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Re: roads are decrepit & will be getting worse! Posted by MI-Roger [Email]  (#882) [Profile/Gallery]
(more from MI-Roger) on Thu, 28 Feb 2008 04:21:02
In Reply to: roads are decrepit, john b, Wed, 27 Feb 2008 18:53:48 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I had a conversation with a Pavement Consultant yesterday who does work for me. He had recently returned from a series of seminars sponsored by the Concrete Industry regarding problems with pavements, and recent discoveries with use of concrete.
It has just been learned that the problem Michigan is facing with the rapid deterioration of our concrete roads is caused by an internal chemical incompatibility between the portland cement and the aggregate mixed into the concrete, primarily the sand found in Michigan. You can think of the roads as suffering from a cancer.
This chemical attack is ascerbated by both water and chlorine. Spreading salt on snow covered roads during the winter provides both agents. Past theory has been that the concrete was too weak, so extra portland was added to achieve higher compressive strength in the finished concrete. This just provides additional fuel to the chemical reaction; and these higher strength, more expensive roads, will fail faster!
Addition of fly ash, a waste product from the steel and power generation industries, stops or significantly slows the internal chemical reaction. In Michigan, the DOT allows up to 30% fly ash in the mixture, but the addition of this much fly ash also slows the hardening or drying of the concrete. Again, the past practice to correct this "too long of curing time" has been to add more Portland. And we are back at the beginning all over again!
This internal chemical reaction is called Alkali Silica Reaction or ASR, and although all sand is made of silica, the type of sand prevalent in Michigan has a specific crystaline structure that makes it more susceptable to this process. Water and chlorine cause the formation of a gooey material where the reaction is occuring on the exterior of the sand particles. As this material freezes, and as the chemical process continues, this goo grows and expands until it shatters the concrete from the inside out.
So, as horrible as our roads are now they will only get worse. Much worse! We can start importing all the sand used to make roadway concrete from deposits in other states, or we can start adding Lithium to the wet concrete mixture to stop the process.
Maybe this is a way to recycle the spent batteries from our alarm sirens?
posted by 198.208.25...
_______________________________________ Saabs owned: 2008 9-5 Aero Sedan, sold at 227K miles 2006 9-3SC 2.0T - Wife's daily driver 2000 Viggen Convertible - Sold May, 2022 1964 Quantum IV Formula Car - Retirement project 2000 9-5lpt Sedan, sold at 318K miles
, Wed, 27 Feb 2008 14:13:16
, Fri, 29 Feb 2008 06:32:37, Fri, 29 Feb 2008 09:13:31, Thu, 28 Feb 2008 04:21:02 <-- Viewing This Message, Wed, 27 Feb 2008 14:57:09
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