# Presentation: 471208

## Polymer Modified Asphalt & Performance Graded Spec’s

***What, How, Why?***
***FAA Regional Meeting***
***April 5, 2005***

## What is Asphalt ??

***The “tar-like” residue that remains when petroleum crude oil is evaporated.***
***A coloidal suspension made up of asphaltenes & maltenes***
***Maltenes (resins, aromatics, saturates)***

## What is a Polymer?

***“******Poly”  =  many***
***“******Monomer”  =  small molecule***
***“******Polymer”  =  many small molecules***
***Properties determined by sequence and chemical structure of monomers***

## Sequence  (Block, Random, Alternating, Linear, Radial)

**M1****   =   Monomer   =   small molecule #1**
**M2****   =   Monomer   =   small molecule #2**
_**Random**_** Copolymer     ~~****M1****M2M2****M1****M2****M1M1****~~**
_**Alternating**_** Copolymer    ~~****M1****M2****M1****M2****M1****M2****M1****~~**
_**Block**_** Copolymer    ~~****M1M1M1M1****M2M2M2M2****~~**
_**Radial**_** Block CoPolymer    ~~****M1M1M1****M2M2M2****~~**
**  ****(aka **_**Graft**_** copolymer)                 ****M2M2M2****M1M1M1**

## Types of Polymers most used

***Elastomers***
***Plastomers***

## Slide 6

## Elastomers

***Can be stretched, get stronger as they are pulled***
***Recover their shape when released ***
***Give more resilient, flexible pavements***

## Types of Elastomers

***Styrene Butadiene Block Copolymers (SB, SBS)***
***Styrene Butadiene Rubber Latex (SBR)***
***Natural Rubber Latex***

## Plastomers

***Form rigid three-dimensional network***
***Give early high strength, less resistant to strain***
***Give mixes with higher stabilities and stiffness moduli***

## Types of Plastomers

***Ethylene Vinyl Acetate (EVA)***
***Polyethylene/Polypropylene***
***Polyolefins***

## What about Crumb Rubber?

***Often confused with polymer modification***
***Suspended, not dissolved, in asphalt***
***Doesn’t give same benefits as polymer modification***

**Notes:**
Behaves more like an aggregate or filler fraction
Wet and Dry Processes
	Wet-added to liquid asphalt before mixing with aggregate
	Dry-added directly to aggregate

## Asphalt compatibility important

***Continuous network desired***
***Stable structure***
***No separation***

## Photomicrographs of styrene-butadiene (SB) polymer in asphalts

***Reflective Fluorescence Microscopy***
***Lighter color is polymer; darker is asphalt***
***Ideal: ***
***small structure - polymer and asphalt phases networked***
***Undesirable: ***
***Discrete polymer particles - polymer will separate during storage***

## Examples of several asphalts (all  AC-20s with same SB polymer)

- Asphalt A

- Asphalt C

- Asphalt D

- Asphalt B

## Examples of SB and SBS polymers in two asphalts

- Asphalt F
- SB Polymer

- Asphalt F
- SBS Polymer

- Asphalt E
- SB Polymer

- Asphalt E
- SBS’  Polymer

## Why modify?

***Extra performance and durability***
***Reduced life cycle costs***
***Special techniques not possible with unmodified AC***
***Microsurfacing***
***Emulsion chip seals on high traffic areas***

## Properties of Polymer Modified AC determined by...

***Type of polymer system used***
***Compatibility with asphalt***

## Performance properties vary with...

***Concentration***
***Molecular weight***
***Chemical composition***
***Crude source***
***Refining process***
***Grade of base asphalt***

## Asphalt Specifications

***S******trategic ******H******ighway ******R******esearch ******P******rogram***
***	******	******	***_***(SHRP)***_
_***SUP***_***erior ***_***PER***_***forming Asphalt ***_***PAVE***_***ments ***
***	******  ******	******	******	******(Superpave)***
***P******erformance ******G******raded specifications for ******A******sphalt ******B******inders***
***	******	******	******	******(PGAB)***

## SUPERPAVE - Why?

***Better ways of measuring asphalt physical properties and predicting performance***
***Asphalt strength is highly sensitive to: ***
***temperature***
***rate of loading***

**Notes:**
With conventional testing, binders with different temperature susceptibilities meet the same grade.

  Two binders may have the same viscosity or the same penetration however they may behave very differently at high or low temperatures.

