ASPHALT EXPERT SYSTEM ®©

 

 

- FUNDAMENTAL MISTAKES IN PREVAILING RATIONAL -

 

 No COMPARABILITY, WHY?

 

1.      THE MASS ASPHALT MODEL Is Wrong!

 

Asphalt Mix Constituents Are Defined In TWO PHYSICAL SYSTEMS! Mineral Material And Binder Are Expressed In Mass Units. Voids Are Expressed In Volumetric Units.

MUST BE ONE PHYSICAL SYSTEM!

Voids Could Be Expressed in Volumetric Units ONLY. Therefore, All Functional Constituents Have To Be Expressed In Volumetric Units.

 

PROOF: We Have Two Asphalt Mix Compositions Both Expressed In A Conventional Way.

WE CANNOT LEARN ANYTHING ABOUT THEM THROUGH THE GIVEN DATA ON COMPOSITIONS. IN FACT, WE ARE NOT ABLE TO COMPARE THEM. WHY?

What Two Sets Of Data Represent Might Be Either Two Different Asphalt Mixes Or Just ONE Represented By Two Various Compaction States.

 CONCLUSION: This MASS ASPHALT MODEL ‘Rational’ Is Not Able To Provide Us With Any Clear Idea On Functional Mix Constituents.

Therefore, Any Comparison Between Two Or More Asphalt Mix Compositions Based On THE MASS MODEL IS NOT POSSIBLE. (See Picture Bellow)

 

 

 

2.      THE SIMPLE VOLUMETRIC ASPHALT MODEL IS GROSSLY INADEQUATE

 

Brief Explanation of The 'Voids' Dogma (As Slight Digression)

 

Basic Role Of The ACCESSIBLE* Voids in The Asphalt Layer Is:

To Assure Flexible System Response In The ‘Critical’ Conditions (Heavy Loads, Very High Temperature)

To Prevent Accelerated Binder Aging

*This Is Not The Same As ‘Voids Total In Mix’ (VTM)

 

Note: WHEN TEMPERATURE RISES THE LOW VISCOSE BINDER PARTS EXPAND AND MIGRATE OUT BY ‘FORCE’.  

ACCESSIBLE/’OPEN’ VOIDS MUST BE SUB-DESIGNED IN A WAY TO DECREASE MOISTURE SUSCEPTIBILITY.

Therefore, THE ACCESSABLE VOIDS CONCENTRATION MUST BE CAREFULY QUANTIFIED AND OPTIMIZED IN EACH PARTICULAR CASE AND

ESPECIALLY WHEN HIGHLY POROUS FINE AGGREGATE FRACTIONS ARE USED IN THE ASPHALT MIXTURE.

 

Now, Back To The Main Subject!

 

PROOF: We Have ONE ASPHALT MIX COMPOSITION Expressed In The Conventional Way: Binder Content & Mineral Material Content In Mass Units, And The VOIDS (VTM).

MILLIONS OF DIFFERENT ASPHALT MIX COMPOSITIONS CAN BE ‘DERIVED’ FROM IT IF THE MASS COMPOSITION ‘TRANSFORMED’ INTO VOLUMETRIC SYSTEM.

COMMON TO ALL OF THEM WOULD BE THE IDENTICAL VOIDS CONCENTRATION AND NOTHING ELSE (just three such compositions are shown on the picture bellow).

COULD WE LEARN ANYTHING ABOUT THEM THROUGH THREE SETS OF GIVEN DATA?

  WE ARE NOT ABLE TO COMPARE THEM. WHY?

Besides The Fact, That All Of Them Have The Same Concentration Of Voids, And Significantly Different Volumetric Concentrations Of TWO KEY FUNCTIONAL CONSTITUENTS (Mineral Material And Binder), We Cannot Logically Conclude More Then Just That All Three Compositions Would Show Different Physical Behavior Under Identical Conditions. WHAT KIND OF BEHAVIOR IT WOULD BE WE ARE NOT ABLE TO PREDICT. WHY?

