Mixing Concrete

“Concrete” is a mixture of Portland Cement, Aggregate (sand & rocks), and Water

Portland Cement is the name for all cement of this type, “Portland” has the same meaning as “Stainless” in ‘Stainless Steel” or like “Sterling” in ‘Sterling Silver’, and is a generic term for this cement, which is used around the world. The name “Portland” comes from the rare mineral “Portlandite”, which is synthesized during the cement-making process.

Portland Cement Production creates 5% of the total of all carbon emissions in the world’s atmosphere.

Here is the basic recipe:

  • 1 part Portland Cement
  • 2 parts Sand
  • 3 parts Gravel (rocks)
  • Add clean water until it becomes workable, water should be fit for drinking (there are limits to the amounts of chlorides, sulfates, alkalies, and solids that can be in the water used to make concrete. bad water may result in a number of problems)

The official formula is:

  • 11% Portland Cement
  • 26% Sand
  • 41% Gravel
  • 16% Water
  • 6% Air (from mixing)

Typically, a mix is about 10 to 15 percent cement, 60 to 75 percent aggregate (sand & gravel) and 15 to 20 percent water. Entrained air in many concrete mixes may also take up another 5 to 8 percent. Entrained air increases durability, and resistance to freezing and other extreme and rapid weather changes

Excess air is different from “entrained air”, and is undesirable in concrete forming, so u need to eliminate as much as possible, by tapping the container, slicing through it in stripes, etc.. Entrained air is incorporated using special “A” types of Portland Cement

The Rule of 6’s:

  • A minimum cement content of 6 bags per cubic yard of concrete,
  • A maximum water content of 6 gallons per bag of cement,
  • A curing period (keeping concrete moist) a minimum of 6 days
  • An air content of 6 percent (if concrete will be subject to freezing and thawing).

Things you need:

  • Concrete ingredients – Portland Cement, Sand, & Gravel
  • A Rubber Concrete Bucket. – Its thick flexible rubber, dont use any other other kind of container unless you have a garden area to wash it out in immediately after using it, before it dries. Otherwise, just let the concrete dry out completely before you clean the bucket, and clean it simply by bending the bucket or hitting it with a hammer etc.
  • Mixing Stick – can be made of wood or metal, and should be strong enough that you can hit it hard to break off concrete after its dried
  • Water Container – big enough to hold all the water you will need for the amount of concrete you are mixing
  • Scooper – an old rice scoop or other plastic scoop you will only use for scooping the concrete out of the bag.
  • Drop-Cloth – any old fabric, towels, shirts, or even newspaper which you will set on the ground or table to prevent concrete from contacting any tile or wood surfaces in your home
  • Rubber Gloves – strong gloves for cleaning the kitchen, or you can get stronger ones with fabric inside and rubber outside at hardware markets
  • Sealed Safety Goggles – be sure they protect the top, bottom, and sides of your eyes from any cement dust in the air, as well as from splashing concrete when mixing
  • Particulate Air Filter Mask – 3M brand is the best, or any professional air filter mask which filters out harmful particles in the air to prevent cement dust from entering your respiratory system. Regular cloth is not ok, be sure to protect your health with a proper air filter
  • Work Clothes & footwear – wear clothes and footwear that you don’t mind getting dirty or ruining
  • Wet and Dry Work Hand-Towels – for cleaning your skin
  • Wet Concrete Towel – another towel just for cleaning concrete on your project before it dries

Safely Handling Concrete:

  • After you buy cement, be sure to put it inside of another high-quality plastic bag and seal it tightly. It’s a good idea to put it in a covered plastic container. Put it in a safe place where it will not be opened by children and can sit undisturbed until it is needed.
  • Dry Cement – when cement is dry, the powder is dangerous to the lungs mouth, nose, eyes, and respiratory system, so a Particulate Air Filter and Safety Goggles are important when handling dry cement, to prevent any dust powder from contacting those areas of your body. Any cement powder on your skin can be easily washed off.
  • Wet Cement / Wet Concrete – after cement contacts water it becomes caustic, meaning it will burn your skin. So Rubber gloves must be worn whenever cement and water are mixed. If you mix carefully and there is no dry powder on the sides of the bucket or mixing stick, you don’t need your air filter anymore, but till need Safety goggles and rubber gloves, to prevent accidental splashing cement from entering your eyes or contacting your skin. Wash any wet cement or concrete off of your skin immediately

Mixing Procedure:

  • Gather all items together in your work area
  • Put on your work clothes
  • Lay down the Drop-cloth in the area you want to work
  • Put the rubber concrete bucket and the mixing stick, and filled water container on the drop-cloth
  • Put on your particulate Air filter and Safety Goggles
  • Carefully open the cement container and bag, and take out the scoop
  • Scoop out the amount of dry cement you need, and place it carefully in the bottom of the bucket, so as not to create a dust cloud, and try not to get any on the sides of the bucket
  • Replace the scoop into the cement container and seal the cement up tightly. Wipe up any dry dust that may have fallen outside of the bucket with the wet concrete towel
  • Add the correct amount of sand and gravel, and mix the dry ingredients carefully with your mixing stick. Mix slowly to prevent cement dust from rising up out of the bucket
  • Wipe your hands and forearms with the wet and dry towels, otherwise the cement dust on your hands will mix with the sweat in the rubber gloves and burn your skin
  • Put on your rubber gloves
  • Slowly add clean water in portions, mix it carefully and completely after each addition. when the entire mixture becomes workable and there is no more dry ingredients, start adding water very slowly until the right consistency is achieved. Be sure to get all the dry dust from the sides of the bucket and mixing stick so there is no more dry cement dust in your work area
  • When there is no more dry cement dust anywhere, you may take off your Particulate Air Filtration mask, but leave your goggles and gloves on
  • The mixed concrete is now ready to be poured into your form.
  • After pouring, wipe off any extra concrete from your project
  • When you are finished, set the bucket and mixing stick aside to dry, after it is completely dried in the next day or two, you can just bend and bang the bucket and mixing stick to get the dry concrete to fall off.

Curing:

Concrete gets harder the older it gets, ultimate strength will take several years to achieve. At 28 days over 90% of the hardness will have already been achieved. 28 days is the standard measurable strength of concrete hardness,

Concrete hardens as a result of hydration (the chemical reaction between cement and water), thus water must always be present for a minimum of 6-7 days.

Concrete continually loses water, so begin hydrating with water as soon as moisture seems to be disappearing from the surface

Curing Methods:

  • Soak with water 2 or 3 times a day, and keep it covered with plastic so the water doesn’t escape
  • Cover in absorbent material, like burlap or even towels, and keep the material wet all the time.
  • Place the product underwater.
  • Place under misting sprinklers which are kept on most of the time
  • Brush Aquafaba or plant yogurt on it, it will stay moist under the thick gel for quite a while
  • Pour rice water on it, or thicken boiling water with cornstarch to a gel, then brush the gel over the product

Coloring & Decorations:

  • Dry coloring powder can be added to the dry mixture of White Portland Cement, with the dry ingredients, or liquid color can be added after water is mixed in to the cement or concrete
  • Paint can be added after curing
  • Stamps, designs, rocks, or other decorative materials can be added or etched in during the first few hours of setting
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s