Civil Engineering: Concrete Technology I Chapter 1

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Questions and Answers

What is concrete?

A type of gravel used in construction.

A type of cement used in concrete.

A manmade building material that looks like stone. (correct)

A manmade material that resembles wood.

What does the word 'concrete' come from?

Latin word for stone.

Latin word for 'to grow together'. (correct)

Latin word for 'building'.

Latin word for 'strong'.

What are the components of concrete?

Aggregates, sand, and gravel.

Aggregates, usually sand, and either gravel or crushed stone, held together by a binder of cementitious paste. (correct)

Aggregates, cement, and supplementary cementing material.

Aggregates, cement, and water.

What is the estimated annual consumption of concrete worldwide?

11 billion metric tonnes. Signup and view all the answers

Why is concrete widely used?

Because it is used for many different structures and its production exceeds that of steel. Signup and view all the answers

What is one advantage of concrete?

It is the most inexpensive. Signup and view all the answers

What is another advantage of concrete?

It can gain its strength at ambient temperature. Signup and view all the answers

What is another benefit of concrete?

Fresh concrete is flowable like a liquid. Signup and view all the answers

How does the production of concrete compare to steel?

It exceeds steel by a factor of 10 in tonnage. Signup and view all the answers

What is the ratio of concrete production to steel production by volume?

More than 30:1 Signup and view all the answers

What is the typical range of cement content in mass concrete?

160-200 kg/m3 Signup and view all the answers

What is the main influence of maximum aggregate size on concrete?

Cement paste requirement Signup and view all the answers

What is aggregate grading related to?

Space filling or particle packing Signup and view all the answers

What is affected by the aggregate shape and texture?

Bonding and compressive strength Signup and view all the answers

What is affected by the aggregate/cement ratio?

Concrete cost and workability Signup and view all the answers

What are admixtures in concrete technology?

Chemical and mineral additives Signup and view all the answers

What do mixing procedures in concrete refer to?

Sequence of putting raw materials into a mixer Signup and view all the answers

What is curing in the context of concrete?

The measures for taking care of fresh concrete Signup and view all the answers

What is the typical range of cement content in normal strength concrete?

Less than 400 kg/m3 Signup and view all the answers

What is the typical range of cement content in high strength concrete?

400-600 kg/m3 Signup and view all the answers

What is an advantage of concrete compared to steel?

Lower energy consumption in production Signup and view all the answers

What is a characteristic of concrete related to its coefficient of thermal expansion?

It has a similar value to steel Signup and view all the answers

What is a limitation of concrete?

Low tensile strength Signup and view all the answers

What is a classification of concrete based on?

Compressive strength and additives Signup and view all the answers

What is a factor that influences concrete properties?

w/c ratio Signup and view all the answers

What is a consequence of a lower w/c ratio?

Stronger and more durable concrete Signup and view all the answers

What is a characteristic of concrete in relation to water?

It can withstand the action of water Signup and view all the answers

What is a mode of failure of concrete?

Quasi-brittle failure Signup and view all the answers

What is a requirement for fresh concrete?

Formwork is needed to hold its shape and support its weight Signup and view all the answers

What is a classification of concrete based on its compressive strength?

Four categories Signup and view all the answers

Study Notes

Concrete as a Construction Material

Concrete is a manmade material composed of aggregates (sand, gravel, or crushed stone) held together by a binder of cementitious paste.
The paste is typically made up of portland cement, water, and may also contain supplementary cementing materials and chemical admixtures.
Concrete is the most widely used material in the world, with an estimated annual consumption of 11 billion metric tons.

Advantages of Concrete

Economical: low cost of production compared to other engineered construction materials.
Ambient temperature-hardened: can gain strength at ambient temperature without high heat.
Ability to be cast: can be poured into various shapes and sizes on a construction site.
Energy efficient: low energy consumption during production compared to steel.
Excellent resistance to water: can be hardened in water and withstand water action.
High-temperature resistance: conducts heat slowly and can store considerable heat.
Ability to consume waste: can incorporate waste materials.
Ability to work with reinforcing steel: similar thermal expansion coefficient to steel.
Low maintenance required.

Limitations of Concrete

Quasi-brittle failure mode.
Low tensile strength: only about 1/10 of its compressive strength for normal-strength concrete.
Low toughness (ductility).
Low specific strength (strength/density ratio).
Formwork is needed to hold its shape and support its weight.
Long curing time.
Prone to cracking.

Classification of Concrete

By unit weight: classified into four categories.
By compressive strength: classified into four categories.
By additives: classified based on materials added to the mixture.

Factors Influencing Concrete Properties

w/c ratio (water-to-cement ratio): affects compressive strength, permeability, and diffusivity.
Cement content: influences workability, heat release rate, and volume stability.
Aggregate:
- Maximum aggregate size: affects cement paste requirement.
- Aggregate grading: affects space filling and particle packing.
- Aggregate shape and texture: affects workability, bonding, and compressive strength.
- Aggregate/cement ratio: affects cost, workability, mechanical properties, and volume stability.
Admixtures: chemical and mineral additives that improve concrete properties.
Mixing procedures: sequence of putting raw materials into a mixer and mixing time required.
Curing: measures taken to care for fresh concrete right after casting.

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Description

This quiz covers the basics of concrete as a construction material, including its definition and uses. It's designed for 2nd year civil engineering students in the first semester.