Agricultural and Industrial Waste Modified Asphalt Binders Characterization Using an Atomic Force Microscope

Presenter: Feroze Rashid1, Faculty Mentor: Zahid Hossain2

1Graduate Assistant; 2Assistant Professor of Civil Engineering at Arkansas State University

Increasing use of Atomic Force Microscope (AFM) in material science encouraged its use in pavement industry to characterize asphalt. Featuring sustainable engineering, current practices and future potential, three industrial waste additives i.e., Ground Tire Rubber (GTR), Reclaimed Asphalt Pavement (RAP), and Recycled Asphalt Shingles (RAS) and an agricultural waste, i.e., Rice Hull Ash (RHA) have been used to modify virgin asphalt binder which were tested by an AFM in this study. The morphology of different samples were different but followed a common trend to have phases like Catana (Bee) phase, Peri-phase, and Perpetua phase. Properties like Derjaguin-Muller-Toporov (DMT) modulus, adhesion, deformation, and energy dissipation of the tested materials were found to be related with the morphology.

ABSTRACT

OBJECTIVES Assess the viability of an AFM to characterize asphaltsCharacterize asphalt binders modified with different agricultural and industrial waste using an AFM Determine micro-structural properties (e.g., DMT Modulus, Adhesion, Energy Dissipation and Deformation) of different morphological phases over different scan area. Observe the correlation among surface morphology and mechanistic properties of asphalt blends.

What is AFM ?Advanced technology, nano-scale measurementMorphology at atomic resolution, mechanistic properties

INTRODUCTION

TEST RESULTS AND DISCUSSIONS

CONCLUSIONS

ACKNOWLEDGEMENTS NSF:Major Research Instrument (MRI) grant Asphalt Binder and RAP suppliers The Office of Research and Technology Transfer at A-STATE

Industrial and agricultural waste materials possess burden to the businesses and societies. These waste materials can be used to enhance engineering properties of asphalts. Help to achieve economic and material sustainability.

MOTIVATION

Label Sample Description Source of Materials

Sample 1 PG 64-22 (Control) Ergon Asphalt & Emulsions, Inc., TN

Sample 2 PG 64-22 + 15% GTR Mesh #30 Liberty Tire Recycling, Pittsburgh, PA

Sample 3 PG 64-22 + 15% GTR Mesh #40 Liberty Tire Recycling, Pittsburgh, PA

Sample 4 PG 64-22 + 40% RAP I-40 near Forrest City, AR

Sample 5 PG 64-22 + 25% RAP + 5% RAS RAS from a stockpile of tear off roof

Sample 6 PG 64-22 + 4% RHA RHA from Riceland Foods, Stuttgart, AR

TEST PLAN

Figure: Morphology of (a) Sample 1, (b) Sample 2, (c) Sample 3, (d) Sample 4, (e) Sample 5, and (f) Sample 6

The height sensor features the morphology of scanned samples. Five modified sample along

with a control sample have been scanned over 20 μm square area.

All samples had three distinct phases [Catana (Bee), Peri-phase and Perpetua] except GTR-modified samples (#2 & 3), which showed four phases.

For GTR samples, the boundary between the Peri-phase and the Catana-phase is indistinguishable.

Sample 2 (GTR Mesh #30) showed “Sal-phase,” which comes in form of small extrusion in round or oval shape.

The overall surface irregularity for all samples ranged from 50 to 80 nm, while RHA showed the highest ups and downs.

DMT modulus increases due to the addition of any of the additives in the base binder.

DMT modulus was found to be related to the morphology. The Control sample showed the lowest modulus of 90 MPa,

while RHA-modified samples showed highest modulus of 800 MPa.

The adhesion force in the Peri-phase was found to be higher than that in Catana phase and Perpetua-phases except for the GTR-modified samples where almost uniform adhesion value was observed all over the surface.

Figure: DMT modulus of (a) Sample 1, (b) Sample 2, (c) Sample 3, (d) Sample 4, (e) Sample 5, and (f) Sample 6

The Catana and Peri-phase areas for all samples had higher energy dissipation values than the Perpetua-phase.

The additives changed the deformation values of modified samples considerably, indicating the Peri-phase being a harder area than the viscoelastic Perpetua-phase.

Selected recyclable modifiers made significant changes in microstructure and mechanistic properties of asphalt binders.

Reuse of waste materials will reduce environmental burdens AFM can be used as a viable tool to effectively characterize

paving asphalt materials. Because of asphalt’s adhesive nature, it DMT modulus instead

of Young’s modulus should be taken as a design parameter. Selected modifiers increase asphalt’s modulus and hardness,

indicating improved rutting resistance and longer lasting pavements

Note: This study has been accepted for presentation at the 2016 GeoChina Conference and publication in the American Society of Civil Engineers (ASCE), and an extended version of the manuscript is under review for publication in the ASCE International Journal of Geomechanics (IJOG).

AFM system Conical Tip scanning sample

Figure: Construction of Force-Distance Curve

Hypotheses Recyclable waste materials can be used as modifiers, which are expected to change asphalt’s micro-structures and properties An AFM can be used to detect changes in microstructures, which are correlated with material’s surface morphology

Ground Tire Rubber (GTR)Use of GTR in pavements would help to manage about 253M of scrapped tires/year the U.S. Will reduce disposal costs and environmental hazards

Reclaimed Asphalt Pavement (RAP)Produced from old road repair worksRAP in new roads improves certain pavement performancesRAP as construction materials reduces construction and waste management costs, and environment impacts

Recycled Asphalt Shingles (RAS)Originates from old roofsRAS contains asphalts, which can be used in new asphalt mixesOld roofs meet new roads

Rice Husk Ash (RHA)Worldwide production of 27M tons/year from rice millingLand filling or open dumping incur costs, create environmental threats

MATERIALS