History and Properties of Masonry

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Questions and Answers

What is the primary purpose of precise control during the firing of masonry units?

To decrease the size of the kiln compartments.

To increase the production rate.

To reduce the energy consumption of the kiln.

To achieve a specific firing curve that suits raw materials. (correct)

Which factor does NOT affect the properties of masonry?

Workmanship and supervision during construction.

Properties of the mortar.

Properties of the masonry units.

Consistency of weather during construction. (correct)

Which variability is NOT typically associated with masonry properties?

Natural variation in materials.

Difficulty of controlling site-batched mortar.

Database errors in design calculations. (correct)

Variability in site workmanship.

What does the typical coefficient of variation (CV) for compression indicate?

0.15 reflects consistency in the material's compressive strength. Signup and view all the answers

What failure mechanism occurs in masonry due to mortar joints?

Tensile splitting of the units. Signup and view all the answers

Which of the following statements about masonry strength is true?

Masonry strength is always less than the compressive strength of the units alone. Signup and view all the answers

Which process occurs after firing in the manufacture of masonry units?

Packing of the masonry units. Signup and view all the answers

What is the primary reason for ensuring compatibility of the units and mortar in masonry?

To ensure structural integrity and performance. Signup and view all the answers

What material was primarily used in the earliest known uses of masonry?

Sun-dried earth Signup and view all the answers

Which structure is noted as the last great example of a gravity masonry structure?

Monadnock Building Signup and view all the answers

What does modern masonry, particularly fired clay brick, provide?

Strength and water-tightness Signup and view all the answers

Which of the following is NOT a characteristic of gravity masonry structures?

Rely on tensile stresses Signup and view all the answers

What was a significant ancient masonry construction technique mentioned?

Kiln-fired bricks Signup and view all the answers

Which of these is an example of a modern use of masonry?

Arched doorways Signup and view all the answers

What is one of the earliest regions known for masonry construction?

Mesopotamia Signup and view all the answers

What type of kiln was used for the convict bricks brought by the First Fleet?

Clamp kiln Signup and view all the answers

What significantly reduces masonry strength?

Thicker joints Signup and view all the answers

Which factor is NOT related to the reduction of masonry strength?

Higher compressive strength tests Signup and view all the answers

What is used for compressive strength testing of masonry units?

Height-to-thickness ratio of five Signup and view all the answers

As the joint thickness increases, what happens to compressive strength?

It decreases Signup and view all the answers

For traditional bricks with a height-to-thickness ratio of 7.6, what is the compressive strength factor?

1.0 Signup and view all the answers

What does the adjustment for joint thickness account for?

Unit height to joint thickness ratio Signup and view all the answers

Which of the following statements is correct regarding weaker units?

They lead to a reduction in masonry strength. Signup and view all the answers

What must be tested for masonry to be classified as Special Masonry?

Masonry strength during construction Signup and view all the answers

What is the default characteristic tensile strength value across bed joints in masonry when not tested?

0.2 MPa Signup and view all the answers

Which type of bending in masonry is associated with tensile stress normal to the bed joints?

Vertical bending Signup and view all the answers

In masonry, what is the effect of various levels of bending stress in joints during analysis?

It makes analysis more difficult Signup and view all the answers

What is the value of tensile strength that can be used for special masonry, subject to testing?

1.0 MPa Signup and view all the answers

What is a characteristic of masonry's flexural behavior?

Masonry is anisotropic due to joint orientations Signup and view all the answers

What does the weakest link analogy suggest about vertical bending in masonry?

Failure is expected at the weakest joint Signup and view all the answers

In horizontal bending of masonry, which of the following describes a mode of failure?

Through bed and perpend joints Signup and view all the answers

How does AS 3700 address the analysis of joints subjected to bending stress?

It ignores variations in bending stress levels Signup and view all the answers

What type of shear action occurs in a bracing wall?

In-plane shear Signup and view all the answers

How is shear strength in masonry typically determined?

By the bond at the unit-mortar interface Signup and view all the answers

What is the range of elastic modulus values for short-term loading according to AS 3700?

$500 f 'm$ to $1000 f 'm$ Signup and view all the answers

What does the friction factor represent in masonry shear strength calculations?

