Taking out old concrete and pouring new - questions

[Code54]

Im not a concrete guy but have a little project that I thought I would get some opinions on. The slab outside our garage has a break in it and I have another right inside the garage door. Today I started looking at it and pulled a piece out of the outside slab at the break and found there is some type of drain line running right where the concrete broke. It appears the pipe is only under about 1.5-2" of concrete so I know that is problem. Right now I am planning on tearing out the entire outside pad (total 9'x12'), taking up the part in the garage that is bad (maybe 18"'s of floor), redoing that line and making it deeper, then repairing everything. I am doing this on my own and don't really plan on asking anyone to come and help as all my friends are super busy on there own homes and I don't want to bother them. I did price ordering 2 yards of concrete and with delivery it is a hair more than using bagged mix. I also have a mixer I can use so that is not a problem and I like the idea of being able to work on this over several days/evening after work.
Now I just am not sure what size pad I can pour with bags (5'x10' maybe) and what is the best way to join the different pads? Also in the garage do I need to have a square cut line to join the new concrete to or can I drill into the rounded edge, put in rebar, and join it without cutting it square (I don't have a saw for concrete so that is why it is a bit of a pain)
I attached a few photos so it may help with the description of what I am doing. The reason I am doing it is because it looks bad, and water drains toward the garage. I plan on giving it a slight slope away from the garage to solve the problem in the future.

 

[boggen]

call 811 (juelie) get lines marked for gas,electrical,telephone, sewer,water, etc... free service be safe than sorry.

pouring that much with bags by yourself *yuck* i hope you are really in shape! and have a couple strong in shape friends to help out.

rent a concrete saw to cut out the bad stuff, the saw will also create "joints" were once you start with a sledge hammer or jack hammer to keep the cracking to going to rest of the concrete. if you make some extra cuts with saw, you might be able to use some pry bars to wiggle out and bust out smaller chunks easier without using of a sledge or jack hammer.

if ya taking out the entire pad outside, get an electrical jack hammer rental, TIP do not force it, all you do is hold it, you let the jack hammer do the work. your body will love you for not trying to force the jack hammer.

concrete is better off being poured all at one time. vs over multidays. tearing it over multi days no big deal, just the pouring and curing of concrete. get it done at one time.

 

[schmism]

call 811 (juelie) get lines marked for gas,electrical,telephone, sewer,water, etc... free service be safe than sorry.

they only mark utilities on easements. They have no way of marking random "stuff" that may be on private property.

Will JULIE, Inc. tell me the specific location or depth of the public utilities?
No. JULIE does not have information on the specific location or depth of underground lines.

The only information that julie has is information provided to them. It is not uncommon for contractors to call for julie locates, have nothing marked, and still dig up un-reported utilities.

What julie will and wont locate.
-locate the water line to the meter. your water service after the meter is your responsibility, not marked.
- locate gas line to the gas meter. Additional gas lines run underground to an outbuilding would not be marked.
- locate underground power/cable to the electrical box or demarcation point. any additional underground wiring installed on private property (again to supply a shed etc) will not be marked.

So by all means call julie for a locate, but dont be shocked when nothing is marked outside of the ROW for utilities.

 

[roadhunter]

call 811 (juelie) get lines marked for gas,electrical,telephone, sewer,water, etc... free service be safe than sorry.

pouring that much with bags by yourself *yuck* i hope you are really in shape! and have a couple strong in shape friends to help out.

rent a concrete saw to cut out the bad stuff, the saw will also create "joints" were once you start with a sledge hammer or jack hammer to keep the cracking to going to rest of the concrete. if you make some extra cuts with saw, you might be able to use some pry bars to wiggle out and bust out smaller chunks easier without using of a sledge or jack hammer.

if ya taking out the entire pad outside, get an electrical jack hammer rental, TIP do not force it, all you do is hold it, you let the jack hammer do the work. your body will love you for not trying to force the jack hammer.

concrete is better off being poured all at one time. vs over multidays. tearing it over multi days no big deal, just the pouring and curing of concrete. get it done at one time.

Gread advice.

I would suggest making a project out of the removal exactly as sugested and leave the concrete mixing to the truck. You have much better things to do than mix 2 yards of concrete plus it will likely be better coming from the plant. Can probably make some 1" deep cuts every couple of feet with a rental saw and remove it with a FEL on your tractor. Should break into manageable pieces. If you want to do some extra work find another place you need a couple yards of concrete. Around here you can usually just buy and extra yard or two and not pay a delivery fee and come out ahead versus ordering 2 yards and paying a hefty delivery charge.

Get a long straight piece of 2x4 or 2x6 lumber to use as a screed. Take another piece of 2x lumber and drill a hole so you can screw a broom handle it it to use and a float. Buy a trowel and use your shop broom to finish. Use a rake and shovel to help place. Watch a few you tube videos on how the process works and you should be able to complete a project like that by yourself. Biggest thing is getting the right amount of mud from the discharge shoot. PITA having to move it by hand later if you are way urshort or long, especially by yourself. Just leave a pile outside yoru form if you think you might need extra so you can add accordingly.

Good luck and let us know how it turns out.

 

[Egon]

Diamond blades for a skill saw are available at most any hardware/box store.

Adding a little Portland cement and air entrainment additive to your bagged mix can give you some pretty nice concrete.

