I’d had a finisher lined up to do my slab tomorrow. He has 4 guys and can work quickly. Unfortunately, they are all apparently either dead or in jail, so he’s cancelling. I already put this off once and I’ve got to go for it tomorrow. I have one guy coming who is very good with mud, and I’m alright myself. I can get two other guys to rake, screed, and generally hump, but they don’t have finishing experience.
The finishing sub asked for 1% calcium, hot water, and a mid-range water reducer (3″ slump extended to 7″). For him this would be a good mix and would allow them (and require them) to work quickly.
I’ve poured several slabs and always with un-modified mixes. They take most of the day to get to where you can hard-trowel them, which is what I’m doing tomorrow, not a broom finish. I’ve been caught a few times finishing under lights or after dinner. I don’t want that.
Anyway, I can leave the mix order as it stands, or I could change it. The slab is 23×31 and the weather will be 45, partly sunny, and breezy. I want enough time to get the mud on the ground and finish it before dinner. I obviously do not want a crazed, panic-stricken half-day that results in a lousy looking job.
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1st i'd ask the plant for their ideas.... second I'd go to whatever area has the hispanics in it and 5 out of 10 can finish concrete @ $10-$15 an hour... to you have a power trowel ? if not u need to head to ur nearest HD and rent it for the day... around here all their stuff is NEW never rented it but looked at it and knew it was there if one of mine puked mid job... so many things can affect when you can get your final finish... last year i spent many nites til after midnite run'n my trowels after everyone else was gone... it takes what it takes and it's not going to wait on you when it's time... plan on & expect to be there til midnite... and be happy if you get to leave before that
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Unless you can get the first trucks, sounds to me like you want to wait for a warmer day. As for hispanics, the by far worst slab I ever saw came from hispanics here who had no idea how to screed. Sometimes cheap labor isn't.
You've got enough labor, but the final guy's going to be there awhile even with calcium if the high's 45º. Pony wasn't kidding about being there late. But it's your job, so it's your call. You can always quit working the slab and accept whatever you get.
Postpone.
PAHS Designer/Builder- Bury it!
That is not a bad mix, or temperature.
But there is nothing so indefinite in all of construction as your question and the answer to it. I have seen finishing crews work their butts off to stay ahead of it, and I have had crews have to stay 'till 2 AM to geterdonme.
I'd say that your odds are better to the latter, gioven the reducer and the temperatures so I don't think that you to worry about it kicking too quickly for you
BTW, Good luick! I have had my share of sleepless nights ovcer crete. The whole job moving forward depends on it, and it depends on so many other factors, all of which are magnified by working on an island
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I did a slab under almost identical circumstances a year ago. A little cooler, and it misted a bit, but the walls were up and the roof was on, so no sunlight hit it and the wind was not as much of a factor. We were there 'til 9.
This one is out in the open and it's been consistently windy, so I expect more kick, sooner. I think this is a game-time decision. If I look out there at 7:30 and see four trucks in the driveway and guys drinking coffee, I call the plant and go with the calcium. If it's just me and Mark and my neighbor, we go with a plain mix. I put in several calls today to see who might help, and will have somewhere between 3 and 7 people tomorrow. Some of them might even call tonite to RSVP.
There are very few Hispanic folks here. One concrete contractor has a complete crew of them and they do good work. There is virtually no casual labor available. That's the breaks in a resort area... folks with money who don't work much, if at all, and the few others who can afford to live here and do the work.
leave the 1% calicum out of it. with the water reducer and calicum it will give you about 45 minute before you be walking on it. That is a very hot mix. use a high range water reducer like " super P". 2+3=7
You forget that this is up north and you are down south. A hot mix is needed for the low temps
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but calicum, hot water with mid range water reducer is a very hot mix. we might use calicum but with cold water and no water reducer.. 2+3=7
that be my choice
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I,m not really scare of the mix but the crew, it take a good crew with alot of help to handle an hot mix.. 2+3=7
Edited 3/2/2006 9:43 pm by brownbagg
I'm expecting 4-5 guys total to place 11 yards, a 5-inch slab approx. 23x31, with a boom pump. 2-3 guys on the screed, 1 rake, 1 on the hose. It will take about a hour to get the mix on the ground and screeded. I think I'm either going plain or maybe 1/2% calcium. Hotter than that and I could be looking at an ugly shop floor for the rest of my life. I am also going to talk to the plant in the morning for their recommendation. The pumping will start at 8:30, and I'll tell them I want to be on kneeboards by about noon and power troweling by 3, done by beer:30.
Along the same lines, I'm going to score the slab on Saturday morning. I was thinking one down the middle to divide the 23 feet in half, and two across to divide the 31 feet in thirds.
A little follow-up on this one.
Four of us poured the slab, one left after the mud was placed, and a second one left after we had gone around the edges a few times. The mix was 6-sack with hot water, 1/2% calcium and Polyheed 997 water reducer, measured to produce a temporary 7" slump from a batch that had enough water for a 4" slump.
The mud came out of the hose quite runny. It was almost no effort to get it screeded off, two guys pulling the board and one guy raking but mostly leaning on the rake. We got 13 yards down in about 30 minutes of pumping. I have done other slabs where screeding and raking was a major amount of work. This was incredibly easy by comparison.
We poured until about 9:30, and by about noon the mud was starting to act like ordinary concrete as the water reducer wore off, ready to start working by hand. It did not 'kick' quickly, as I was told it probably would. It was 4:00 or so before we could start getting a really tight finish by hand, and 5:00 before the power trowel was working correctly on the half that we poured first. It was too dark to see the work by about 6:30, so we called it done.
It would have been nice to have another hour of working time. In retrospect, more calcium or another accelerator would have been good. The Polyheed has a slight retarding effect, and the 1/2% calcium we added probably corrected that, but didn't provide any additional acceleration. On a hotter day this would have been the perfect mix.
Anyway, it's done, it's in there, I give us a B for finish quality--some visible trowel marks and such, stuff that you can't prevent when you finish in the dark. I could have brought out lights and stayed on there with the power trowel but I needed to be elsewhere last night and I am quite sure my tablesaw will not mind living on top of a trowel mark. All-day-every-day concrete guys would have used a mix with 2% and been done with a shiny slab by about 2:00 or so.
I only use 2% with walls or footings. Too hot for slabs, even with good crew, IMO.But I told BB that you needed a hot mix for cold weather!
Thanks for the updayte! We all learn from each other.
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In a lot of cases, the plasticizer could be useful for walls and footings. A lot less work to rod and vibrate it into the nooks and crannies, easier to avoid any honeycomb, and less water is used so it's better concrete in the long run. The exception might be a monopour T-footing, where the mud would gush out the top of the footing as you filled the wall. Otherwise it makes it a LOT easier to place.
I've only seen one pro flatwork crew here. They came from the mainland to do a couple of large slabs with Bomanite color. Everything 2% calcium, plus the Bomanite speeds things up more. They always made the afternoon ferry back, if you know what I mean, and had no problem getting the work right.