# US 5,704,971 A · Homogeneous crumb rubber modified asphalt

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- Number: US 5,704,971 A
- Document ID: US5704971A
- Status: Granted
- Kind: A
- Application number: 08/810,046
- Filed: 1997-03-04
- Granted: 1998-01-06
- Earliest claimed: 1997-03-04
- Inventors: Mohammed Memon
- Web page: https://patentgrep.com/patent/US5704971A

## CPC

- C08L 95/00: Compositions of bituminous materials, e.g. asphalt, tar, pitch
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

An improved asphalt composition for pavement and a method for producing the same is characterized by mixing peroxide with crumb rubber to modify the crumb rubber so that mixes more evenly with the asphalt when added thereto. A compatibilizer/polymer is also added to the asphalt. The resulting composition is homogeneous and demonstrates improved settling and rheological properties at high and low temperatures.

## Claims

### Claim 1

A method for producing crumb rubber modified asphalt, comprising the steps of
(a) heating a quantity of crumb rubber to a first temperature;
(b) mixing peroxide with the crumb rubber;
(c) adding the crumb rubber to asphalt binder;
(d) adding a compatibilizer to the asphalt; and
(e) continuously stirring the asphalt while maintaining the asphalt at a second temperature greater than said first temperature, whereby the crumb rubber is evenly disbursed throughout the asphalt to improve the settling characteristics thereof.

### Claim 2 (depends on 1)

A method as defined in claim 1, wherein said peroxide mixing step comprises continuously stirring the crumb rubber for a period of between 20 and 30 minutes.

### Claim 3 (depends on 2)

A method as defined in claim 2, wherein said first temperature is in the range of 65.degree.-85.degree. C., whereby a carbonium ion is generated on the crumb rubber.

### Claim 4 (depends on 3)

A method as defined in claim 3, wherein said asphalt is maintained at said second temperature for a period of between 25 and 35 minutes while the compatibilizer is being added thereto.

### Claim 5 (depends on 4)

A method as defined in claim 4, and further comprising the steps of maintaining said asphalt at said second temperature for a period of between 1 and 2 hours following addition of said compatibilizer and subsequently allowing said asphalt to cool to ambient temperature.

### Claim 6 (depends on 5)

A method as defined in claim 5, wherein said second temperature is in the range of 160.degree.-170.degree. C.

### Claim 7 (depends on 1)

A method as defined in claim 1, wherein the peroxide has a concentration of 0.02-0.06 millimoles/gram weight of the asphalt binder.

### Claim 8 (depends on 7)

A method as defined in claim 7, wherein the compatibilizer has a concentration of 0.015-0.045 millimoles/gram weight of the asphalt binder.

### Claim 9 (depends on 1)

A method as defined in claim 1, wherein said compatibilizer comprises methacrylate with glycidyl containing monomer, ethylene based glycidyl containing monomer, or a terpolymer of ethylene, butyl acrylate and glycidal methacrylate.

### Claim 10

An improved asphalt composition formed by a process comprising the steps of
(a) heating a quantity of crumb rubber to a first temperature;
(b) mixing peroxide with the crumb rubber;
(c) adding the crumb rubber to asphalt including a binder;
(d) adding a compatibilizer to the asphalt; and
(e) continuously stirring the asphalt while maintaining the asphalt at a second temperature greater than said first temperature, whereby the crumb rubber is evenly disbursed throughout the asphalt to improve the settling characteristics thereof.

### Claim 11

An asphalt composition, comprising a mixture of asphalt, crumb rubber modified by hydrogen peroxide, and a compatibilizer.

### Claim 12 (depends on 11)

An asphalt composition as defined in claim 11, wherein the weight by volume percentages for the components are 84.28-93.42% asphalt, 12.64-4.68% crumb rubber, 2.45-1.36% hydrogen peroxide, and 0.63-0.53% compatibilizer.

### Claim 13 (depends on 12)

An asphalt composition as defined in claim 12, wherein said compatibilizer comprises methacrylate with glycidyl containing monomer, ethylene based glycidyl containing monomer, or a terpolymer of ethylene, butyl acrylate and glycidal methacrylate.