What are the types of Concrete and their uses?

There are different types of concrete. Based upon the requirement of project, different types of concrete are, ready-mixed concrete, high-performance concrete, self-compacting concrete, lightweight concrete, autoclaved aerated concrete, fibre reinforced concrete, ultra-high-performance concrete, ferrocement, polymer concrete, prestressed concrete and slurry infiltrated fibrous concrete.

Concrete can come in two variations depending on the location: site-mixed or pre-mixed (also called as ready mixed). Mixing concrete at the site is not advised since it may not be mixed properly and its water/cement ratio cannot be thoroughly regulated. Hence, it is mainly applied to those areas where Ready Mixed Concrete isn’t accessible easily.

Plain concrete is concrete without reinforcement. Whereas, reinforced concrete is concrete with reinforcement. Concrete is good for compression but not for tension so reinforcements are used to counter this tensile force and avoid cracking. Reinforced Concrete is the primary material utilized in structures due to its greater strength in tension zones. Therefore, it is the best option for construction of many structures.

After 28 days, the strength of concrete can be classified as ordinary, standard or normal, and ultra-high-strength. This allows us to use the right type of mix for the project based upon the required strength.

High-performance concrete (HPC) is a type of cement with superior technical properties compared to traditional concrete. One particular kind of HPC is Self-compacting concrete, which can be compacted without the use of vibrators and with certain added ingredients. Structural engineers should work towards attaining HPC by finding the right combination of ingredients and also taking advantage of chemical and mineral admixtures.

Fibre-reinforced concrete (FRC) is formed by adding fibres to the concrete mix. It is an effective way to regulate cracking due to plastic shrinkage, drying shrinkage, which can otherwise damage the structure of the building.

High-performance FRCs are referred to as ductile fibre-reinforced cementitious composites, ultra-high-performance concretes and engineered cementitious composites. These materials provide increased strength and flexibility compared to traditional concrete. To lower the total weight of a structure or when aggregate availability is limited, lightweight aggregates can be used to create Structural Lightweight Concrete or Autoclaved Aerated Concrete. This article provides a brief overview of different types of concrete mixtures and uses of concrete.

1. Ready-Mixed Concrete

Ready-mixed concrete is an excellent choice which is why it has gained popularity in recent years. It is one of the different types of concrete mixtures. It is made up of a standardized mix design created in a factory or batching plant and delivered to the job site by truck-mounted transit mixers. This helps reduce time and effort, allowing the construction workers to get the job done quickly and efficiently.

Ready-mix concrete is becoming a popular choice in the construction industry because of its accuracy and high quality standards. It is being used to build bridges, flyovers, as well as large commercial and residential projects.

For efficient production, ready-mixed concrete plants should be equipped with the most current equipment like transit mixer, concrete pump and batching plant. Its production occurs under computer-controlled operations and afterward, it is placed at its site with advanced equipment & techniques.

One of the main issues with using ready-mixed concrete is that the distance from the central plant to where it’s needed can be a problem. To ensure the highest quality, it is best to have the material delivered within 90 minutes of being mixed at the plant. Using admixtures in concrete can help to reduce the amount of time taken for it to set and harden, but the characteristics may vary depending on the admixture used and its quantity.

2. High-Performance Concrete

High-Performance Concrete (HPC) is one of the different types of concrete mixtures. that offers enhanced performance properties for specific uses. It is hard to define HPC without specifying the purpose and performance desired for the given application.

ACI has classified HPC as any combination of performance-based requirements and uniformity criteria that cannot be obtained through conventional materials, mixing, placing and curing techniques. In other words, HPC allows for larger-scale projects to be completed with precision and consistency.

A wide range of parameters need to be considered for successful completion of construction projects, ranging from easy placement and compaction without segregation to long-term mechanical properties and heat of hydration. Other factors such as permeability, density, toughness, volume stability and service life in difficult conditions also have to be taken into account.

