Not M/C related--concrete question

[Aimhigh]

I want to put in a platform and sidewalk. I'm sure I won't be able to mix enough concrete to do the job in one fell swoop. Is is okay to add new concrete to concrete that has already set?

[utadventure]

Yes and No.

 

What do you mean by platform? Porch?

 

How big of an area are you talking about?

[Rickster]

Yes but how thick are you talking? If possible you should try to avoid cold joints

[Aimhigh]

the larger platform will be approx 12 X 12

[utadventure]

Jim-

 

Two things guaranteed about concrete..... it gets hard and it cracks.

 

Like Rickster mentioned, you want to avoid cold joints if possible. The lines you see in most concrete are not usually cold joints but points put in the concrete to hopefully manage/control the cracking that will happen.

 

Without knowing the specifics of your 12 x 12 pad, at 4" thick, you're talking about less than 2 yards of concrete which can be purchased from a "haul your own" supplier. Cold joints increase the possibility of the concrete shifting or settling at different rates. Thickness and psi for the concrete would be based on the planned use.

 

If the pad has room to expand/contract then cold joints can be directly against each other. If the pad is confined on the sides, you'll want to place expansion joint material between the pad sections.

 

General rule is 10 X 10 without control joints marked in the pad. You could divide it in half or quarters.

 

Good luck with your project!!

[Aimhigh]

Thank you so much.

 

As someone said in another thread...it is info like this, in addition to motorcycle info, that makes this site a real bargain for the pittance we pay.

[Yammer Dan]

Thank you so much.

 

As someone said in another thread...it is info like this, in addition to motorcycle info, that makes this site a real bargain for the pittance we pay.

 

 

 

Its not IF its going to crack its When. No set rule for avoiding them I don't think. Some crack some don't. Mine did!!

[ragtop69gs]

When I poured the slab for my garage 30x48, I used wire reinforcement 8x8 suspended in the slab at half the thickness and fiberglass fiber in the mix, even if it does crack one day ( poured in '96, no cracks) it will not shift or raise. Where I joined it to the old slab we drilled and installed 1/2" steel rods every 12" and felt expansion joints. Keeping the slab damp and covered to slow cure time, that will strengthen the concrete.

 

Pay the money to have enough delivered to do the whole thing at once, it's money well spent.

 

DO NOT USE THE READY MIX YOU BRING HOME IN A TRAILER UNLESS YOU LIVE WITHIN 1 MILE OR THE TRAILER HAS A MIXING AUGER. You don't want the aggregate settling out in transit as its next to impossible to remix in the trailer

[pmelah]

i dont know if this is avalible to the public but dimond seal is a great product for sealing the concrete i use to use this when i polish concrete to a mirror finish like what you see in home depot or lowes dimond seal helps strengtin the concrete and is guaranteed not to crack for 10 yrs we used this stuff at stenis space center (NASA) here on the MS coast before Katrina and at the coast coliseum in biloxi and both places the concrete has not cracked and looks as good as the day we did it 1/2 gal. should do what you need it for if you can get it it is water activated so you have to spread it first with a squeegee ad water then continue to spread it after 10 min suck it up with a shop vac and let set i imagin that by now it should be availible to the general public

[Rickster]

Yes you should always try and pin old concrete to new and using the fiber mesh that you can get added by your ready mix company at the batch plant is a good idea. Also keeping it wet for some time 5 to 7 days helps with the curing process and a nice concrete sealer after is a good idea. After you pour it And its set like you can walkmon it, try to keep it wet I use soaker hose, it has little holes all through it and works like a sprinkler. I also put burlap over the pour after it sets to help holded the water from the hoses. You can cut your control joints after a few days even if the concrete still looks green it will be fine. Oh if you do get fibers in your mix when you finish it it will look like there are little hairs sticking out don't worry they will go away after you start to use it.

[Sylvester]

I am retired from fifty years in the concrete field and I have become very wise at my age, finally. The one thing I have learned is that concrete will never be fully understood. The ancient Egyptians began this process and it is still evolving. :backinmyday: