How-to Guide to Make Lightweight Concrete and Cement Formulas for Stone Veneer and Man-Made Stones

Lightweight and Medium-Weight Concrete Mix Designs

This information is provided as a basic introduction to making light-weight and medium-weight concrete stone and stone veneer. It is intended to supplement our Commercial Producer Training Manual. It is designed for those consumers wanting to make stone and stone veneer for what are typically small, do-it-yourself and homeowner projects. For very large or multiple projects, we offer our complete stone and tile business training manuals, video, etc., as well as D-I-Y Kits and Packages, in our www.TheMoldStore.us eStore Shopping Cart website. 

The mix for lightweight concrete can be altered from using all lightweight aggregate… down to a small percentage of light-weight aggregate, predicated on the installation application. A true light weight stone is much easier to install, handle, cut, etc. A medium weight concrete mix gives you all of those benefits, plus the benefit of strength, while still offering a savings on weight versus the much heavier natural stone. Keep in mind that the more lightweight aggregate you use in your mix… the weaker the stone will be. And, your cost may go up as well. Both cement stone formulas will last many, many years, depending on location, wear factors, and whether they are vertical or horizontal installations. In a typical exterior wall installation, such as on a house, light-weight cement stone will probably last 30-50+ years or more. If covered in the medium-weight concrete cement stone, it should last 100+ years and more.

As for applications… Never use a full lightweight mix to make steppingstones, tile, pavers, etc. And though there are some who use it for exterior applications… I don't really recommend it, unless the wall or whatever it's being applied to is under a roof and protected from the elements. For interior applications, the lightweight concrete formula is fine. The medium-weight concrete formula is much better, and will hold up many more years in exterior applications.

A medium mix was used for the stone on the castle in the photos below. This was mostly due to the fact that some of the “Olde Castle Stone” that was made and used was 18”x18”x1-1/2” thick. That's getting pretty heavy to put on a vertical surface like a castle wall. The other reason is that it was chosen is that it will weather great, and last virtually forever, even though there may be over half Perlite aggregate used to make it. The Perlite also acts as an additional insulation barrier, and does not negatively affect the cement stone's fireproof benefits. We normally recommend that a straight sand, cement, and aggregate mix be used for stone that is used on a floor or terrace, or any other surface that will have foot or vehicular traffic.

I use Perlite as my lightweight aggregate. You can also use expanded shale, volcanic rock, vermiculite, etc. It happens that in North Carolina, Perlite is readily available, and relatively inexpensive. It comes in 4 cubic ft. bags, so it's easy to use. You get about six 5-gallon pails of the aggregate to a bag, so it is somewhat economical to use, as well. Check your local area for availability of the various lightweight aggregates. Buying in bulk will normally save you a lot of money over purchasing bags of aggregate.

NOTE OF CAUTION:
Be sure to wear a dust mask when handling Perlite… the dust can be very irritating to the eyes, throat, and nasal passages. It's a good idea to fill your buckets out of doors, or have an exhaust fan going to get the dust out of the area as quickly as possible when using it in a mixer. If you are mixing cement, concrete or plaster by hand, the dust will not be as bad, but you should still wear eye protection like goggles and a dust mask to prevent breathing in the dust.

Everything will be the same as a basic concrete tile or stone mix formula except for the sand, which is the variable. You may want to experiment with different lightweight aggregates, if they are readily available to you locally. The use of lightweight aggregate other than Perlite, will affect the weight and strength of your stone. Ask your local supplier for specs and suggested formulations for using the specific lightweight aggregate that you are considering.

CHANGE IN MIX SEQUENCE WHEN USING A LIGHTWEIGHT AGGREGATE LIKE PERLITE:
1. For both the Lightweight and Medium Weight full-batch formulas do the following…
2. Start with five gallons+/- of water in the mixer, any additive and colorant, if being used. Mix well.
3. Add half of the 94 lb. bag of Portland cement, ALL of the sand, then the second half of cement. Mix well.
4. Mix for one minute. Be sure that the mix is on the wet side. (soupy)
5. Start adding the Perlite, one bucket at a time.

Perlite will absorb much of the liquid when added to the mix. If the mixer starts to strain because the mix is too stiff, add more water to bring it to a wetter consistency. You will probably have to add water after each bucket of Perlite. Keep adjusting the consistency of the mix with water until all of the Perlite is in, and covered with cement. Once the Perlite is covered… STOP. Pour your mix into molds. Clean up.

IF MIXING BY HAND… MIX HALF BATCHES OF THE ABOVE FORMULA.

VIBRATION: Either hand vibrate or use a vibrating table. See our
MAKING A $50.00 VIBRATING TABLE instructions elsewhere on our website. If using a vibrating table, vibrate for about ten seconds. DO NOT over vibrate. Over-vibration will separate the Perlite into layers, and weaken the stone. It may even split or delaminate when dry. The best method when using a vibrating table is to cover the table with molds. Fill the molds with your mix. Turn on the vibrating table for five seconds. Adjust the fill levels of the molds. Vibrate for another five seconds or until the concrete mix levels out. STOP. Do not over-vibrate. Your final mix should be like a very stiff or thick pancake batter.

If you are vibrating by hand, do about a half dozen molds at a time. Bounce and shake them for about twenty seconds on a flat and level surface, or until the mix in the mold levels out.

Once vibration is complete, put the filled molds aside on a level surface and cover them with plastic to firm up and start the curing process. After about 24 hours, you may uncover the filled molds and demold your stone. Put the stone in a storage area, out of breezes and direct sunlight. Make certain it is re-covered in plastic. REMEMBER… covering the stone in plastic helps the hydration and curing process, making the stone much stronger. It normally takes about a month to fully cure, though installation can be done after about two weeks if necessary. For complete information about the concrete curing process, and about concrete characteristics and benefits, see our CONCRETE BASICS tutorial elsewhere on our website.


LIGHTWEIGHT FORMULA - (Interior): MEDIUM WEIGHT FORMULA - (Exterior)
One 94 lb. bag of Portland Cement One 94 lb. bag of Portland Cement
One 5-gallon bucket of sand. Two 5-gallon buckets of sand.
Five 5-gallon buckets of Perlite. Four 5-gallon buckets of Perlite.

Should you need molds or moulds, colorant, concrete sealer, stains, or other concrete, cement, or plaster supplies for your handyman or 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.  If you are interested in starting a concrete stone and veneer, or concrete and cement paver, brick or tile business, visit our Olde World Stone & Tile Business Opportunity website at www.Oldeworld.com for full details, instructions and various stone making and other concrete product making packages.  We also offer D-I-Y Packages in our catalogue and on our shopping cart websites.

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