Q&A for How to Make Bricks from Concrete

There are multiple ways you can do it. Trying using a masonry blade on a skill saw, hand grinder, or brick saw.

Install a schedule-40 rated PVC pipe in the form before adding concrete, and it should work well. Perhaps add another PVC pipe for floral arrangements as well.

Cement is the 'glue' that holds the sand and gravel, the aggregate, together; all forming concrete. Cement is made out of limestone that is heated to drive out the water and ground into a fine powder. Adding water causes a chemical reaction called hydrolysis, that creates heat and causes the whole mix to turn into concrete, basically a form of sedimentary rock like the original limestone. Concrete is man-made rock. Glass is also clear rock. The same cement is used with sand and water to make mortar used for laying brick. Cement by itself, mixed with water, will crumble and is not very useful.

Only if the brick isn't some cheap material. Pour hot water over the stone so that the edges can relax then firm.

They do address that in steps 3 & 4. Allow to dry for 24 hours & strip the forms from the bricks the next day. The bag may say to let cure over night, and keep moist (not drenched) by misting the bricks while they cure overnight.

Yes, but you need a special material. Check with your hardware store or a concrete company that specializes in it.

No. Mortar mix is intended as an adhesive. For thin bricks, use high-strength or "structural" concrete.

A structure that is meant to hold more than just its own weight. For example, in homes, some walls help hold up the roof, some do not.

'Fire Bricks' are specially made for exposure to the high temps of fire. Use these and thin joints of clay fire mortar for the bricks that form the firebox. Other bricks can be used outside of the fire bricks to thicken the walls or form a chimney. It's very important that you follow a professional diagram for the fire box, smoke shelf and flue design.

Yes. I use metal mold for all my brick projects. They are easy to maneuver and reusable.

As mentioned above, one 80-pound bag yields 64 bricks. 500 / 64 = 7.8125 80-pound bags.

Glue Styrofoam in the forms where you want the holes to be. After the concrete cures, melt out the Styrofoam either with a solvent or burn it out with a torch.

Use Liquid Cement Color. It comes in different colors and you can buy a liquid or powder form. Quikrete liquid cement color is the one I've used: one 10oz bottle will color 2 60 or 80lb bags of concrete.

Lava rock makes great aggregate. It is very porous, so “locks” the other materials together well. Be sure the lava rock is washed well, as it can be harvested near the sea, and salt ruins concrete. Do not use lava rock in an application like a fireplace or oven, as the air pockets in pours material can expand and crack or even explode.

Straw is traditionally used in mud brick to reinforce it. It shouldn't be necessary in concrete and, depending upon the amount and characteristics of the straw, could actually weaken it. If you're using the bricks for a structural wall, as opposed to for decorative purposes, I wouldn't recommend the straw. If you do add straw, I recommend reading up on its use. Look up "rammed earth construction" as a starting point. Straw is frequently used there, and it is sort of a hybrid between mud brick and concrete (Frankly, I wouldn't recommend homemade bricks for anything structural. You won't save that much money and may lose far more from a bad batch.)