Concrete Calculator

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This concrete calculator can be used to estimate the volume of concrete necessary for projects involving common shapes. It can also estimate the material cost of the concrete. To use the calculator, please click the tab for the desired shape, provide the dimensions, and click the "Calculate" button. The "Area" tab is for projects of known area and thickness.

Types of concrete available

There are many different types of concrete available. The terms concrete and cement are often used interchangeably, but the two are not the same. Cement is a dry powder, that when mixed with water, binds materials together; the most common kind of cement used to make concrete is called Portland cement.

Concrete is a composite material made up of cement, water, and aggregates like sand and gravel. The mixture of the components determines properties of the concrete such as strength, durability, workability, resistance to heat and radiation, and more. Below are some of the types of concrete that result from different mixes.

Ordinary concrete:

Ordinary, or plain concrete, is the most commonly used type of concrete. It is made using a ratio of cement:sand:coarse aggregate of 1:2:4 and has a durability that makes it suitable for light to medium construction projects such as pavements, roads, or buildings that do not require high tensile strength (amount that something can be stretched or pulled before breaking).

Ordinary concrete is available in pre-mixed bags. Most other concretes are available typically as ready-mix concrete, or may instead be mixed on site. There are also a variety of pre-mixed bags of concrete that are used for different purposes. Bagged concrete requires you to mix the concrete with carefully measured amounts of water, pour it, then allow it to set and firm up over time. A typical 80-lb bag of concrete will be strong enough to support weight in approximately 24-48 hours, but will take around 28 days to fully dry and reach its full strength. Note that when buying bagged concrete, it is recommended to buy approximately 5-10% more than you will need. This is because there will likely be some waste, so it is advisable to have an excess of concrete to ensure that any waste does not leave you with too little concrete.

Bagged concrete differs from ready-mix concrete in that ready-mix concrete is prepared off-site at centrally located concrete plants, where the mix is produced in a highly controlled environment to very precise specifications. The mix is then transported in cement trucks to a given work site, where the cement can be immediately used, since it requires no further treatment. It is important that the plant is not too far from the work site. If it takes too long for the concrete to reach the work site, it may set too early and be unusable. Ready-mix concrete can be used for many more applications than bagged concrete since its strength and other properties can be very carefully controlled, while bagged concrete can have variations, but to a much lesser degree.

Lightweight concrete:

Concrete that has a density below 1920 kg/m3 is classified as lightweight concrete. It is also referred to as low-density concrete. Its low density makes it easy to level due to its consistency, but also means that it has lower strengths than higher density concretes. Lightweight concrete also has low thermal conductivity. Thus, heat does not transfer as well through lightweight concrete as it would through materials such as metal. This makes lightweight concrete useful for protecting structures made out of materials such as steel, constructing floor slabs, roofs, window panels, and more.

High-density concrete:

High-density concrete, also referred to as heavyweight concrete, is concrete that has density values between 3000-4000 kg/m3. The high density of the concrete makes it difficult to mix and manipulate, but results in high strength concrete that is suitable for large structures, even those that emit radiation, such as atomic plants. The high density of the concrete prevents radiation from passing through the concrete, safely containing radiation within appropriate spaces. High-density concrete is typically costly and requires professionals to mix the concrete.

Precast concrete:

Precast concrete is concrete that is prepared and cast, typically in a concrete plant, under highly controlled conditions. Precast concrete is usually used when the project requires concrete made to very precise specifications, which involves carefully controlling proportions and the mixing process. It is commonly used to fabricate walls, beams, tunnels, columns, staircases, concrete blocks poles, and more.

Concrete curing

Concrete curing is the process of maintaining the moisture of freshly poured concrete in order to facilitate hydration, which allows concrete to properly harden and strengthen. Concrete that is properly cured will reach its maximum strength and durability and should not crack. The curing process also helps to protect concrete surfaces from erosion.

How long does it take concrete to cure?

The duration of the curing process differs to some degree based on the type of concrete used. Generally, most concrete mixes will be strong enough for people to walk on the surface within approximately 24-48 hours after it is poured. Within 7 days or so, concrete should be able to handle heavier loads, such as vehicles and equipment. By about 28 days, most concrete mixes should reach approximately 90% of its strength. From this point on, concrete will still strengthen over time, but at a much slower rate on the order of years, or even decades.

Factors affecting curing:

Curing is mostly dependent on moisture, but it is also affected by temperature. Especially during the first few days after being poured, it is important to ensure that the concrete has sufficient moisture for the hydration process. Otherwise, the hydration process will not occur properly, and the concrete will not be able to reach its maximum strength. Concrete that does not have enough moisture during the curing process is susceptible to early shrinkage, which can crack the concrete. On the other hand, concrete that contains too much moisture during the curing process can also weaken the concrete. It is therefore important to balance the amount of moisture in the concrete.

If the weather is hot and dry, it is likely necessary to maintain more moisture in the concrete than normal. This is because the hot and dry weather will make the concrete more susceptible to drying out more quickly, which as mentioned above, can lead to early shrinkage and cracking. Having a shelter above the concrete in these conditions can prevent the concrete from drying more quickly than normal.

Freezing temperatures also affect the curing process. It is important to take measures to cover and insulate the concrete if temperatures are below freezing, especially in the first few days of the curing process. If the concrete freezes or cools too rapidly, it will lead to cracking, which will weaken the concrete.

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