called me a liar! hey concrete experts
So I was sharing some intoxicating beverages with friends over the weekend. I mentioned to a buddy about something I observed a few months ago. I was driving home on the interstate, and they were doing some work. It was about 9:00 in the evening, and they had several concrete trucks lined up and were pouring a new section of the road. The next morning on the way back to work, the barricades were down and we were driving on the pavement that they had poured just last night.
Now I’m certain of the details here. They were definately pouring at 9-10 oclock that evening, and we were definately driving on it at 6:00 the next morning. It certainly struck me as odd. I know that when we pour a driveway, we always wait at least a week if not 2 before we let anyone drive or park on it.
Anyway, my buddy said that there is no way they would be letting interstae speed traffic on a pour that was less than 8 hours old, and I either was lying, or just didn’t know what I saw. We are both in the construction industry, but he is a bit more experienced with concrete than I am.
So, what is is? Is there some sort of “super crete” that they can use for situations like this? or did I oversleep for an extra day or two?
Replies
Could they have been pouring something other than road bed at the time? Like jersey type barriers or some such. I worked on a crew doing that once. They have a forming machine on crawlers with a conveyor belt for the concrete. I was the guy who got to man the concrete truck chuite and keep the concrete feeding onto the conveyor as the machine moved and I kept the truck moving when the arc of the chute reached it's limit. I'll admit, some concrete manure piles hit the pavement from time to time when some fo the truck drivers were not as good as others on the clutch. Hot work in July on 10 hour shifts!
You observed right. This type of work is standard practice today. The concrete used is not the same as what is usedon your driveway or any other place used in residental work. My boss went to world of concrete in vegas and watched a demo off rapid concrete. It was mixed in a volumetric mixer truck and poured in a pad. After been screeded off. They took Q and A. About an hour had lapsed they put a ramp on the side of the pad and drove the mix truck over it. The truck was near full.
I have used simular products here in Canada, but we have little in the way of concrete roadways but use it on bridge repair.
You aren't a liar. No doubt they were using a fast setting mix that was probably traffic ready within four to six hours of the pour. The technology of concrete mix design has advanced rapidly enough that that's easily possible. Admittedly, it's something that could have been done forty years ago, but the major discoveries have been made in the design and not the materials.
Concrete is great stuff - "liquid stone".
Like in other posts, the answer is "it depends" I'm thinking.
IIRC, most interstate specs call for roadmetal separate to the subsurface. So, there's a base, then the wear surface. I want to remember that the specs permit using either asphalt or concrete for the roadmetal.
If it's concrete on concrete, then that roadmetal only needs to be as strong as asphalt when poured. That means the mix can be optimized for speed of setting to some specified compressive strength.
Using a production highway box, which places, screeds, and starts the finishing of the concrete in the length of th machine will speed things up, too.
Now, getting that subpavement in takes some time. All the subgrades have to be set in lifts, then compacted, then the compaction has to be tested--all before the next layer can be started. Which is what makes highway projects long on the calendar.
we once got a load of concrete that was supposed to go to a bridge construction, because of problems they couldn't pour at the last minute, so we got a call from the company, asking if we wanted it. We were using it for a floor in our storage shed, and they poured, and did a rough level, and then took a break for lunch, and came back, and it was too solid to do much of anything too. Fortunately we had gotten it fairly smooth on the first try, otherwise we would have had problems.
You are correct in what you saw. I am sure the concrete was air entrained with additives to make it set up fast. This method has been around a number of years, guessing at least 25 years. Air entrained concrete has been around much longer, used on bridges elevated highways etc for as long as I can remember. I go back to 1961 on construction.
In the winter the roadbed will take longer to set up and be okay for traffic. You had ideal conditions I'm sure this past weekend.Depending on the mix, temperature etc, an ordinary driveway usually can be parked on after three days.Waiting a week or more is fine, better to be cautious than screw up a new driveway.
mike
we have highway mixes that are so hot they will get 4000 psi in two hours. they are really fun to play with. a workable time of ten minutes
When do they add the water?
they will drt batch it, then arrive on site where they will add water and chemicals, more chemical than water, 180 revoulution then the race is on. It goes into a paving machine, like an asphalt spreader then it finish.
