pouring concrete dry

[don45640]

Finally!.......CurlyDave hit it.....you can't expect much strength from a 4"thick retaining wall. Do at least a 6"thick wall for even a 3' high wall. Notice I said pour it......if you hand mix it,add extra cement to each bag,unless you buy the hi-strength type. Just one bag of 94 lbs. cement(one cubic foot)will add a lot of strength to one cubic yard of crete. don-ohio Concrete contractor for many years. ^)

I know there are going too be some comments because i always here you can't pour dry concrete for fence poles but my 2.5 acres has a 6 ft fence around it coming on 15 years know & is solid as a rock, anyway what i'am getting @ is, i want to pour a retaing wall 4 inch thick with rebar & about 25 ft long & probally 3 ft tall & was considering pouring it dry & was wondering if anyone has any experience with this i want to put a car port next to my shop with gravel base to park a boat but it slopes away & will need to raise the outer side up 3 ft to make a leval pad, will frame up & pour H20 as i fill & probally keep a sprinkler on the forms to keep wet for a couple of days any exp. doing this???

 

[bigdeano]

I built a house using tip up concrete walls 8' high by 4" thick. One wall was 9' high. None of them cracked when I tipped them up with my loader. I had to use 6000# concrete and rebar on 1' centers both directions if I remember correctly. A thin wall can be quite strong, but of course will tip over easily if not held up somehow.

 

[handirifle]

Nothing wrong with what you describe just a finished appearance that won't please most head landscapers AKA "She who must be obeyed".

Actually momma preferred the look of the blocks over poured concrete. :thumbsup: I do agree that some do not like the looks of blocks. It was a simpler way for me to build a wall. The only forms needed were for the footer.

 

[CurlyDave]

Actually momma preferred the look of the blocks over poured concrete. :thumbsup: I do agree that some do not like the looks of blocks. It was a simpler way for me to build a wall. The only forms needed were for the footer.

1. The OP did not mention any plans at all for a footer.

2. The forces on a tilt-up wall are much different that those on a retaining wall. A relatively thin wall is fine for the tilt-up design, but a retaining wall must resist much higher lateral forces.

 

[paulharvey]

You really should look into calling an onsite dry mix truck. They can mix any slump you want, can carry roughly 8 CY (although if making 4000+ psi they probably don't carry the Portland for 8 CY). You pay about $150 per CY (compared to $110 for ready mix truck) but you only pay for what you need, and they can change the slump as you go. Works great, but may or may not be available in your area. My old project manager told me anything less than a yard quikcrete is cheapest, more then 1 but less than 6 dry mix truck, anything 6 or more ready mix.

As to strength, we regularly pour 18" trench curb (12" above ground, 6" in ground, 6" thick) as a micro retaining wall, but 3 ft tall screams for at least an 8" x 8" footer and 6" wall at a mininium. Personally I would probably do 12" wide at base, formed face with plywood and strongbacks, and taper from 12" at bottom to 4" at the very top, vertical face, and use earth formed back, pulling dirt down as you pour to create the taper. Tap the face board as you pour to minimize honey comb. Don't strip form for 8 hours.

 

[don45640]

Yes,the footer is important,as Dave says,and you can just widen the bottom as paul suggests.I've done it both ways and other ways,and the strength gained is enormous over just pouring a 4" wall. Sure ,a 4"wall at SIX THOUSAND PSI test full of rebar perfectly placed with vibration is as strong as a 4000 psi, 5" thickness, but who wants to try that(with home-made forms) on a retaining wall 3' high? Just pour it 6-8" thick,with some rebar and specify mix without a lot of entrained air(total 5% is way plenty) and NO flyash,just 6 bags of cement per yd. and you'll be fine. Take a coupla test cyls. if you doubt the veracity/integrity of the batch man or concrete company you're dealing with. don-ohio ^)

 

[vtsnowedin]

A retaining wall is a dam that is holding back the weight of the dirt piled behind it and is trying to flow down hill when it is saturated with water in the spring. Ret walls don’t break they tip over.
I worked on one that was up to twenty feet high. The footers were a minimum of two feet thick and ten feet wide poured on solid ledge blasted and hand cleaned to a pay line. Then rock bolts one and a half inches thick were drilled through the footers and ten feet into the bottom ledge and epoxied into place. They were all jack tested to 100,000 lbs tension and passed. Then the mass concrete was poured above in thirty foot wide sections with a vertical front face and the back battered three on twelve. The wall was a foot thick at the top and up to six feet wide at the bottom. The whole wall was over 1000 cubic yards of 3000 psi min. concrete. It only takes the flow of the Connecticut River when it is in flood and holds up forty feet of fill with a highway on it so I expect it will serve for five hundred years or so.
Build it right the first time and be done with it.

