Rapid-strength concrete: As the name implies, rapid-strength concrete becomes strong within a few hours after being prepared. It guarantees that buildings and roads are built quickly. Road rehabilitation is one of the most prevalent uses for rapid-strength concrete. When used in this application, it usually takes less than a year before you have to recast the damaged pavement.
Conventional concrete: Conventional concrete can be used as long as it's not needed immediately. It can be mixed and placed at home or in a ready-mix truck delivery service facility. It can also be mixed at the job site with additional materials such as sand and stone. This type of concrete can last for many years if properly maintained.
It's important to note that although rapid-strength concrete is better for road repairs, conventional concrete is still necessary for major projects because it has greater strength when it's set. Also, rapid-strength concrete is more expensive than conventional concrete because it requires more material per batch and produces fewer free-flowing particles.
The best type of cement for any application depends on how long you expect the concrete to stay in place. If you need it fast-acting but not permanent, use rapid-strength concrete. If you want it to last longer, use conventional concrete.
Cement is best suited for larger tasks, whilst concrete is best suited for smaller operations. Concrete, one of the toughest and most durable materials known to man, is used to construct schools, bridges, sidewalks, and countless other structures. It is estimated that there are more than 30 million square feet of concrete pavement in urban areas alone!
Concrete is a mixture of water, gravel, sand, aggregate, cement, and additives. The two main types of concrete are ordinary concrete and pre-cast concrete. Ordinary concrete can be mixed at the site and usually requires additional ingredients such as plasticizers, fiber additives, or accelerators to allow it to set up within an acceptable time frame. Pre-cast concrete is molded in molds at a factory location and then transported to the job site where it is un-molded and finished off with an additive to ensure easy release from the mold. Pre-cast concrete is used for large-scale projects like highways, bridges, and buildings because it saves time and money compared to ordinary concrete which must be poured one section at a time.
Sidewalks are part of the street surface and require maintenance just like any other road surface. They are also prone to some unique problems that only make sense when you consider how much traffic they must withstand every day.
Highly workable concrete is a more fluid mixture that is simple to mix, transport, put, and compress. This type of concrete is typically utilized in situations when adequate concrete compaction is not possible, such as in mass concrete. It flows effortlessly and settles with little effort. Its weakness is its lack of durability; high temperatures and humidity cause the cement paste to dry out and the voids within the concrete to expand, causing it to deteriorate.
Concrete that is workable but not highly workable can be difficult or impossible to compact by hand, requiring the use of equipment for forming a flat bed of concrete. This type of concrete is suitable for applications where smooth, even surfaces are required and compacting would be impractical or impossible due to surface conditions (i.e., gravel roads). It has greater durability than highly workable concrete because there are fewer voids to fill with water.
Concrete that is moderately workable can be worked by hand or with minimal equipment. It is the most common type of concrete and suitable for most applications.
As you can see, there is more than one reason why concrete might be considered "workable." The main thing to remember is that if you cannot adequately compact the concrete, it was probably made too stiff. Follow the guidelines below to ensure you get the right kind of concrete for your project.
High early strength concrete (2500–3500 psi compressive strength in 24 hours) is often achieved by utilizing Type III high-early strength cement (see Table 1), a high cement content (600–1000 lb/cu yd), and lower water-cement ratios (0.3 to 0.45 by weight). High-early strength cements have higher calcium carbonate contents than standard strength cements (which typically have calcium carbonate contents of 15%–20%). The higher carbonate content results in greater pH levels during hydration, which leads to the formation of more reactive calcium carbonate species that contribute to early strength.
Type III cements have a maximum aluminum content of 3%. Higher amounts can affect the setting time of the concrete. Iron and zinc may be present as impurities. These elements are usually not a problem but if they are then Type I or Type II cements should be used instead.
Type IV cements have a minimum calcium carbonate content of 20%. They are used when ultrahigh early strength is necessary. These cements are very expensive and only available from a few manufacturers. Examples include Super-Early Cement and Vulcan Cement.
Type V cements have a minimum calcium carbonate content of 35%. They are used when extra-high early strength is necessary. Examples include Maximus VI and Thermatech Ultra-High Performance Cement.
The compressive strength of high-strength concrete is more than 40 MPa (6000 psi). In the United Kingdom, BS EN 206-1 defines high-strength concrete as having a compressive strength class more than C50/60. To make high-strength concrete, reduce the water-cement (W/C) ratio to 0.35 or below. This reduces the amount of cement in the mix and increases the amount of sand and gravel used as aggregate.
Concrete's tensile strength depends on the quality of the aggregate and the type of cement used. Concrete with good quality aggregate and a Type 1 or Type 2 ordinary cement will have a tensile strength of at least 20 MPa (3000 psi). Concrete with poor quality aggregate or a Type 30 cement will be much weaker—about 5 MPa (700 psi). High-strength concrete has a tensile strength of at least 45 MPa (6,500 psi), which is enough to resist common loads such as people walking on it.
Compressive strength determines how long a slab will last before it needs to be repaired or replaced. Slabs that are thicker or wider than required for a given application will age more quickly because more material is involved in each load step. For example, a concrete floor that is too thick for its use factor will need to be resurfaced every few years instead of once, like a slab that is the correct thickness.
High-strength concrete is used in many applications where resistance to compression is important.
Let's start with the basics: concrete is far more powerful than cement. Cement is a strong substance in its own right, but it pales in comparison to concrete. Cement is composed of calcium and silica-rich elements, which makes it prone to breaking on its own. Concrete, on the other hand, is made from cement mixed with sand and gravel, which gives it greater strength and durability.
Now, what are the advantages and disadvantages of cement versus concrete? Cement is easy to work with and inexpensive, while concrete requires special tools for mixing and shaping. Concrete is strong and durable, while cement can only be as strong as its weakest link. Cement will always let you down if you use bad practices like using old or damaged materials, while concrete can withstand many things so long as it is done properly. Cement will always get the job done, but if you need something permanent, then concrete might be your best option.
So, cement is better for small projects because it's easier to work with, while concrete is better for large projects because it can handle more stress. Both are useful materials that can be used for different applications. As a rule of thumb, if you need something fast-acting and temporary, use cement. If you want something lasting, use concrete.