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Special Concrete – Types, Advantages and Disadvantages

Recent advancements in construction technology have resulted in concretes that have almost surmounted these constraints and are close to optimal circumstances. Modifying the microstructure of the cement paste, inducing more air to make it lighter, allowing flexibility in reducing or raising the setting pace, and so on are some of the ways used to improve its qualities.Concrete’s versatility allows it to be used for a variety of applications. However, it has several disadvantages, including low tensile strength, reinforcement corrosion, and vulnerability to chemical attacks, all of which limit its endurance.

What is Special Concrete?
“Special concrete” is described as “concrete that must meet special performance and consistency standards that are not always met by normal materials and mixing, installation and curing processes.”.” Technology is used to improve its special features that are helpful for specific types of work, such as structures, where lightweight concrete is favored for roofs to save money while maintaining the aesthetic element while taking into account the surroundings.

Fig 1- Special Concrete
Fig 1: Special Concrete
Courtesy: aboutcivil.org

Types & Properties of Special Concrete

Lightweight Concrete:
Lightweight concrete is constructed of lightweight coarse materials like shale, clay, or slate, which give it a low density. Lightweight structural concrete has 90 to 115 lb/ft3. As a result, lightweight concrete is excellent for modern constructions with small cross-sections in the foundation It’s becoming more popular as foundation material, and it’s proving to be a viable alternative to normal concrete. On the other hand, lightweight concrete can have a compressive strength of 7000 to 10,000 psi. However, because it necessitates the addition of extra pozzolans and water-reducing admixtures to the concrete, this may weaken the mixture’s density. The Bank of America Building in Charlotte, North Carolina, is one of the most well-known structures made of lightweight concrete.

Fig 2- Lightweight Concrete
Fig 2: Lightweight Concrete

Ultra-Lightweight Concrete
Fig 3- Ultra-Lightweight Concrete
Fig 3: Ultra-Lightweight Concrete
Courtesy: specialconcretesolution.com

The density of this type of concrete is between 600 and 1000 kg/m3. It comprises cement, sand, and expanded polystyrene beads with a diameter of 6 mm. It is made by a polymerization method that requires spreading liquid styrene and a polymerization catalyst in an aqueous solution.

Mass Concrete:
Fig 4- Mass Concrete
Fig 4: Mass Concrete
Courtesy: concretecivil.com

The volume of concrete is large enough to require methods to cope with heat from cement hydration and the resultant volume change. Thermal behavior is the only feature that distinguishes mass concrete from other types of concrete work. The cement-water reaction raises the temperature within a huge concrete mass, which can be fairly high if the heat is not dispersed. The restricted volume change associated with a drop in temperature when the heat of hydration dissipated may cause significant tensile stresses and strains. The Bank of America Building in Charlotte, North Carolina, is one of the most well-known structures made of lightweight concrete.

Vacuum Concrete:
Fig 5- Vacuum Concrete
Fig 5: Vacuum Concrete
Courtesy: altasouthwaeast.com

Vacuum concrete is a mixture of concrete in which the surplus water has been evacuated to increase the strength of the concrete. Vacuum mats attached to a vacuum pump are used to remove the water. In the form-works, a concrete mix with good workability is normal. The application of a vacuum to the surface concrete results in a considerable quantity of vacuum to the surface of the concrete because fresh concrete comprises a system of water-filled channels. As a result, a considerable amount of water is drained from the concrete at a specific depth. A vacuum is created by connecting porous matting to a vacuum pump. Vacuum concrete has a stronger strength, density, lower permeability, and improved durability since the final water-cement ratio before setting is lowered.

Roller Compacted Concrete:
Fig 6- Roller Compacted Concrete-
Fig 6: Roller Compacted Concrete:
Courtesy: civilplanet.com

Roller-compacted concrete comprises cement, aggregates, water, and, in some situations, water-reducing additives. It stiffens the mixture and gives it the consistency of moist gravel. Because the water content of such concrete is minimal, it is put continually. Compaction of the concrete requires a customized asphalt paver and roller. It possesses the strength and properties of traditional concrete.