 

[don45640]

Hey,PaulHarvey!We used to have the dry mix trucks(they would carry 12 cu.yds.!) here in Jackson and Wellston,Ohio in the mid-seventies to maybe 1983 or so. I poured thousands of yards with them,but a problem developed which made me quit using them. The cement bin apparently was getting wet and clumping causing a shortage of cement richness per cubic yard.I poured one driveway which came out spotted with the richer gray color and weaker whitish color every few square feet.
Have you ever had this problem? don-ohio ^)

You really should look into calling an onsite dry mix truck. They can mix any slump you want, can carry roughly 8 CY (although if making 4000+ psi they probably don't carry the Portland for 8 CY). You pay about $150 per CY (compared to $110 for ready mix truck) but you only pay for what you need, and they can change the slump as you go. Works great, but may or may not be available in your area. My old project manager told me anything less than a yard quikcrete is cheapest, more then 1 but less than 6 dry mix truck, anything 6 or more ready mix.

As to strength, we regularly pour 18" trench curb (12" above ground, 6" in ground, 6" thick) as a micro retaining wall, but 3 ft tall screams for at least an 8" x 8" footer and 6" wall at a mininium. Personally I would probably do 12" wide at base, formed face with plywood and strongbacks, and taper from 12" at bottom to 4" at the very top, vertical face, and use earth formed back, pulling dirt down as you pour to create the taper. Tap the face board as you pour to minimize honey comb. Don't strip form for 8 hours.

 

[paulharvey]

I have not, but I haven't used onr in 4 years, dry mix isn't FDOT approved because they can't give a true "mix design". We used to use it pouring curb, were you need about a 1.5" slump, and if the ready mix driver brings a 3" you either have to send it back, add Portland into the drum, or make him sit till the mud first starts to get hot and then pour like heck. Another thing is I guess a lot depends on the quality of the dry mix driver, in Gainesville FL, they made good mud, but everyone in Ocala FL, says there locals make crap mud and don't seem to know how to fine tune slump and water-cement ratio.

 

[nimblemotors]

To bring back a 5 year old thread..I recently poured about a yard of concrete. Sprinkled might be a better word, since my concrete mixer broke right as I started the job,
and doing it wheelbarrow at a time not appealing. So what I did was a) wet up the dirt good. b) pour/spinkle/spread out the dry concrete in the form, sprinkled water on it until all wet. Repeat again. One thing this does is keep the rebar/mesh from just pushing to the bottom which happens when you dump a big load in. Since I had no real support for the mesh, the concrete goes under it and lifts it. Once I got 3/4 of it filled this way, the mesh is then sitting on top of the concrete. Now I mixed the rest in the wheelbarrow and poured it on top, and fininshed it as usual. Came out great. This was a **** of lot faster than mixing it all in a mixer even, let alone a wheelbarrow.

I am thinking of doing this on a bigger scale for my barn floor, so went searching if others did it. Of course most say 'no way, won't work', but then other examples are given showing it works. HA. And it worked for me. And btw, at 1 yard size, homedepot discounts a pallet so it is say $120/yard. The onsite-mix people wanted $200 for a yard. The uhaul-it-mixed guys wanted $160, and you need 3/4 ton truck I don't have.
I usually make my own with cement/sand/gravel, but not at just 1 yard. If you make your own you have to mix it anyway, so this approach only works with premixed bags,
but at 5 yards the cost figures don't change too much. And let me also add I work alone, no way I can deal with 5 yards dumped at once, and the onsite guys start charging big money after 20 minutes of being there.