Rheological and energetic characterization of wax-modified ... This techniques are something new: the

ALMA MATER STUDIORUM - UNIVERSITÀ DI BOLOGNA

FACOLTA’ DI INGEGNERIA

Corso di Laurea Magistrale in Ingegneria Civile

Context sensitive design in transportation infrastructures

RHEOLOGICAL AND ENERGETIC CHARACTERIZATION

OF WAX-MODIFIED ASPHALT BINDERS

TESI DI: RELATORE:

Riccardo Lamperti Dott. Ing. Cesare Sangiorgi

CORRELATORI:

Prof. Gordon Dan Airey

Dott. Ing. Claudio Lantieri

Dott. Ing. Matteo Pettinari

Anno Accademico 2011/12

Sessione II

Ai miei cari

INDEX

Introduction ...................................................................................................................... 1

1 Characteristics and Rheology of the Bitumen........................................................ 5

1.1 History ......................................................................................................................... 5

1.2 Origin and chemical composition of bitumen .............................................................. 6

1.3 Bitumen as colloidal model ........................................................................................ 10

1.4 Manufacture of bitumen ........................................................................................... 14

1.5 Types of bitumen ..................................................................................................... 16

1.6 Rheology of bitumen ................................................................................................. 18

1.7 Viscoelastic behaviour of bitumen ............................................................................. 21

2 The Bitumen-Aggregate Affinity .................................................................................. 23

2.1 Introduction ............................................................................................................... 23

2.2 Forces involved in adhesion ....................................................................................... 23

2.3 Theories on adhesion .................................................................................................. 26

2.3.1 Theory of (weak) boundary layers ...................................................................... 26

2.3.2 Electrostatic theory ............................................................................................. 27

2.3.3 Chemical bonding theory .................................................................................... 28

2.4 Bitumen Functional Groups ...................................................................................... 29

2.5 Aggregate Functional Groups ................................................................................... 31

2.6 Surface energy and wettability .................................................................................. 32

2.7 Theory for surface energy calculation from contact angle data ................................... 36

2.7.1 Geometric Mean Approach .................................................................................. 36

2.7.2 Critical Surface Tension Approach ...................................................................... 36

2.7.3 Acid-Base Approach ........................................................................................... 37

2.8 Thermodynamic theory ............................................................................................. 37

3 Reserch Project and Test Methods ............................................................................... 47

3.1 Introduction ............................................................................................................... 47

3.2 Ageing of bitumens .................................................................................................... 49

3.2.1 Rolling Thin Film Oven Test (RTFOT) .............................................................. 49

3.2.2 Pressure Aging Vessel (PAV) ............................................................................. 52

3.3 Dynamic Shear Rheometer (DSR) ............................................................................ 55

3.3.1 General concepts ................................................................................................ 55

3.3.2 Dynamic Mechanical Analysis ........................................................................... 57

3.4 Bending Beam Rheometer ........................................................................................ 60

3.5 Dynamic Contact Angle ............................................................................................. 64

3.6 Dynamic Vapour Sorption-DVS Technique .............................................................. 66

4 The Rheology Reserch ...................................................................................................... 71

4.1 Introduction ............................................................................................................ 71

4.2 Dynamic Shear Rheometer test ............................................................................... 72

4.2.1 Setting of the test and specimen preparation ....................................................... 72

4.2.2 Data analysis and representation ......................................................................... 76

4.2.3 Mastercurves ...................................................................................................... 76

4.2.4 Isochronal Plots .................................................................................................. 83

4.2.5 Black Diagram ................................................................................................... 87

4.2.6 Ageing Index ...................................................................................................... 89

4.3 Bending Beam Rheometer test .................................................................................. 90

4.3.1 Setting of the test and specimen preparation ....................................................... 90

4.3.2 Results ............................................................................................................... 92

4.4 Performance Grade ................................................................................................... 93

5 The Affinity Reserch ....................................................................................................... 103

5.1 Introduction ............................................................................................................ 103

5.2 Dynamic Contact Angle tests ................................................................................... 104

5.2.1 Setting of the test and specimen preparation ...................................................... 104

5.2.2 Surface energy of bitumens .............................................................................. 117

5.3 Dynamic Sorption Device tests ............................................................................... 120

5.3.1 Setting of the test and specimen preparation ..................................................... 121

5.3.2 Surface energy calculation of aggregates .......................................................... 129

5.4 Moisture damage parameters ................................................................................... 132

6 Conclusions ........................................................................................................................ 139

Introduction

1

INTRODUCTION

The first and more reliable technique to build up a road pavement is without any doubt

the hot mix asphalt. It is produced by heating the asphalt binder to decrease its viscosity,

and drying the aggregate to remove moisture from it prior to mixing, that is generally

performed with the aggregate at nearly 160 °C. The quality of hot mixtures obtained by

following the protocols, that are confirmed over the past is, in fact, an absolute

reference. The recent tendency of reduce the exploitation of non-renewable resources

and the need to ensure the environmental protection has moved the attention to find new

ways of construction and maintenance. The asphalt paving industry is for this reason

constantly exploring technological improvements. For instance, an excellent solution is

achieved by lowering the production and placement temperatures of hot mix asphalt:

these technologies are generically referred to as warm-mix asphalt (WMA). The

benefits are multiple, starting from the energy savings ranged from 20 to 35 % at the

plant depending on the system and the efficiency of the WMA plant. Data indicate plant

emissions are significantly reduced: typical expected reductions are 30 to 40 percent for

2 a