Mn/DOT Shingle Study By Jim McGraw HMA Shingle Workshop July 12, 2006
Shingle Study Objectives Variability of Shingles Effect on Mix & Binder Deleterious Material
Study Mix Design
Material Variability 10 Random Samples % Binder PG Grading Extracted Gradation Deleterious Material Paper/Glass Fiber Procedures Mixture Testing
Material Variability- Binder RAP Average 7.0 % S.D. 0.2 % Tear-Off Average 36.4% S.D 1.9 % Manufacture Waste Average 19.6 % S.D. 2.3 % 5% Addition-Binder 1.0% MW, 1.8% TO TO Stiffer
Extracted Gradation Tear Off finer on sieves less than #10 Additional Processing to remove metal TO mixes less -#100 & #200
Extracted Gradation
Effect of Hot Mix Plant Unexpected RTFO Losses TO- Average 1.30%, S.D.0.4% MW- Average 0.80 S.D. 0.4% RAP-Average 0.7% S.D. 0.1% Binder – %
Shingle HT PG Grade MW- Average S.D. 6.1 TO-Average S.D. 4.5 RAP- Average 76.1 S.D. 0.9
Mix HT PG Grade TO- Avg 73.2 S.D. 0.2 MW-Avg 70.9 S.D. 0.4 RAP-Avg 64.2 S.D. 0.3 MW- Full grade stiffer TO- 1 ½ grade stiffer RAP Grade - soft
Shingles LT PG TO- Avg 1.1 S.D. 5.1 MW- Avg –11.0 S.D. 1.9 RAP- Avg –25.8 S.D. 0.7
Mix LT PG TO- Avg –28.8 S.D. 2.4 MW- Avg –26.2 S.D. 0.2 RAP- Avg –29.2 S.D. 0.9 PG PG Good low temp from RAP % Mixing ???
Deleterious Materials MW- Average 1.74% glass fibers with S.D of 1.15 Average of 1.34 % paper and a S.D of 0.48 Tear Off- Average 0.66 % glass fibers with S.D of 0.17 Average of % paper and a S.D of 2.12 AASHTO Spec- 0.5%
Shingle Blending Chart
TH 10 Shingle HMA- SP PG 64-28/30% RAP - PG PG /27% RAP and 3 % shingles PG PG 64-28/5% shingles/25% RAP- PG Adding 3% shingles it increases stiffness on both ends by ½ grade over that of the 30% RAP. Adding an additional 2% for a total of 5% increases the high end by an additional ½ grade but doesn't effect the low temp grade Some cracking seen
Conclusions More mixture testing with true control Mix Fatigue Test Verify binder grade Shingle Only Study Softer Binder Field Review Revisit present spec