A Study of Crumb Rubber Modified Asphalt Slurry Seal Emulsions.
The suitability of Crumb Rubber (CR) to partially modifying bitumen in Asphalt Emulsion production for use as slurry seal was investigated.
Bitumen was replaced with 0%, 5%, 10%, 15%, 20% and 25% Crumb Rubber, and subjected to methyl blue, sand equivalency, cohesion, wet track abrasion (WTA) and loaded wheel tracks (LWT) tests.
Preliminary tests: using Penetration, Softening point, Viscosity and Flash and Fire point tests were also performed on the bitumen.
Based on the result of the tests, optimum CR content of 17.5% was recommended for use, because it achieved a smooth texture, within mixing time of 200 Seconds and Cohesion at 30 and 60minutes of 23 and 28 Kg-cm respectively. WTA Loss of 365.2g/m2 , are within the limits specified by the International Slurry Seal Association.
Above the Optimum Crumb Rubber the texture of the mixture was not smooth enough for use as slurry sealant. Successful use of CR will serve as an effective way of converting rubber waste to beneficial use, thereby saving the environment and conserving bitumen
Roads are built by a high-tech process that involves the use of aggregate, heavy machinery, and the hard work of road crews. Carefully constructed roads last for decades. However, the performance of the roads may be affected by wheel load pressure. To overcome the adverse effect of traffic on pavement, there is need for regular maintenance, whether it’s crumbling at the edges, developing pot holes, or cracking across the middle. One of the most important measures used in road maintenance is Crack Sealing.
There are several crack sealing materials in use in pavement; each designed to keep the road smooth and safe during its life. (Atkinson, 1997) Roads endure enormous stress and strain as vehicle tires continually push and pull at paved surfaces. The faster or heavier the vehicle, the more the pavement is compressed and then tensioned.
Temperature changes, within 24-hour can cause expansion and contraction of the pavement sheet. Traffic and temperature create small surface cracks. When water seeps through such cracks to the base materials it weakens the pavement, resulting in more crack formation which becomes wider if not repaired.
Crack sealing is an inexpensive routine maintenance treatment that will significantly delay roadway deterioration. It is done through the use of local road crews that apply sealing material directly into cracks before cracks become too large or before the roadway is subject to failure. Flexible rubberized asphalt sealants bond to crack walls and move with the pavement, preventing water from entering the road base.
Thereby extending the life span of roads and reducing the cost of maintenance. (Atkinson, 1997) Pavement cracks can be repaired with either cold or hot sealants. Cold applied materials include liquid asphalt and polymer-modified liquid asphalt.
Hot applied materials include bitumen, mineral-filled bitumen, fiberized asphalt, asphalt rubber, rubberized asphalt, and low-modulus rubberized asphalt. To effectively seal a crack, the material must move with the road surface and remain adhered to crack walls. Mixtures of asphalt and rubber are long-wearing and can move with pavement during weather changes.
One such mixture, commonly called “asphalt-rubber,” is a special mixture of bitumen and used car tires. Asphalt-rubber is especially effective on roads subject to high traffic volume and heavy loads. Other mixtures are effective for wide (high severity) cracks. These include polymer-modified liquid asphalt, rubberized asphalt, and low-modulus rubberized asphalt.
Polymer-modified liquid asphalt is a mixture of natural and synthetic compounds with liquid bitumen. Rubberized asphalt and low-modulus rubberized asphalt are made by adding rubber to asphalt for flexibility. The choice of material depends on the type and amount of rubber in the mixture, and the type of asphalt used. Some materials, although often used because they are inexpensive, have little flexibility.
These include bitumen, liquid asphalt, mineral-filled asphalt cement, and fiberized asphalt.
Atkinson, J.K. (1997) “Highway maintenance handbook” Second edition. Parkman Consulting Engineer, Highway Agency South London, Trunk Road Maintenance Agency London. Published by Thomas Telford service Ltd, 1 Heron Quay, London E14 4JD.
American Society of testing and Materials, D8 (2001): “Standard Terminology Relating to Materials for Roads and Pavements”, Road and Paving Materials; vehicle-Pavement Systems Annual Book of ASTM Standards, ASTM, Vol. 4.03 West Conoshohocken, PA,.
Asphalt Institute SP-2 (AI SP-2) (1995) “A Manual for Design of Hot Mix Asphalt with Commentary” Transportation Research Board, Washington, D.C. (Report 675)
British Standard, BS EN196 Part 3 (1995): “Determination of Setting time and Soundness Tests”. Technical Information Department, CNL Information Services Centre, BSI, 389, Chiswick Road, London 1
California Department of Transportation, Caltrans (2007) “Flexible Pavement Preservation” 2nd Edition, Volume 1 Chapter 8. Page 6 – 20
Crumb Rubber Modifier Workshop Notes (1993): “Design Produces and Construction Practices,” FHWA-SA-93-011, Federal Highway Administration
Crumb Rubber Manufacturers’ (2007): (CRM) News, Vol. 1, 2007). (www.asphaltrubber.org)
Chehovits, J.G and Hicks, R.G, (2000) “Mix Design Procedures” Session 10, Workshop Notes, FHWA Crumb Rubber Modifier Workshop, Atlanta, GA, Caltrans, “Flexible Pavement Rehabilitation Manual” Sacramento, CA
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