## PG Binder Spec Table

- Example . . .
- 	 AASHTO M 320
- 	 PG 64-22

## Slide 22

## SUPERPAVE gives us the tools to define the temperature range
Grading System Based on:
Climate (Temperatures in °C)
Risk (Reliability Factor)
Traffic speed and load (Grade “Bumping”)

***Grading System Based on:***
***Climate (Temperatures in °C)***
***Risk (Reliability Factor)***
***Traffic speed and load (Grade “Bumping”)***

**PG 64-22**

**Performance**
**Grade**

**Average 7-day**
**max pavement**
_**design**_** temp**

**Min pavement**
_**design**_** temp**

***Performance Graded Binders***

**Notes:**
Note that it is the design pavement temperature.  A design engineer may choose a 50% reliability for a low volume traffic country road, or a 98% reliability for a city Interstate or street.  FHWA is recommending we use a 98% reliability to reduce rutting risks.  The reliability indicates the probability that a pavement will see the extreme highs and lows during its service life.

PG 64-22 is the designated binder for Reno / Carson City @ 98% reliability.
PG 58-15 is the designated binder for Reno / Carson City @ 50% reliability.

Grade bumping:  the next slides will discuss reasons to use higher high temperature grades.

## Four Principle Reasons a Pavement Fails

***  ******Rutting***
***  ******Fatigue Cracking***
***  ******Thermal Cracking***
***  ******Lack of Cohesion or Adhesion***

## Dynamic Shear Rheometer

***Reasons 1 & 2***
***   ******Rutting***
***  ******Fatigue Cracking***

## Spindle

- Fixed
- Base

- Proper Amount
- of Asphalt

**Notes:**

The DSR instrument is about the size of a breadbox.  The test involves placing a sample of asphalt between two parallel plates.

This test is run three times on the asphalt binder.
1)  original asphalt sample.
2)  rtfo conditioned asphalt sample.
3)  pav conditioned asphalt sample.

## Spindle Moves From A to C

**Spindle**
**Position**

**Time**

**A**

**C**

**Notes:**
The upper plate (or spindle) occillates back and forth at a set frequency.  The bottom plate remains stationary or moves ever so slightly dependent on the stiffness of the asphalt binder.

The bottom plate is connect to an LVDT which measures very slight movements.

## Spindle Moves from C to A

***One cycle***
***is complete...***

**Spindle**
**Position**

**Time**

**C**

**A**

**Notes:**
As the upper spindle moves back and forth in a sinusoidal motion, the bottom plate responds.

The upper spindle moves while applying constant stress (hence stress controlled).  The movement of the bottom plate is referred to as the strain response. 

## Elastic:   = 0 deg

- time

- Elastic:   = 0 deg

- Viscous:   = 90 deg

******max**

******max**

******max**

******max**

- time lag = 

- Applied
- Shear
- Stress

- Resulting
- Shear
- Strain

**Notes:**
#1-32
These diagrams show both the oscillating shear stress and the resulting shear strain during the DRS test. For a perfectly elastic material, one which exhibits zero permanent deformation when loaded, the applied load causes an immediate response. In this case, the time lag is zero and the load and response curves are “in phase” with each other. Thus, the phase angle is zero and the maximum strain occurs at the same time as when the stress is at a maximum level.

A viscous material, such as hot asphalt binder at mixing temperature, has a larger time lag between load and response. An angle of 90 degrees would suggest a perfectly viscous material.

## max

- Resulting
**S**hear
- Strain

- Applied
- Shear
- Stres**s**

- max

- 

**G* = **

******max**

******max**

****** ****= time lag**

- time

- time

******max**

**Notes:**
The DSR measures two things:
1) G* (complex modulus)
2) “delta” (time lag or phase angle)

The G* is the ratio of the max shear stress to the max shear strain.

The specification dictates the following at the specified test temperature:

1)  G* / Sin d  must be > 1.0 KPa for original binder
2)  G* / Sin d  must be > 2.2 KPa for rtfo binder.
3)  G* x Sin d  must be < 5000 KPa for pav binder.

## Bending Beam Rheometer

***Reason 3***
***   ******Thermal Cracking***

## Specimen Preparation

**Notes:**

The BBR is run on the binder sample after the binder has been conditioned in the RTFO followed by conditioning in the PAV.

