Concrete mixing and placing processes lead to inevitable
voids entrapped in the concrete – typically 1%-3%. Where temperatures vary
widely, 5% total air or more is needed to allow the concrete to resist
freeze-thaw damage. To achieve this high level of air content, additives known
as air entraining agents (AEA) are added to capture the necessary additional
air. However, these additives weaken concrete, requiring the use of more cement
to compensate. This drives up the price of concrete substantially, as cement is
the costliest ingredient.
Researchers at Arizona State University have developed an
improved concrete mixture to address this problem. Specific quantities of crumb
rubber are added to the concrete mix. Improved thermal cycling resistance is
achieved without the expense of additional cement. Additionally, the concrete is
lighter and displays increased traction, reduced contact noise, and superior
crack resistance. It is well suited for use in areas where repeated freezing and
thawing occur and can also be poured in larger sheets than conventional
concrete. As a side benefit, this technology provides an attractive end use for
the millions of rubber tires discarded each year.
Potential Applications
- General Concrete Construction – Sidewalks, parking lots,
and roadways will last longer when created with crumb rubber concrete
- Large-Pour Concrete – Items such as tennis courts can now
be poured in a single slab, eliminating ‘section’ lines which must be smoothed
after curing
- Lightweight Concrete Products – Roofing tiles and other
concrete products can now be made lighter
Benefits and Advantages
- Improved Crack Resistance - Impact or other damage is
locally contained and does not propagate
- Reduced Weight – Substantial weight savings compared to
ordinary concrete
- Improved Durability –Less likely to crack and shatter
under repeated freeze / thaw cycles
- Promotes Recycling – An economical use for the millions
of discarded vehicle tires waiting for recycling
- Low Cost – Costly additional cement is
eliminated
Download Original PDF
