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Hot Mix Asphalt Advancements April 7 th , 2021 Amy Beise, PE – Materials & Research Justin Ramsey, PE – Environmental &Transportation Services
Hot Mix Asphalt AdvancementsApril 7th, 2021
Amy Beise, PE – Materials & Research
Justin Ramsey, PE – Environmental & Transportation Services
2020 Hot Mix Asphalt Program
$99+ Million
How do we protect our investment?
Density
Rule of Thumb
1% increase in density
results in
10% increase in service life
Density 101
What is it?
Density =
m = mixtures = stoneb = binder
Specific Gravity =
Density 101
How it’s Measured
𝑩𝒖𝒍𝒌 𝑺𝑮 𝑭𝒊𝒆𝒍𝒅 𝑪𝒐𝒓𝒆 𝑻𝒉𝒆𝒐𝒓𝒆𝒕𝒊𝒄𝒂𝒍 𝑴𝒂𝒙 𝑺𝑮 𝑴𝒊𝒙𝒕𝒖𝒓𝒆
% Density = 100*
% Air Voids = 100 ‐% Density
Examples:
92% Density means 8% Air Voids
95% Density means 5% Air Voids
Density
What are the benefits?
Increased Densities Reduce:• Structure Weakening
• Oxidation Aging
• Cracking
• Rutting
• Raveling
• Stripping
Density
How do we improve?
Specification Changes
Rolling & Paving Operations
Increase Lift Thicknesses
Modifications to Mix Design
Percent within Limits
Statistical Acceptance
Goal – Reduce Variability
87% 88% 89% 90% 91% 92% 93% 94% 95% 96% 97% 98% 99% 100%
Standard Acceptance
Based on specified average
Disadvantage: Many cores can fall below the desired value
Specified Average
87% 88% 89% 90% 91% 92% 93% 94% 95% 96% 97% 98% 99% 100%
Upper Spec Limit
Specified Average
Lower Spec Limit
Percent within Limit Acceptance
Statistical percentage between upper and lower spec limit
Advantage:Variability is part of acceptance
Disadvantage: Learning Curve
87% 88% 89% 90% 91% 92% 93% 94% 95% 96% 97% 98% 99% 100%
Lower Spec Limit
Upper Spec Limit
The future is only as good
as your lowest density areas
Percent within Limits
Pilot Project #1NH‐6‐001(041)162; PCN 2259138,500 Ton FAA 43 RAP
SS‐2‐046(048)030; PCN 2157852,000 Ton FAA 43 RAP
Percent within Limits
Pilot Project #1
Percent within Limits
87 88 89 90 91 92 93 94 95 96 97 98 99 100
% Density
SS‐2‐046(048)030
Project Average % Density
Standard Deviation
PWL
SS‐2‐046(048)030 93.7% 1.5 85%
Percent within Limits
Pilot Project #1
87 88 89 90 91 92 93 94 95 96 97 98 99 100
% Density
SS‐2‐046(048)030 NH‐6‐001(041)162
Percent within Limits
Project Average % Density
Standard Deviation
PWL
SS‐2‐046(048)030 93.7% 1.5 85%
NH‐6‐001(041)162 93.8% 1.2 91%
Percent within Limits
Pilot Project #1
87 88 89 90 91 92 93 94 95 96 97 98 99 100
% Density
SS‐2‐046(048)030 NH‐6‐001(041)162 Historical FAA 43
Percent within Limits
Project Average % Density
Standard Deviation
PWL
SS‐2‐046(048)030 93.7% 1.5 85%
NH‐6‐001(041)162 93.8% 1.2 91%
Historical FAA 43 92.7% 1.5 66%
Percent within Limits
Pilot Project #1Observations
• Very few cores fell below the 92%
• Extra Contractor Quality Control
• Reduced Disincentive Paving
Quality is everyone's
role