WE NEED TO KNOW THE SPECIFICS - PHYSICAL COMPOSITION ‘BREAKDOWN’ FOR EACH OF THE COMPOSITIONS

 CONCLUSION: Any Valid Comparison Between Asphalt Mix Compositions Presented By SIMPLE VOLUMETRIC MODEL IS NOT POSSIBLE.

 

 

 

3.      THE ASPHALT INSTITUTEVOLUMETRIC MODEL LACKS CRUCIAL RELATIONS

 

“A sound understanding of spatial composition is necessary to predict the effects of changes” (1999 Van de Ven)

 

Several Crucial Relations/Elements in Rational Are Missing:

 

1.      AGGREGATES MUST BE FUNCTIONALLY DIVIDED INTO:   FILLER MIX AND SKELETAL STRUCTURE

2.      ALL THREE FUNCTIONAL BINDER PARTS MUST BE DETERMINED

3.      FUNCTIONAL INTERELATIONS WITHIN BITUMINOUS MORTAR PARTS MUST BE DEFINED

4.      ACCESSIBLE AND THE TOTAL VOIDS MUST BE DETERMINED

 

FACT OF LIFE:

·          First, When Binder Is Added To And Mixed With Mineral Material FIRST THING THAT WOULD HAPPEN IS THAT FILLER AND BINDER IMMEDIATELY DO ATTRACT EACH OTHER – INTERACT And TRY TO ‘ABSORB EACH OTHER’. This Reaction Is Significant And Distinct In Physical And Chemical Terms. It Must Be Closely Followed And Quantified. Filler Material Is Substantially Different In Fundamental Behavior Properties From Aggregate Skeletal Material (Fine And Coarse Particles)  

·          Second, The Filer Mix with Bound Part Of Binder Belongs To T-Susceptible Sub-System Called Filler Mortar, And

·          Third, Such Sub-System Has A Tendency To Contract/Expend (Only Inert Filler Such As Glass Does Not Produce Such ‘Spatial Disturbance’)

 

·          There Are Three Functional Parts Of Binder: ‘Free’ Binder For Coating Of Skeletal Aggregate Particles, ‘Absorbed’ Binder Into Pores Of Skeletal Aggregate Particles, And Previously Mentioned Filler Mix ‘Bound’ Binder. ALL THREE FUNCTIONAL BINDER PARTS MUST BE ACCURATELY DETERMINED, QUANTIFIED AND OPTIMIZED.

 

·          If One Ignores The Issue Of Quality Of Grading Design, As It Is In This Occasion, It Must Be Stressed Out That Mass Grading Curve Is Gravely Misleading And ABSURD, Especially When Mineral Material From More Then One Source Is Used. Identical Mass Grading Curve Of Two Different Mineral Compositions Is Absolutely Misleading. It Does Not Reflect ‘Spatial Packing’ Of Particles AT ALL. Volumetric Grading Is Mistaken Too If Does Not Represent (Sub) Fractions With Determined Densities With Pores Included.

 

·          There Are Inaccessible/’Closed’ And Accessible/ ‘Open’ VOIDS. Together They Make Total Voids In Asphalt Mix (VTM). There Is A Way To Determine The Amount/Concentration Of Both. Why? In Some Critical Scenario Development Such Knowledge Could Play Significant Role In Performance Assessment and Reliable Prediction of Behavior Of Asphalt Layer. 

 

 

 

THIS ASPHALT MODEL CANNOT BE USED AS VALID TOOL  

 FOR COMPARIOSON BETWEEN THE ASPHALT MIX COMPOSITIONS,

AND AS LOGICAL BASE FOR AN ASPHALT MIX PERFORMANCE EVALUATION

 

 

 

 

 

VALID PERFORMANCE BASED SPECIFICATIONS DEVELOPMENT IS IMPOSSIBLE,

 UNLESS

ONE IS IN CAPACITY TO DEFINE FUNCTIONAL CONSTITUENTS OF THE ASPHALT MIX.

 

JUST FOLLOWING THE ‘ROUGH’ LOGIC OF THE CURRENT ASPHALT MODELS,

WE ARE AFRAID, IT CANNOT BE DONE?

 

FORTUNATELY, SOONER OR LATER EVERY BUBBLE BURSTS.