAC=5.3% Recycling Agent Asphalt Binder Content, % RA % 100% CO (No RAS) Mix 1 52PG5P-RA 1-B Mix 4 52PG5P-RA 1-A Mix 4 Mixture Type RAS Binder Virgin Binder Available PCWS RAS Binder = 28 * 0.05 = 1.4 Available Binder Factor = (1.4/1.4)*100 = 100%

20 Design Consideration OAC=5.3% Recycling Agent (RA) 6.0 RA 1 RA 2 Asphalt Binder Content, % % 100% 100% % CO (No RAS) Mix 1 52PG5P-RA 1-B Mix 4 52PG5P-RA 1-A Mix 4 70PG5P-RA 2-B Mix 5 70PG5P-RA 2-A Mix 5 Available PCWS RAS Binder = 28% * 0.05 = 1.4% Mixture Type Available Binder Factor = (1.2/1.4)*100 86%

21 Design Consideration OAC=5.3% Recycling Agent (RA) 6.0 Virgin Binder: 87%, 74%, 77% RA 1 RA 2 RA 3 Asphalt Binder Content, % % 100% 100% 100% 86% 100% CO (No RAS) Mix 1 52PG5P-RA 1-B Mix 4 52PG5P-RA 1-A Mix 4 70PG5P-RA 2-B Mix 5 70PG5P-RA 2-A Mix 5 70PG5P-RA 3-B Mix 6 70PG5P-RA 3-A Mix 6 Available PCWS RAS Binder = 28% * 0.05 = 1.4% Mixture Type Available Binder Factor = (1.2/1.4)*100 86%

22 Recycled Binder Ratio 0.30 No Recycling Agents Recycling Agents Recycle Binder Ratio Mixture type

23 Laboratory Performance Tests Quality vs Quantity Intermediate temperature Performance semi-circular bending test Low temperature performance Thermal Stress Restrained Specimen Test Triplicates VTM: 7 ± 0.5%

24 l Fracture mechanics used for evaluating fracture resistance in rock mechanics l Temperature: 25 C l l l Half-circular Specimen Laboratory prepared Field core 150mm diameter X 57mm thickness simply-supported and loaded at mid-point Notch controls path of crack propagation 25.4-, 31.8-, and 38.0-mm Loading type Monotonic 0.5 mm/min To failure l Aging: 5 days, 85 C l l Semi Circular Bend (SCB) Test Record Load and Vertical Deformation Compute Critical Strain Energy: Jc Load (kn) Peak Load U 1 notch a Deflection (mm)

25 Thermal Stress Restrained Specimen Test AASHTO TP10-93 Apply thermal loading -10 ± 1 C per hour until specimen fracture Continuously record Load, displacement, temperature Determine the low-temperature cracking susceptibility of asphalt concrete Determine temperature and tensile strength at fracture

26 Results

27 Semi-Circular Bend Test Results, 25 C 0.60 No Recycling Agents 0.50 Jc, KJ/m Virgin AC = % RAS AC = % Mixture type

28 Semi-Circular Bend Test Results, 25 C 0.6 No Recycling Agents Recycling Agents 0.5 Jc, KJ/m Virgin AC = % RAS AC = % Virgin AC = 4.6 RAS AC = 0.7% Virgin AC = 3.9% RAS AC = Mixture type

29 Thermal Stress Restrained Specimen Test No Recycling Agents Recycling Agents Fracture Temperature, C Virgin AC = % RAS AC = % Virgin AC = 4.6 RAS AC = 0.7% Virgin AC = 3.9% RAS AC = Mixture type

30 Binder Experiment: Investigation of the Impact of Recycling Agent Concern with mixture performance NRA vs RA Chemical analysis Gel Permeation Chromatography, FTIR Binder extracted from aged HMA mixtures 5 days, 85 C

31 Oxidation of Asphalt Matrix Dispersed asphaltenes Oxidative aging Polar groups stabilize aggregation COOH COOH Polar groups may enhance adhesion to binder HOOC Asphaltene aggregation Asphalt aggregates reinforce matrix

32 Typical GPC Chromatogram Asphalt Characterization Utilizing Gel Permeation Chromatography (GPC) William Daly, Ionela Glover, Ioan Negulescu, Christopher Abadie, Louay Mohammad,Rafael Cueto 34

33 MW distribution of molecular species of extracted binder: HMA mixture containing 0% RAS and PG70-22M binder RI (Relative Units) % MW 870 PG 70-22M 50 MALTENES ASPHALTENES % MW 8, % 30 MW 3, % POLYMER MW 50, J c = 0.5 kj/m MW (Daltons x 10-3 ) 0.2

34 Typical MW Distributions of PMAC s Modified with RAS RI (relative Units) RAS M RAP MW 110,000 MW 30,000 RAS M RAP RI (Relative Units) PMAC PG RAS P Polymer MW zone Associated Asphaltenes MW zone PMAC RAS P Maltenes MW zone MW Associated Asphaltenes Maltenes K MW 50K-3K Low-end MW Asphaltenes MW < Molecular weight (MW, dalton) RAS M contributes higher conc. of associated asphaltenes with very high molecular weights than RAP TIME (min) Associated asphaltenes overlap polymer molecular weights

35 GPC data of Air Blown shingle coating asphalt and MWS (RAS M) extracted binders RI (Relative Units) MWS BLOWN ASPHALT 14K 17.5% 28K 6.5% 53K 1.15% 3K 45.0% 0.8K 29.85% Binder of RAS M is practically identical to blown asphalt MW (Daltons x 10-3 ) 0.2

