Clean and environmentally friendly
Coordinated control of gradation and temperature
Recycled asphalt (RAP) is made by recycling old asphalt pavement materials, crushing and screening them, and then mixing them with new aggregates and regeneration agents in a scientific ratio to form an environmentally friendly mixture that meets engineering performance. Its core lies in breaking through the linear resource consumption model of traditional asphalt production and realizing full life cycle recycling. It has become a technical focus in the field of global road construction.
Why Recycled Asphalt Become Global Necessity?
| The inevitable choice of resource recycling: | Global recycled asphalt market: Traditional asphalt relies on oil resources, while the world produces more than 700 million tons of waste asphalt mixture every year. Direct landfill will occupy land and pollute the soil. |
| Alternative value: | Recycled asphalt can reduce 30%-50% of natural stone mining and oil consumption, and recycling technology can save material costs. |
| Dual promotion of policies and markets: | International legislation: The EU requires the use of recycled materials in road projects, and the utilization rate of old materials in Germany and Belgium has reached 100%. |
| Technical maturity verification: | Performance benchmarking new materials: The full-proportion medium-temperature recycling technology makes the rutting and cracking resistance of recycled asphalt mixtures close to new materials, and even performs better in high-grade highways. |
| Economic feasibility | The recycling process reduces construction costs by 20%-50% and extends the life of the road surface by 5%-15%. The Shenzhen Expressway project verifies its comprehensive cost-saving benefits. |
The Necessity of Recycled Asphalt
Regional Demand Differences Drive the Diversification of Technology Development
- European and American Markets: Relying on mature highway networks and policy support, these markets focus on refined construction and long-life design of high-dosage recycled asphalt, emphasizing high-quality and durable technology.
- Emerging Economies (e.g., Asia and Africa): Prioritize low-cost, fast-construction cold recycling technology to meet large-scale infrastructure needs, highlighting the economy and timeliness of the technology.
The Promoting Role of International Technical Standards and Certification Systems
The improvement of international technical standards and certification systems has accelerated global coordination of the recycled asphalt industry chain, driving its upgrading from a regional solution to a global green building material, enhancing industry standardization and cross-regional compatibility.
Future Development Trends and Key Points for Recycled Asphalt Market Expansion
- Technology Export and Local Adaptation: The key for companies to expand international markets lies in technology export and local adaptation capabilities, requiring adjustments to technical solutions based on regional needs and balancing performance, costs, and construction conditions.
- Strategic Value in Belt and Road Countries: In countries along the “Belt and Road,” recycled asphalt is expected to become a core carrier of low-carbon infrastructure cooperation, facilitating the globalization of green infrastructure and advancing the implementation of sustainable development goals.
Technological breakthroughs create new scenarios of Recycled Asphalt
- Intelligent proportioning system: AI algorithm optimizes the proportion of old materials, with an error rate of <0.8%, adapting to different climate and load conditions;
- Low-carbon process: Microwave heating technology reduces energy consumption by 40%, and warm mixing process reduces greenhouse gas emissions to 2% of traditional processes.
Core Analysis of Recycled Asphalt Aging and Regeneration Technology
The essence of asphalt production performance degradation is the oxidation damage of the colloidal structure. Under the long-term action of ultraviolet rays and oxygen, the oil and resin in the asphalt undergo molecular chain cross-linking reactions and gradually transform into more stable asphaltene. This molecular reconstruction leads to a decrease in the flexibility of the material, an increase in brittleness, and a significant decrease in the bonding ability, which manifests as cracking and loosening of the road surface.
Critical Path of Regeneration Technology
- Physical fusion repair: Through the full mixing of new and old asphalt, the unaged soft components in fresh asphalt are used to penetrate and dissolve the hardened structure of aged asphalt to rebuild the dynamic balance of the colloidal system. This process relies on precise temperature control and mixing technology to ensure the molecular fusion of new and old materials.
- Chemical component activation: As a functional additive, the regeneration agent can replenish the light oil lost during the aging process and repair the broken molecular chain network through polar molecules. For example, the ester compounds in the bio-based regeneration agent can combine with the polar groups in the oxidized asphalt to restore the ductility of the colloidal structure.
Analysis of major process systems of recycled asphalt
- Thermal Regeneration Technology: Softens aged asphalt via precise temperature control, repairs colloidal structure through regenerant molecular penetration, and uses dual-drum gradient heating to avoid aggregate secondary aging. Relies on infrared monitoring and dynamic weighing (error ≤±1%) for uniform temperature and accurate regenerant mixing, focusing on molecular-level fusion of old and new asphalt to restore performance.
- Full-Depth Regeneration Technology: Targets deep structural damage (≥20cm) by adding cement/lime to trigger hydraulic reactions, repairing both surface and base layers simultaneously. Requires balancing recycled aggregate gradation and stabilizer dosage to avoid grading faults, focusing on integral strength regeneration of deep structures.
Recycled Asphalt Core Plant
Thermal regeneration equipment
Plant Mix Hot Regeneration Equipment
- Regeneration drum: heats and softens the old asphalt mixture (usually at 150~180℃).
- Mixer: evenly mixes new asphalt, regeneration agent, new aggregate and old material.
- Metering system: accurately controls the ratio of new and old materials and the amount of additives.
- Hot material bin: stores preheated old materials to avoid heat loss.
In-situ heat regeneration equipment
- Pavement heating machine: This specialized equipment heats the old pavement efficiently to a range of 120~180℃ through advanced infrared technology or gas combustion.
- Milling machine: The milling machine then actively loosens the heated old material and performs an initial crushing process for better recycling.
