caltrane74
Senior Member
Alright Brethren, here are some of mine.
Last edited:
- Thread starter Condo George
- Start date
Xray_Crystal_Junkie
Senior Member
Thanks all around to all you contributing great updates and accompanying photos.
Between all the new ambitious proposals lately, so much already under construction and the contributions from some newer posters (as well as the continuing effort by veterans) these threads have been especially fascinating the last six months or so.
Thanks to you all!
Between all the new ambitious proposals lately, so much already under construction and the contributions from some newer posters (as well as the continuing effort by veterans) these threads have been especially fascinating the last six months or so.
Thanks to you all!
AlbertC
Superstar
someMidTowner
¯\_(ツ)_/¯
Thanks for all the updates today AlbertC. Really appreciate it, especially on a cold rainy day where I am relegated to a desk chair.
innsertnamehere
Superstar
another 2 floors. jeez this one is flying!
Jasonzed
Senior Member
caltrane74
Senior Member
From yesterday
SkyJacked
Active Member
Impressive isn’t it? All of the building materials being delivered must be keeping them on their toes. The backup alarm must be the anthem over there.
I have a few pictures from the last month that might give you a different look at how fast they are going.
November 27th
December 06th
December 11th
December 13th. One reason why they’re doing so well, you see them placing concrete with the pump and the crane.
December 14th
December 19th
000
Senior UT Member
SkyJacked can you tell us more about the construction materials. Eg. why is the Delta being made with reinforced concrete but the podium is steel frame vs. making the whole thing steel frame? People say reinforced concrete lasts on average about 60 years with good maintenance - does that mean these buildings have to be torn down and rebuilt again later on? How does the maintenance work?
SkyJacked
Active Member
That’s an inquiry that would take two or more university degrees to properly address and I don’t have any. I can give you an opinion but you need at least Civil Engineer and an architect to get to the bottom of it.
I haven’t done my homework on this thread as to why they would use structural steel in that one area. Long spans for open spaces are one common reason for using steel instead of reinforced concrete. You can span greater lengths with steel having less material volume. Sometimes it’s just easier to use steel compared to very complex concrete formwork in a tight space. Maybe it is for the look of things, I’m just guessing. Maybe someone actually qualified to address the structural steel question can take it from here.
As for the concrete part of your question, I can address some of that using one of the Southcore projects closest neighbours as an example. I took the picture below and selected the visible portion of the CN Tower to demonstrate. I would assume it happens every summer but certainly last summer workers on swing stages could be seen inspecting and repairing the exterior concrete surface of the CN Tower. The crop/zoom picture clearly shows patches on the surface of the concrete and some major horizontal patches along nearly equidistant lines up the tower.
I can speculate and I emphasize speculate that the larger horizontal patches are at a point along the construction of the tower that required changes to the formwork to accommodate the smaller size of the tower higher up. These changes would have taken enough time to interrupt the “monolithic†aspect of concrete placement. Changing the slip form to make it smaller could have stopped concrete placement long enough to cause what’s called a “cold joint†where the concrete on one side of the stoppage was too hard to bond monolithically with the fresh concrete added after the forms were reduced in size.
In any case, this patching can clearly be seen at very regular intervals and there is an explanation but I am just making an educated guess. The patching is done by cleaning away all loose material from the patch area and applying a bonding agent before putting the concrete patch material (grout) in position. The grout mix design is very specific for different applications.
The reason they are so carefully maintaining a surface of the CN Tower is to prevent water from reaching the reinforcing steel within the concrete. Steel exposed to oxygen will rust, the rust is bigger than the steel it is replacing (added oxygen molecules), the rust forces the concrete apart like a tree root causing the concrete to spall or break away starting near the surface. If this maintenance is not ever done you could be looking at that 60 year life span as you suggested, much like another close neighbour to Southcore, the Gardiner Expressway. Bad examples like the Gardiner and the Elliot Lake Algo Mall are out there for sure but that is not the plan. Quality concrete properly maintained is expected to last much longer than 60 years. In fact, there are many examples of reinforced concrete structures from the Second World War in very good condition without ever having had any maintenance at all.
