Scientists Have Created Quality Concrete With 100% Tire-Rubber Aggregate

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Recently, there have been developments where used tires were made a part of concrete. Now, scientists have produced good quality concrete in which all of the aggregates have been replaced with tire particles.

Concrete has three parts: water, a cement that binds everything together, and an aggregate like sand or gravel. That aggregate has to be mined from the ground and is now facing a global short supply.

Multiple groups have substituted ground-up tires for a portion of the sand or gravel. The resulting concrete has proven to be tougher than regular concrete, as the rubber particles within it have enabled it to bend under pressure instead of breaking.

If an excess of the aggregate is replaced with tire particles, the concrete falls short in compressive strength and splitting tensile strength.

Building on research conducted by their colleagues, scientists at Australia’s RMIT University determined that the bonding problem is due to the porosity of the tire rubber. Specifically, the pores in the rubber fill with water when the concrete is initially mixed, but those pores simply become empty voids at the rubber/cement interface once the water evaporates and the concrete sets.

In order to address that problem, the researchers started with wet concrete in which all the aggregate consisted of tire particles, then placed that concrete in special steel molds as it was setting. These molds placed pressure on the concrete, compressing the particles and the pores within them.

As a result, once the concrete had dried and set, the cement was much better bonded to the “preloaded” tire particles. When compared to 100% tire-aggregate concrete produced by conventional means, the preloaded concrete exhibited 97%, 59%, and 20% increases in compressive, flexural, and tensile strength, respectively.

“As a major portion of typical concrete is coarse aggregate, replacing all of this with used tire rubber can significantly reduce the consumption of natural resources and also address the major environmental challenge of what to do with used tires,” said study co-author and team leader, Prof. Jie Li.

A paper on the research was recently published in the journal Resources, Conservation & Recycling.

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