High Strength Concrete (HSC) and High Performance Concrete (HPC) are two different types of concrete, with HPC having superior strength characteristics. Typically, HPCs will have strengths greater than 50-60 MPa, making them extremely strong and reliable materials. Even though HSCs are not necessarily classified as HPCs, they can still exhibit impressive levels of strength.

HPCs are created using only top-grade ingredients that are expertly combined for optimal performance. The entire process of batching, mixing, placing, compacting and curing is rigorously monitored to make sure the quality standards are met. This way, the finished product has all of the desired characteristics it needs. Generally, these types of concrete have a water-cement ratio ranging from 0.22 to 0.40, which is rather low.

Superplasticizers are commonly used in making workable concretes. It is worth noting that without these chemical additives, the water/cement ratio cannot go below 0.40, making its usage essential. By utilizing a much lower amount of water, the particles in cement get more compact and create a stronger cement matrix than normal strength concrete. This has a huge impact on the strength of the concrete.

Particle-packing formulation is one of the most efficient techniques to develop a stronger and longer lasting design mixture with cement content below 300 kg/m³. Its compressive strength lies between 70 to 80 MPa, which is enormous.

By crushing the parent rock, the smaller particles of coarse aggregates become more durable than larger ones. This process removes those weaker regions, making the end product much stronger. For concrete with a strength greater than 100MPa, the biggest size of aggregate should be restricted to 10-12mm. Where strength is lower though, 20mm aggregates are allowed.

HPC requires clean, strong crushed aggregates with cubic shapes and minimal elongation and flake formation. These aggregates are usually derived from fine-grained rocks which provide the desired shape. To ensure appropriate packing of particles in the mix, increasing cement content should be accompanied by using coarser-graded fine aggregates with a fineness modulus of 2.7–3.0.

HPC has very little water in it, so it’s essential to properly cure HPC at the earliest. Fog curing or wet curing are ideal for curing HPC as opposed to membrane curing which is not suitable for this concrete mix. This will help to limit plastic and autogenous shrinkage cracking.

High Performance Concrete has a great ability to resist compressive and tensile forces, making it an ideal choice for constructing structures such as tunnels, bridges, offshore structures, chimneys and more. It is also highly durable in aggressive environments that involve the usage of sewerage pipes or tall buildings. The modulus of elasticity it provides adds to its attractiveness.

HPC has found many applications such as shotcrete repair, poles, parking garages and agricultural uses. However, during severe fire cases, the cement paste bursts and can cause concrete spalling.

3. Self-Compacting Concrete

Self-compacting concrete, is one of the types of concrete, also referred to as high-workability, self-consolidating or self-levelling concrete, was innovated by Prof. Okamura and his team at the University of Tokyo in Japan back in 1988. It is a type of High Performance Concrete.

Self-Compacting Concrete (SCC) is the perfect choice for structurally complex elements that require dense reinforcement. It has the remarkable ability to flow and fill all the voids on its own, without requiring external help like vibration or other forms of mechanical consolidation. Additionally, it does not cause segregation, excessive bleeding or air migration.

SCC is famed for its exceptional flowability, which can be attributed to its precise mix proportions that involve replacing most of the coarse aggregate with fines, cement and incorporating chemical admixtures. Plus, it is easily manufactured either in a batching plant or in RMC factory and transported to the job site through a truck mixer. Superplasticizers based on polycarboxylic esters, are used to provide fluidity. This modern solution allows for better water reduction rate and slower slump loss than traditional superplasticizers.

The concrete may be poured into horizontal or vertical forms, however it can also be pumped if necessary. Achieving stability in a fluid mix can be done by either increasing the fine particles content or through the addition of viscosity-modifying agents.

As SCC use has become more prevalent, multiple tests have been developed to assess the appropriateness of a mixture. These include the slump flow test, V-funnel and Orimet, which focus on flowability and filling ability.

It is worth noting that the slump flow test measures flattening of concrete horizontally, rather than measuring vertical slump as in conventional slump tests. Also, passing ability (L-box, J-ring, an alternative to U-box), durability, and segregation resistance or stability test (column box test, sieve stability test) is an important part of assessing the effectiveness of SCC.