This “Dead Giant on the Beach†at Cape May in New Jersey was built by the US Army Corps of Engineers early into of the Second World War. Today’s modern concrete mix designs and improved quality control is allowing for stronger and lighter product. This is permitting many ambitious projects like the Burj Khalifa in Dubai that are expected to have life spans greater than 60 years. The Hoover Dam has been in use since 1936 and they are counting on many many more years of service from it.
I can assure you, the collective “they†are hoping for much more than 60 years from the Southcore buildings or the CN Tower for that matter. The acknowledged oldest reinforced concrete building, The Ward House in Port Chester, NY, was built in the 1870’s., and the Ingalls Building in Cincinnati, Ohio, built in 1903, was the world's first reinforced concrete skyscraper (15 stories). Both buildings are still in use today.
A few notes about concrete;
Concrete is not poured; it is placed, as close as possible to its final destination.
Concrete does not dry, it hardens. Water reacts chemically with the cement causing it to bond with adjoining particles (sand and stone, called aggregate) creating concrete. If the concrete were to “dry†and all of the water was to leave the mix, too much volume would be lost and the concrete would become unstable.
The water/cement ratio in a concrete mix is one of the most important factors in the overall strength of the product. Too much water in the mix effectively causes too much space between particles for the best bond. Modern concrete uses add mixtures know as plasticizers or “Super P†to mimic additional water in the mix. These additives allow for a more plastic or sloppier mix for use in long pump runs and concrete forms with a lot of rebar preventing complete consolidation of the concrete.
In my opinion proper use of concrete as a building material will yield buildings with great longevity requiring little or no maintenance. As long as accepted construction standards are properly applied and water is not permitted contact with reinforcing steel, concrete buildings can last for hundreds of years.
I haven’t done my homework on this thread as to why they would use structural steel in that one area. Long spans for open spaces are one common reason for using steel instead of reinforced concrete. You can span greater lengths with steel having less material volume. Sometimes it’s just easier to use steel compared to very complex concrete formwork in a tight space. Maybe it is for the look of things, I’m just guessing. Maybe someone actually qualified to address the structural steel question can take it from here.
As for the concrete part of your question, I can address some of that using one of the Southcore projects closest neighbours as an example. I took the picture below and selected the visible portion of the CN Tower to demonstrate. I would assume it happens every summer but certainly last summer workers on swing stages could be seen inspecting and repairing the exterior concrete surface of the CN Tower. The crop/zoom picture clearly shows patches on the surface of the concrete and some major horizontal patches along nearly equidistant lines up the tower.
I can speculate and I emphasize speculate that the larger horizontal patches are at a point along the construction of the tower that required changes to the formwork to accommodate the smaller size of the tower higher up. These changes would have taken enough time to interrupt the “monolithic†aspect of concrete placement. Changing the slip form to make it smaller could have stopped concrete placement long enough to cause what’s called a “cold joint†where the concrete on one side of the stoppage was too hard to bond monolithically with the fresh concrete added after the forms were reduced in size.
In any case, this patching can clearly be seen at very regular intervals and there is an explanation but I am just making an educated guess. The patching is done by cleaning away all loose material from the patch area and applying a bonding agent before putting the concrete patch material (grout) in position. The grout mix design is very specific for different applications.
The reason they are so carefully maintaining a surface of the CN Tower is to prevent water from reaching the reinforcing steel within the concrete. Steel exposed to oxygen will rust, the rust is bigger than the steel it is replacing (added oxygen molecules), the rust forces the concrete apart like a tree root causing the concrete to spall or break away starting near the surface. If this maintenance is not ever done you could be looking at that 60 year life span as you suggested, much like another close neighbour to Southcore, the Gardiner Expressway. Bad examples like the Gardiner and the Elliot Lake Algo Mall are out there for sure but that is not the plan. Quality concrete properly maintained is expected to last much longer than 60 years. In fact, there are many examples of reinforced concrete structures from the Second World War in very good condition without ever having had any maintenance at all.
