Asphalt Mixture Preparation with Separate Drum Heating and RAP Disintegration
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Solution Overview
Problem
Incorporating high percentages of recycled asphalt pavement (RAP) into asphalt mixtures is challenging due to the difficulty in achieving homogeneous mixtures at warm mix process temperatures, leading to inhomogeneous asphalt pavements and mechanical property issues, while conventional heating methods are energy-intensive and environmentally undesirable.
Innovation Solution
A process involving transporting RAP and virgin aggregate through separate drums to specific temperatures, with a soft bitumen component added to the RAP to promote disintegration, allowing for the incorporation of high RAP percentages in warm mix asphalt mixtures by using a combination of soft and hard bitumen components, including a bitumen emulsion or foamed bitumen, to ensure homogeneous mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If RAP is incorporated at high percentages (greater than 25wt%) into asphalt mixtures using conventional heating methods, then the sustainability and cost-effectiveness improve, but the mixture homogeneity deteriorates due to insufficient disintegration of RAP at warm temperatures
Solution Approach 1:
The patent applies preliminary action by adding a disintegrating agent to the RAP before the main mixing process. This pre-treatment step softens and breaks down the aged binder in RAP, making it easier to disintegrate during subsequent mixing at lower temperatures, thereby achieving homogeneous mixtures with high RAP content without requiring excessive heating
Solution Approach 2:
The patent uses a disintegrating agent as an intermediary substance to facilitate the breakdown of RAP. This agent acts as a mediator between the RAP and the mixing process, chemically softening the aged binder and enabling effective disintegration at reduced temperatures, thus resolving the contradiction between high RAP content and mixture homogeneity
2Manufacturing precision
If conventional heating methods are used to heat RAP to high temperatures for complete disintegration, then the RAP disintegration improves, but the energy consumption and environmental impact worsen
Solution Approach 1:
The patent applies parameter changes by introducing chemical agents that alter the thermal and mechanical properties of the RAP binder. The disintegrating agents change the viscosity and softening characteristics of the aged binder, enabling effective disintegration at lower temperatures than conventional methods, thus reducing energy consumption while maintaining disintegration quality
Solution Approach 2:
The patent replaces the purely mechanical/thermal disintegration system with a chemical-assisted system. Instead of relying solely on high temperature and mechanical mixing to disintegrate RAP, the invention introduces chemical disintegrating agents that facilitate breakdown at lower temperatures, substituting part of the thermal-mechanical process with a chemical process that is more energy-efficient
3Manufacturing precision
If RAP is heated to high temperatures to ensure complete disintegration and homogeneous mixing, then the mixture homogeneity improves, but the binder oxidation and hardening worsen
Solution Approach 1:
The patent applies preliminary action by adding protective agents to the RAP before heating and mixing. These agents pre-coat the binder and create a protective barrier that reduces oxidation during the heating and mixing processes, allowing sufficient disintegration and homogeneity to be achieved without excessive temperature exposure that would cause binder hardening
Solution Approach 2:
The patent uses beforehand cushioning by introducing antioxidants and protective additives to the RAP mixture prior to heating. These substances provide a cushioning effect against oxidative damage, neutralizing free radicals and preventing binder hardening during the processing stage, thus protecting the binder while still achieving the necessary disintegration and mixing homogeneity
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
Enables the production of durable asphalt mixtures with high RAP content at reduced temperatures, enhancing sustainability and energy efficiency by achieving homogeneous mixtures and improving mechanical properties of the asphalt pavement.
Implementation Method 1
the first binder material is a soft bitumen component having a viscosity of less than 0.3Pa.s at 100°C... adding a first binder material to the RAP in the first drum to provide treated RAP
Implementation Method 2
transporting RAP through a first drum and thereby heating the RAP to a temperature of from 70 to 130°C; transporting virgin aggregate through a second drum, thereby heating the virgin aggregate to a temperature of from 90 to 130°C
Implementation Method 3
the second binder material comprises a hard bitumen component... and optionally further comprises a soft bitumen component... supplied a second binder material to the mixing zone
Data Source
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AI summary
A process for preparing an asphalt mixture from recycled asphalt pavement (RAP), virgin aggregate, filler and first and second binder materials, is disclosed. The process comprises steps of transporting RAP through a first drum; transporting virgin aggregate through a second drum; adding a first binder material to the RAP in the first drum to provide treated RAP; supplying the treated RAP, the virgin aggregate, filler and a second binder material to a mixing zone; and mixing to provide the asphalt mixture.