Proper Concrete Mix Procedures for Making Manufactured Stone,
Tile and Driveway Pavers Using Portland Cement

BASIC MIX INSTRUCTIONS WHEN USING PORTLAND CEMENT AND A MORTAR MIXER:
Start the mixer.  Add a five-gallon pail of water and the Olde World Additive #140-SL to the mixer.

The water temperature is very important.  You want room temperature water if possible.  If the temperature of the mix is about 65 to 70 degrees, the mix will vibrate out better, give better homogeneity, and will also set up better.  The warmer the water... the faster the Portland cement will set up.

Oxides are next to go into the water.  To insure that you get the right coloration in the mix, stop the mixer and pull open the top grate so that your oxides are added directly into the water, and that they don't get stuck to the grate top or on the mixer blades.

Turn the mixer back on. Now add half of the Portland cement and three (3) buckets of sand.  Let the mixer run for about a minute or two.  Now add remaining cement and 2-1/2 buckets of sand. (cement first, sand second).  Add the Olde World Additive #219 and continue mixing for no more than another three minutes.  Over-mixing with the #219 Additive in the batch may cause excessive air entrainment, which may result in "bug holes" (bubbles) on the face of the stone or tile.  Bug holes, or pinholes at the corners of your manufactured stone or tile are usually caused by excess mold release being left in the mold prior to pouring in your concrete.

Remember: Olde World Additive #219 should be in the batch for only the last three minutes of mixing.

When adding the remaining sand, (aggregate), and cement, note how much the mixer slows down.  Be sure to keep a gallon of water on hand in case the batch needs more.  Generally, we have found that for each of the basic colors, using dry sand and following all other directions properly, between 9 and 10 gallons of water is needed.  You'll find that very dry sand may require ten gallons, and wet or moist sand may only need as little as eight gallons of water to get it to work correctly.  (Start with about seven gallons in the mixer)

Mix temperature is very important.
We suggest covering your sand with a tarp if it's outside.  We also suggest bringing in your sand the day before you are mixing if you are in a cold area.  This way your sand can warm up overnight.  The whole reason for having the mix warm is that it will vibrate out quicker, freeing the trapped air and thus eliminating air voids.  It will also set faster.  The batch may not slump correctly if the water temperature is well below 55 degrees.

BASIC MIX FORMULA FOR THIN STONE VENEER AND TILE:
Cement.......................................................One 94 lb. bag of Portland cement (gray or white)
Coarse Sand................................................5 - 1/2 - Five Galloon Pails full
Water..........................................................8 - 10 Gallons
Olde World Additive #140-SL..........................4 - Ounces
Olde World Additive #219...............................4 - Ounces
Color Oxides................................................Per Color Formula

WHEN MAKING THICK (2"+) STONE OR PAVERS, REPLACE TWO BUCKETS OF SAND WITH GRAVEL.

When making smaller batches, as when you don't have a vibrator table and mortar bixer, use all of the ingredients in relative proportions.  In other words...for a half batch, which will make about 40-45 tiles that are 12" x 12" x 1/2" if mixed correctly, use 47 lbs. of cement, start with about 4 gallons of water, use 2 oz. of Additive #140-SL, 2 oz. Additive #219, 2-3/4 buckets of sand and half of the color oxides called for in the full batch formula.  If you are going to make a "quarter" batch, cut the full-batch ingredients to 25% of each.  I wouldn't go much smaller than that unless you are experimenting with the color or trying for a specific color.  This is covered elsewhere on this website.

In the cases of half or quarter batches, you will most likely be mixing your material in either a wheelbarrow or a square cement box by hand.  Mix all ingredients together at once except for the cement and sand.  Use about half of these ingredients initially, and add the second half once your batch is thoroughly mixed, and the color is uniform.  You need to accomplish this as quickly as possible.  You don't want your mix setting up before you are able to pour it.

The vibrating will be done by hand, after the mix material is poured into your molds.  In the case of hand-vibrating, you may want to fill more than the three molds called for when using a vibrator table.  Start off by filling six molds with your mix.  Bounce the filled molds on the table for about 15 seconds each....#1, then #2, then #3, etc., etc.  Do this twice for each mold, in succession.  This gentle "hand vibrating" should disburse any air bubbles in your mix, compact the solids, and give a nice smooth face on your stone or tile.  It may take a little trial and error before you get the right combination; so feel free to experiment with different techniques.