4. Structural Lightweight Concrete

The Pantheon is one of the few ancient structures from the Roman Empire that has managed to survive the test of time, and it is made up of lightweight concrete. Lightweight concrete, is one of the types of concrete, technology has been around since the early 1900s, when Steven J. Hayde from Kansas City, Missouri first developed a process for expanding clays, shales, and slates using a rotary kiln. Since then it has become much more popular and widely used in the modern age.

Structural lightweight concrete is primarily composed of lightweight materials like natural pumice, scoria aggregate, expanded slag, sintering-grate expanded shale/clay/fly ash and rotary-kiln slates/shales/clay.

Structural lightweight concrete has a lower density than that of normal weight concrete, ranging from 1360 to 1850 kg/m3 instead of 2240-2400 kg/m3. They must be stronger than 20 MPa in order to be used for structural applications. The implementation of structural lightweight concrete gives us the opportunity to reduce the weight of concrete components, eventually resulting in overall financial savings.

The cost of structural lightweight concrete (SLWC) may be higher than traditional concrete, but the money saved from reducing the mass of concrete makes up for it. Furthermore, seismic performance improves significantly since the lateral & horizontal forces acting on a building during an earthquake are proportional to the building’s mass.

For nearly 80 years, structural lightweight concrete has been implemented in numerous areas due to its advantages. The ACI code even considers the reduced strength of structural lightweight concrete and multiplies it by factor alfa during design.

Autogenous shrinkage and self-desiccation are main problems of SLWC. Internal curing is a useful strategy employed to counter the issues of autogenous shrinkage and self-desiccation. Autogenous shrinkage describes the change in volume of concrete that takes place without any moisture loss to its external environment.

Autogenous shrinkage is associated with self-desiccation during the hardening process of concrete which results from the cement reacting with water. This occurrence is known as internal drying. Reacting with water and solids, the total aggregate volume reduces. Additionally, lightweight aggregates are porous and provide a source of internal healing for the concrete, leading to improved strength and durability. This process is known as internal curing. Nevertheless, external curing remains necessary.

 5. Autoclaved Aerated Concrete

Autoclaved aerated concrete, also referred to as autoclaved cellular concrete (ACC) or autoclaved lightweight concrete (ALC), is a ground-breaking invention dating back to the 1920s. It was created by Swedish architect Johan Axel Eriksson and has commercial names such as Siporex, e-crete, and Ytong.

Precast building materials offer strength, insulation, fire, mould and termite resistance. Additionally, they are light-weight as well as inorganic and non-toxic. Therefore, they are indeed the perfect choice for construction work. AAC is not as prevalent in the USA, India, Australia, and China compared to other countries like the UK and Germany. In fact, it accounts for over 40% of all construction jobs in UK and more than 60% of construction works in Germany.

Autoclaved aerated concrete is a precast product that uses a combination of quartz/silica sand or recycled fly ash, cement, lime, water and an aluminium powder expansion agent at the rate of 0.05-0.08%. It’s important to note that this method does not include any coarse aggregates. When aluminium powder is combined with calcium hydroxide and water, a reaction takes place that results in the expansion of concrete up to five times its original size.

The hydrogen created during the reaction evaporates quickly, leaving behind an aerated concrete structure with a high density of closed cells. After the material has been stripped of its forms, it remains in a solid but in pliable state. It subsequently gets cut into blocks or panels which are then put into an autoclave chamber for 12 hours.

AAC blocks are an alternative to the more traditional CMU construction. These pre-fabricated blocks measure approximately 600mm x 200mm x 150 mm and can be easily stacked together without the need for mortar. This method of construction is time-saving and cost effective.

6. Fibre-Reinforced Concrete

Adding fibres to concrete is an effective way to reduce cracking, particularly due to plastic and drying shrinkage. The addition of small, even fibres to concrete can make it more resistant to cracking, fatigue, impact, and abrasion. It can also lower the permeability of the material. This helps ensure that concrete is strong and durable in challenging conditions. Although fibres may slightly increase flexural strength, they cannot fully replace flexural steel reinforcement. The idea of using fibres for reinforcement is nothing new; it has been around since ancient times with the use of horsehair in mortar and asbestos fibres in concrete as examples.

