Rocks having the needed specific gravity are generally cheap, do not deteriorate or absorb water, do not incur air into the concrete, and are found in masses in concentrated areas, so there is not a strong drive to use a replacement aggregate, especially one that weakens the concrete. Waste materials are not as dense as are needed to serve as intended for good quality concrete where compressive strength is desirable.
There are some who are trying to find ways to use waste materials, such as tires, for coarse aggregate, but rubber weakens the compressive strength by more than 30%, although this could work for some applications, such as sidewalks or residential slabs on grade. But then there is the cost for shipping the tires from tire dumps, handling, shredding, etc. of the used tires, when we usually have the rocks already at the plant where the concrete is being made. Although a noble cause to reduce used tire waste, it results in inferior quality and higher cost of concrete.
Here is a link to a paper on using rubber as coarse aggregate:
https://www.codot.gov/programs/research/pdfs/2013/rubberconcrete.pdf
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William Norman P.E., M.ASCE
Structural Engineer
Keeler-Webb Associates
Carmel IN
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Original Message:
Sent: 09-16-2017 02:43
From: Muhamad Madhat
Subject: Source of aggregates that can be used for construction as a substitute to virgin rocks
Hi,
I was wondering if there is a new unconventional source of aggregates that can be used for construction as a substitute to virgin rocks?
This is a school project, but I found it really interesting to me since I want to do a transportation so that new aggregates can be used.
Thank you
Madhat
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Muhamad Madhat S.M.ASCE
San Antonio TX
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