There are traditionalists out there who, when you ask for advice, insist that you must mix your concrete from scratch. You will see them slaving away over a mixer with a pile of sand, a pile of portland, and a pile of gravel. They will work tirelessly trying to achieve the perfect oatmeal like consistency. You, however, will already be done. There are times, places and projects that require a custom mix. The basic walkway that you are constructing is not one of those.
When you go to your local home improvement store you will most likely be met with a large number of choices. There are quite a few pre-mixed masonry products on the market and most are packaged in heavy paper bags that look quite a bit alike. You are looking for a basic concrete mix - a "just-add-water" formula that already has portland cement, sand, and gravel in it. You really do just have to add water.
Remember, you do not want mason mix, mortar mix, sand mix or a re-surfacing mix. There are some basic concrete mixes available that are high strength mixes. It will not hurt if you use these, but they are designed for floors that take a lot of heavy abuse, like the floor of a truck garage or a warehouse. You may also find some quick drying mixes. If this is your first time working with concrete, I would recommend that you stay away from this until you are comfortable with how long it will take you to screed and float your surface. If you use the quick dry formula and it starts to set up before you are ready, then you've got big problems.
Determining how much product you need to buy requires a little bit of math, and the number of bags that you will buy depends on how big the bags are. Most manufacturers print a chart on the outside of the bag that will allow you to figure how much you will need. You need to know how many square feet the area of your pour is and then use the chart to figure that area by 4" deep. A little hint is to take a calculator to the store with you. It will come in handy when you are standing in the aisle trying to figure square footage and cubic feet in your head.
Once you get the product home, you will need something to mix the concrete in. You can buy a plastic mixing tub that will work quite well. I prefer to use a wheelbarrow because I can dump the wet concrete out of it instead of having to shovel it out like I would if I used a mixing tub.
When you are finally ready to start mixing, there will be a ratio printed somewhere on the bag that tells you how much water to use. This is difficult to measure when you are doing large scale projects. I would recommend mixing one batch up slowly. Keep adding water a little at a time until the concrete mix reaches a nice oatmeal like consistency and then pour it. The rest you will be able to do by sight and should go faster.
Depending on the budget for your project, you can also look into renting a portable mixer. This has a drum on it that spins, much like a smaller version of the drum on a cement truck. You pour the dry bag into the drum, add water, plug it in and watch the drum do some of the manual labor for you. Typically the drum is emptied into a wheelbarrow and you can wheel it and dump it exactly where you want. Keep adding concrete to the form until it comes right up level with the top. You want to fill it up so it just begins to overflow. This will ensure that you don't have any low spots once you begin to screed the surface.
Brian Simkins is a freelance writer living in Chicago. He enjoys using his 14 years of home improvement experience to educate and equip new home owners.