This video demonstrates the [AWESOME] ability of pourous concrete. Here it is being deluged with water from a concrete mixer. What is so amazing is how quickly it drains through the concrete.
As I watch this questions flood my mind. How deep does this slab have to be to resist uplift? Is there a special method required for the substructure? Are there special rebar requirements, or other installation requirements?
If anyone out there knows of some helpful links, please drop them in the comments section. So far all I have found is this site for pervious concrete paving.
Thursday, October 1, 2009
Parking Garage 093009
Wednesday
10 am
On Wednesday I watched as a steel rebar cage for the new parking garage structure was lifted and set in place. My assumption was that it would simply be lifted and set within a matter of seconds or minutes. The reality was much more involved. Also the crew members and additional equipment was insightful.
Within the steel rebar cage a constellation-like arrangement of bars was located in the center. This I learned was to give the cage stability when going from a horizontal to a vertical position.
A 1-foot portion of the cage had to be to size before it was lifted. A front-end loader was linked to the cut end and used to move scrap to a nearby pile. The loader was repositioned and a chain was used to attach the bottom of the cage to a hook on the loader bucket.
After readjusting the straps which connect to the crane the lift was underway. The loader was used to assist the crane in getting the cage vertical. Once it was vertical and hovering about one foot off the ground, the loader was unchained. Workers then used a torch to remove half of the interior supports. The cage was then lifted to about midway between its lift and final location. Here two workers take what appear to be rigid foam feet to the bottom of the cage. This must provide the required amount of concrete coverage below the cage.
The cage is lifted in to place and lowered to about half way in to the caisson. At this point the cage is held in place while the remaining interior supports are cut and carefully removed so that no rebar fall in to the caisson excavation. With the supports removed the cage is sufficiently flexible and drops right in to place.
10 am
On Wednesday I watched as a steel rebar cage for the new parking garage structure was lifted and set in place. My assumption was that it would simply be lifted and set within a matter of seconds or minutes. The reality was much more involved. Also the crew members and additional equipment was insightful.
Within the steel rebar cage a constellation-like arrangement of bars was located in the center. This I learned was to give the cage stability when going from a horizontal to a vertical position.
A 1-foot portion of the cage had to be to size before it was lifted. A front-end loader was linked to the cut end and used to move scrap to a nearby pile. The loader was repositioned and a chain was used to attach the bottom of the cage to a hook on the loader bucket.
After readjusting the straps which connect to the crane the lift was underway. The loader was used to assist the crane in getting the cage vertical. Once it was vertical and hovering about one foot off the ground, the loader was unchained. Workers then used a torch to remove half of the interior supports. The cage was then lifted to about midway between its lift and final location. Here two workers take what appear to be rigid foam feet to the bottom of the cage. This must provide the required amount of concrete coverage below the cage.
The cage is lifted in to place and lowered to about half way in to the caisson. At this point the cage is held in place while the remaining interior supports are cut and carefully removed so that no rebar fall in to the caisson excavation. With the supports removed the cage is sufficiently flexible and drops right in to place.
I was so impressed with how my assumptions were trumped by the reality of the operation. Last semester we had performed a rough estimate and schedule for caisson work on the new addition to the building department facility. Our estimate focused on the macro estimating and scheduling tasks, but on observing the actual operation I learned the micro-processes. It was a nice reminder that that is what matters. I need to understand the micro-processes in order to truly understand a job. This job is not simply a caisson drill and crane. It is a crew of 8+, a loader, a rebar cage station, drilling spoilage, caisson excavation safety, a welding torch, etc.
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