Dry mix concrete question.

[Frank]

I've used the ready mixed in a bag and mix my own by adding cement to the con mix. I usually get a better finish with the ready mix - smoother, more butter. The con mix consists of sand and 3/4" or smaller rocks. I'm using 1 part cement to 5 part con mix ratio. The problem is most of the rocks are large with very few aggregates smaller than 1/2" so the results are lumpy after bull floating. I needed to use the tamper to drive the rocks down before bullfloating. Both supplier in my are has this problem regarding the lumpiness.

Am I doing something wrong or should I add smaller rocks to the mix (eliminate the temping process) to get a smooth finish like the ready mix bags?

Also for straight lines, an edger is great but on radius bends where the edger doesn't conform to the curves, what tools should I use?

[Robert Allison]

Are you using 1 part cement, 2 parts sand, and 3 parts aggregate? That should do it. What kind of aggregate are you using? Larger aggregate will contribute to higher PSI, so I wouldn't put in smaller unless you don't care about strength. I haven't had lumpiness problems, so I can't help much.

We have always used standard radius edgers. When the radius wall gets short, you sometimes have to lift up the front of the edger and just use about half of it to make the radius. When doing this, it is important to have the curved edge radius edger. Here is an example:

[Frank]

Don't know what the ratio is as its pre mixed sand and 3/4" aggregate. I get

15 yards and they dump it on my driveway. All its needed is water and cement. Vibrating the concrete helps and the walk behind tamper is great pushing the 3/4" lumps down, leaving more butter on the surface. Still not as good as the pre mixed bags where you just add water.

This is the tool I use and having problems with small radius curves even after lifting the edger up. The problem is its too long but I have an extra one and will saw it off and play around with it.

[DanG]

I thought everyone had one of these in the collection"

I sure don't use it often, but when needed . . . . ..

Never throw out old edgers, cut some real narrow to get past anchor bolts, etc. cut some short.

[Jim Elbrecht]

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I can't imagine that being a good idea. I am anal about keeping my cement/sand/gravel ratios.

How much cement do you add to your premix? That premix has to vary from a 1-3 to a 3-1 by the time it ride in a truck, gets dumped, gets moved around while shoveling-- and hopefully it is covered as a few drops of rain will bring all your sand to the bottom of the pile.

What are you mixing it in? Are you letting it set up too much before screeding?

Jim

[Frank]

Thanks DanG, this is a cool tool. Don't see it in the local big box stores.

[Frank]

One to five ratio.

That premix has to vary

This one except its by Husky and about $200 cheaper - I had this Imer before and couldn't tell the difference from the Husky. Very nice for small jobs, I also have a Red Lion mixer and its crap.

Are you letting it set up too much before

No, at time of screening my feet would still sink into it. Tamping helps a lot. If I have more projects, I would get the dual roller temper - such a time saver and eliminate the concrete mess on my pans after temping.

[Jim Elbrecht]

There's one problem. Sounds like you're shooting for the very common and good all around, 1,2,3 mix. But even if you managed to get lucky and you got 2 parts sand and 3 parts gravel- [and I still don't see that as likely] once mixed your 2+3 probably equals about 4 - not 5.

I use #2 crushed stone & mason's sand. . . . I just tried it- 3 stone plus 2 sand = just over 4 of the mix.

Your smaller stone might have a different yield. But I still suspect that the top of that pile is more like 1 sand & 3-4 stone, and the bottom will be 3-4 sand to one stone. Especially if it is as dry as it ought to be.

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That's an awful lot of mixing - 15 yards of sand/gravel. I was looking at a job half that size a couple summers ago and my brother-in-law talked me into the redi-mix truck. Ended up actually saving me money after I called around a bit. Done in 1/2 a day, more options, and a better mix besides.

We were just doing footings which didn't have to be pretty- but it sounds like you might be doing a sidewalk/patio. [I hope not a driveway because you've started with a pretty weak mix if it is.] I'd be thinking about it though if I needed more than a couple yards of concrete. [you pay extra for a short load- when I did it, I was quoted a price for 4 yards- then raised it to 5 yards and the last yard only cost me about $10] Even at the high price per yard it was cheaper than buying sand, gravel and portland.

Jim

[Robert Allison]

Not to mention spending all the energy to mix it. Even with a mixer, it is a lot of work. Ready mix trucks are the only way to go for anything over a yard, if you ask me. Plus, as you mentioned, the mix is waaaaay better. (And guaranteed if you pour a test cylinder or two.)

[Frank]

I hear you guys but its just the wife and me, not 7 guys and 3 finishers. Next time I'll try the self consolidating concrete - no need to vibrate, screed or even spread it.

[Jim Elbrecht]

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There is never time/money to do things right the first time- but there is always time/money to do it over when it fails.

Except for special occasions when I call my son or brother-in-law, I work alone, so I know what you're up against. But concrete is one of those occasions. You don't say what you're making. If it's a driveway- forget it, take out what you've done and start over. If it is squares for a sidewalk or patio you can remove what you've done in a few years when it gets too ugly to look at.

But at any rate- you've started off with an impossible task. IMHO there is no way to make a decent mix using premixed sand and gravel. [maybe if you did the work every day, could eyeball the slurry in the mixer and tune it up as you go-- but you and I can't do that]

If you and your wife can handle all the bullwork, find a mason that will let you be helpers, offer your services and see what he'd get to do the job. I'll bet there's a guy with all the tools that make life easy-- the contacts to get you the best price on concrete-- and you'll end up with less work- probably very little more money- and a job that will last as long as concrete ought to.

Hang onto your mixer for pouring posts & doing small repairs- not some honking 15yard pour.

Good luck- Jim