Grind my floor 2x, is it enough?!

[K04GTI]

I'm going to apply epoxy from Legacy, I decided I'd do it right and rent a power grinder + angle grinder. My local rental place had an edco dual head grinder with 24 grit grinding stones. I called Scotty and he said they use 25 grit, so that seemed very reasonable.

A week earlier I had swept and pressure washed my floor well with simple green (cleaner+degreaser). I also applied the dry absorbent powder material to an oil stain and swept it up after letting it sit for awhile multiple times over the course of a week. It came out looking much better, but I can still see the stain..?

Anyway, skip to this morning and the equipment arrives. I had watched the Edco Training Video on Youtube. I grind the floor up and down the garage slowly while moving side to side, overlapping my runs slightly. I then took the angle grinder and went around all the edges of the garage and the tight spaces I couldn't get to with the big machine. Afterwards, there was one notable section of my floor that seemed rough, and uniform. If you didn't look closely it looked like there was dust on the floor, but in fact it was a uniform cream color and very rough to the touch. The rest of my floor was not as rough, and you could seek darker spots mixed in with the white spots.

Therefore, I decided to grind my floor a second time. This time I went from left to right slowly while moving the machine side-to-side. I even usually went forward then backward over each strip.

It was raining outside, and I figure too humid to apply the epoxy any time soon. So I swept off the floor, then pressure washed it again, and squeegeed most the water out the garage doors. I set a fan on it to help it dry.

So.. I'm kinda beat.. was a lot of work grinding it 2x, sweeping, power washing etc. But, I'm still not sure that it is good enough.. I was told it should feel like 80 grit sand paper. Maybe I'm not that familiar with 80 grit sand paper, but it still feels pretty smooth to me. Not that rough.. I swept up quite a bit of dust. So I must have ground something off.

Here's some pictures... can you tell me if this is prepped well enough? The one patch of concrete that is extra rough makes me feel like the rest is not good enough!



Web Album (easier to share several photos this way) (also I did wear a mask most the time)
Please click the pictures, you can see some captions. There are pictures before, during, after
https://plus.google.com/photos/113726528639745523052/albums/5765150930686307905?authkey=CPOw2OiDvenrNQ

 

[LegacyIndustrial]

Per our talk, your stones are clogging. You can try adding more weight but it may be a losing battle. These machines work poorly without the dymaserts.

 

[K04GTI]

Today has not been my day. Ground the floor 2x and it was so-so. I had some acid left over from an old block wall job. I put it on full strength on a portion of the concrete. Etched it very well. I quickly washed it off completely with tons of water because I figured that test area was awful strong. I went to the store bought more of the same. Put 4 parts water in my chemical sprayer and 1 part acid. Pumped up the sprayer, only to find the bottom of my sprayer was leaking since the last time I've used it.

Next, I had to spend forever spraying out the remaining portion of the acid pressure so I could take the top off without it spraying out (which would be bad regardless of goggles and gloves). I didn't have anything else to do with the acid so I carefully poored it over the floor and squeegeed it around. I went back in nuetralized it with baking soda and sprayed a ton of water on it after and pushed the water out. That didn't work very well, concrete doesn't look etched.

So... tomorrow it looks like I'm going to buy MORE acid and a new sprayer. I think I'm going to test it out in very small section (like 2x2 inches) and whip up an extra strong batch to see how strong I have to make it.

So I have ground my concrete 2x, put some acid on it, and still haven't gotten it prepared well enough. Tempted to use the stuff full strength, it did a good job on that small test area I did that way. I guess I'll try to be cautious and mix it up 3-1 and 2-1 in a very small plastic cup and try out a few square inches to see if that works before I go into crazy mode.

Is it just me, or mixing 5-1 or 4-1 etc, isn't very clear. The bottle of acid I bought didn't really even say what percentage acid it was. It would seem that if it were better labeled someone could tell me what percentage acid I'm looking to achieve and I could reference some old chemistry books and make a batch that strength. Sure I suppose it depends on the makeup of your concrete, but I still feel it would be better.