The slope of the shear strength line Signup and view all the answers

What happens to the long-term modulus of elasticity in masonry compared to the short-term modulus?

It is about 1/2 to 2/3 of the short-term modulus Signup and view all the answers

Which property is defined as the combination of shear strength and shear friction in masonry?

Shear resistance Signup and view all the answers

What is the role of density in the context of masonry properties?

Provides values for loading codes Signup and view all the answers

In masonry, what does the shear strength $f 'ms$ typically relate to?

The bond at the unit-mortar interface Signup and view all the answers

Study Notes

History of Masonry Use

Earliest masonry applications were used in Egypt, Mesopotamia and the Indus valley (ca 8,000 BCE)
Earliest uses of kiln-fired bricks date back to 5,000 BC
Single brick structure provides: Strength + Water-tightness + Thermal protection
First Fleet brought bricks to Australia
Convict built hand-moulded wet clay bricks using clamp kilns
Masonry uses include: Bridges, Vaults, Arched doorways, Retaining walls, Tunnels, Buildings, etc.
Massive masonry walls were the standard until the 19th century
Gravity was the force used to keep walls stable with no tensile stresses present

Manufacture of Masonry Units

Modern Kiln Tunnel and Gas Burners are monitored and controlled by a computer room to ensure appropriate firing curve
Firing is an important step in masonry unit manufacture and is dependent on raw materials

Masonry Properties

Masonry Properties Depend on:
- Properties of the masonry units
- Properties of the mortar
- Compatibility of the units and mortar
- Bonding pattern
- Workmanship and supervision during construction
Variability in Properties:
- Natural variation in materials
- Variation in the manufacturing process
- Variations in site workmanship
- Difficulty of controlling site-batched mortar
- Variation in porosity, moisture content etc
Typical Coefficient of Variation (CV) is 0.15 for compression and 0.30 for flexural tension
Masonry strength is always less than the compressive strength of the units alone
Masonry strength is reduced by:
- Weaker units (lower tensile strength)
- Greater thickness of joints
- Weaker mortar (i.e.lower stiffness)
To accommodate the lower elastic modulus of mortar compared to units, tensile stresses are induced in the units
An unconfined strength based on a height-to-thickness of five is used for compressive strength tests
AS 3700 (Australian Standards) provides tabulated compressive strengths (f 'mb) based on unit strength and mortar class
Higher strengths from compressive tests can be used but the masonry is then Special Masonry and must be tested during construction
Compressive Strength is reduced as the joint thickness increases for a given unit height
Tensile strength is usually tested by the bond wrench method
A characteristic value of 0.2 MPa across the bed joints is used for design, unless tested
A value up to 1.0 MPa can be used for Special Masonry, subject to testing.
Masonry is anisotropic because of the bed and perpend (perpendicular) joints
Three types of flexure in masonry:
- Vertical bending (tensile stress normal to the bed joints)
- Horizontal bending (tensile stress parallel to the bed joints)
- Two-way bending (principal tensile stress at an angle to the bed joints).
Vertical Bending - joints usually have different levels of bending stress
Two modes of horizontal bending failure:
- Through bed and perpend joints: When units are strong relative to bond
- Through perpend joints and units: When bond is strong relative to the units
Shear resistance in masonry combines shear strength and shear friction
Shear strength f 'ms is related to bond at the unit-mortar interface and is usually proportional to f 'mt
The friction factor is the slope of the shear strength line
Values for the elastic modulus E are required for deflection and relative movement calculations
AS 3700 provides values for short-term and long-term loading, where values are proportional to f 'm and range from 500 f 'm to 1000 f 'm for short-term loading
Long-term modulus of elasticity is approximately 1/2 to 2/3 of the short-term modulus due to creep, mostly in the mortar
In the absence of more accurate data, the Australian loading code gives masonry density values, for example 0.19 kN/m2 for each 10 mm thickness of clay brickwork

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Description

Explore the rich history and essential properties of masonry through this informative quiz. From ancient applications in Egypt to modern manufacturing techniques, you will learn about the various uses and characteristics that define masonry. Test your knowledge about the development and significance of this crucial building material.