IIRC it's a modified type IV crete.. same that's used on climbing forms..
OK so whats a climbing form? Are you talking about a rock climbing wall? Or something else? -MSYSOP[email protected]Have you updated your forum profile lately? Please Do!
A climbing form, or a jump form, is used in high rise construction. I built the 49 floor Arco Tower in Dallas, and we poureed a core wall floor every three day. One day to pour, one day to strip and jump, and one day to set rebar and get ready for the pour. Roughly speaking, it is a set of plywood forms that can be loosened and jacked up to the next level. The top of the last pour forms the bottom of the new pour. You jump it up, get it tight, align for plumb and level, spray with form release, add rebar and all the embedments, and call for concrete. We pumped all the way to the top.
A variaytion on the jump form is the slip form, like they use for curbs and highway dividers, and grain silos. It is a form that sloooowly moves up (or along the highway) as concrete and rebar are added at the top. the theory is the the concrete hardens fast enough to support its own weight and the weight of the stuff being add above. Pretty simple for horizontal stuff, a little tricky 15-20 floors in the air.
I'm sorry, I thought you wanted it done the right way.
Cool thanks Ed for the explanation. The reason I ask is I have been doing some research into building home climbing walls, as in Rock climbing walls and the stumbling block I keep running into is how to surface the panels so that they feel like rock and look like rock. All of the solutions out there are proprietary formulas... -MSYSOP[email protected]Have you updated your forum profile lately? Please Do!
I,m curious. Do you want the hand holds cast in the rock like face, or an actuall replica of rock face?
Shot crete seems most doable, but maybe not the texture you want for say cliffs on the Delaware river, vs, sandstone of Monument Valley.
I saw a TV show sometime ago, about the limestone from Mt.Rushmore, being a good climb.
Lemme think on it if ya have a plan. Spheramid Enterprises Architectural Woodworks
Well my thought was to take plywood panels and build some type of frame on the face that I would then cover with something... To acheive both a real rock feel and to add some texture to the surface for footholds. I would be using hand holds that would be bolted through to the ply. I made many many holds over the past winter out of clay that I have had fired and now I just need to start constructing the walls. Let me know if you come up with anything. TIA -MSYSOP[email protected]Have you updated your forum profile lately? Please Do!
Well, chicken wire and paper mache' could work. Spray foam is another option, it can be worked to look like rock. Both of these are the lightweight ideas. Shot crete is the heavy method. Spheramid Enterprises Architectural Woodworks
I built the 49 floor Arco Tower in Dallas
Oh, so that was you . . . <G>
I was next door for part of that--sorry about dropping all that veneer brick on your building after that straight-line wind.Occupational hazard of my occupation not being around (sorry Bubba)
Which building were you on?
We had one incident, well into construction when the core was near the top and the perimeter floors were up around 30 or so, no granite yet so all there was for a safety barricade was two rows of 3/8" steel cable. Rather windy day. I forget wht trade it was, sheetmetal I think, they had a rolling scaffold up around 25 or so and the wind caught it while they were moiving into position. The two guys couldn't catch it in time, and the wind pushed it hard against the cables and it flipped over ... took all their tools and supplies over the edge and down to the roof of the 5 story building across the street. Dam lucky it had enough speed to land on the adjacent building and not on the sidewalk or street.
Had another problem, one of the younger crane operators was a smart a$$ and a bit of a rebel. He tried to snatch up a load too fast and it fell out of the sling. Piece of red iron I think. Fell about 5-6 floors onto a Cadillac parked in a No Parking - Fire Lane area. We didn't have to pay cuz it was illegally parked.
I'm sorry, I thought you wanted it done the right way.
