How to Make Blocks With Rocks & Concrete

You will need to make many identical concrete blocks when building walls.

Blocks made with concrete are a common and important building material. While there are many different ways to make a concrete block, a few simple instructions will allow you to make many different types and styles. Concrete can be a puzzling material but is, in fact, not difficult to work with. Making concrete blocks at home can save you money and allow you to work with material designed to meet your needs.

Things You'll Need

• Molds
• Light vegetable oil
• Cloth
• Container
• Mixing tools

Instructions

1. Prepare the mold for your blocks. If you do not want to buy a mold, you can make one out of most any material, ranging from wood pieces to milk cartons. If you want to reuse your mold, coat the inside with a light vegetable oil or commercial mold release product. Be sure to make a very light coating and wipe the excess off with a clean cloth.

2. Mix the concrete in your container. Concrete is comprised of cement, sand and gravel. Check to see if you are using premixed concrete or cement that will need sand and gravel added. You can also add rocks to the concrete mixture for extra filler. Prepare the concrete, mixing all the dry ingredients very thoroughly, then adding just enough water to wet the mixture. It should be thick and heavy.

3. Pour the concrete mixture into the mold. After filling the mold, jiggle or vibrate the mold to ensure that all the air pockets come out and that there is good adhesion within the concrete. Allow the mold to dry for approximately 24 hours in a dry place with a temperature above freezing.

4. Remove the mold from the block. If you want to reuse the mold, flip it over so the open side is down, then gently pull the mold off the block. You may need to tap the bottom of the mold to get the block to let go. Be sure that it does not fall out and break. If you do not want to reuse the mold, simply break it off the concrete block.

Tips & Warnings

• You can make more lightweight concrete blocks, replacing the sand and gravel with expanded rock or another hard, lightweight material.

• Allow the concrete to dry at above 40 degrees Fahrenheit for best results.

• Before building, allow the blocks to cure in a protected area for up to two weeks.

• Too much oil in the mold can cause unsightly pockmarks on the finished surface of the block.

• If the mixture is too wet, all the gravel and rocks will go to the bottom of the mold and the block will be prone to breaking.

References

• The Mold Store: Do It Yourself Guide
• ENotes: Concrete Block
• Quality Books: Make Concrete Blocks -- How To Mix Concrete Properly