Session 40 Prabir Kumar Das

KTH – Väg- och Banteknik Oct 26, 2011

Page 1

Oct 26, 2011

The objective of this work was to investigate the influence of commercial wax additives for lowering energy consumption during asphalt production and paving with a focus on:

1. Cracking performance 2. Moisture Damage3. Low Temperature-Cracking

Page 2

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Oct 26, 2011

The effects of wax additives for lowering energy consumption during production and construction is known, but no study has focused explicitly on the cracking and durability properties of the resulting asphalt pavement.

Page 3

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Commercial Wax Oct 26, 2011

• Commercial wax (Sasobit, Montan wax) is used as energy reducing agent and flow improver

• Lower the mixing temperature of the asphalt, thus reducing energy consumption and emissions

• Wax may increase the asphalt pavement resistance to plastic deformation

Page 4

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Introduction To Test Materials Oct 26, 2011

Aggregate: Two different types of dense graded aggregate (crushed granite and feldspar, Skärlunda)with maximum size of 11mm used according to Swedish road standards (ATB VÄG, 2004)

Binder:Original (70/100) - as a base binderOriginal + 4% Sasobit Wax (FT-paraffin)Original + 4% Montan Wax (asphalten B)

Page 5

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Binder Test Results shows the improvement in Rutting Resistance

Oct 26, 2011

Page 6

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Characteristics UnitsOriginal 70/100

Original + 4%Sasobit

Original + 4% MW

Softening Point oC 46 89 85

Penetration dmm 81 45 52

Brookfield visc. At 1350C mPas 345 270 263

Brookfield visc. At 1650C mPas 101 80 82

Force Ductility Nm 1.38 4.03 3.54 Bending Beam Rheometer

S / m-value -120C Mpa 150 / 0.395 208 / 0.311 182 / 0.323

S / m-value -180C Mpa 414 / 0.3 462 / 0.252 421/ 0.271

S / m-value -240C Mpa 832 / 0.205 881 / .195 796 / .214

LST 0C -16 -15 -16

LmT 0C -18 -13 -15

Complex Modulus Increase for Improved Rutting Resistance

Oct 26, 2011

Page 7

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

CRACKING PERFORMANCE USING SUPERPAVE IDT Oct 26, 2011

Three specimens from each mixture were tested at 0 0C:

Resilient modulus testStatic creep testIndirect tensile strength test

Page 8

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

ENERGY RATIO CONCEPT Oct 26, 2011

Page 9

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Ref: Florida Cracking Model

HMA FRACTURE MECHANICS PERFORMANCE PREEDICTION Oct 26, 2011

Page 10

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

For example, AG1-O = Aggregate type 1 mixed with Base binder….etc

CONCLUSIONS FROM MIXTURE PERFORMANCE Oct 26, 2011

Page 11

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

• Addition of wax makes the binder stiffer

• Complex modulus results on binder showed improve stiffness at higher temperatures (i.e. improved rutting resistance!)

• Adding wax to the binder increases the cracking resistance measured by the Superpave IDT

APPROACH Oct 26, 2011

Page 12

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

• Moisture damage in asphalt mixtures is typically evaluated by the tensile strength ratio of moisture conditioned and dry samples

• However a single parameter such as tensile strength is not enough to conclude moisture damage performance (Birgisson et al. 2003, 2004)

• In this study the HMA fracture mechanics framework was used to evaluate moisture damage

Creep rate at 1000 sec of the mixtures Oct 26, 2011

Page 13

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

For example, AG1-O = Before Conditioned and AG1-O-C = After Conditioned

Moisture Damage Ratio of ER Oct 26, 2011

Page 14

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

For example, AG1-O = Aggregate type 1 mixed with Base binder….etc

Conclusions from Mixture Performance tests Oct 26, 2011

Page 15

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Compared to unmodified mixtures, wax modified mixtures gives :

- Lower Creep rate.- Higher Energy Ratio

So, addition of wax shows better moisture damage performance.

Low Temperature Cracking Oct 26, 2011

Page 16

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Laboratory Experiments:

Binder Test:DMA (Dynamic Mechanical Analysis)BBR (Bending Beam Rheometer)

Mixture Test:TSRST (Thermal Stress Restrained Test)Superpave IDT (Indirect Tensile Strength Test)

SUMMARY OF MIXTURES FRACTURE PROPERTIES Oct 26, 2011

Page 17

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

TSRST TEST RESULTS Oct 26, 2011

Page 18

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

Conclusions For Low Temperature Performance Oct 26, 2011

Page 19

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking

So, Using 4% commercial wax as an additive has a minor or may be no negative effect in Low Temperature Cracking performance.

Test Result

Binder DMA and BBR Minor Negative Effect

MixtureTSRST Minor Negative Effect

Superpave IDT Small Positive Effect

Thank You Oct 26, 2011

Page 20

Motivation

Materials

Cracking Performance

Moisture Damage

Low Temperature Cracking