Resurfacing concrete

[Stan in Oly, WA]

Is there any way to resurface the concrete of an old, badly worn area that will be subjected to only pedestrain traffic? I'm putting in sidewalks that will surround the 4' X 8' concrete pad at the bottom of my front porch steps. The concrete is worn to the point that it appears to be a badly done exposed aggregate finish although it was originally a regular trowelled finish when it was installed 50 years ago. Almost any amount of labor spent in prepping the concrete for resurfacing would be a big saving in time and cost compared to breaking out the old concrete and repouring it.

Thanks, Stan

 

[Gary from Muleshoe]

I just spoke with a concrete man here in TX and his opinion was that the cheapest without replacing it is to tile with a good quality outdoor tile. I am going to that with my MIL's patio. He said to make sure you have all the loose and flaking concrete off and pressure was it good. Then make sure your thin-set is for outdoor use, or you can use mortar mix.

 

[Anonymous-0]

Ardex. It is self leveling.Another one is Mapei.In stores they have a machine that shot blasts the deck first.Not sure how good it is without good prep.

 

[Bob S.]

Howdy
Be sure to use the bonding agent (white milky looking stuff, about $13.00 a gallon at Fleet Farm), well worth the money, worked good for me.
Bob S.

 

[Billy NY]

Stan, I would think there must be a product out there that could be applied to the existing, you need to research concrete products and or speak with someone that is current on the latest materials out there, like the sales rep at the local masonry or commercial building supply house.

Surface preparation of the existing, chipping cleaning, etching, etc. will be one important aspect, the others are bond strength, compressive strength of the new material and abrasion resistance of same.

There are self leveling products out there that are commonly used on precast concrete plank buildings, whereas the individual sections of precast are placed, keyways formed between them, bond beam perimeter is formed, and the entire deck is fully grouted with a 4000 psi flowable grout, which in turn makes the entire deck or floor monolithic, like a poured in place slab or deck typical on structural steel buildings whereas the concrete is placed on Q deck/metal decking and is one slab or monolithic.

On the precast concrete plank jobs there is often times a need to put a leveling coat over the precast deck after it has been grouted, to provide a level sub surface for flooring systems. I did this for a developer on a multi-story high rise building, the material was mixed on the street, sand was the aggregate and it was portland cement based, it was pumped to each floor, was like a slurry and self levelled, thickness was less than 1", it had the bond strength, the floors were cleaned and loose scale chipped off by my laborers. It also had satisfactory compressive strength for the application, but was not suitable for a wear coarse.

There has to be a material that will provide the characteristics you are looking for, bond strength, compressive strength, abrasion resistance and do not forget a non slip surface or finish.

You ought to see how strong the existing slab is, if it is weak,you won't get the bond strength no matter what you use, if it still has good compressive strength, and just a finish issue, then you could also chip it down to a depth that would increase your new material thickness, clean, apply epoxy adhesive and place a portland cement based product with a small or fine aggregate. I would think that there has to be a material out there, it's common problem, we get it in garages, as the salt water from snow and salt in the winter time does a number on concrete finishes in conjunction with vehicle tire abrasion, one side of my garage has exposed aggregate and I've often wondered about re-finishing it with something that would actually hold, no sense in doing it if it will de-laminate.

I like the tile suggestion, just make sure you have a non slip surface, surface prep is done and the thinset or adhesive will bond to your existing, and that there is no danger of freeze thaw cycles becoming a problem if moisture gets under it.

 

[Anonymous-0]

If affordable, go with the tile.. Salt isn't a good idea afterwards though. Flagstone would look nice too....

what if you'd clean it real good, fasten on some rabbit wire, and poor a 1-2 inch skin on what you have?

 

[Buzzle]

Whether you use thin set or mortar mix, soak the concrete for a few days ahead of time,it will make the bond much stronger.

Thinset is portland, silica, and a latex modifier. Cement cure through "hydration", the best way to think about it is that cement is like epoxy. It doesn't "dry out", it needs both the portland cement and the appropriate amount of water to get hard.

If you apply a thin layer of any kind of cement over existing concrete which is dry, it will immediately suck the water from the fresh cement right where the two meet, the fresh stuff will not have enough water and will form a poor bond.

