Basic Concrete Help

[Dragster Racer]

Going to do a pour myself with a friend who has some experience with concrete. I am doing the prep work this week. It is a 15'X15' approach to my pole building, which already has a concrete floor. I need to pour this area before driving over the ground since there is a septic tank that I am using for the shop bathroom under this area.(it was there before I built, and I discovered it before they poured the floor.) I will leave an access hole with a steel plate over the cleanout lid. I want to spread the weight of the motorhome out using the concrete and rebar.

So, I have strung out the 15X15, and given it a 1/4"/ft slope out, and 1/8" to the side. I dug deep enough to lay out a few inches of gravel, which I will tamp with a gas tamper tomorrow night. I have 2X6's for forms, which I will start building tomorrow night also. I plan to use 2X10's to form around the cleanout. I will make a lip for the form to make a recess for the steel plate.

I plan to drill into the garage slab for the rebar to connect, drilling through the expansion joint. I will pour up to the end of the slope of the garage floor.
Not sure what spacing to use for the rebar. Any help? I will use stands to keep it up. Also what spacing between 2X4 stakes for the forms?

Really nervous about pouring day. Pour, shovel, rake, skreed, bull float, long trowel, rest, broom? Details would be nice.
It is cooling off here, and I am hoping for a warm Saturday. I understand that they put in calcium to aid curing in colder weather. Probably mid 50's. I plan to order with fiber.
I can use all the advice I can get here.

 

[Dragster Racer]

Not all at once.

 

[scofo]

Hi Dragster, I've helped on a few pours and I would suggest, unless you're in good shape, to get one more hand. Have one guy save his back and legs for the Bull float. Good luck

 

[Torque1st]

1 inexperienced guy around is enough. Make sure you get at least three experienced persons.

Stakes every 3-4' for the forms.

My recommendation even with the fiber reinforcement would be #4 rebar on 24" centers. #4 on 12" centers over the septic tank extending 24" beyond the tank. Stands won't keep the rebar up if someone accidentally steps on it. 1.5" minimum coverage over the rebar. You will need 1 guy with a hook to pull the rebar back up when it gets stepped on.

 

[Dragster Racer]

Thanks guys! We poured this morning. Went very smoothly. I think the driver added more water than I would have liked, so it is curing slowly. Plenty of time to work. My wife isn't afraid to work, and she pitched in. I have to say it wasn't really that much work. I would do that again for sure. Now, if I can keep the deer and racoons off it overnight! I'm putting black plastic on pretty soon.

 

[Jaguar Fan]

Thanks guys! We poured this morning. Went very smoothly. I think the driver added more water than I would have liked, so it is curing slowly. Plenty of time to work. My wife isn't afraid to work, and she pitched in. I have to say it wasn't really that much work. I would do that again for sure. Now, if I can keep the deer and racoons off it overnight! I'm putting black plastic on pretty soon.

Good luck on keeping the local wildlife off!

Did you take some pictures? Can you post a few?

 

[Torque1st]

Added water = lower strength but easier working.

 

[Pritch]

Added water = lower strength but easier working.

True enough, but for a re-inforced driveway, unless you place with a 10 slump or so it won't be a problem. Fiber goes a long way to adding strength. Remember, mix designs are based on 28 days to design strength. Concrete keeps getting hard for like 75 years. Now, having said all this, the longer the OP can stay off the slab, the better. And if he lives in an area where road salt is used, I would recommend staying off of it until spring. Salt dripping off a vehicle will eat up the top of a slab faster than anything else.

 

[Torque1st]

I am well aware of the curing and strength properties of concrete.

The primary components that control the strength of concrete are the water and the cement contents. These two components are commonly referred to as the water/cement ratio. While properly graded sand and stone, and their relative amounts can affect the overall strength of the mix, the water/cement ratio has the greatest effect on the strength of the mix.

Every gallon of water added to a cubic yard of concrete, above the designed water/cement ratio, will decrease the compressive strength of that concrete by approximately 200 psi. So by adding an extra 5 gallons of water to one cubic yard of concrete, you will decrease the compressive strength by about 1000 psi!

Concrete leaves the batch plant at the designed water/cement ratio. Adding water at delivery degrades the concrete.

Normal concrete is designed with a certain workability, which means it can be conveyed to the pour site using smooth rounded chutes and still maintain its composition and not segregate. Adding more water to make it pourable or looser usually causes segregation, not to mention the adverse effects of the additional water on the strength of the concrete, slower setting times and increased cracking.

He can help with salt penetration by using a sealer. A sealer will often help with curing by retaining moisture in the surface.