THE PROPER WORKING CONSISTENCY OF THE PORTLAND CEMENT MIX:
If your mix is too thick, it won't vibrate out correctly, and may cause pin-holes on the face of your manufactured stone or tile.  It's also more work to get it out of the wheelbarrow, into the scooper can, and then into the mold.  Conversely, if it's too thin, you won't be able to heap the correct amount into the can.  It would just flatten out, creating too thin a stone or tile.  They would also be much weaker.  The water content eventually evaporates and will be displaced by air, which means more shrinkage in the stone and more weakness.  If the mix is too thin, there is also a tendency for the mix to scum when vibrated.  The "scumming" on the backs of the stone or tile is actually a thin layer of the cementitious material that never really sets correctly.  If you get "scumming" on the tile, the next day when pulling the product from the molds, the layer has to be removed by scraping.  If you don't, the tile or stone may pop loose after installation due to the setting material not grabbing the back of the stone or tile sufficiently.

On average, the batch should mix in the mortar mixer for about ten minutes total.  At six to eight minutes you can still have some un-dissolved color particles, or dry aggregate.  The unmixed color will come out as blotches on the man-made stone or tile.  Proper mixing also helps to accelerate the mix setting time.

When mixing your batch by hand, you should mix the color in your batch water first, being sure all colorant is dissolved.  By doing so, you don't have to worry about splotches or un-dissolved colorant.

USING A VIBRATING TABLE TO MAKE STONE AND TILE:
Our tabletop vibrating table is perfect for small commercial operations, or if you are going to be doing a number of good-sized projects.  The costs of a vibrating table may be prohibitive for most personal projects.  You can check our on-line catalogue and web store for pricing to make that determination.

Our H.D. Floor Model vibrating table has thick rubber (donuts), on the four corners.  These give a stiff vibration, with minimal up and down movement.  The two things that you want to achieve with a vibrating table are the frequency of vibration and the distance of travel up and down.  Also, the pattern of the vibration is important.  You want a pattern of vibration that is circular and contained within the perimeter of the mold.  You need to keep your table clean.  If the table isn't level, the tile or stone won't be even.  You need to check the level of the table periodically and make adjustments accordingly.  All of these variables have to be correct so that in combination with the proper thickness of mix, the desired result is achieved...a strong stone and tile. 

We also now offer free plans and instructions on our TheMoldStore.info website to make an inexpensive Vibrating Table for about $50.00 or so, yourself.  The plans were submitted by one of our customers.  We have another set of plans now as well.

When vibrating by hand, you want to "bounce" the filled mold from side to side a couple of times, then turn the mold 1/4 turn and repeat so all areas of the mold have been "bounced".  Turn 1/4 turn and bounce from side to side again.  Keep doing this for about 15 seconds with each mold you have filled on the table.  Then start over again with the first mold you started with for another 15-30 seconds.  After that, put the molds into your curing rack if you have one, or set aside to cure, covered in plastic, on a level surface.  As you place the mold down, give it a slight shake from side-to-side to help level the mix.  Not so hard as to "splash" the mix to one side though. Doing so will also help to get your faux stone and tile with an even thickness.

BUBBLES, BUG-HOLES OR PINHOLES ON THE SURFACE OF YOUR STONE OR TILE:
Suppose everything looked great the day you made the stone or tile.  You put it in the production racks, but the next day, when you pulled the product, the surfaces along the perimeter and around the corners have "bug holes" or pinholes on the face!

There can be several reasons for the bubbles.  Consistency of the mix, (it may have been too thick).  Too much mold release, (you didn't wipe into the corners and the edges to make sure you got it all out).  The velocity of vibration versus the frequency was not right (if tile or stone is left on the table too long, or not long enough, the air is not going to come out).  You left your molds too long between applying mold release, and pouring your stone or tile.  The release will settle and accumulate into the low parts of the mold, displacing wet concrete mix and leaving voids when the water evaporates.

Too cold a mix temperature can also cause bubbles due to less slump under vibration.  Another possible cause for bubbles on the face of the tile or stone is that your aggregate size doesn't have enough fines in it (very seldom the problem).  If it's too coarse, we suggest going to a ceramic supply store and get some 200-mesh silica flour.  Sometimes they call it flint.  If you add from two to five pounds to the mix, you will have added the necessary fines for compacting and eliminating bubbles.  (This is a last resort and should only be used if all else fails). Probably 90% of the time, the problem is too much mold release left in the mold.

