Concrete help ?

[R Socey]

Re: Concrete help ?

No, actually it was my foreman at the time which gave me an even bigger kick!

I can honestly say I've done my share of the "bucking bronco" (you'll see what I mean) though. It's not as easy as it looks.

Equipment operators may not look or be very smart, but good ones are hard to come by and worth their weight in gold.



... but what about ceement? You know, ceement floors and ceement walls! I like to tell the people that use that term that it's concrete and cement is just one ingredient of concrete.

Here's a tip for Socey:

Over excavate and back fill with granular fill, most use 57 stone but I prefer 89-10. Grade you fill flat and uniform, thick and thin spots in your slab will cause undesirable cracking outside of control joints.

Ask your contractor about cut control joints instead of tooled, cut joints are deeper, usually straighter, and narrower.

4000 psi concrete withstands the elements much better than 3000, especially in a freeze thaw zone.

Rebar on chairs is much better than WWF. After the wire is tromped on by the finishers it's always at the very bottom of the slab and will rust to nothing in time.

Don't let your contractor add too much water to the concrete before placing, one of the biggest and most common mistakes made when placing concrete. If the mix "breaks" over the blades in the concrete drum on the truck, it's too dry. If the mix looks like split pea soup and comes flying down the chute it's too wet. The mix should flow over the drum blades without breaking, but be thick and come out of the end of the chute like tapioca pudding.

Ask your contractor to use a vibra strike of similar method of consolidation when placing the concrete.

My whole life people have told me: you need experience to do this or that. What better place to learn than on my own job. I pick up hands on stuff real fast, and I am very cordinated. You have to climb on a bull to ride a bull - your remarks were out of line.
You have made up for it with some useful info so I forgive you whether you like it or not. I am going to bite this off - the savings is well worth it. I do appreciate your help. Maybe I'll teach you how to catch a big cats - forget the sabiki rigs. Strike that - you can use those to catch bait!

 

[foodfisher]

Re: Concrete help ?

Tyrran/dinasaur long poster nailed it. I'd like to emphasize, pick a referred finisher to lead and you follow. Blow it and it's a permanent mistake.

 

[minuteman62-64]

Re: Concrete help ?

I stumbled across one of my old (2009) invoices for concrete. The price I cited ($360/CY) in my initial post was way off. Actual price was $115/CY delivered (there was also a $25 charge because I wanted it pumped and then I paid the pumper guy another $150). Anyways, the prices in your area are obviously what will matter to you - easy to determine with a few phone calls.

You now have lots of good suggestions, all designed to give you a stronger and more durable slab. That "cha-ching" noise you hear in the background is the sound of the cash register running as you upgrade your project. For example, increasing your slab thickness from 4" to 6" (in the real world usually 3.5" to 5.5"; which I would do assuming I could afford it) will proportionally increase the amount of concrete you will use - so your purchase would increase from about 20 CY to about 30 CY.

Keep in mind that the load on your slab(s) wil be equavalent to that on a driveway (unless you've got one of those really big boats), so the construction standards for driveways in your area would be the minimum you would shoot for. I'd guess that the quote you received from the contractor was based on that level of construction.

If you need to watch your dollars you might get some interesting feedback on priorities for upgrading from that minimum construction standard. Personally I'd prioritize extra resources towards site prep/compaction and increasing slab thickness.

 

[FlaCowboy]

Re: Concrete help ?

Something to consider...may want to add footers just incase down the road your brother might want to add walls and a roof over the slab.

 

[Tyrannosaurus]

Re: Concrete help ?

Regarding your question about separate placements to break the slab up into bite-size pieces: Good idea, and has been done, but not really necessary. And checkerboarding can cause other problems. But maybe you've hit on something: practice on a smaller pilot project - say half the smaller slab (similar to a common 12' x 16' patio placement). Then you get the advantage of going through the learning curve before getting in over your head or can decide after that to call in the troops for the rest of it. Nonetheless, glad to see you're interested in a quality job. There's a certain satisfaction to doing it right with your own two hands.

I don't understand the comment regarding 2" expansion joints - maybe you meant 1/2" (?), which is standard.

Get references for concrete suppliers. (Mixing it yourself will not turn out well for a large job like this.) Heed the other advice about watching that they don't add excess water when the truck arrives. That's a common trick to ease conveyance and placement and to try to extend the workability of concrete that's getting too old. Adding water will significantly decrease quality unless they've left some of the water out at the batch plant. Tell them ahead of time that you want a batch / truck ticket with the delivery - that will tell you how much of each constituent is in the mix. Watch for water-cement ratio (w/c) - that's the weight of water divided by the weight of cement in the mix. (If listed in gallons of water, multiply by 8.33 to get pounds and then do the math.) The lower the w/c, the better. I'd recommend not more than 0.50 to limit drying shrinkage and bleeding. Placement can get difficult under 0.45, so that's a practical minimum. But get details of exactly what the mix is supposed to be ahead of time and have that in hand when the truck arrives.

Consolidation was also mentioned by jigngrub - another key to quality.

Invest some time into learning more about flatwork before tackling this job. There are quality assurance tests that can be done on site (e.g. someone mentioned coning the concrete), but frankly, I think that's overkill for a driveway slab, especially if you get a reputable supplier.

 

[fishrdan]

Re: Concrete help ?

I no pro by any means, but we put in a couple concrete slabs 2 years ago, around 250 sq' 4" thick , 7x25 and 3x20 tapered. The concrete was $65/yard and totaled $330 or so with their short load fee. All the major work was prep work. Once the truck arrived with our load, we had it finished in a couple hours. The only mistake I made was waiting too long to tool in the expansion joints, so I cut them in. My project wasn't too big, but I don't know if I would attempt 1200 sq' in one shot on my first project, I'd break it up into smaller slabs.

Just saying, if I can do it, you probably can too...

 

[R Socey]

Re: Concrete help ?

Hey guys my power was out for a week, then another day so I am belated on this: thank you all very much for the copious amount of really good info for my project . It will take me some time to assimilate the integral aspects, and helpful tips. Thanks again!