36 MW distribution of molecular species of extracted binder: HMA mixture containing 5% RAS-M and PG70-22M binder % MW 940 MALTENES RI (Relative Units) ASPHALTENES 3.0 % MW 24, % MW 6,400 J c = 0.5 kj/m PG5M MW (Daltons x 10-3 ) 0.2

37 MW distribution of molecular species of extracted binder: HMA mixture containing 5% RAS-P and PG70-22M binder PG5P % MW 930 MALTENES RI (Relative Units) ASPHALTENES 12.6 % MW 12, % MW 33, % MW 4,300 J c = 0.5 kj/m MW (Daltons x 10-3 ) 0.2

38 MW distribution of molecular species of extracted binder: HMA mixture containing 5% RAS-P and PG76-22M binder % MW RI (Relative Units) % RAS-P Asphaltenes? 36% MW 5,140 MALTENES J c = 0.7 kj/m % SBR ASPHALTENES 76PG5P MW (Daltons x 10-3 ) 0.2

39 MW distribution of molecular species: Recycling Agent 2 RA GREEN REJUVENATOR 39.0% MW % MW <200 RI (Relative Units) % MW 1, % MW 1, TIME(min) Highest molecular weight component only 1,500 daltons

40 Impact of Recycling Agent 2 100k 10k 1k 250.0k 200.0k MW 1100 With HG MW 850 RI (Relative Units) 150.0k 100.0k 50.0k k 70PG5P RA-2 NHG 70PG5PNHG 70PG5P SCB NRA-2 AGED 70PG5P5HG SCB AGED J c = 0.2 kj/m 2 J c = 0.4 kj/m 2 RAS = 5% PCWS RA 2 = 5% PG 70-22M 10k MW (Daltons) 1k RAS = 5% PCWS No RA PG 70-22M

41 Impact of Recycling Agent 3 J c-aged = 0.3 kj/m 2 = J c-unaged = 0.3 kj/m 2 1M 100k 10k 1k 100 MW 1090 Not Aged MW 850 Aged RI (Relative Units) MW 26,000 70PG5P12CYCLO NOT AGED 70PG5P12CYCLO SCB AGED RAS = 5% PCWS RA 3 = 12% PG 70-22M 1M 100k 10k MW (Daltons) 1k 100

42 Estimation of Extent of Aging by FTIR ν as CH 2,CH 3 ν as CH 3 X, CH 3 aryl ν a CH ν s CH 2,CH 3 ν C=C δ as CH 2,CH 3 ν CH 3 ν S=O Wavenumber cm -1 FTIR spectra of the aged samples show a peak around 1700 cm -1, characteristic of C=O species. The carbonyl index was calculated from the band areas measured from valley to valley as shown above*: Area of the carbonyl centered around 1700 cm -1 Carbonyl index = Σ Area of the spectral bands between 3500 and 500 cm -1 Absorbance Wavenumber, cm -1 C=O } ν CH aro r(c *J. Lamontagne et al., FUEL, 80(4), (2001)

43 Correlation of VHMW, Carbonyl Index, and Jc Mixture Type Total VHMW % Polymer & Highly Associated Asphaltenes >20K C=O Index x10 3 J c KJ/m 2 70CO CO PG5P PG5P-RA 1-B PG5P-RA 2-B PG5P-RA 3-B

44 Correlation of VHMW, Carbonyl Index, and Jc Mixture Type Total VHMW % Polymer & Highly Associated Asphaltenes >20K C=O Index x10 3 J c KJ/m 2 70CO CO PG5P PG5P-RA 1-B PG5P-RA 2-B PG5P-RA 3-B

45 Correlation of VHMW, Carbonyl Index, and Jc Mixture Type Total VHMW % Polymer & Highly Associated Asphaltenes >20K C=O Index x10 3 J c KJ/m 2 70CO CO PG5P PG5P-RA 1-B PG5P-RA 2-B PG5P-RA 3-B

46 Summary / Conclusions Laboratory performance evaluation of asphalt mixtures containing RAS Design / Durability Design of Asphalt Mixtures Availability of binder from RAS AASHTO PP78 over-estimates the actual shingle asphalt binder availability factor 36% - 46% -- W/O RA 86% - 100% -- RAs Volumetric-based design Not sufficient Compliment with mechanistic tests Performance related Criteria Intermediate Temperature (SCB) No adverse effects Mixes 1 3 (NRAs) Lower Jc values Mixes 4 6 (RAs)

47 Summary / Conclusions Effect of Recycling Agents Use of soft binder (RA 1) did not improve fracture properties. RA 3 performed better than RA 2 at intermediate temp. RA 2 enhanced the extraction of the asphaltenes from the RAS. Molecular fractionation through GPC of RAS samples confirmed the presence of associated asphaltenes in great concentrations. High concentrations of HMW asphaltenes decrease the fracture resistance of the asphalt mixtures Presence of SBS additives enhances the compatibility with the HMW asphaltenes. C=O is not reliable indicator of intermediate fracture resistance performance. Use of RAs evaluated in this study did not reduce the concentration of the highly associated asphaltenes Did not improve the cracking resistance

48 Thoughts! Is 100% blending of available RAS binder desired? Consideration of Addition of additives that enhances the compatibility with the HMW asphaltenes

49 T H A N K Y O U