In order to make concrete, you will need Portland cement to act as a binder, sand, and water. Now, depending on what type of concrete you are using, small stone, or gravel also known as concrete aggregate is added to the mix.
Mortar is just a sand base with cement, and the material that cab be used to make sidewalks, post anchors, columns. All of these will require the use of sand and gravel, cement mixture and water. The gravel gives larger surfaces additional strength. The water acts as an activation ingredient. Without the water, dry materials cannot be converted to a solid mix.
What makes Concrete Strong?
An interesting fact about concrete is that the more water there is in the mix, the stronger the concrete becomes. But, there is a catch, you cannot have the extra water while the concrete is in a pure liquid state, you need to wait until the concrete begins to firm up before you can add more water. The reaction of Portland cement mixed with water is called Hydration, and it is this chemical reaction that gives concrete its strength.
How to attain proper curing of concrete
Whenever possible, you should allow concrete to slow cure over the course of a few days. To do this, mist it down for 10-20 minutes once the concrete starts to harden up, and becomes firm to the touch. Also, whenever practical, shelter and cover up the hardening concrete from the sun to reduce evaporation. The longer the hydration process can last the stronger the mix and final product will be.
Here is another interesting concrete fact for you to ponder; Did you know that on a concrete dam, the concrete that is exposed to the dammed up water is always harder than the rest of the dam?
When you purchase a bag of concrete, most of the time all of your dry ingredients are already pre-mixed in the bag. When you are ready to make a concrete mixture, just add a recommended amount of water to the concrete. If you are creating a small project (one bag or less) you can simply mix it in a bucket. If you plan on doing multiple projects, you can purchase a hand crank mixer, or you can rent a cement mixer at an equipment rental shop, or at one of the large retail home improvement stores. By using a portable cement mixer you can save a lot of time and energy that you would waste on manual mixing.
When you open up a cement bag, and are ready to start pouring, make sure that you do so in a well ventilated area. You should wear safety goggles and a dust mask. Concrete is water sensitive when mixing. Unlike the curing process, which requires more water, for a stronger bond, the mixing process requires as little water as possible. Try to get your mixture damp enough to a point where you can make a “mud ball”, which should hold its shape for about 30-45 seconds. It is important to make sure that your entire mix is wet. Mixing should take no longer than 10 minutes, but careful and proper mixing is the key to a total and complete saturation of your concrete mixture.
Step 1. – Preparing a Concrete Mixture
A one 80 pound bag of concrete will require about 5 gallons of water per bag. Start out with about 2 ½ gallons of water in your mixing container, then add in your bag of concrete. This will help keep some of the cement dust down, and help prevent dry materials from sticking to the bottom of your container.
Step 2. – Mixing concrete with a rake for a small project.
Mixing concrete with a rake works very well, and requires far less energy than it would with a shovel. Keep adding water slowly and gradually until you get a proper consistency to your mix.
Step 3. – Pouring Concrete
Once your concrete is properly mixed to the right consistency, you are ready for the pour. Keep in mind that you are working against the clock, which started ticking when you stated mixing. From this point forward, you need to move quickly.
The average pot life (working time) for a concrete is roughly 20 minutes. Some concrete is fast setting, so you have to be careful and read the data on the cement bag to see what type of concrete you are purchasing. Make sure you only mix what you can use during the pot life window. Once water makes contact with the mix, the timer starts and the mixing reaction has begun.
When you pour your mixture, spread and smooth it with a flat edged surface, or tool such as a trowel, or concrete rake. It is very important to make sure that all the voids in your project get properly filled. TO ensure this, you can tamp it gently (as not to splash the concrete), or you can rent a vibration tool that will assist in settling the concrete to fill the voids and purge the air pockets.
Pour your material in your mold. You may have to spread it as you pour/dump it, if you have more concrete than the pour area can hold. If you make multiple dumps, keep them close enough together so they can be joined together evenly.
Once you pour your concrete, you need to tamp it to compact and fill the concrete into all the cracks and crevices of the pour area. Proper concrete tamping will also help to remove and possible air pockets that will almost certainly cause a failure eventually.
After you tamp the concrete its time to smooth it out. This process further tamps the concrete mixture, and creates a smooth level surface.
Using an edging trowel helps create firm clean corners and edges. This will help prevent weak edges and crumbling of the concrete.
For the moment you are all finished. After an hour, lightly mist the concrete and cover it. Do this for a duration of about 3 days, misting twice a day. After the concrete has fully cured, it is a good idea to apply a sealer. This will protect the concrete from freezing and thawing of absorbed water, and maintain a more even color throughout the finished project.
There are quite a handful of projects a DIY person can do without the assistance of professionals. Some examples include the following:
* Pouring supports for fencing
* Pouring steps
* pouring small slabs for sheds
* Making your own decorative pathway stones
* Pouring a small sidewalk
* Making cement ponds
* Pouring your own support columns for a porch
The list can go on and on. You are only limited by the scope of your imagination. Keep in mind that concrete can also be colored, so decorative work can be done even from a plain concrete.
Concrete Mixing Tips and Good to Know Facts:
Concrete is not flexible, therefore it has zero tensile strength. When it comes to impact or load weight, concrete is very strong. In order to strengthen concrete, a material known as a re-bar can be used. Re-bar can be made of steel rods, or a steel mesh, which when properly set in concrete, gives it a much added strength to a project such as a sidewalk, pouring of a concrete slab, or a support column.
Concrete is a somewhat porous material, so it is recommended to apply a concrete sealer after a full cure (about 3 days) for a longer project lifespan. When pouring a sidewalk, or slab, it is important to cut in expansion joints. This gives room for the concrete to expand and shrink without cracking. Expansion joints can be added once the material is slightly firm. You can use a thin straight edged piece of metal, or wait until the cure, and then use a tile saw.
Preparing a strong foundation for a concrete pour:
When laying a slab, sidewalk, or a concrete step, make sure you prepare the location in order to provide a firm foundation for the concrete. Dig down about 6 inches deep, and lay a layer of about 2-3 inches of crushed stone in the bed. Then pack it down as firmly as possible. You can tamp it, or rent a roller to assist you in this process, or if you have enough room, you can actually drive your car’s tires over it.
Concrete Mixing and Pouring Project – Proper Planning and Preparation Tips:
The bigger the project, the more help you should have. You cannot delay the curing process of the concrete, so once it sets, you are all done. A good rule of thumb is to have one extra person for every five bags of concrete you plan to mix.
To give you an idea of how far an 80 pound bag of concrete would go, a one yard of concrete is approximately 48 bags of cement. This can provide enough concrete mixture to cover a sidewalk that is 21 feet long, 4 feet wide, and 4 inches deep.
Concrete Mixture Area Coverage and Prices:
As you can see, 1 bag does not go very far, and it is a lot of hard work mixing that much. Many concrete companies require a 2 yard minimum for delivery, and concrete mixture prices will range based on your location, but a ballpark price is $400.00 for 2 yards of concrete delivered.
Keep your concrete as dry as possible during the mixing, then as wet as possible during the cure. Do not wet concrete until at least 2 hours after the pour. Always take safety precautions when mixing concrete. Rinse out mixers and tools before the concrete cures, or you will never get them clean again.