When it comes to special applications, FRC (Fibre Reinforced Concrete) is becoming increasingly popular due to certain advantages. This concrete contains a variety of fibres such as steel, glass, polypropylene, carbon and basalt that contribute to its enhanced properties. Of all the types of fibres used in FRCs, steel fibres are the most common; these may be crimped, hooked or flat.

The amount of fibres used when making concrete is expressed as a percentage of total composite volume, often referred to as the Volume Fraction (Vf). This can range from 0.25% to 2.5%, with 0.75-1.0% being the most commonly used fraction for fibre inclusion in concrete mixes. Fibres come in different sizes, with the aspect ratio being the ratio of their length to their diameter. Generally, it’s between 30 and 150. As far as steel fibres are concerned, they range from 0.25 mm to 0.75 mm in diameter.

Increasing the aspect ratio can enhance flexural strength and toughness of the matrix material significantly. It’s important to note that long fibres can cause issues when mixed and interfere with workability. Thus, it’s recommended to use superplasticizers in order to achieve satisfactory workability. Furthermore, the tensile strength of steel fibres needs to exceed 350 MPa.

7. Ultra-High-Performance Concrete

Ultra-high-performance concrete (UHPC) is an excellent material for a variety of applications. It is extremely strong, stiff and self-consolidating, and has good ductility. Its formula consists of Portland cement, silica fume, quartz flour, fine silica sand, high-range water reducer, water and either steel or organic fibres. Multi-scale fibre-150 reinforced concrete was first developed by Laboratoire Central des Ponts et Chaussées, France. It is made up of a combination of both long and short metal fibres.

It is important to note that UHPC doesn’t use coarse aggregates, while they are common in normal strength concrete (NSC). Additionally, the water-to-cement ratio of UHPC is much lower than NSC which has a range of 0.4 – 0.5.

This substance can exhibit compressive strengths ranging from 120 to 240MPa, flexural strengths of 15-50MPa, and post-cracking tensile strength in the range of 7.0 -10.3MPa with a modulus of elasticity that spans 45GPa to 59GPa. UHPC is renowned for its superior strength and resilience, and this can be attributed to its finely-graded particles that create a denser mix, reinforced with steel fibers and using very minimal water-to-powder ratio.

UHPC has a diverse range of uses, from prestressed girders and precast deck panels in bridges to columns, piles, claddings, overlays and noise barriers in highways. All these applications can be extremely beneficial to the infrastructure industry. A remarkable achievement in architectural engineering, the 60 m span pedestrian bridge in Sherbrooke, Quebec (built in 1997) was the world’s first Ultra High Performance Concrete bridge without steel reinforcement.

Shepherds Creek Road Bridge in New South Wales, Australia, which was completed in 2005, is the first highway bridge to use Ultra High Performance Concrete (UHPC). Since then, many bridges and other constructions have been made with UHPC worldwide.

Manufacturers offer UHPC mixtures that come pre-mixed in three components – powders, superplasticizers, and organic fibres. The powders are typically composed of Portland cement, silica fume, quartz flour and fine silica sand. Care should be taken when mixing, placing and curing concrete. Its ductile nature allows it to flex or bend under loads after initial cracks appear, helping it take the strain of tensile and flexural forces. With this sturdy material, reinforcing steel is not necessary during construction. Furthermore, the material can be easily placed on its own and hence simplifying the building projects.

8. Ferrocement

Ferrocement, which dates back to the 19th century when it was invented by Jean Louis Lambot from France, is a composite material much like Reinforced Cement Concrete (RCC). In RCC, steel bars are embedded in the tension zone for reinforcement, whereas ferrocement is based on a thin RC matrix of cement and sand (in a 1:3 ratio) reinforced by closely-spaced layers of small diameter wire mesh, welded mesh or chicken mesh. Mesh can be constructed with either metallic or synthetic materials; and the diameter of the wires used can range between 4.20 mm and 9.5 mm, at maximum spacing of 300 mm apart.

