We developed this formula as a diamondcrete alternative or substitute to commercially available stepping stone cements. It is about 1/5 the cost and can be made in any color imaginable. The basic formula is simple and other additives can be included to speed up set time and add even more strength. The formula and mixing instructions are as follows:
- White Portland Cement – available at some hardware stores & bldg supply stores. (used in making stucco)
- Fine or medium White Sand – widely available (whiter the better)
- Acrylic Polymer Emulsion (also called Acrylic Admixture) – available at some hardware stores or can be shipped from the following companies (strengthens cement)
- Color – (red, yellow, blue) Available online at the link below. Also, many hardware stores carry both liquid and powdered coloring. Kover Krete sells almost every color you can imagine.
Additional ingredient for quicker set time or higher strength –
- Calcium Chloride (cement accelerator) – Kover Krete, Air products Chemicals, and some hardware stores carry this. Its accelerates the set time of concrete or cement. KoverKrete carries Quik Set.
- Micro Silica / Silica Fume – To add more strength to your cement you can add a tablespoon of microsilica otherwise known as silica fume to a batch of cement. This is a little hard to find in small quantities but you can google it and possibly find some. It is not essential in the formula but if you like to experiment and you can find some you may want to try it.
White Portland Cement – $18.00 – $25.00 per 94 lb bag
Sand – $3.00 – $5.00 per 100 lb bag
Acrylic Admixture – $40 – $60 per 5 gallon pail or $10 – $18 per gallon
Calcium Chloride – $4.00 – $8.00 per 8 lb bucket (takes very little per batch)
Color – $13.00 per quart ( most colors go a long, long way)
* 5 gallons of acrylic can treat approximately 300 lbs of cement mix. Thus your per pound cost of mixed and colored cement would be approximately 28 – 30 cents. (diamondcrete runs about $1.50 per pound)
-1 part White portland Cement – scoop as much as you think you will need into a 5 gallon bucket. I use a scoop that holds 2 cups and I put in about 4 scoops.
-2 parts Sand – Mix into the portland cement. If you used 4 scoops of cement, put in 8 scoops of sand.
-Replace the water required in mixing cement with Acrylic Admixture or replace at least half of your water with Acrylic. The more Acrylic the stronger the stone. You can go 50/50 or 75/25 etc… (note – Acrylic slows the set time but Calcium Chloride speeds the set time back up.) Acrylic gives you a denser stone with tremendous strength and more flex (crack resistance) than standard cement. It also waterproofs the stone so sealing is not necessary.
-Mix with a drill driven cement/paint mixer until creamy like pancake batter. Press out the lumps as you mix with a masher (kitchen tool).
-Mix in your color. Add a small amount and mix well. Repeat until the desired color is achieved. Red and Blue make plum, Yellow and Blue make green, Red and yellow make orange and so on. With this formula, your colors should come out extremely uniform and smooth.
-Dissolve (completely) 1 ounce of Dry Calcium Chloride into a small amount of water and add to the mix. (not so much water as to dillute your mix. Just enough to dissolve the accelerator) Stir at least another minute. The more Accelerator (calcium chloride) you add the faster your mix will set. The slower the mix sets the stronger it will ultimately be so do not overdo it. If you want it to set in 45 minutes it will but I would recommend a 2 – 3 hour set time. Just experiment until you are satisfied. 1 ounce should give you a 2 – 3 hour set time depending on the temperature. The accelerator will come with instructions.
-Once the mix is thoroughly blended you are ready to pour. Once you pour, be careful not to move or shake the mold or you may allow cement to go under your glass and bury it. Do not attempt to pop the stone out of the mold until it is hard to the touch. If the cement feels soft and pliable let it set longer and just add a little more accelerator next batch. When in doubt, wait longer.
** You can shorten the mixing process by mixing your color and accelerator into the acrylic before you add it to the cement. Put the color in first and right before you add it to the cement dissolve in the accelerator. The liquid may start to get warm but do not be alarmed, it is supposed to.
Tip : once you have poured the cement into your mold, vibrate out air bubbles with a hand type vibrator or by tapping the mold or table the mold is on. (1 – 2 minutes) This will greatly strengthen your finished product.
Also, experiment with a few small batches of cement. Make a few trivets or coasters with scrap glass. When you are satisfied with the results and confident about set time, begin using the mix for the real thing.
Steven Cole (Economics, MBA – University of West Florida, Business & Innovation – Stanford University) 22 years experience in the safety business.