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Recycled materials reinforcement?

News, Q&A: GMA Techline | June 1, 2016 | By:

Questions and answers from the GMA Techline

We are soliciting information on the use of recycled materials in the reinforced zone of MSE walls. I recall you as the keeper of many case histories. Do you have any success or failure stories about such recycled content in a reinforced zone? I’m mindful of chemical attack and alkali clogging of drainage systems. That said, it seems a frictional material, whether recycled or not, would offer some design strength that could be taken into account in MSE design.

Then again …?

Carl | USA

Hi Carl,

We (GSI) have a database of 236 MSE wall failures and not one was backfilled with recycled materials. In fact, 70% were backfilled with fine grained silts and clays and, furthermore, 62% were caused by water.
Regarding your specific question, none had recycled materials in the backfill zone. I presume you are thinking of rubbleized concrete and/or milled pavement asphalt. Certainly these are high frictional materials, which is good, and can drain well due to their relatively large size.
However, they could cause damage to geosynthetics (thus a high reduction factor for installation damage should be used) and might result in high pH values that could pose an issue for polyester geosynthetics. (That said, the value would have to go above 10.)

Keep in touch,

Bob Koerner | GMA Techline

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