The mortar matrix must have a good consistency that allows for smooth application and will be hard-wearing to ensure its durability. Incorporating pozzolanic mineral admixtures, such as fly ash (getting a 50% replacement of cement), as well as using superplasticizers can help lower the water–binder ratio down to 0.40–0.45 by mass. This will not only facilitate easier construction but also greatly enhance the durability of the concrete matrix. It is suggested that a mortar compressive strength of 40–50 MPa is desirable.

Pier Luigi Nervi was a ground-breaking engineer, architect, and contractor who revolutionized the world of construction during the 1940s. His innovation, ferrocement, allowed for the construction of aircraft hangars, boats and buildings at a fraction of the cost and with greater strength than traditional materials. This breakthrough has since then adopted by many industries in both residential and commercial applications.

It is worth noting that though Nervi’s designs incorporated extensive mesh reinforcement, many modern day uses of this technique only require two layers for adequate reinforcement. Ferrocement is incredibly useful and its applications include a host of structures like vessels, pipes, biogas digesters, septic tanks, water storage systems, dual purpose toilet blocks and even entire houses.

Recently, ferrocement panels have been used as an effective load-bearing formwork for slabs that are either single or double-way. This type of panel offers several economic advantages and makes the slab’s serviceability performance exceptional. The iconic Sydney Opera House has had its roof sails covered with ferrocement panels, which provide a waterproof layer for the underlying reinforced concrete. This new addition to the iconic building has had a great panel effect.

9. Polymer Concrete

Polymer concrete is created by saturating traditional concrete with a monomer and then polymerizing it through radiation, heat, catalytic elements or a mixture of both. This process has become increasingly popular due to its improved properties over ordinary cement-based materials. Polymeric materials can be categorized into three groups based on their incorporation process:

(a) Polymer Concrete

(b) Polymer Impregnated Concrete

(c) Polymer Modified Concrete

Polymerization leads to improved material properties, making it possible to use polymer concrete for the repair of deteriorated concrete structures. This provides a cost-effective solution and enhances the strength of construction components.

10. Prestressed Concrete

Aside from the conventional concrete, prestressed concrete is commonly seen in bridges and long-span structures. A prestressed concrete member is built to handle external service level loads. To do this, compressive stresses are introduced internally which reduce the tensile forces that these loads cause.

Prestress is often achieved through tensioning the high-strength steel reinforcement, utilizing either pre-tensioning or post-tensioning methods to apply pre-compression to the member.

11. Slurry Infiltrated Fibrous Concrete and Slurry Infiltrated Mat Concrete

Lankard developed Slurry Infiltrated Fibrous Concrete (SIFCON) back in 1979. Reinforced Concrete formwork is made by combining cement slurry (using 1:1, 1:1.5 or 1:2 ratio of cement, sand and adding 10-15% fly ash and silica fume by weight of cement, 0.3-0.4 water/cement ratio and 2-5% superplasticizer) with pre-positioned steel fibres.

It is importance to note that this material does not have any coarse aggregates and is quite high in cement-based materials. Additionally, the pre-placement of fibres can increase the volume of fibres as high as 6–20%.

Structural integrity is highly ensured in SIFCONs due to being built with numerous fibres. This helps both compressive strengths and tensile strain hardening behaviour reach satisfactory levels between 90 MPa and 210 MPa.

Slurry Infiltrated Mat Concrete (SIMCON) is designed to provide the same levels of ductility as SIFCON and is thus ideal for seismic retrofit applications. However, it uses pre-placed fibre mats instead of steel fibers. Both SIMCON and SIFCON remain extremely ductile despite the difference in construction materials.

Not only do these materials offer an increase in uniaxial tensile strength, flexural and shear strength, as well as greater impact and abrasion resistance. SIFCON is an ideal solution for numerous applications ranging from pavement renovation to safety vaults, refractory applications, bridge decks/overlays, restoration and renovation of structures in seismic areas as well as military and mega-structures.

Read More:

What are the Advantages and Disadvantages of Reinforced Concrete ?

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