LEADCAP - Iowa City, IA

Construction of the road in Iowa City, Iowa

On August 15, 2011, City of Iowa City requested warm mix asphalt to be used on a section of Capitol Street. 350 tons of LEADCAP WMA were used to overlay the street at full-width. The existing pavement was milled and replaced with 1.5-inch HMA binder course and 1.5-inch WMA surface course.  A total of 327 tons of a 1 million ESAL 12.5-mm WMA surface mix with 10% RAP was used. The asphalt mixture was stored in a holding container until it was ready to be loaded onto dump trucks at 265°F. It was then driven to the jobsite and placed on top of the binder course at 240°F. The WMA mixture was compacted at a temperature of 230°F. On September 27, 2012, due to the underground utility rehabilitation, a part of the Capitol Street was reconstructed using the 100 tons of the same LEADCAP WMA mixtures.Temperature for both production and compaction was 45°F lower than HMA. LEADCAP additive was used for this mixture at a rate of 1.5% of the total binder content. Traffic was allowed on the new mat as soon as each side was compacted. Field implementation results are summarized in the table below.

Job Site

Miami (HMA)

Capitol 1 (WMA)

Capitol 2 (WMA)

% RAP

10%

10%

10%

Actual Virgin Binder Content

4.60

4.60

5.40

Actual Total Binder Content

5.17

5.17

5.85

Dust (-No. 200)

4.1

4.1

5.7

Dust-Binder Ratio

0.84

0.84

1.12

Lab Compacted Gmb

2.366

2.369

2.402

Gmm

2.476

2.467

2.480

VTM (%) of Lab Comp. Specimens

4.4

3.97

3.10

Gmb of Field Cores

2.302

2.240

2.331

VTM (%) of Field Cores

7.01

8.97

6.01