Report of Optimum Binder Content and RAP Binder

ReplacementReplacement

Dry Weight of Aggregate (DWA) versus Total Weight of Mix (TWM)

RAP Binder Replacement Calculation

For Bay Area Tech Committee Meeting - Feb. 4, 2014

From DWA To TWM

DWA vs. TWM - Quick AnswerFrom DWA To TWM

3.00 2.913.50 3.384.00 3.854.50 4.315.00 4.765.50 5.216.00 5.666 50 6 106.50 6.107.00 6.547.50 6.988.00 7.418.50 7.839.00 8.26

e.g., 5.75% DWA => 5.44% TWM

FootnoteFootnote• Va = Volume of air voids, percent• Vb = Total volume of asphalt binder, percent• Vba = Volume of absorbed asphalt binder, percent

V V l f ff ti h lt bi d t• Vbe = Volume of effective asphalt binder, percent• VFA = Volume of voids filled with asphalt binder, percent• VMA = Volume of voids in mineral aggregate percentVMA = Volume of voids in mineral aggregate, percent• Vmb = Bulk volume of compacted mix• Vmm = Voidless volume of paving mixmm p g• Vsb = Bulk volume of mineral aggregate (for bulk specific gravity)• Vse = Effective volume of mineral aggregate

E ampleExample

Example Using the MatrixExample Using the Matrix

T t l W i ht f B D W i ht f B T t l W i ht W i ht f W i ht f

9

Total Weight of Mix, g

By Dry Weight of Aggregate

By Total Weight of Mix

Weight of Asphalt, g

Weight of Aggregate, g

C E D=E/(1+E) A=C*D B=C-A9

1200.0 0.0600 0.0566 67.9 1132.1

8

Total Weight of Mix, g

By Total Weight of Mix

By Dry Weight of Aggregate

Weight of Asphalt, g

Weight of Aggregate, g

C D E=D/(1-D) A=C*D B=C*(1-D)8 1200.0 0.0600 0.0638 72.0 1128.0

1200.0 0.0566 0.0600 67.9 1132.1

More ExamplesMore Examples

Total Weight of Mix, g

By Dry Weight of Aggregate

By Total Weight of Mix

Weight of Asphalt, g

Weight of Aggregate, g

C E D E/(1 E) A C*D B C AC E D=E/(1+E) A=C*D B=C-A

1200.0 4.50% 4.31% 51.7 1148.3

1200.0 5.00% 4.76% 57.1 1142.9

1200.0 5.50% 5.21% 62.6 1137.4

1200.0 6.00% 5.66% 67.9 1132.1

1200.0 6.50% 6.10% 73.2 1126.8

RAP Use: % RAP vs. BRRAP Use: % RAP vs. BR• Use RAP in HMA based on RAP percentage by p g yweight of aggregate or by weight of the total mix. 

• The use of RAP can reduce the need for virgin• The use of RAP can reduce the need for virgin binder and impact the binder properties, thus RAP may also be specified according to percentage binder replacement (BR). 

• The percentage of RAP used in the mix can be selected by determining the contribution of theselected by determining the contribution of the RAP binder toward the total binder in the mix by weight. 

Section 39Section 39

“For HMA mixtures using RAP theFor HMA mixtures using RAP, the maximum binder replacement is 25.0 

f f dpercent for surface course and 40.0 percent for lower courses.”p

Binder Replacement (BR)Binder Replacement (BR)

CT - Binder Replacement (BR)CT Binder Replacement (BR)CT: The amount of total binder replaced byCT: The amount of total binder replaced by binder in RAP is computed as follows:

A

BC

AA

BR

)1(

1

Where:

BC

BR

A = binder content from RAP, in decimalB = total RAP in total mix, in decimalC = total binder content in total mix, in decimal

CT - Example 1CT Example 1

CT - Example 2CT Example 250%

% RAP =

Binder in RAP

25.0

30%35%40%45%50%

men

t, % 7.0%

6.5%

Binder in RAP

BR % = 25.0

15%20%25%30%

der R

eplacem

6.0%

5.5%

5.0% 40%45%50%

BR, % =

4.0%

Binder in RAP

25.0

0%5%

10%

4% 5% 6% 7%

Bind

4.5%

4.0%

20%25%30%35%

% RAP

4.5%

5.0%

5.5%

Total Binder in Mix, %

0%5%

10%15% 6.0%

6.5%

7.0%0%4% 5% 6% 7%

Total Binder in Mix, %

7.0%

ReferencesReferences• Caltrans Construction Practice Directive (CPD) 13‐4Caltrans Construction Practice Directive (CPD) 13 4• California Test 367 ‐Method of Test for Determining Optimum Bitumen Content (OBC) Nov 2010Optimum Bitumen Content (OBC), Nov. 2010

• Caltrans, Section 39, Proposed 2015 SSFHWA R l i d A h lt P t i A h lt• FHWA, Reclaimed Asphalt Pavement in Asphalt Mixtures: State of The Practice. http://www fhwa dot gov/publications/research/inhttp://www.fhwa.dot.gov/publications/research/infrastructure/pavements/11021/003.cfm