Proper Concrete Mix Procedures for Making Manufactured Stone,
BASIC MIX INSTRUCTIONS WHEN USING PORTLAND CEMENT AND A MORTAR 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.
BASIC MIX FORMULA FOR THIN STONE VENEER AND TILE:
WHEN MAKING THICK (2"+) STONE OR PAVERS, REPLACE TWO BUCKETS OF SAND WITH GRAVEL.
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:
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 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.
CLEAN-UP PROCEDURES AFTER CONCRETE STONE AND TILE PRODUCTION:
When ready to start the next day's pouring, skim any residue off of the top of the water surface and pour the water from the pails into the mixer for the day's first production. Note that the sand/cement that was suspended in the water has now solidified to the bottom of the five-gallon pails and the water left over is clear and clean.
After a period of time doing this, the five-gallon pails will be filled with solid cement and can be disposed of properly. Some Producers peel the plastic pail away, leaving a sturdy base for small tables, benches, etc. Now that's total recycling!
If you are not using a mixer, perform the same procedure with whatever you are using to mix your batches in. Remember, this procedure is for the last batch of the day. If making another batch of stone or tile, especially the same color, there is no need to empty out the entire residue.
CARRYING AND CURING PROCEDURES FOR CONCRETE STONE AND TILE
Place the palm of your hand up underneath the stone or tile, making sure not to put your hands or fingers on the face. If you do, the oil from your hand or fingers combined with the sensitivity of the surface of the tile at this stage may create a dark mark that will remain on the face of the stone or tile even after you seal it. This is caused by oil transfer. Place the stone or tile into the curing racks or shelves with about one inch hanging out over the edge of the shelf. This will make removal of the stone or tile easier, and not necessitate touching the faces when removing them.
Leave the stone or tiles in the curing racks or shelves, for at least 2 1/2 to 3 days. Attach a date slip on the rack where the new stone or tiles are so you know how old the batch is. After three 3 days, the tile is normally ready for sealing. If using a water-based acrylic sealer, you can seal the stone or tile right out of the mold. Be aware that the color mottling will be stronger though. If you want a very "even" color on the face...give them a few days more curing before sealing. Other tips and techniques are covered under the various finishing sections.
POURING CANS, OR SCOOPERS, HELP WITH STONE AND TILE THICKNESS CONSISTENCY:
MAKING A "SCOOPER" TO USE TO FILL YOUR MOLDS TO A CONSISTENT THICKNESS:
BUBBLES, BUG-HOLES OR PINHOLES ON THE SURFACE OF YOUR STONE OR TILE:
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.
SCUMMING ON THE BACK OF YOUR STONE OR TILE:
Salt slows down, or can ruin the set of cement. Worse yet, urine can also make the mix foam. This is another reason for covering your sand...to keep animals out. Constantly watch for scumming, as it is highly undesirable. If scumming does occur, be sure it is brushed off the backs of the stone or tile. If tile or stone is installed without removing the scumming, it can pop loose later as the scumming delaminates from the adhesive mortar or thinset.
Be sure to scrape the backs of the stone and tiles, and the sharp bottom edges also. This will help the tile or stone lay flatter, and will lessen the chance of you getting cut by the sharp edges during handling. It can also help prevent "hollows" in the backs of your stone and tiles. (Air pockets under installed tile or stone). NOTE: Scumming is seldom a problem when mixing by hand.
DEMOLDING YOUR NEW CONCRETE STONE OR TILE:
Care should be taken when you peel the mold off. The corners of the mold will eventually break down and the center at the edge of the tile mold will start bowing out if you de-mold improperly. Never "bend" or "twist" a mold to get stone or tile out. Never place a mold inside of the other and press down or pile other molds on top. Never touch the face of your stone or tile with your fingers if at all possible. (It may leave an oil mark).
NOW COVER THE STONE OR TILE WITH PLASTIC AGAIN. - Remember, "drying" is not "curing"
CONTROLLING THE QUALITY OF YOUR CONCRETE STONE AND TILE:
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.
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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