 

[Stan in Oly, WA]

Hi Billy,

I like the tiling idea, too, but there are several problems with it. It introduces a new design element where we're already struggling to tie together too many different surfaces, textures, colors, and materials. The other serious concern is that steps come up to this area from the driveway, and steps go up from it to the front porch. Changing the height of any single level in this system means that at least on rise will be too high or too low. I know that this isn't the end of the world, but this is the most conspicuous place on the property to have what I've always considered to be a sign of ignorance, poor planning, or low standards. Of course I could tile all the stairs, too, and then break out and repour the driveway to raise it the height of a tile. I'll have to give that some thought.

Thanks, Stan

 

[kab_IA]

Google: concrete polishing

 

[Stan in Oly, WA]

Hi Gary,

I've considered tiling, but see my response to Billy NY above.

Thanks, Stan

 

[Stan in Oly, WA]

Hi Dave,

Changing the height of one single level in the middle of what can be seen as a flight of steps is the problem here. See my response to Billy NY for more detail about my specific concerns about tiling.

Thanks, Stan

 

[Billy NY]

Yes, that is so true, I always soak the surrounding substrates, when laying brick, does not hurt to soak em in a bucket, neighbor across the road, took down the brick veneer and the mortar had no bond at all, the bricks were clean and could be re-sued easily, soapstones too with the indent to hold morter, not one of them bonded, was there from '64 to '02 overhang protected it from the elements.

 

[Billy NY]

Stan, I'm thinking you have 2 options here, either demo it and do it over or chip it down so you can get at least 2" of new material, 3" would be better, and if you go that far, just demo it, see if you can rent a 45 lb electric hammer like a Bosch Brute, and hire a laborer for a day, and get it done. Good chance it may come right out, some old material can be easy to chop out, never know what you are dealing with.

I mean 4'x8', thats 32 sq. feet x 4" thick (4/12=.33) so x .33 =10.56 cu. ft./ .66 cu ft. per 80 lb. bag = (16) 80 lb bags if my math is correct, it's not really that much material if you can get a mixer and set up the material near the form. Heck, it's worth paying a laborer to mix and place, you can screed and finish, a 3 bag mixer would work if you keep the pace going. I did a 3' x 6' 5" thick, (was 12 80 lb bags I think) 2 years ago the one I posted a photo of, with a friend, mixed by hand and though one end of the form started to set up, I got it done and finished, a mixer would have increased the flow of material and not cut it so close on setting up

Placing a thin layer of material over an old slab is kind of questionable even today, it needs to meet the criteria for bond and compressive strength and be suitable for a wear coarse/abrasion and not be vulnerable to freeze thaw, to perform and I am sure years back the only way to deal with an old slab is to demo it, re-do the sub-base and pour a new one, at least for the best results and service life, some of these material solutions may just be mediocre at best, so you really need to see what kind of products are out there, or bite the bullet and do it over, you will get the best results that way.

 

[Stan in Oly, WA]

Thanks, everyone. Very, very good advice here---as is generally the case whenever I have a concrete question. I'd give all of you the day off tomorrow if it was in my power to do so. I've got to work, though, and I suspect the rest of you do, too.

Here's a thought for the upcoming 4th of July: No government gives people their rights, though many governments---including ours---take rights away. On July 4th we celebrate the genius of a group of very intelligent, very ------ off ex-British subjects who founded a new nation on the premise that the most important laws are the ones that protect us from the government. This point of view has fallen out of favor in our lifetimes (no finger pointing---every party is guilty one way or another.) So on the 4th, raise a toast to the inalienable rights that make us free men and women.

Stan Lewis

 

[Anonymous-0]

Hello, Stan!

Here is another thing to consider.

At our carwash, some of the concrete bay floors eroded over time and the aggregate was exposed and uneven.

I cleaned the floor thoroughly and applied a very rich (1 part Portland to 1 part fine sand) cement mix. ....I mixed it to a soupy mix and troweled it out to even the finish. ....Thickness varied from 1/8" to 3/8".

Many "pros" and "old-timers" told me I was wasting my time because it would never last.

They may be right, but so far it has held up over 12 years!

I have also used a similar mix applied with a coarse brush to "paint" exposed aggregate on curbs, and the coating is still there.

While I agree with your thoughts on changing the rise on just one step, I don't think your foot can discern a difference of 1/8" or 1/4" in the rise, if just one step is changed.