High-RAP Asphalt Cement Concrete with Binder Modifier and Aramid Fiber
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Solution Overview
Problem
Existing asphalt cement concrete (ACC) formulations using recycled asphalt pavement (RAP) face performance issues such as cracking and rutting due to the differences between aged and virgin bitumen, limiting RAP usage to 10-25% by weight, which reduces the economic and environmental benefits of recycling.
Innovation Solution
A combination of a liquid binder modifier and aramid fibers is added to the HMA mix, where the liquid binder modifier lowers the performance grade of virgin bitumen and the aramid fibers enhance the flexibility and cohesion of the mixture, allowing RAP usage up to 60% by weight without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RAP usage is increased to reduce costs and improve sustainability, then the economic and environmental benefits increase, but the performance deteriorates due to cracking and rutting caused by aged bitumen
Solution Approach 1:
A liquid binder modifier is introduced as an intermediary substance between the aged bitumen in RAP and the aggregate structure. This modifier penetrates and rejuvenates the aged bitumen, restoring its flexibility and bonding properties, thereby enabling higher RAP content (up to 60% or more) without sacrificing cracking and rutting performance
Solution Approach 2:
The patent creates a composite binder system combining virgin bitumen, liquid binder modifier, and optionally polymer modifiers. This composite material leverages the advantages of each component: virgin bitumen provides structural integrity, the liquid modifier rejuvenates aged bitumen properties, and polymers enhance elasticity and crack resistance, allowing high RAP content while maintaining performance
2Quantity of substance
If RAP usage is limited to 10-25% to maintain performance, then cracking and rutting resistance is preserved, but the economic and environmental benefits of recycling are reduced
Solution Approach 1:
The patent changes the chemical and physical parameters of the bitumen binder system by introducing liquid binder modifiers that alter the viscosity, softening point, and aging characteristics. These parameter changes enable the binder to accommodate higher proportions of aged bitumen from RAP while maintaining the flexibility and strength required to prevent cracking and rutting
3Quantity of substance
If liquid binder modifier and aramid fibers are added to enable high RAP usage, then RAP content can reach 60% or more, but the mixture complexity and processing requirements increase
Solution Approach 1:
The liquid binder modifier is pre-mixed with the virgin bitumen before combining with RAP and aggregate. This preliminary action ensures uniform distribution of the modifier throughout the binder system, simplifying the overall mixing process and eliminating the need for complex multi-stage mixing procedures despite the high RAP content
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The combined use of these additives results in ACC with improved cracking and rutting performance comparable to formulations with less RAP, while reducing costs through increased RAP usage, thus enhancing the economic and environmental benefits of recycling.
Implementation Method 1
the liquid binder modifier lowers the performance grade of virgin bitumen
Implementation Method 2
the aramid fibers enhance the flexibility and cohesion of the mixture
Data Source
AI summary
The Present disclosure is related to hot-mix asphalt (“HMA”) for asphalt cement concrete (“ACC”) pavement. Equivalent-performing pavement may be made at lower cost, or higher-performing pavement may be made at equivalent-to-prior-art cost. The amendments, recycled asphalt pavement (“RAP”, and including recycled asphalt shingles [“RAS”]), and reinforcing fiber (aramid fiber) may be adjusted as described herein to achieve a desired price/performance target.