Uh, trust me, I've forgotten more about the Gardiner than you'll ever know.tboy said:and it's still going strong. Imagine if it was built with today's technology? It'd probably last another 100 yrs easily........using an example of something built 40 yrs ago as a reason to not doing it now is asinine. If that were the case in other examples you'd be living without: cellphones, cordless drills, cars, trucks, anything made with titanium, etc etc etc
But would it be better to have all those cars that travel on the gardiner on lakeshore and queen st? It'd be (more of) a nightmare getting into and out of the city......
While I agree with the need, and would oppose tearing the Gardiner down because it would cause traffic chaos, the fact remains that it's a pig and an eyesore. The only way I'd ever want it torn down was if the City put it in a tunnel (which isn't going to happen any time soon.)
I'd be very curious to know exactly what technology you are referring to today that is so superior to 50 years ago though?
The problem with the Gardiner, like any other trasnportation structure, is that it is made of reinforced concrete. The chlorides from road salt penetrate the concrete and initiate corrosion in the reinforcing steel which causes the concrete to delaminate and spall. This then makes the problem even worse as now you begin to expose the rebar to the elements and the road salt.
This is the exact same problem we face today.
In some ways the Gardiner is suprerior to what we build today because they used steel girders in its construction. Today, we would use CPCA Girders (Precast Concrete) which are truly garbage. At least with steel, you can repair it when you get a crack or a hole. Not true with concrete girders. Once they start to fail, they're done. We use concrete girders today simply because they are CHEAP. Plain and simple. But don't expect to get more than 40 years out of them. Some in fact - 25 years and done.
The concrete today is arguably WORSE than it was back when the Gardiner was built. They try to come up with all these "High Performance Concretes" containing silica fume and the like, but all they do is crack.
The only problem the Gardiner's design had that I am aware of was too many expansion joints and low cover on the reinforcing steel. That's about it.
For a while, the City used Epoxy coated rebar (a la MTO) however, it was found that the epoxy coated rebar could actually be worse than black bars because if the epoxy coating gets knicked, you get localized corrosion and pitting in the rebar which is worse. As a result, the City will only specify black bars, or stainless rebar on their jobs now. Gerideau Ameristeel has their "Z-bar" which is essentially galvanized with an epoxy coating, however, it's expensive. Then there's stainless steel rebar, however, it's 6 times the cost of black reinforcing steel. They are trying out polymere rebar, however, you can't bend it like you can rebar.
So much for the brave new world of concrete technology.