If "hand mixing" you may not have vibrated the tile molds enough to get the bubbles out. If not using a vibrating table, pour six molds at a time.  If two people are doing the pour, take turns "vibrating" and turning each mold for about a minute total.  Allow each mold to "rest" for a short period while vibrating the others...then go back to it.  Use 15-second intervals on each mold. So each mold should be handled four times before racking.

If you get a lot of holes... fill them with some of your mix from your next batch.  Just rub the concrete into the mold to "save" it. Be sure that the stone or tile is wet. If necessary, soak the stone in a pail of water prior to filling in the voids. The water allows the concrete to fill the hole better, as well as helps it blend into the existing void. Then seal the stone as you normally would.

CONTROLLING THE QUALITY OF YOUR CONCRETE STONE AND TILE:
If you perform on-going quality checks, you should never run into any quality control problems.  As an example; if you check the backs of the stone or tiles (for scumming), the thickness (too thin or too thick), and the face of the stone and tiles (for bubbles), there is very little else that can go wrong with your batches, as long as you follow proper procedures.  All of these "checks" can be performed as part of the demolding process and caught immediately.  Remember, very tiny pinholes usually do not present a problem, as they will be filled with either sealer or grout, and will seldom be noticed.

If you have a laborer doing the manufacturing process...It is imperative to instill in your laborers the fact that the stone or tile must be perfect.  Get them used to performing quality assurance checks, but don't scold them if too many air bubbles are found, or if the stone or tile is not level, etc.  If you do...they may not look for the quality YOU are looking for.  It may cause them to try to sneak some "less than perfect" stone or tiles into the boxes before you see them....NOT GOOD!

REMEMBER...THIS IS A HAND-MADE, CUSTOM PRODUCT.  YOU WANT A CERTAIN AMOUNT OF WHAT SOME MIGHT CONSIDER DEFECTS.  THESE ADD CHARACTER TO YOUR STONE OR TILE.  JUST BE SURE THAT THE "CHARACTER" YOU ARE GETTING IS WITHIN YOUR GUIDELINES.  DON'T BE TOO PICKY.  LOOK AT OTHER HAND MADE PRODUCTS. THE UNIQUE NATURE OF EACH STONE OR TILE IS WHAT IS FOUND IN PRODUCTS MADE BY MOTHER NATURE.  THEY MAKE YOUR PRODUCT LOOK MORE LIKE REAL STONE PRODUCTS!

Should you need molds or moulds, concrete colorant, concrete sealer, stains, or other concrete, cement, or plaster supplies for your home improvement project, please visit our Catalogue Website at www.TheMoldStore.com or our shopping cart website at http://www.TheMoldStore.us  to get ideas and supplies.  If you are interested in starting a concrete stone and veneer, or concrete paver, brick or tile business, visit our Olde World Stone and Tile Business Opportunity website at www.Oldeworld.com for full details, instructions and various stone making and other concrete product making packages.  We offer Complete D-I-Y Packages in our Product Catalogue and on our Shopping Cart websites.

YOUR PRIMARY CURING PROCEDURE IS VITAL - You must now cover the filled molds with plastic sheeting.
This helps the hydration of cement by keeping the temperature up chemically and maintaining an extremely humid condition inside the sheeting.  This is very important in creating a harder and stronger stone or tile, and is especially critical the first day when water retention and heat are so necessary.

If the weather is really hot and dry when you are making your faux stone or cementitious tile, and it seems that any water on the floor is drying up quite quickly, remember that this is also what is happening in the molds.  What you want to do is keep that floor wet, every hour, half hour, or even 15 minutes, depending on how fast the water evaporates, spray the floor so that the moisture can keep the whole area wet.  If you don't, the face may stick around the edge or corners of the mold due to rapid drying at those "air-exposed" areas. If making stone or tile in a basement or other "indoor" facility, this may not be practical, but then the dryness, or low humidity will probably not be a problem, either.

If volume production pressures do not force you to remove the stone or tile from the molds the following day, let them stay under the plastic longer.  This will further aid the curing process.  Under no circumstances should you force dry stone or tiles by blowing a fan on them, putting them in the sun to dry, or using any other artificial "drying" method.  The stone and tiles need moisture for curing.  The only method for accelerating the curing process is through a steam curing process used commercially.  That would involve expensive equipment, etc.  Also, be careful not to place your curing stone or tile where there are breezes present.  Improper accelerated drying will crack your tile.

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Photo of a Stone mortar mixer used to make faux stone and cementitious tile.
Photo of a commercial vibrating table for casting stone with molds.

Stone 6 Cubic Foot
Mortar Mixer

Commercial 
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