The roller-compacted concrete is laid out in thin layers that allow thorough compaction. The ideal layer thickness is between 20 and 30 cm. A high plastic concrete from developing countries’ bedding mix at the installation ensures proper bonding between the new and old layers. It is necessary to obtain a compressive strength of between 7 and 30 MPa. Roller compacted concrete must be both dry enough to sustain the mass of the vibrating machinery and sufficiently wet enough to allow the cement paste to disperse throughout the mass during the mixing and consolidation process for optimal consolidation.

Fibre-Reinforced Concrete:
Fig 7- Fibred-Reinforced Concrete-
Fig 7: Fibred-Reinforced Concrete:
Courtesy: civilplanet.com

Fiber Reinforced Composite Mixture of cement is a fibrous material that adds structural strength. It consists of cement, mortar, or concrete mixed with appropriate fibers that are discontinuous, distinct, and uniformly scattered. Fibers are commonly used in concrete to prevent cracking caused by shrinkage of the plastic and drying shrinkage.

Shotcrete:
Fig 8- Shotcrete
Fig 8: Shotcrete
Courtesy: ataneconsulting.com

Shotcrete is usually one part cement and four parts sand by weight, with around 7% water in the dry materials. It can also comprise admixtures and coarse aggregate. Dry mix shotcrete is made by mixing dry ingredients and adding water to the nozzle. All materials, including water, are premixed in wet-mix shotcrete. One of the benefits is the capacity to lay concrete on irregular, vertical, and overhanging surfaces that are difficult or expensive to create. Materials can be blended and pumped over large distances to where needed. The limits are the dependence on the nozzle man’s competence and training for a good application and the dust and rebound that occur during the application.

Nuclear Concrete:
Fig 9- Nuclear Concrete-
Fig 9: Nuclear Concrete:
Courtesy: scbiznews.com

Nuclear concrete is used for effective radiation shielding. Different chemicals, such as colemanite, boron glass, and borocalcite, are sometimes added to concrete to boost its neutron attenuation capabilities.

Uses of Special Concrete:

Advantages of Special Concrete:

Special Concrete Cost-Benefit Analysis;
Fiber-reinforced concrete has a high starting cost when utilized as translucent concrete. However, some businesses have devised a solution. An economic building can be considered if fiber reinforced concrete is constructed from naturally available, low-cost fibers. Furthermore, while air-entrained concrete uses fewer raw materials to manufacture, the method is more expensive than traditional concrete. The application and purpose primarily determine it. In short, it is cost-effective in the long run because it requires little maintenance and requires less labor to install. On the other hand, regular families may not prefer special concretes high initial cost since they would likely prefer to repair conventional concrete rather than use special concrete, despite its durability.

Conclusion:
However, because the mechanism is costly, more research is needed before being used widely. Special concretes are extensively employed in affluent countries because the cost is not a key consideration. Because of their special properties, special concretes are slowly gaining traction in the construction industry. , It is, nonetheless, a significant role in developing and developing countries. They are commonly employed in large industries since durability is more important than cost. Aside from these, it’s a good idea to employ unique concrete forms because it has modified features that overcome ordinary concrete’s flaws. Special concretes can also make houses safer by improving their properties. In earthquake-prone areas, such constructions will be extremely beneficial.

References:
1. Mass Concrete Topic. (n.d.). Mass Concrete Topic. https://www.concrete.org/topicsinconcrete/topicdetail/Mass%20Concrete?search=Mass%20Concrete.
2. Posts By Kishan Mudavath, V. A. (2018, September 12). What Is Special Concrete? & Types Of Special Concretes. – We Civil Engineers. we civil engineers. https://wecivilengineers.wordpress.com/2018/09/12/what-is-special-concrete-types-of-special-concretes/.
3. Fiber-reinforced Concrete – Advantages, Types, And Applications. (2020, July 24). Constro Facilitator. https://www.constrofacilitator.com/fiber-reinforced-concrete-advantages-types-and-applications/.
4. Author, G. (2021, January 13). Types Of Special Concrete: Uses, Advantages & Properties.GharPedia.https://gharpedia.com/blog/types-of-special-concrete-and-its-uses-advantages-properties/.
5. Shotcrete: What Is It & Why Is It Useful? | Easy Mix Concrete Services LLC. (2018, August 31). Easy Mix Concrete Services LLC. https://www.easy-mixconcrete.com/news/shotcrete-what-is-it-and-why-is-it-useful/.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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