Which building were you on?
Less on than in. Memory kicks in, and ARCO is across T-Giving Sq from the LTV Building, where I was coordinating moving a corporate hq from 1501 Elm. Not a bad project, moving 160K sf into 180K sf--excepting those department which did not know they were getting an sf reduction; or those who did not know we were ripping out entire floors of bloated offices*.
Was a bad night, the night LTV shed the top 18' of face brick on the east side. Turns out they had a "race" between the two crews of masons. Ah, it's 30 stories up, do we really need brick ties more'n 30-36" OC EW? Oops. Was good for about 25 years, until 1600 Pacific went in, then the was enough wind vortex to peel the brick out in a big sheet, right back to where the brick ties were 18" OCH & 16" OCV--per spec.
*Jimmy Ling must have been fascinating the work for, his moat dragons had moat dragons. There was a core restroom, and executive restroom, and then, for the top twelve honchos, they all got their own restroom. So, the CEO office is 40 x 48 or so, his PA was in 28 x 40, the PA's receptionist had about 20 x 28--or about the same as a jr jr VP. Yet, not one of tese high panjandrums had a back door from any of their offices--very bad exec planning.Occupational hazard of my occupation not being around (sorry Bubba)
Yep, Arco was/is on the north side of the square. Directly across the street was the old downtown post office, then south of that was the old Republic Bank which I think may have finally morphed into BA but I'm not sure. Was LTV on the south side of the square? We built Arco in about '82, so my memory is a bit weak, and I don't remember the brick incident. Is the LTV building the one with the hole in the top for the trees?
I remember another fun time we had during construction. Aboutr half way through construction we had a leak. There were three basement levels, not very big, but they held the main electrical switchgear, executive parking, fire pumps, loading dock, access to the tunnel, etc. Telephone contractor, working for somebody else beside the gc (that was us), maybe the owner directly or the city ... who knoes. Anyway, they did some excavating at the curb for their phone lines, went down pretty deep (8-10 feet), did their work and backfilled. During the process they managed to excavate the soil around the thrust block for a 36" water line, and a few days later the water pressure nudged the block ouit of the way and opened a joint in the pipe. Didn't take long to flood the basement, including the switchgear (water about 3 ft high) and the spools of high voltage cable waiting to be pulled up the tower.
I'm sorry, I thought you wanted it done the right way.
Was LTV on the south side of the square? We built Arco in about '82
Yeah, from ARCO, the RNB buildings would bo on your left, then there's; well, now I can't remember the stinkin building's name--I want to say it was brownish and vaguely diamond-shaped in plan. LTV, which had no sign saying so, was next, then a parking garage, and then a short 16 story bank building on the Akard side.
LTV is rectangular, glazed N&S, with brick veneer on the e/w sides. Relatively nondescript for downtown. No connection to the u/g mall, either.Occupational hazard of my occupation not being around (sorry Bubba)
There was a cool TV segment about the construction of some cooling towers for a nuke plant. The forms were as you described, and were moved up one lift at a time. The kicker was that the whole thing was tapered, getting narrower as it went up and then flaring out at the top.
I've seen the same thing done in miniature by some guys who came and poured a 24' deep in-ground round water tank. Forms were 4' tall and they poured one lift per day... high early strength mix... not sure what the components of that are.
I spent the early eightys working on highrises in Dallas. We used the same system to pour the elevator shafts. Post tension cables in deck slabs only seven inches thick. Pretty cool stuff.
Mark
it's a hydraulicly operateded forming system that climbs upwards (vertical slip form) on it's own... you have to stay ahead of it with the steel and crete... it's not at all like a jump system.. go at it 24/7.. 20 stories a week and no stopping...
Edited 8/3/2005 2:03 am ET by IMERC
Thanks I got that from Ed's post, sounds like a lot of work... -MSYSOP[email protected]Have you updated your forum profile lately? Please Do!
Ahhhh...concrete. Gauranteed to get hard and crack.