Devulcanized Tire Rubber Asphalt Storage Stability
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Solution Overview
Problem
Existing methods for modifying asphalt with recycled and devulcanized tire rubber face challenges in achieving storage stability and miscibility with asphalt, leading to phase separation and degradation, which affects the performance and cost-effectiveness of the modified asphalt.
Innovation Solution
The use of devulcanized tire rubber combined with compatibilizers/stabilizers such as Epoxidized Natural Rubber, Methyl Methacrylate grafted Natural Rubber, and Styrene Butadiene Styrene copolymer, heated and mixed with asphalt at specific temperatures to create a stable and miscible mixture that prevents phase separation during storage and transportation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If recycled tire rubber is added to asphalt to reduce cost and improve softening point, then the economic benefit and high-temperature performance are improved, but phase separation occurs during storage and transportation
Solution Approach 1:
A compatibilizer is introduced as an intermediary substance between the recycled tire rubber and asphalt. The compatibilizer has molecular structures that are compatible with both phases, reducing interfacial tension and preventing phase separation. This mediator allows the rubber particles to remain uniformly dispersed in the asphalt matrix during storage and transportation while maintaining the cost benefits of using recycled rubber.
2Temperature
If polymer modification is used to increase softening point, then high-temperature performance is improved, but miscibility with asphalt deteriorates leading to phase separation
Solution Approach 1:
The chemical parameters of the polymer modifier are changed to improve compatibility with asphalt. Specifically, polymers with appropriate molecular weight, branching structure, and chemical composition are selected to ensure they can dissolve or disperse uniformly in asphalt at the intended service temperatures without phase separation. The polymer modification process is optimized to achieve the desired softening point increase while maintaining miscibility.
3Stability of the object's composition
If continuous mixing at high temperature (260-310°C) is used to prevent phase separation, then storage stability is improved, but rubber degradation occurs above 180°C
Solution Approach 1:
The rubber is pre-processed and devulcanized before being incorporated into the asphalt mixture. This preliminary action breaks down the cross-linked rubber structure into smaller, more compatible segments that can be evenly distributed in the asphalt at lower temperatures. By preparing the rubber in advance, the need for prolonged high-temperature mixing is eliminated, preventing thermal degradation while achieving uniform dispersion and storage stability.
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 solution results in a storage-stable devulcanized tire rubber modified asphalt binder with improved softening point and resistance to phase separation, meeting the Performance Grade PG 82-22 standard, while maintaining low viscosity for effective pavement construction.
Implementation Method 1
The use of devulcanized tire rubber combined with compatibilizers/stabilizers such as Epoxidized Natural Rubber, Methyl Methacrylate grafted Natural Rubber, and Styrene Butadiene Styrene copolymer, heated and mixed with asphalt at specific temperatures to create a stable and miscible mixture that prevents phase separation during storage and transportation
Implementation Method 2
heated and mixed with asphalt at specific temperatures to create a stable and miscible mixture
Implementation Method 3
heated and mixed with asphalt at specific temperatures to create a stable and miscible mixture
Data Source
AI summary
This invention relates to a storage stabilized recycled and devulcanized tire rubber modified asphalt composition, which comprises: 65.0 to 90.0% by weight of a neat asphalt, 3.0-50.0% by weight of a recycled and devulcanized rubber from used tires and/or other scrap rubbers, 0.01-15.0% by weight of a compatibilizer/stabilizer derived from Natural or Synthetic Rubbers, which composition passes the “cigar tube” softening point test difference of less than 5° C. between the top and bottom layers; and, the process for the said asphalt composition comprises mixing 65.0% to 90.0% by weight of a neat asphalt, 3.0 to 50.0% by weight of a recycled and devulcanized rubber from used tires, 0.01-10.0% by weight of a compatibilizer/stabilizer derived from Natural or Synthetic Rubbers, using high shear mixers at elevated temperatures of between 120° C. and 175° C. for between 15 minutes to 6 hours, to obtain storage stabilized asphalt composition that is stable in hot storage and transportation conditions.