What is concrete?

Concrete is the fundamental material used in civil engineering such as building materials for building structures. Concrete is an aggregate mixture of cement, sand, and fine and coarse rock pieces. The cement acts as a binding material that holds the compositions together, sets, and hardens with time. Apart from cement, there are other different types of binding materials used, such as lime concrete, bitumen, asphalt, and so on.

The main constituent in a concrete mixture is the cement which is a finely powdered substance that typically hardens due to water hydration and so it is also known as hydraulic cement. Concrete is separately studied as a separate branch of civil engineering, known as concrete technology. Concrete has many uses and they are mainly used for the construction of foundations, columns, slabs, beams, and the majority of load-bearing structures.

Cement, as the major constituent of concrete

Cement acts as the binding material and a primary constituent of concrete. It appears grey, having its constituent materials in powdered form. Cement is mainly processed in mills with limestone, clay, and marl as its primary constituents.

Cement is used to produce two forms of mixtures, concrete, and mortar. In both cases, water forms the main primary agent to set up the hardness. To create a mixture of mortar, sand, water, and cement are generally mixed. While preparing concrete, additional ingredients like gravel, stones, and other materials are added to the mortar. In both cases, the mixture sets and hardens with time, upon mixing with water.

There are various types of cement that are used for building construction, out of which Portland cement is most commonly used. Clay, shale, limestone, alumina, and chalk are the main ingredients of Portland cement. Portland cement is prepared after a series of processes, which includes mixing, burning, and crushing the components.

Apart from Portland cement, there are other varieties of cement like white cement, air-entraining cement, quick-setting cement, water repellent cement, hydraulic cement, non-hydraulic cement, and so on.

Types of concrete

As outlined below, concrete is an aggregate mixture of sand, cement, rocks, pebbles, granites, and water. It may also contain other components depending on the application.

Different types of concrete are used for various applications. Some of the different types of concrete are outlined below.

Vacuum concrete

Vacuum concrete is the concrete, from which water is sucked out by vacuum pressure. This technique induces high strength and durability to the concrete mix than ordinary concrete mixtures. In ordinary concrete, the water evaporates out from the mixture after hardening, which leaves behind capillary pores. this ultimately reduces the durability of concrete. This technique ensures and fills the drawbacks which engineers face while working with ordinary concrete.

Plain concrete

Plain concrete has no material that provides strength like bars and rods used for reinforcements. More precisely, plain concrete doesn't have two-tenths or even one percent of reinforcements. Plain concrete is characterized by hydration upon adding to water. Plain concrete forms strong chemical bonds with water and turns into a rock-solid mass.

Polymer concrete

In polymer concrete, the polymer replaces the traditionally lime-composed cement as a binder. Thermoplastic polymers and thermosetting polymers form the main composition of polymer concrete. Aggregates of silica, quartz, limestone, granite and other superior quality materials additionally form a part of polymer concrete.

Glass concrete

Glass concrete forms a major part of architectural designs and falls under the category of decorative concrete. Mixing glass crystals in a concrete mix, induces shine and sparkling properties to the concrete. This concrete is primarily applied to the walls and floors for eye-catching effects and to impose a high-quality finish.

Roller-compacted concrete

Roller-compacted concrete is popularly known as RCC. It acquires the name from its method of application. RCC and high-density asphalt form the major combination during road pavement construction works. The mixture is compacted by a roller after its application. Sometimes, other than asphalt, RCC has the same ingredients as regular concrete.

Self-compacting and self-consolidating concrete

This category of concrete sets and consolidates due to its weight. It doesn't require any vibratory means to perform the compacting process. The property of deformability is one such property that makes this concrete crowned by the name "self-compacting".

Stamped concrete

This concrete is primarily used for road, footpaths, driveways, and sidewalk constructions. The concrete after the application is embossed or patterned with replicas of rocks, bricks, slabs, and tiles. This category of concrete is comparatively less expensive than normal strength concrete.

Concrete uses

Although concrete forms a major constituent for building construction and structural applications, there are several other uses of concrete. Some of the main uses of concrete are indicated below:

• Construction of concrete dams and large structures to support the surge tanks
• Residential building construction and its structures like beams, and columns
• Commercial building construction
• Forming the primary element in building the foundation
• Roadways and driveways
• Marine construction, for building ports, seawalls
• Construction of culverts and sewers
• Building strong walls and fences
• Building bridges of concrete
• Building of airports and stations
• Construction of motorways, roads, highways, expressways, and gate footings, and other varieties of concrete constructions

Context and Applications

The topic is majorly taught in different undergraduate and postgraduate degree courses of:

• Bachelors in Civil Engineering
• Masters in Civil Engineering
• Masters in Building Construction
• Masters in Structural Engineering

Practice Problems

1. Which of the following concrete uses a vacuum to remove water?

1. Ready-mix concrete
2. Strength concrete
3. Vacuum concrete
4. Self-compacting concrete

Answer: Option c

Explanation: Vacuum concrete is a class of concrete, where the water is removed through a vacuum. This increases the strength and durability of the concrete.

2. Which of the following concrete is used for architectural purposes?

1. Glass concrete
2. Ready-mix concrete
3. Decorative concrete
4. Both a and c

Answer: Option d

Explanation: Glass concrete and decorative concrete are majorly used for architectural applications.

3. What is the main ingredient to induce hydration in a concrete mixture?

1. Limestone
2. Silica
3. Aluminate
4. Water

Answer: Option d

Explanation: Water induces hardness in a concrete mixture by hydration and setting up new bonds.

4. What differentiates mortar and concrete?

1. Its aggregate raw ingredients.
2. Its aggregate water-cement ratio.
3. The aggregate size of the rocks or pebbles.
4. None of these.

Answer: Option a

Explanation: A mortar mix is different from concrete, based on the raw materials used in the preparation of the mixture.

5. What is the full form of RCC?

1. Reinforced cement concrete
2. Reinforced compacted concrete
3. Roll-compacted concrete
4. Roller-compacted concrete

Answer: Option d

Explanation: The full form of RCC is roller-compacted concrete.