 

[Dragster Racer]

Good stuff guys! I don't think that all that much water was added, but hard to tell. It didn't take him more than a few moments to add. It was really thick coming out at first. I think part of the slow cure is it is in the shade, and it hasn't been above 55 degrees all day. Strangely, it only got down to about 50 degrees overnight. Great, but strange.
So now...How long do you wait before removing forms? Is there such a thing as waiting too long? How long should I wait before driving the motorhome on it (medium sized one--14,500 lbs)?
No salt concerns. Not living at the build site, and won't park anything there.

 

[Dragster Racer]

Oh, pictures. I think my wife got some. I have to figure out picture posting here.

 

[AlphaGarage]

To post pics they need to be hosted online elsewhere. If you need a place to store them try tinypic.com. Pretty easy & free.

Once you have them hosted, start a post here and when you want to insert your picture click the

icon and paste in the picture's url in the dialog box that will pop up. If you have additional pics... rinse & repeat.

 

[Dragster Racer]

http://uploads.bizhat.com/view/352541
Let's try this. She didn't have any picts of the pad.
At least this shows the consistancy coming out of the truck.
So, how long before driving motorhome on it? 15'X15'. Should I score it? How deep?

 

[Dragster Racer]

LOL! Need to work on picture hosting. Little big. At least it shows a nice picture of my son! Obviously he gets his looks from his mother.

 

[Dragster Racer]

<a href="http://uploads.bizhat.com/view/352541"

http://uploads.bizhat.com/file/352541

 

[Dragster Racer]

Not quite yet I see.

 

[AlphaGarage]

Not quite yet I see.

But close!

That does look a bit thick down the chute. Have you removed the forms?

In my neck of the woods scoring concrete usually refers to cutting into the concrete primarily for decorative purposes.

Expansion and/or contraction joints are about 1" thick. With 15' x 15' it's almost a toss up as to whether or not you need any control joints.

Check out tinypic.com, it's the only pic hosting site that even I can figure out.

 

[Dragster Racer]

Will do. If I ever decide to post picts of my manhood, I will try something other than tinypic.com though! I need all the help I can get.

 

[Dragster Racer]

Let's see how I did this time. I never have posted picts of my shop or dragster. I will have to get a pict of the pad after I get to the land again. It is sitting on 24 acres which we hope to build a house on next year.

 

[Dragster Racer]

Hoo hoo! Your host site worked much better.

 

[AlphaGarage]

Hoo hoo! Your host site worked much better.

Which just goes to prove - "It's not the size...."

 

[Dragster Racer]

Sooo. Anyone on the when to drive on and whether to score and how deep question?

 

[Torque1st]

Concrete is normally scored 1/4 of the way thru every 10-12 feet. With your 15x15' dimension you are probably OK. I like to fill the control joints with self leveling urethane concrete filler to keep water and crud out.

Your picture shows that the concrete is too dry coming out of the truck. It may be an error by the truck driver in his holdback allowance. Every driver is asked for a holdback by the batch operator for water he has in the tank after cleanup. Otherwise the concrete could look that way because it was largely "old" concrete from a prior job or had been on the truck too long. Without feeling it I could not tell. The only other way to definitely tell would be if you had made arrangements with a testing company to test the concrete. If the concrete is curing well don't worry about it.

Don't drive anything heavy on it for at least 30 days. The cold will delay the curing slightly. Ask your local batch plant for their recommendations on curing and loading. They would know best. Ask them about a sealer also. They may know of a contractor or product available in your area. A sealer would be good for your shop floor also.

I use ImageShack for hosting:

 

[Dragster Racer]

Thanks for the good advice! It was a first thing in the morning pour, so I don't think it was old. It was too dry though. Seemed like we just went right past when he added water. May be too cold now for sealer? I did seal the floor with a sealer/curing agent that the contractor recommended. I need to recoat. May go with something better in a year or so. I'm not excited about epoxy since I need to bring in the tractor sometimes, and may have to with chains now and then.

 

[Torque1st]

Check with the concrete company and your contractor and the sealer manufacturer. I like sealer rather than epoxy or any "floor paint". Sealer is not as pretty as paints etc but it is great for a working floor. Sealer also helps reduce "dusting" of concrete floors. Sealer also helps reduce salt damage in those areas prone to salt use on roads. Some sealers help with concrete curing.

 

[Wardster]

Concrete looked pretty dry to me as well. You could ask for a copy of the batch ticket from the supplier if you wanted to see how much of each item was used. It would also tell you how old the mix was when it got to you.

Wait a month before parking your RV on the concrete since you did not make any cylinders to check strength.

-Wardster