Increasing volumes of waste tires create environmental concerns for countries around the world. Disposing the tires as crumb rubber in construction materials is one alternative sought after by researchers. While this alternative is easily achieved, a challenge in producing a product that provides benefits in performance and specific engineering applications is highly desirable. The state of Arizona is well known for the use of recycled waste tire rubber (crumb rubber) in asphalt rubber hot mix. In the past three years work between the Arizona Department of Transportation (ADOT) and Arizona State University (ASU) was extended to evaluate the use of crumb rubber usage in Portland Cement Concrete (PCC) mixes for civilian development related projects. Examples are: roadway intersections, sidewalks, recreational courts and pathways, and wheel chair ramps for better skid resistance. These efforts have been recently documented and recognized by the scientific community through a Journal article published at the Transportation Research Board in January 2005 (attached).The distributed rubber crumbs function as mini expansion / control joints inside the concrete. Thus, the crumb rubber concrete may exhibit good characteristics in controlling crack initiation, propagation and most importantly, reduce impact energy. Several Crumb Rubber in Concrete (CRC) test sections were built through out the state and are being monitored for performance as documented in the above referenced article. Laboratory tests were conducted at ASU to support the knowledge learned in the field. These preliminary results were very encouraging and some of the perceived advantages are summarized as follows: Resistance against cracking Reduces thermal expansion and contraction Less drying shrinkage Less susceptible to freeze thaw damages Light weight Improved skid properties Noise reductionIn laboratory compression and indirect tension failure tests, the CRC specimens stayed intact (did not shatter) indicating that the rubber particles may be absorbing forces acting upon it (see the next couple of figures). Such behavior may be beneficial for applications that require good impact resistance properties. The project team believes it can also support military applications such as the mission of the United States Army by designing and testing CRC mixes for use in defensive applications such as mitigating ballistic and ordinance impacts. Additionally, the research has a strong civilian benefit, for which CRC mixes can be used in highway or safety barriers. Advantages are: light weight, energy absorbent during vehicle collision (more forgiving upon impact than normal PCC), and lower thermal conductivity.
|Original language||English (US)|
|State||Published - Jun 29 2005|