Unless your patio is going to be the size of your driveway, you can pour concrete you mix yourself. Buy your favorite brand and follow the instructions on how to mix. Once you have your concrete mixed, start pouring in the frame over the leveled and flattened ground.
Fast-setting concrete is ideal for setting posts because there's no mixing—you simply pour the dry concrete from the bag right into the hole, then add water.
If the weight of the concrete deforms the dirt base in any way, the entire concrete structure will be flawed. All of that is not to say that it is impossible to pour concrete over dirt. You can absolutely do it successfully, but you need to follow a specific process.
You'll save 40 percent to 50 percent by pouring your patio yourself. (Taking the DIY route also means you can be sure the technical details are done correctly.) You'll save even more if you mix your own concrete instead of having a ready-mix truck deliver it.
It is cheaper to mix concrete by hand, but it will become less cost-effective as your project size increases.
Keeping concrete moist is essential to the concrete curing process, but too much water and the concrete may not form in the way it needs to. If it loses too much moisture through evaporation, it will not cure properly and will become prone to cracks.
Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.
Before you can put down a concrete slab, you have to lay down a base. A solid base protects the concrete from settling dirt, water runoff, and other natural hazards. Though all outdoor fixtures are subject to natural wear and tear, concrete will break and deteriorate more quickly without a base to support it.
Most concrete contractors want a mix of coarse and fine aggregate to create a compactable base that is going to be safe for settlement and drainage. Crusher run (a mix of crushed stone and stone dust) and #57 coarse aggregate are two of the best base materials for concrete slabs.
Working With Ready-Mix Concrete
And, if you mix it yourself, it's the cheapest way to make your slab. For most do-it-yourselfers, the best material for building a concrete slab is a ready-mix, crack-resistant concrete product. The wet mix is poured into a prepared wood form, then left to cure.
The simple answer is to prevent the concrete from cracking and breaking.
Technically you can, but you really shouldn't pour concrete over grass. To maintain its tensile strength, concrete needs to be laid on a firm, even, and dry foundation. Grass and soil will naturally channel moisture into the concrete from below, which will likely result in it cracking over time.
Portland cement is the most common type of cement used in construction projects because of its hydraulic properties — it sets and hardens quickly when combined with water. You can't use cement by itself — it only serves as a binder when manufacturing other products.
Although dry pouring of concrete might be fine for filling fence-post holes, it should be avoided as a placement method for concrete slabs if you want the concrete to look good and last for the long term.
Moist curing is a common method of concrete curing. It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.
Rebar is not necessary for every concrete project. The general rule of thumb is that if you are pouring concrete that is more than 5 inches in depth, you are probably going to want to add in some rebar to help reinforce the entire structure.
How thin can you pour concrete over concrete? Your new layer needs to be at least 2 inches thick. If it's any thinner than that, it'll easily crack under pressure and won't adequately bond to your surface.
The Issue with Pouring Concrete in Cold Weather
When temperatures dip below 40 °F, the chemical reactions that strengthen concrete slow down and can lead to weaker concrete. If concrete curing temperatures are below freezing, the water inside the concrete can freeze and expand, resulting in cracks in your surface.
Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting. Gravel is especially important in clay soil because it doesn't drain well, which results in water pooling under the concrete slab and slowly eroding the soil as it finally drains.
Standard concrete floor slab thickness in residential construction is 4 inches. Five to six inches is recommended if the concrete will receive occasional heavy loads, such as motor homes or garbage trucks. To prepare the base, cut the ground level to the proper depth to allow for the slab thickness.
DO spray new concrete with water. One of the most common methods for curing concrete is to hose it down frequently with water—five to 10 times per day, or as often as you can—for the first seven days. Known as “moist curing,” this allows the moisture in the concrete to evaporate slowly.
Concrete that is not moist-cured at all dries too rapidly, and reaches less than half its potential design strength. It will also have a greater number of shrinkage cracks.
Rain can influence the surface appearance of the concrete and its internal strength. It can cause the concrete surface to become soft, which reduces the abrasion resistance and strength of concrete. At the same time, it increases the tendency for dusting and cracking to develop.