Whether you want to pave your patio or give someone cement shoes, here's how to mix concrete like an expert.
Step 1: Make the dry mixture Basic concrete is made by adding water to a mixture of gravel, sand, and a kind of cement called portland cement. To make the dry mix, combine one part portland cement, two parts sand, and four parts gravel (also called coarse aggregate) in a wheelbarrow or trough. For smaller jobs, you can purchase bags of premixed dry ingredients.
TIP: Start with a moderate amount of dry mix; it becomes difficult to mix large quantities when water is added.
Step 2: Add water Take a hose and slowly add water to the mix. If using premixed concrete, consult the directions on the bag for the amount of water needed — then measure it into a bucket, and add it to the mix.
TIP: Too much water will result in weak concrete, while too little water will make the concrete unworkable. It’s better to start with less water. You can always add more if needed.
Step 3: Begin mixing the concrete With a hoe or a shovel, begin mixing the concrete. Make sure all the ingredients are uniformly mixed.
TIP: For large projects, use a gasoline or electric power mixer. Concrete mixed by machine will typically be more consistent — and require a lot less elbow grease!
Step 4: Check the consistency After mixing thoroughly, check the consistency. Punch the bottom out of a Styrofoam or paper cup and fill it with your concrete, as if you were making a sand castle. Remove the cup and watch the pile slump down — ideally it should sink to about half the height of the cup. Add water to the mix to adjust the consistency as needed.
Step 5: Pour concrete Now pour your perfectly mixed concrete quickly, as it will begin to dry within 15 minutes.
TIP: To increase the setting time of concrete, add a small amount of sugar (0.01% to 0.05% the weight of the cement). Sugar acts as a retarder and increases the setting time one to four hours.
FACT: The Pantheon in Rome, built around 125 A.D., still holds the record for the largest unreinforced solid concrete dome in the world.