- Mixer: On-site, the mixer carefully adds new asphalt and a precise amount of regeneration agent before thoroughly mixing them together.
Cold recycling equipment
Factory Mixed Cold Recycling Equipment
- Crusher: crush the old material to the required particle size (usually ≤40mm).
- Stabilized soil mixer: add cement, lime and other stabilizers to mix with the old material.
- Conveyor belt and storage silo: realize continuous transportation and temporary storage of materials.
In-situ cold recycling equipment
- Cold milling machine: directly mills the old road surface and breaks it into particles.
- Asphalt spreader: sprays emulsified asphalt or foamed asphalt as a binder.
- Tire roller/steel wheel roller: preliminary compaction of the recycled layer.
Other auxiliary Recycled Asphalt Equipment
Transport equipment
- Dump truck: transports old materials to the mixing plant or construction site.
- Closed material truck: prevents dust pollution during transportation.
Screening and sorting equipment
- Vibrating screen: Separates impurities (such as wood chips, plastic) from old materials.
- Magnetic separator: Removes metal fragments.
Additive Systems
- Automatic regeneration agent spraying device: accurately control the regeneration dosage.
- Asphalt temperature control storage tank: maintain the fluidity of new asphalt.
Dust removal and environmental protection equipment
- Pulse dust collector: handles dust during heating or crushing.
- Asphalt fume purification device: reduces harmful gas emissions.
Recycled Asphalt Material Performance Guarantee System
The performance assurance of recycled asphalt mixture runs through the coordinated regulation of material matching verification and production process, and realizes the quality closed loop through the dual paths of molecular-level compatibility analysis and intelligent process control.
Material compatibility verification
- Technical Approach: Infrared spectroscopy technology compares molecular structure characteristics of new and old asphalt, focusing on detecting functional group matching and polar molecular activity. This ensures regeneration agent components and aged asphalt form a stable colloidal system.
- Simulation Validation: A rotating thin-film oven simulates the long-term aging process to verify the activation effect of regenerated asphalt and the recovery of its durability, ensuring material compatibility meets standards.
Coordinated Control of Gradation and Temperature
- Gradation Optimization: A laser particle size analyzer monitors real-time aggregate particle size distribution. Combined with the Bailey method’s CA value, it dynamically adjusts crushing and screening parameters to eliminate “false particle size” interference with mixture void ratio, ensuring precise gradation.
- Temperature Management: An infrared thermal imaging system tracks the mixing temperature field. A gradient heating strategy prevents secondary aging of asphalt caused by local overheating, ensuring uniform fusion of new and old materials.
Key Performance Control
Finished mixtures must pass three core verifications:
- Rutting resistance verification: hot recycled mixtures are evaluated for high temperature stability through rutting tests, and the dynamic stability is required to be significantly higher than the standard benchmark;
- Water damage resistance verification: freeze-thaw splitting tests verify water stability, focusing on the degree of recovery of the adhesion between the asphalt and aggregate interface;
- Fatigue life verification: four-point bending tests simulate long-term load effects to test the ability to inhibit crack growth.
Full Process Intelligent Monitoring
- Real-Time Tracking: The mixing station is equipped with an IoT sensor network to monitor key parameters like oil-stone ratio and gradation curve in real time, triggering automatic deviation warnings for dynamic process control.
- Intelligent Optimization: The cloud data platform uses machine learning algorithms to analyze historical production data, automatically optimizing parameter combinations (e.g., regeneration agent dosage, mixing time), and forming a mechanism for continuous quality improvement.
Macroad Recycled Asphalt Technology Breakthrough Direction
Currently, recycled asphalt technology is focusing on intelligent decision-making systems, low-carbon regeneration processes and self-healing material innovations, and is pushing the industry towards ultra-long life and zero-carbon goals through interdisciplinary technology integration.
Intelligent ratio optimization system
- AI-Driven Multi-Source RAP Database ModelL: Built on AI neural networks, the model dynamically analyzes the composition and gradation characteristics of recycled asphalt pavement (RAP) through machine learning. Automatically generates optimized blending plans for new and old materials based on real-time material property insights.
- Real-Time Mixture State Monitoring: Employs infrared thermal imaging and laser particle size analyzers to capture real-time data on mixture temperature distribution and particle size composition. Provides instantaneous feedback on material state during the recycling process to enable precision control.
- Dynamic Process Adjustment for Molecular-Level Fusion: Uses real-time monitoring data to dynamically adjust the injection volume of regenerants and mixing temperature. Achieves precise control over the molecular-level fusion of new and recycled materials, optimizing performance and durability.
Precision energy control technology
Microwave selective heating technology is used to activate the aged asphalt molecular chains in a targeted manner, and the colloid structure is softened by focusing electromagnetic wave energy to avoid secondary aging caused by traditional high temperatures. This technology is combined with warm mixing technology to reduce the mixing temperature, and simultaneously reduce fuel consumption and harmful gas emissions.
Development of long-lasting self-healing materials
The surface modification of nanomaterials enhances the bonding force between asphalt and aggregate, and the microcapsule technology is used to embed the repair agent. When microcracks appear on the road surface, the capsules rupture and release the active ingredients, triggering the molecular chain reorganization to achieve self-healing. This technology significantly improves the anti-stripping and anti-fatigue properties of recycled asphalt and extends the service life of the road surface.
Recycled asphalt is not only a technological innovation, but also a green action to protect the earth. In the face of resource shortages and environmental challenges, every application of RAP is a firm commitment to a sustainable future. Let us work together to accelerate the promotion and innovation of recycled asphalt technology, reshape road construction with circular wisdom, and pave the way for green development for future generations!