This “Dead Giant on the Beach†at Cape May in New Jersey was built by the US Army Corps of Engineers early into of the Second World War. Today’s modern concrete mix designs and improved quality control is allowing for stronger and lighter product. This is permitting many ambitious projects like the Burj Khalifa in Dubai that are expected to have life spans greater than 60 years. The Hoover Dam has been in use since 1936 and they are counting on many many more years of service from it.
I can assure you, the collective “they†are hoping for much more than 60 years from the Southcore buildings or the CN Tower for that matter. The acknowledged oldest reinforced concrete building, The Ward House in Port Chester, NY, was built in the 1870’s., and the Ingalls Building in Cincinnati, Ohio, built in 1903, was the world's first reinforced concrete skyscraper (15 stories). Both buildings are still in use today.
A few notes about concrete;
Concrete is not poured; it is placed, as close as possible to its final destination.
Concrete does not dry, it hardens. Water reacts chemically with the cement causing it to bond with adjoining particles (sand and stone, called aggregate) creating concrete. If the concrete were to “dry†and all of the water was to leave the mix, too much volume would be lost and the concrete would become unstable.
The water/cement ratio in a concrete mix is one of the most important factors in the overall strength of the product. Too much water in the mix effectively causes too much space between particles for the best bond. Modern concrete uses add mixtures know as plasticizers or “Super P†to mimic additional water in the mix. These additives allow for a more plastic or sloppier mix for use in long pump runs and concrete forms with a lot of rebar preventing complete consolidation of the concrete.
In my opinion proper use of concrete as a building material will yield buildings with great longevity requiring little or no maintenance. As long as accepted construction standards are properly applied and water is not permitted contact with reinforcing steel, concrete buildings can last for hundreds of years.
000
Senior UT Member
SkyJacked, thank you so much for your elaborate contributions! Your posts have taught me more about building construction than my entire time on this forum. Hopefully there are more professionals lurking that will willingly chime in on these topics and help the general public understand some of the intricacies of your trade. 
DarkSideDenizen
Senior Member
Great information Skyjacked, concerning the application of steel-reinforced concrete in building design and construction.
When there is a "cold joint" will they drill into the set surface to insert extra rebar, abrade the surface of the set concrete so it adheres better to the next layer, or is the rebar that is already set into the structure and extending into open space (ie. the next level) enough to meet structural integrity standards?
When there is a "cold joint" will they drill into the set surface to insert extra rebar, abrade the surface of the set concrete so it adheres better to the next layer, or is the rebar that is already set into the structure and extending into open space (ie. the next level) enough to meet structural integrity standards?
DtTO
Active Member
SkyJacked, thank you so much for that wonderful post! I had not even considered many of the points you made, such as concrete hardening vs. drying. Very interesting stuff.
SkyJacked
Active Member
Nobody likes an actual cold joint and every effort is made to avoid them. When it does happen unintentionally, the surface is roughed up while the concrete is still workable in anticipation of a delay causing the cold joint. It doesn’t take long for a cold joint to appear so it’s not that unusual. In the context of my previous post, it just represents a potential location of future deterioration. In most cases, if it is properly patched soon after placement it will never be noticed.
Where a cold joint is planned, a trapezoid shaped keyway is formed into the concrete and when it is stripped, thoroughly cleaned of loose material and wood from the key form in preparation for the adjoining concrete. It is at this time and not always, holes will be drilled and steel dowels will be epoxy glued into the concrete. Planned cold joints are ground and patched as necessary soon after stripping.
Please note; I could go on for volumes with more detailed explanations and I am still not a civil engineer. It must be acknowledged that my responses are based more from boots on the floor than books on the table.
DarkSideDenizen
Senior Member
Thanks again for the reply and for your insight on the process Skyjacked. Very interesting and informative as always!
I imagine the weather will have an effect on the curing process also. Can lamps or heaters, chemicals, or even the weatherwall, be used to help slow (or speed up) the curing process?
I imagine the weather will have an effect on the curing process also. Can lamps or heaters, chemicals, or even the weatherwall, be used to help slow (or speed up) the curing process?