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I am making a concrete counter with ready mix concrete. 60 pound bags.
How much cement should be added to get a six-sack mix?
What is the maximum amount of dry powder colorant can I add?
And, How much water so it is a dry mix?
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I've always mixed my own...that way I know exactly what I'm getting. Thus, I can give you some idea's for mixing ingredients, but not how to adulterate a 60-pound sack...
For a generic 6-sack, here's one per-yard formula:
*Cement - 6 bags, 94 lbs each
*Sand - 14 ft
*Stone - 18 ft
*Water - 36 gal
Per one cubic foot, same ratio:
*Cement - 20.88 lbs
*Sand - 0.52 ft
*Stone - 0.67 ft
*Water - 1.33 gal
When you make your samples, try varying amounts of pigment (2, 4, 6, 8, 10%), but try not to exceed 10% by weight, based on the weight of the amount of dry portland cement added to the mix. For example, don't exceed 2.09 pounds of pigment per cubic foot for the mix above.
Use as little water as you can to get a decent mix. I use pea gravel for the aggregate. If trying for a pure color, use white portland instead of gray. I also go for a 7-sack mix.
Most home centers sell bags of portland cement, sand, and stone. Or, some gravel pits retail to homeowners for $15 for a car trunkload of whatever you want.
*Mongo, When you were making samples for your slate colored counter top did you ever get a very black color or were they more of the charcoal ? Who did you get the carbon black from ? I can't find any color darker than a dark gray.
*Don, The carbon black samples varied from light-medium gray to a dark charcoal/gray...nowhere near a pure, or "jet black". It's a nice mix (to me), a somewhat mottled dark gray-"light black?" color. Sounds silly trying to describe it. I should probably take some pics.I get my carbon black from a concrete block manufacturing facility the next town over. They really don't do retail, I just showed up one day and asked. I get it in 50 pound bags. We do have smaller retailers that sell block/brick, masonary supplies, etc, but they just have various pigments in 3-5 pound boxes, and ironically, don't sell carbon black.
*Thanks , None of the suppliers that I contacted had a carbon black . I want to make a jetblack counter top for the basement vanity . I'll keep looking someone will have it somewere.
*You might start hunting through craft and art glass stores. Outdoor Glass mosaic embedded patio blocks are becoming quite popular around here. The mix is claimed to be designed for low shrinkage and resistance to cracking and elements (freezing). Near as I can tell it's some form of concrete. Large assortment of colours. Seems like the ideal material for countertops, but hobby volumes probably throw the whole pricing structure out of wack. Snooping around those circles might open a few new sources for colorant materials and mix formulas.
*Mongo, I have a friend that does his counter tops upside down and not in place, Do you follow this same practice ? They come out very smooth and he grouts any air pockets left over which gives them a nice twist! what would be the mix ratio per portable spinning concrete mixer, in bags and shovel measurements. Concrete - bags Sand- shovelfuls peastone- shovelfuls water- gallons! thank you in advance for your input if any!
*Steve, I agree that casting upside-down is the way to go.I really can't give you ratios or measurements in terms of "shovelfuls". My shovelfuls, for example, are quite a bit larger than those that my wife would portion out. Wet sand clumps, thus you can get more wet than dry sand in a shovelful. Yeah, I'm breaking this "shovelful" thing down, but there's a reason. Instead, I made a one cubic foot "box" that, no matter who fills it, always comes out the same.What I do is take a volume measurement of the form to be filled, and add approximately 10 percent for waste. Take a 4' by 9' island slab with a 36" by 24" cooktop cutout, slab 2" thick. Volume comes out to 5 cu ft. Add a bit for waste, I'll mix 5.5 ft of concrete for this project. Multiply the amount for each ingredient for the cubic foot batch in the above post by 5.5 to get your mix for this slab. After casting the slab, I pour any leftover concrete into drywall buckets to a depth of 3-4 inches. the next day I dump the cured disc out of the bucket and leave these various colored "stepping stones" out on the curb for the neighbors to fight over. Ahhh..recycling.The reason I like using the cubic foot box to measure is that since I'm adding a colorant, batches need to be more specific. If your portable mixer is a small 3.5 ft mixer, you'd have to break this 5.5 ft slab into two batches. Off by a bit on the mix, and you could have two shades of a color instead of two batches of the same color. And, if doing several slabs for the same kitchen it allows better mix control (thus color continuity) from slab to slab. Especially when the slabs may be done over a period of weeks. If multiple-batch coloration needs to be controlled, you need to control the ingredients. I can do that better with the box than I can with the shovel.If you really want to go with the shovel, the only thing I could say would be to build a box and fill it several times, averaging to get your estimated shovels per cubic foot. Portland comes in 94 pound bags, so divide your needed weight by 94 to estimate the number of bags required.Since I make color sample slabs prior to the actual pour, using a more specific means of measuring gives more validity to the color of the end product, and makes replication of the desired color easier to achieve.Didn't really answer your question, but I hope I at least explained why.Regards, Mongo
*MONGO, WHO'S BETTER THAN YOU? THANKS, YOUR RIGHT !IF YOUR COLORING I GUESS YOU WOULD HAVE TO BE PRETTY CONSISTANT WITH A MIX, I WAS JUST THINKING IN TERMS OF SHOVELFULS BECAUSE MASONS I USED TO LAY OUT FOR ON COMMERCIAL JOB WOULD MIX THAT WAY BUT ITS OBVIOUS THAT COLORED COUNTERS ARE FAR CRY FROM MORTER MIX ! THANK YOU AGAIN STEVE
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I am making a concrete counter with ready mix concrete. 60 pound bags.
How much cement should be added to get a six-sack mix?
What is the maximum amount of dry powder colorant can I add?
And, How much water so it is a dry mix?