 

[jaotguy]

cracking is probably from things shifting ( after the original pours )

you might consider the saw rental ... to clean things up ..

do not tie it all together , but pour in sections . let them cure .. then do another section ...

it may not look as nice, but gives it the ability to flex at the joints and not crack again ...

it is doable if you have a mixer ( and a strong back and lots of time )

 

[EddieWalker]

Why would you call to locate lines when replacing a concrete pad?

When taking out the concrete, get it up in the air just a bit and it breaks easy.

Pouring sacks of concrete is going to wear you out quicker then you can imagine. Did you price the quality stuff or just the cheap stuff used for fence posts when comparing it to having a truck deliver it? If your goal is to have a pad that doesn't crack and will last the rest of your life, then bring in a truck and pour it all at once. I've done pads this size by myself and it's all the work I can handle just spreading it and getting it smooth. Picking up sacks and putting them in the mixer, then pouring it and smoothing it out on your own is guaranteed to be more work then you want and the results will be hugely disappointing.

You get one shot with concrete. Do it right with the best materials available.

Do not use wire. It is impossible to keep it in the middle of the pad while spreading the concrete. 100% of every slab I've opened up with wire has the wire on the dirt with the concrete above it. The only time you can use wire is if nobody is walking on it. Those who say you just pull it up while spreading it are either being dishonest with you, or are clueless about what is happening when they walk over it again after pulling it up.

Rebar works. It's easy and it's proven. Put it on chairs to make sure it stays in the middle of the pad.

Dig deeper where the pad begins and where you will drive over the edge. A foot is usually plenty. Add another row of rebar there for added strength.

When installing your forms, make sure the stakes are deeper then the forms. It makes it easier to scree the concrete when your scree board isn't hitting the stakes.

Pick a cool day and start early in the morning. You want temps above 50 and below 80 if possible. The warmer it is, the faster it will set up on you and the harder it will be to work. You want the concrete to be mixed as dry as possible. Extra water makes it easier to spread, but it becomes a lot weaker when cured. Water is the enemy. Once you have it spread, start working on smoothing it out with a float and trowel. A pad this size should probably take you the rest of the day to smooth out. You just keep going over it again and again!!!

As for the pipe, be sure that you don't go too deep and affect the grade of it so water doesn't flow anymore. Even more importantly is to get the ground compacted really good where you remove any soil. Cracking is caused by a variety of reason, loose soil under it is probably number one.

Concrete will crack. It expands and contracts with the increase and decrease of temperatures. This movement leads to it's cracking, so wherever it touches existing concrete, you need an expansion joint. You also need rebar drilled into the existing concrete and secured with epoxy to hold the pad next to the building. It's probably not big enough too really need any cuts in it, but dividing it into quarters shouldn't hurt anything. You can either do this when the concrete is still wet and use a special trowel and your scree board, or let it set up a couple of days and use a diamond blade. The cuts will hide the cracks that will happen no matter what you do.

The goal is to minimize the cracking and keep them as small as possible.

Eddie

 

[Gary Fowler]

You cant place a concrete slab of that size by yourself. It takes at least 2 people to pull a screed, one on each end. Trying to do it from the middle by yourself will be a disaster and your new slab will likely look worse than the old one. That crack inside the garage might have been caused by not having a thickened slab at the very edge. You need a perimeter edge band of at least 12" thick x12" wide minimum with rebar reinforcement tying back into the existing slab. In order to keep the new slab from moving away from the existing slab, you need to drill in some horizontal holes in existing slab, epoxy in some rebar at least 12" in length with half of it epoxied into the slab. Then your new concrete will have something to hold on to so it wont wander away. You will have a line there regardless of what you do simply because new concrete shrinks 5% when drying. You may want to put in a 1/4" wide expansion joint at the tie in point with the old concrete which you can fill with a rubber based liquid to keep water and dirt from filling up the crack. I would cut the slab square to the walls just beyond the crack rather than leaving the ragged edge where the crack is. It would look more professional and more like an expansion joint that way. Rent a water cooled concrete saw to do this.

As for cost of 2 yards of concrete, check with the supplier, but you can likely get 5 yards for the same price and make your slab thicker or larger for the same cost of concrete.
USE a bonding agent at the joint between old and new concrete. They should be available at your local hardware store or maybe even at the concrete supplier. Get the epoxy to glue in the rebar to the old slab at the same time. Make sure it is for use bonding steel to concrete.

Get some help with some concrete experience. You wont regret the cost of hiring someone to place and broom the slab. You can help do this if you want but hire a couple of guys to do this for you. It wont be a great expense but it will be worth it for their expertise and a better looking slab. Also, you wont have to buy all the tools as the finishers would bring their own.

 

[/pine]

An alternative to using epoxy for setting bars into holes drilled in existing pours (as long as the holes are not too much bigger than the dia. of the bars) is a slurry of just portland cement a little course sand and a quality bonding agent (no water, see the instruction on the bonding agent)...when pouring against a shear (sawed) surface...use a chipping hammer and rough up smooth sawed surface...

 

[RobertN]

I worked a couple years with a contractor friend. For that size pad, we'd bust it with a 16# sledge. Wasn't worth the effort to get the jackhammer out.

When you do break it up, break it in chunks that are easy to pick up. If you smash it too small, it is harder to scoop or pick up.