Slurry Process

The first step in finishing, after demolding, is to "slurry". To slurry is to fill any voids and pinholes that remain from the casting or spraying process.

Make your dry mix, if the aggregate is fine enough such as 100 minus glass or 100 mesh sand or Silica Flour divide it into two containers. if your agg (if in fact you use any) is coarse make one container with agg. one without. Slurry coat as Rich and Dave describe with the aggregate mix When the slurry just begins to take a set, cut all excess off the surface with a trowel or putty knife, flush and flat then with your rubber gloved hand but ideally with a piece of burlap rub the dry material over the surface forcing it into the holes, using the burlap to clean the surface and fill the holes. If they are not filled repeat with first slurry then dry. Forcing the dry into the surface helps minimize shrinkage and gets you filled sooner. Very similar to the process of making press encaustic cement tile. You can even force the dry into larger holes with a p. knife orI mix a grout with no fillers at all; just cement paste ingredients and super-p. I also replace about 75% of water with an acrylic bonding agent (such as for GFRC), and reduce pigment amounts by 25-30%. Make a fairly stiff mix that just sticks together and doesn't crumble. Spray the concrete with a fine mist of water and rub a small portion of filler on the surface with either your hands or a very clean and straight putty knife. Approach holes from different directions.Then, about 20 min. later, come back to the same holes and top them up after the initial filler has shrunk in. Do this several times, until the holes are packed and additional filler no longer shrinks. Remove excess filler from the surface, mist, cover and leave overnight, then grind in the morning. You may have to do this one more time, but I usually get by with just one application. Yes, but it seems to help my situation if after slurry, slurry cure (Alla method is a good method) and before polish you use a densifier . I have no way of really proving this in my shop but the piece seems harder, takes a polish better and the softer filled areas don't abraid ahead of the body of the piece.

Polishing

There are many methods, materials, and tooling available for polishing HPC Concrete Countertops. 

• Wet polishing, is using a combination of tools and abrasives that are engineered for processing using water and a lubricant and debris removal.
• Dry polishing is using a combination of tools and abrasives that do not need water as a lubricant and utilized vacuum suction for debris removal.

Here are several considerations to dry/vs wet. Volume you intend to produce to support a 3 man crew. Wet is by far, not even close, faster than dry processing even with the variables of depth and finish. So since time is money, well you can do the math. Processing steps and surface finish based on your products. ie: glass agg., cream finish.

In my opinion there are 2 facets to processing, Grinding vs Polishing. Grinding for material removal is without question faster wet. Its obvious that water as the lubricant makes diamonds cut more efficiently. Polishing for surface finish needs only to remove the last grits scratch pattern. Which happens at a much slower rate dry, but does happen. I can dry polish from start to finish, but there have been very few employees that have come through my shop that can.

Scheduling is also an issue since dry polishing is very time specific. You have to complete your processing before the hardness of the concrete gets away from you. For instance, if you have to cast a project on Fri to meet a deadline, you will have a hard time dry polishing on the 3rd and 4th days post cast than if you were to strip and process next day.

Wet is less specific to stage of cure. Another consideration is tooling cost. Dry pads cause a lot more friction which dulls the diamonds faster, heat increases wears the bond to expose more diamonds. Bottom line is you can process much more surface area for the same money wet. All of these factors may vary depending on your product, how you process, the equipment used and is very dependent on which diamond product is used. Resin bonded pads will always leave residue on the concrete. The plastic has to wear off in order to reveal more diamonds.

Our recommended source for tooling and abrasives is,

Concretecountertopspecialties.com

I have tried all kinds of "dry" polishing pads and IMO none of them work great. I have had the best luck with the new con-dry pads from Concrete Countertop Specialties. The mudslingers weren't bad but were hard to make run flat without swirl marks. I have had better results running between 1500-2500 rpm. I find that the diamond glaze over, heat up and come loose from the bond at higher speeds. I use a plastic dust muzzle and a shop vac with a dust bag for dust control. I only dry polish to remove slurry residue and final polish. I finish up with gray non-woven discs (3m scotch brite or Norton bear-tex) because it has 320 grit silicon carbide abrasive in them and work well for final clean up and plastic residue from the pads.I have the 7" mudslingers that are good for wet polishing, but I do not like using them for dry polishing. I also have some 5" wet or dry pads that do ok with dry polishing but can never get past the swirl marks to a very light degree.

I wet polish usually starting out at 100 grit for cleaning slurry coats off and work up to 400 wet, then let dry to use the 400 dry pad and may even move up to 800 grit depending on color and look. Then use twister pads to clean up. Are any of you getting perfectly smooth finishes just from a specific polishing pad?, or are you using twisters or other pad to clean the swirl marks from the polishing pads.

I use an aluminum rigid backer - for the mudslingers, but have a plastic backer for the 5"- which is also rigid. I have not tried the Con Dry brand yet. I use the solid backer on one of my 301's and the flexible on the other one. I use flexible backers on all my hand polishers. I would say I get very superficial swirls with all my dry polishing...so superficial twisters take them right out. That is why I use the twisters as part of my processing.

Try to figure 3M hookits into your system. They are much ch3M hookits are just different grit/style of scrubby-pads... like a green pad only finer. Twisters are thicker, spun-bonded pad with diamond grit attached to the face of the pad. Dont get that confused with the hookit and hookit2 backers sold for automotive style sandpaper. The 3M red and grey pads will stick to the same backer pad you use for the velcro style resin diamond pads.

If 3m hookits arent available lcal Jon, just get some sq pads from the local auto supply and cut the circles out. The colors are the same (red, grey, white) but the grits are different than the hookit pads. I use a fair amount of the red and grey this way, and then white to buff. The hand cut circles dont stay put (on the backer) as well as a "real" pad, but they get the job done if you dont have stock on the others. We've been toying with this for a long time and have tried lots of different things. We've never achieved absolute matt, and I don't think it's in the numbers for an ICT finish. that said - we come awful close by only using 50muslingers dry and then finishing up with 100 con-dry and CPS pads. this is by a long shot the best looking, most natural ICT finish we've achieved, and we now NEVER polish above 100 dry -- we don't even give people the option. If they ask- thats another story. also, pay close attention to your CH apps - don't let them build. right off the bat it looks much better. Getting a flat finish with ICT.....tough to say the least.