 

[NewShockerGuy]

From personal experience doing this twice via acid etching...

First time I used baking soda to nuetralize it... what a f'ing mess.. I think it took longer for me to clean that and the salts from the acid than anything else...

I messed around with parts per water per parts to acid..etc. Did the recommended 6-10 parts of water per part of acid... that was way too weak. Did a 5 parts water to one part acid... still too weak.. I ended up doing a one to one ration and found this to work best for ME.

I would put a half gallon of acid in the 1 gallon sprayer I own.. the rest would be water.. which would = 1 gallon... I did this with both my floors and it proved to work quite well.

I acid etched my floor close to 8 times before I got it to where I was happy in the house that I am currently in.....

Before: Sorry it's so far away, but I can assure you it was completely smooth to the touch, just extremely dirty with tire marks, paint..etc.

After: Very rough to the touch and very poreous...

I'm sure grinding is much faster and easier honestly but I went acid etch because I was familar with the process... If you are acid etching make sure you pressure wash the salts out... Some people on here say don't do that because you force the water IN the concrete... But if you hose it out with a garden hose you will NOT get the pores clean of the salts that were from putting the acid on the concrete... It's worked very well for me so again I can only speak to what I have done... If you pressure wash make sure you have fans blowing in the garage afterwards to dry it out... I think I ran fans for 5 days constantly blowing air and in the 90+ degree weather we had, kept the garage doors open to let the sun bake the concrete..lol

Don't skip out on prep... if it takes you longer to achieve the desired feel/look of the concrete don't rush it... Prep is key and if you want the floor to last and look good just keep at it.

-Nigel

 

[K04GTI]

Your floor looks very well etched. That is what I want! It is just disappointing because I paid money to rent the grinder so I would get better results. Unfortunately they didn't have the dymaserts just the blocks. The blocks basically don't work at all. I ground part of my garage 3x with the huge machine and didn't even get a satisfactory result. I did make a lot of concrete dust on the floor though. It scratched up the surface some, but never in full coverage.. looking closely maybe 40% of the floor was still smooth and darker color the rest was white color but not that rough. One small patch of the floor was rough and well prepared, but there was no way I was getting the floor prepped with that machine with those accessories.

I will take your advice. thanks

 

[pcaulfie]

I just finished my floor and had the same issues you've encountered. I rented the two headed Edco machine with "medium" grit blocks which they said was 24. On my floor it was slow going. The medium grit didn't give me a rough enough surface, more of a polish. Went back and got the "coarse" grit, which I guess was around 8. That appeared to do a better job for a few minutes but then the blocks got clogged and it wasn't much better than medium. For me the trick was wet grinding with the coarse grit. The water kept the blocks clean enough. The coarse grit did not leave any large gouges in my floor but helped remove the hard smooth layer on top. I was pleased with the Edco for the most part other than it took a whole day to wet grind. I'd definitely try harder to find dymaserts or diamabrush pads if I had to do this again.

In the end I acid etched twice on top of grinding because I also saw Shockers floor. I used a 3000psi pressure washer and blasted the **** out of it (which also helped a bunch) and added at least three days to adequately dry. My floor looked nowhere near as clean as Shockers but I think the surface was rough enough. I was really worried at first about laying down Epoxy-Coat but then called them to ask if I needed to expose the aggregate. They said as long as it was rough like 100 grit sandpaper and there are no stains then I should be good to go. Of course only time will tell. Good luck!

 

[dcs Inc]

The double head edco isn't the best machine to grind with but that is what most rental companies offer. Without the correct tooling they can become labor some. The grinding blocks are slow to say the least. I've used these machines before purchasing my own equipment and put a couple hundred pounds on them to create more down pressure and seemed to help a lot. If going with an edco, try to get the 10" single head machine. With diamond segments, they work pretty well. (Add some weight for added down pressure.