The sample specimen looks like this.

## Deflection

- Transducer

- Asphalt Beam
- Original Position

- Asphalt Beam
- Deflected Position

**Notes:**
The specimen is placed in a bath and held at a test temperature 10C warmer than the temperature the binder is being rated for.  This is due to the time / temperature superposition.

A load of 980 milliNewtons is place in the middle of the beam and the deflection of the beam is measured.

## Data Analysis and Presentation

**60 sec**

**Time**

**Deflection**

******(t)**

***simulates stiffness***
***after 2 hours at***
***10 C lower temp***

**Notes:**
The computer makes a plot of deflection vs. time.

A a point on the curve of time equals 60 seconds the stiffness is calculated.

## Data Analysis and Presentation

***Data Analysis and Presentation***

**S(t) = **

**PL****3**

**4bh****3**** ********(t)**

**creep stiffness**
**at 60 sec**

**load = 100 g**

**length between supports**

**beam width = 12.7 mm**

**beam thickness = 6.35 mm**

**deflection at 60 sec**

**Notes:**
This is the equation for calculating Stiffness.  The Superpave specification dictates the stiffness cannot exceed 300 MPa.

## Data Analysis and Presentation

***Data Analysis and Presentation***

**Log Creep**
**Stiffness, S**

**Log Loading Time**

**slope = m-value**

**60 sec**

**8****	****15****	****30****	****	****   120****	****      240****	**

**Notes:**
The computer further calculates a plot of log Stiffness vs. log time.  At a point on the curve of time equals 60 seconds, the “m” value is read off the curve.

The “m” value is nothing more than the slope of the curve at that point.

The Superpave specification dictates the “m” value must be a minimum of 0.300.

Note for the “m” value were zero, that would translate to no change in stiffness.  For no change in stiffness to occur then no deflection of the beam occurs meaing the beam is very brittle and will like thermally crack.

## Conventional AC Grades vs. SHRP Performance Grades      (typical comparisons)

***AC-5***
***AC-10***
***AC-20***
***AC-40***

***PG 52-34***
***PG 58-28***
***PG 64-22***
***PG 70-16***

_***Typical (not absolute) for unmodified asphalts only***_

## Typical Market PGAB Modified & Un-Modified Grades

***Typical Market PGAB Modified & Un-Modified Grades***

## Modified Asphalt Specifications

***How do you know you’re getting a PMAC?***
-   ***Rule of 90******o******C temperature spread***
***  ******pg 58-28   ----->  86******o******C spread    ******(typically non-modified)***
***	******58******o******C - (-28******o******C)  =  86******o******C***
***  ******pg 64-28   ----->  92******o******C spread    ******(typically modified)***
- 	***64******o******C - (-28******o******C)  =  92******o******C***
***Modification will expand the temperature spread***

## SHRP+ :   Physical Properties

***Insuring that a specific family of modifiers is used for a designated high-performance PG grade ***
***Tests which define elastomers:***
***Elastic Recovery ***
***Toughness & Tenacity***
***Maximum Phase Angle ***

**Notes:**
Several states have added modifier identifiers to the SHRP specs for selected, high performance grades.

## Benefits from modification	

***Network structure in asphalt means:***
***Stiffer at high temperatures ***
*** ******Resists Rutting***
***Less stiff (brittle) at low temperature ***
*** ******Resists Cracking***
***More elastic***
*** ******More durable,  longer pavement service life***
***Improved adhesion and moisture resistance***
*** ******Resists stripping, raveling and loss of aggregate***

## Hamburg Wheeltracking - Same AC-20 unmodified and modified

## Polymer Modified Asphalt Specifications

***Recommend first look at adopting local state DOT agency specifications  !!***

## Polymer Modified AC Product Family

***Modified AC for Hot Mix***
***Modified Rapid Setting Emulsions for Chip and Sand Seal Coating***
***Modified  Medium Setting Emulsions for cold and warm mixes and patching materials***
***Modified Slow Setting Emulsions for industrial and road paving applications, e.g. cold pour crackfiller***
***Quick Setting Polymer Modified Emulsions for Slurry Seal and Microsurfacing***
***Modified Emulsions for cold and hot recycling***

## Thank you

*** ******. . Questions ?***