Civil Engineering Building Materials

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Questions and Answers

What is the main factor that affects the properties of materials?

Micro-structure

Chemical composition (correct)

Macro-structure

Mineral composition (correct)

What happens to the strength, hardness, and toughness of carbon steel as carbon content increases?

They increase (correct)

They remain constant

They decrease

They become zero

Why was stainless steel invented?

To change the color of carbon steel

To make carbon steel more resistant to rust (correct)

To increase the strength of carbon steel

To reduce the weight of carbon steel

What is the term for the structure of materials that can be identified with a magnifying glass or naked eyes?

Macro-structure Signup and view all the answers

What is the term for the chemical constituents of a material?

Chemical composition Signup and view all the answers

What is the main factor that affects the properties of natural stone?

Mineral composition Signup and view all the answers

What level of structure is above millimeter?

Macro-structure Signup and view all the answers

What are the key factors related to the properties of materials?

Macro-structure, meso-structure, and micro-structure Signup and view all the answers

What is the charge of the nucleus in an atom?

Net positive Signup and view all the answers

What is the primary reason for atomic bonding?

To complete or fill their outermost electron orbits Signup and view all the answers

What type of bond involves the transfer of an electron?

Ionic bond Signup and view all the answers

What is a characteristic of ionic bonds?

They can only occur between atoms of different elements Signup and view all the answers

What type of bond is commonly found in organic molecules?

Covalent bond Signup and view all the answers

What is the 'sea of electrons' model used to describe?

Metallic bonding Signup and view all the answers

What is a characteristic of metal materials?

Good thermal conductivity and electrical conductivity Signup and view all the answers

What is the result of the electrostatic attraction between the nucleus and electrons?

The electrons are attracted to the nucleus Signup and view all the answers

What is the minimum scale that must be considered in the engineering level?

The size of the representative cell Signup and view all the answers

What is isotropic material?

A material with the same properties in all directions Signup and view all the answers

What is studied in the meso-structure level?

The size, shape and interface of grains and particles Signup and view all the answers

What is the linear dimension of the representative cell for concrete?

0.1 m Signup and view all the answers

What is the microstructure level?

The molecular level Signup and view all the answers

What is the size of a wood cell wall thickness?

5 × 10^-6 m Signup and view all the answers

What is anisotropic material?

A material with different properties in all directions Signup and view all the answers

What is the length of a brick in the meso-structure level?

0.225 m Signup and view all the answers

Study Notes

Materials Composition and Structure

The composition of materials includes chemical composition and mineral composition, which are key factors for the properties of materials.
Chemical composition refers to the chemical constituents, and various chemical compositions result in different properties.
For example, the increase of carbon content in carbon steel changes its strength, hardness, and toughness.
Mineral composition is the key factor for the properties of some building materials, such as natural stone, inorganic gel, and cement.

Structure of Materials

The structure of materials can be divided into macro-structure, meso-structure, and micro-structure, which are key factors related to the properties of materials.
Macro-structure refers to the thick structure above millimeter that can be identified with a magnifying glass or naked eyes, and is considered at the engineering level.
Macro-structure is normally taken as continuous and homogeneous, and average properties are assumed throughout the whole volume of the material body.
The minimum scale that must be considered is governed by the size of the representative cell, which varies from 10^-3 m for metals to 0.1 m for concrete and 1 m for masonry.

Meso-structure

Meso-structure refers to the micro-level structure that can be observed by optical microscope, and is also known as sub-microstructure.
This level is a step up in size from the molecular level, and the material is considered as a composite of different phases that interact to realize the behavior of the total material.
The size, shape, and interface of grains and particles, and the size, shape, and distribution of pores and micro-cracks are mainly studied in this structure.

Microstructure

Microstructure refers to the atomic and molecular structures of materials that can be studied by electron microscopy, X-ray diffractometer, and other means.
Atoms, the building block of elements, consist of a nucleus surrounded by a cloud of orbiting electrons.
The bonding of atoms is essential to form materials, and there are three types of bonds: ionic bond, covalent bond, and metallic bond.

Atomic Bonds

Ionic bond involves a transfer of an electron, resulting in a high strength, hardness, and melting point, but with a volatile and medium density.
Covalent bond involves the sharing of electrons between two atoms, resulting in a strong bonding force, high strength, hardness, and melting point, and high density.
Metallic bond involves sharing electrons, resulting in a volatile strength and hardness, high density, and good thermal and electrical conductivity.

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Description

This quiz covers the first chapter of building materials for civil engineering students. It tests understanding of fundamental concepts and principles of building materials. For first stage, second semester students.