Crushed Granite Pea Stone in Concrete - Contractor Talk - Professional Construction and Remodeling Forum

jgray152 · 10-05-2009, 05:47 PM

Has anyone ever attempted to use pea stone crushed granite with concrete to make a faux granite step or walkway?

I am in the process of making some samples for practice and so far I am running into a few issues.

1. The portland cement is grey not white or light grey so the cement voids around the crushed granite makes it all look to dark and unnatural. Adding some Tera Cotta integral color helps a little to remove the grey but its still dark.
2. Need a very high granite to cement ratio. Not sure what this will do for durability.
3. I need to grind the cream of the surface to expose the granite. This is very time consuming. I have tried rinsing the cream just before its cured but this does not create the effect I am looking for and causes some granite to be loose.
4. After adding calcium to the portland it still takes so damn long to cure!

I add calcium to the water before putting it in the cement since its not a powder, its small flakes, does this reduce its effect on the portland? I never have to use portland alone so this is a semi new area. The only time I use portland cement is for Fiber Reinforced Concrete which is different. I use Acryl60 at that point and it cures much faster but acryl60 is expensive.

CJKarl · 10-05-2009, 06:27 PM

Your in the granite capital of the united states, just use granite.

If you want more info on exposing the aggregate like that search Terrazzo.

concretemasonry · 10-05-2009, 07:32 PM

If you are grinding granite, you are trying to grind a very hard material.

How do you add "calcium"? Are you just adding milk or something with a different chemical composition. What kind of a mix and type of curing are you using?

Concrete is not for amateur kitchen chemists. Acryl 60 is not expensive if you consider you are working with it for something that is meant for a different purpose.

Tscarborough · 10-05-2009, 07:50 PM

Adding calcium chloride (flakes) is not a recommended practice for concrete or masonry around here. You will have a very hard time trying to do what you want to do. The matrix (concrete) is very much softer than the aggregate (granite), so it will either pull out or be nearly impossible to grind smooth.

For a (gray) granite appearing product, consider using lightweight aggregate and/or coal slag along with white portland. Broadcast and work the aggregate in, then grind it.

jgray152 · 10-06-2009, 01:22 AM

Quote:

The matrix (concrete) is very much softer than the aggregate (granite), so it will either pull out or be nearly impossible to grind smooth.

I personally have no problem grinding granite. It seems to ginde away and smooth out with the cured concrete just fine. The time consuming part is doing it with a 4.5" grinder.

Quote:

How do you add "calcium"? Are you just adding milk or something with a different chemical composition. What kind of a mix and type of curing are you using?

Well here is the thing and the reason why I am using calcium. When I order concrete from the plant, it will set up very quickly, usually within 1 hour its pretty well setup. When making my own mix with portland and sand/aggregate, it takes 5-6 hours for it to even remotely get hard. This is the reason I am using calcium which it seems I am not using enough of it because it still takes to damn long to set up.

Quote:

Concrete is not for amateur kitchen chemists. Acryl 60 is not expensive if you consider you are working with it for something that is meant for a different purpose.

The "milk" or "Acryl60 I am not using unless I am making Fiber reinforced concrete. The Acryl60 helps the curing process when needing this type of application but the Acryl60 compared to a bag of calcium is more expensive. Also, I do not like using Acryl60 when using acid stains because the stains sometimes will not work to well. At least the ones I use.

Quote:

For a (gray) granite appearing product, consider using lightweight aggregate and/or coal slag along with white portland. Broadcast and work the aggregate in, then grind it.

I'll keep this in mind. Thank you.

jgray152 · 10-06-2009, 08:29 PM

Well this is a crappy picture but here is a sample with the granite in the concrete. You really can't see the granite to well in this picture. I'll have to use our other camera when I find it. That top stone is sealed with an acrylic sealer. Really brings out the beauty of the concrete

I made another sample the size of a brick but I really loaded it with granite and very little cement, I also colored the cement terra cotta but after grinding it, after adding a lot more granite, it still doesn't look how I want. Basically the granite pieces are just spaced to far apart. If I want to do this I may have to find a way to get the granite closer together. Maybe finding a small crushed granite pea stone.