Anything you can do to break through the hard glazed surface will help a lot, even if you decide to go the acid route. Oh, use diluted ammonia to neutralize instead of baking soda. A lot easier to wash off.

Be really careful using the muriatic acid in heavy doses. Have air moving because it isn't good to breath that stuff.

 

[LegacyIndustrial]

A really efficient and effective method of preparation is the Diamabrush concrete prep tool. If you are fortuante enough to have a home depot rental center nearby make a call to see if they have this tool.

It is essentially a buffer machine with this ingenious head attached.

Our guys use it for plain vanilla garage work. http://3.bp.blogspot.com/-Nnw4S84ycrY/TzBeC2Cd31I/AAAAAAAAAVk/hfYEWdIfzu8/s1600/diamabrush1.jpg

 

[K04GTI]

A really efficient and effective method of preparation is the Diamabrush concrete prep tool. If you are fortuante enough to have a home depot rental center nearby make a call to see if they have this tool.

It is essentially a buffer machine with this ingenious head attached.

Our guys use it for plain vanilla garage work. http://3.bp.blogspot.com/-Nnw4S84ycrY/TzBeC2Cd31I/AAAAAAAAAVk/hfYEWdIfzu8/s1600/diamabrush1.jpg

Unfortunately, we don't even have a home depot.

 

[Edger]

Regarding acid etch strength, it varies lots depending on the floor hardness and you must pressure blast it thoroughly afterward. For softer concrete we used to mix 8:1, for normal to soft 6:1, for normal to hard 4:1 and for hard concrete 3:1.

Another thing that makes a difference with hard concrete is how long you let it work, don't wash it off too quickly, but try to keep it wet by putting more on and brooming it around constantly. You will need a very wide broom to do that with any efficiency.

It is true that the fumes can rust any metal close by and that is accelerated when you used stronger mixes. Smile and it will clean your teeth for you!

 

[Garage Flooring]

Its funny... We always say for jobs larger than 250 sq. ft rent a walk behind but it almost appears that you would be better off with a 7" grinder and a diamabrush attachment and do it by hand by the time you get the grinder and mess with it enough to get it to work... Maybe we need to increase that to 400 or 500 sq. ft.

 

[Edger]

Walk behinds from rental depots come with hard wearing diamonds that do practically nothing to a hard floor.
Nothing wrong with a walk behind for more than 250sq.ft., but a lot wrong with only getting one diamond choice with it.
I am sure I could prepare a floor with a 7" Diamabrush regardless of hardness at 100 to 150sq.ft. per hour.
With our Situp N Grind (new model next year) which uses a nine inch grinder it was easy to do 250 sq.ft per hour. See http://www.situp.com.au/Concrete Grinding Movies.html

 

[LegacyIndustrial]

Good point Edger. Between the abrasive heads and the kryptonite diamonds, it's hard to say which is less effective.

Incidentally, our hand grinder heads (Diamabrush) will go to approx. 1000 sq ft. and naturally the blades can be changed out to do another 1000 sq ft.

 

[K04GTI]

I'll take some more pictures of the floor later. I acid etched it earlier with a strong solution of acid, helped a lot, but left a chalky residue. Perhaps, I didn't rinse enough, but I did quite a lot. There were parts that were a bit smooth, so I acid etched it again. I nuetralized with a TSP solution and washed it off with tons of water. Then I pressure washed the entire floor with my wife helping me sweep water out of the garage.

My floor doesn't look as good as above.. but it is rough to the touch. It's looking mostly there, probably good enough already. I'll need to check a few spots to be sure and do a moisture test. Raining for quite a while this week so I'm not sure when the weather will co-operate. What is considered "low humidity" ? what percentage?

 

[dcs Inc]

50% is great. 75% is good. 85% get a dehumidifyer

 

[bseant]

my local rental place rents shot blasters. Will this work instead of the floor grinder?

 

[LegacyIndustrial]

Oh yes, very good prep.