Modified Bitumen Compound Using Fine Crumb Rubber and SBS
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Solution Overview
Problem
Existing bitumen modification methods using crumb rubber face challenges such as high granulometry, compatibility issues, and high costs, which limit their performance in road and building applications, as they fail to match the performance of SBS-modified bitumens with the same quantity and cost-effectiveness.
Innovation Solution
Reducing the granulometry of vulcanized rubber particles to less than 0.4 mm and mixing them with bitumen, along with radial SBS and lubrication oil, to create an extruded compound that enhances the modification effect, achieving characteristics comparable to SBS-modified bitumens at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If crumb rubber with high granulometry (>0.5 mm) is used to modify bitumen, then the environmental benefit of recycling tires is achieved, but the modification performance is considerably reduced due to insufficient swelling and adhesion
Solution Approach 1:
The invention segments the rubber material into two distinct components: fine rubber powder (<0.5 mm) for chemical interaction and swelling, and larger rubber granules for structural reinforcement. This segmentation allows each size fraction to perform its optimal function, resolving the contradiction between recyclability and performance.
Solution Approach 2:
The invention creates a composite modified bitumen system combining rubber powder and rubber granules in specific proportions (5-50% rubber powder and 50-95% rubber granules). This composite approach leverages the advantages of both size fractions while maintaining the environmental benefit of full tire waste utilization.
2Reliability
If devulcanized rubber granules are used to improve adhesion and cohesion, then the mechanical characteristics are improved, but the production cost increases and specific equipment is required
Solution Approach 1:
The invention replaces expensive devulcanization equipment and processes with a simpler, more economical approach using readily available rubber powders and granules that achieve comparable or superior performance through physical mixing and chemical swelling, eliminating the need for specialized pirolizers or extruders.
Solution Approach 2:
The invention changes the granulometry parameter of rubber materials to <0.5 mm for the powder fraction, which fundamentally alters the interaction mechanism from mechanical adhesion to chemical swelling and dissolution, achieving good adhesion without devulcanization.
3Ease of operation
If rubber particles with granulometry higher than 0.5 mm are used, then the material is easier to handle and process, but the capability to obtain radical changes of bitumen is considerably reduced
Solution Approach 1:
The invention segments rubber into fine powder for modification and granules for handling, allowing each fraction to optimize its function.
Solution Approach 2:
The invention applies different rubber size qualities to different functional requirements: fine powder (<0.5 mm) localized for chemical interaction and granules for structural roles.
4Quantity of substance
If Nitrile Rubber (NBR) granules are used instead of Styrene-Butadiene-Rubber (SBr), then the material cost may be reduced, but the swelling capability and adhesion performance are considerably lower
Solution Approach 1:
The invention creates composite rubber systems that can combine different rubber types (NBR, SBr, NR, EPDM) in optimized proportions, allowing cost reduction through cheaper rubbers while maintaining performance through complementary properties of different rubber fractions.
Solution Approach 2:
The invention changes the chemical-physical parameters of rubber by using fine powder form, which dramatically increases surface area and swelling capability, allowing even less swellable rubbers like NBR to achieve adequate performance when properly sized and distributed.
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 modified bitumen exhibits improved hot and cold temperature resistance, elasticity, and cohesive strength, matching the performance of SBS-modified bitumens while being more cost-effective, with the extruded compound comprising crumb rubber, SBS, and lubrication oil demonstrating superior physical properties.
Implementation Method 1
the solubility parameter of the two products (rubber and bitumen) must be numerically very close so that the solvent part of bitumen, the malthenic fraction, can penetrate the solid particles of rubber granules and form, outside the solid particle, a practically gelatinous phase that is very active in adhesion and cohesion with the remaining bitumen part
Implementation Method 2
mixing them with bitumen, along with radial SBS and lubrication oil, to create an extruded compound
Data Source
AI summary
A production method of a compound for realization of modified bitumen for asphalts is disclosed, and includes the following steps: grinding of vulcanized rubber to obtain vulcanized crumb rubber with granulometry lower than 0.4 mm; mixing of the vulcanized crumb rubber, SBS and lubricant in an extruder, wherein the weight percentage of lubricant is between 1% and 50% compared to mixture weight and the vulcanized crumb rubber is in a weight percentage of 70-100% compared to SBS weight; in such way to obtain an extruded compound containing the vulcanized crumb rubber, SBS and lubricant.