It takes very little money to do this so if I can perfect it this could be a cost efficient way of making granite steps without spending over $100 for one step. Instead I could make it for less than $20-30.

Doing this on an entire walkway would be time consuming and a lil more expensive I think because I would have to rent a machine to grind the surface of the walkway to expose the granite.

Winter is coming so I will put the sample outside to see how well it does through freeze and thaw cycles. Maybe with some salt in on area, Although this is not air entrained so even if it did flake it really won't tell me anything.

Tscarborough · 10-06-2009, 08:40 PM

Trying to imitate monolithic granite with small pieces of granite may not be the way to go. I would try to imitate the grain itself using similar size and color spicules as are in the granite, and a matrix tinted to be the same color as the matrix of the granite.

Tscarborough · 10-06-2009, 08:43 PM

For example, here is a local ganite that appears to resemble the one you are imitating:

A deep rose matrix with white marble dust aggregate and a medium grade of coal slag broadcast in, then ground would imitate this almost exactly.

jgray152 · 10-06-2009, 09:13 PM

If I could get it to look like that, that would be great. When you say broadcast, you mean spread over the wet concrete and worked into the surface a little?

This is my beginner version so far.

Here are close up shots of the larger sample.

Not Sealed. Not ground as smooth as the image below this one.

Sealed

Tscarborough · 10-07-2009, 08:09 AM

I just mixed one up. White portland, white and black marble dust, white sand, and coal slag, colored with bright red and antique rose color. I'll grind it tomorrow.

jgray152 · 10-07-2009, 08:19 AM

Excited to see results!

I'll pick up some coal slag and some point. I'll have to find out where to get marble dust from.

GrasshopperPete · 10-07-2009, 10:49 PM

I was going to call these guys tomorrow to see if they recommend for Chicago winters..if it works I`ll offer it for driveways, walkways , pool areas and front steps, etc.

http://www.advancedsurfaces.com/

What do you guys think of this?

TimelessQuality · 10-07-2009, 11:17 PM

Hey jgray (and TS), Have you tried an acid stain? Seems like it would stain the cement, and leave the granite unaffected...maybe..

Tscarborough · 10-08-2009, 08:44 AM

It is still pulling aggregate, so I will do more grinding tomorrow.

Tscarborough · 10-08-2009, 02:21 PM

Slightly better picture, anyway.

jgray152 · 10-08-2009, 05:18 PM

Quote:

Hey jgray (and TS), Have you tried an acid stain? Seems like it would stain the cement, and leave the granite unaffected...maybe..

I have thought about that. I have a few colors, nothing really light. I do have greenish color, I wonder how that would look. The next colors I have is black (really dark dark red) and dark walnut (turns gold, copper or brown, lol)

jgray152 · 10-08-2009, 05:19 PM

Good work tscar. Looks better than mine. I wonder if using larger coal slag would look better?

Tscarborough · 10-08-2009, 07:42 PM

If it was graded right. Lightweight aggregate (expanded shale), is not easy to get, much less request graded for a small, small amount. The product branded as Maximizer does use lightweight aggregate, but it is graded for concrete, i.e. fines to 3/8". I have some ground somewhere in the yard, I will see if I can find the chunk.

Tscarborough · 10-08-2009, 07:54 PM

Nope, can't find it in the dark. It doesn't look right for the bigger agg anyway, it is "ringed" when ground.

concretemasonry · 10-08-2009, 09:44 PM

If you have a source for expanded clay or shale, try to find an uncrushed natural fines aggregate (rounded) that is clean or could be washed more for casting. It is tough to find to find and is costly, but the amount needed is really pretty small and not a major cost factor, and the use can be learned.

I have found this at the plants from the old (epanded rotary kiln shale ot clay) Arkalite and Gravelite plants near West Baton Rouge, LA and West Memphis, AR (now probably Olcastle plants now) a number of years ago. Very good, but saturate it in water for a day or two before using because the absorption is very low and very sloooow. It is rounded, so it can pull out easily, but is great when bonded into the matrix before grinding.