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Questions and Answers
What is the common dimension of a clay masonry unit?
Which of the following types of masonry units is known as sand-lime?
What does a 'stretcher' refer to in wall construction terminology?
What is the typical mix ratio for mortar consisting of cement, lime, and sand?
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Which of the following is a characteristic of concrete masonry units?
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Which term describes a brick laid on end in wall construction?
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What is the primary purpose of using plasticizer in mortar?
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What is the primary function of mortar in masonry?
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What is the minimum strength requirement for grout used in filling reinforced masonry cores?
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What does the term 'pig in a wall' refer to in masonry construction?
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Which type of ties and connectors must comply with AS2699 and AS3700?
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What is a potential consequence of salt attack on masonry?
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What characteristic of efflorescence distinguishes it from other masonry problems?
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Which type of grout is considered unsuitable for use in reinforced masonry?
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What factor significantly affects the load capacity of a masonry wall?
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How does the type of cement influence masonry performance?
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What is the role of bonding polymers in mortar?
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Which statement is true regarding the design for flexure in masonry walls?
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What defines a wall experiencing double curvature?
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What is a key characteristic of vertical bending in masonry walls?
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Which of the following factors is NOT considered in the design for compression in masonry?
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In the context of lateral loads on masonry walls, which mode of failure typically occurs first?
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What does the section modulus of the bedded area influence in masonry wall design?
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Which bending mode occurs when sections of a wall are supported only at the sides?
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What can cause shear failure within a wall?
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What is shear capacity a combination of?
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Which construction type relies on the frame for support?
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What is the typical width of the drained cavity in cavity wall construction?
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How does a cavity wall resist lateral load?
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Which factor contributes to slippage under earthquake loading?
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What must masonry veneer and connections resist?
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What specifies the bedding requirement in wall construction?
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What is a common fault associated with poorly filled joints in masonry construction?
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Which issue is caused by clogged weepholes in cavity walls?
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What flaw may occur due to inadequate embedment in masonry work?
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What phenomenon is associated with ties being bent up and not engaged?
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Which feature is characteristic of the Malbork Castle?
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What is the significance of common faults like poor bonding at joints?
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What is a consequence of mortar on wall ties?
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In masonry construction, excessive cavity can lead to which issue?
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Study Notes
Masonry Units
- Clay masonry units are commonly extruded or pressed and have typical dimensions of 230x110x76mm.
- Concrete masonry units are typically hollow and vibrated, with common dimensions of 390x190x190mm.
- Calcium silicate units are also known as sand-lime and are a type of autoclaved aerated concrete (AAC) masonry.
- Stone is a natural material also used for masonry construction.
- The relationship between the three dimensions of masonry units is important for proper bonding and corner construction.
Masonry Wall Terminology
- Stretcher: A brick laid along the length of the wall.
- Header: A brick laid across the width of the wall.
- Soldier: A brick laid on its end.
- Closer: A brick less than full size, used to finish a wall to a vertical face.
- Pig in a wall: A situation where the number of courses in a wall varies at different heights, resulting in a different number of bricks at each end of the wall.
- Full Bedding: Mortar covering the entire bed joint of the masonry unit.
- Face Shell Bedding: Mortar covering only a portion of the bed joint of the masonry unit.
Arch Terminology
- Voussoirs: Wedge-shaped building blocks that form the arch.
- Keystone: The center voussoir that locks the arch together.
- Springing Line: The line where the arch starts to curve.
- Soffit: The underside of the arch.
- Haunch: The section of the arch between the keystone and the springing line.
- Impost: The support upon which the arch rests.
Mortar Properties
- Mortar functions as a binder and load distributor in masonry construction.
- Mortar typically contains cement, lime, sand, and water, with the addition of additives sometimes used.
- Mortar is typically batched by volume, with a common mix ratio of 1:1:6 (Cement:Lime:Sand).
- Mortar is classified into types M1, M2, M3, and M4 based on increasing strength and durability.
- It is essential to specify the correct type of cement and verify it on the construction site.
Mortar Additives
- Plasticizer (entrained air): Enhances workability, especially for sands with low clay content.
- Water thickener (methyl cellulose): Retains water against the suction of the masonry unit, useful for sharp sands and recommended for concrete and calcium silicate units.
- Pigments: Add color to the mortar.
- Set retarders: Slow down the setting time of the mortar.
- Bonding polymers: Improve the bond between mortar and masonry units.
Grout and Reinforcement Properties
- Grout is used to fill cores and cavities in reinforced masonry.
- Grout strength should match the masonry unit strength but not be less than 12 MPa.
- Specially designed, pourable grout mixes should be used, not slurries made from mortar.
Masonry Ties and Accessories
- Masonry ties and connectors must comply with AS2699 and AS3700.
- They must be designed to carry imposed loads according to the procedures outlined in AS3700.
- Corrosion protection is required depending on the exposure conditions.
Masonry Durability: Deterioration Mechanisms
- Salt Attack: Salts dissolved in water can crystallize below the surface of the masonry, causing expansion and spalling.
- Efflorescence: A white powdery deposit caused by soluble salts migrating from within the masonry. Common on new construction but usually diminishes with time.
Design for Compression
- The compressive load capacity of a masonry wall depends on various factors including:
- Wall slenderness.
- Effective eccentricity at the ends.
- Characteristic compressive strength of the masonry.
- Cross-sectional area.
- Effective eccentricity is derived from the combined effects of compressive load and bending moments.
Design for Flexure
- Most masonry walls in Australia fail in flexure due to lateral loads such as wind and earthquake forces.
- Design for flexure focuses on ensuring the wall's resistance is higher than the potential bending stresses.
- Flexural resistance depends on:
- Characteristic flexural tensile strength (f’mt).
- Section modulus of the bedded area (Zd).
- Compressive stress due to vertical load (fd).
- Vertical bending involves a wall spanning between top and bottom supports, exhibiting elastic brittle behavior.
- Horizontal bending refers to sections of a wall supported only on the sides, resisting lateral loads through horizontal bending.
Design for Shear
- Overturning, sliding, or localized failure can all lead to shear failure within the wall.
- Shear failure is caused by principal tensile stresses causing cracking.
- Compressive stresses at the base of the wall can lead to crushing and spalling.
- Shear capacity depends on both shear bond strength and shear friction strength.
Shear Factors
- Slippage can occur over damp-proof courses or flashing, particularly under seismic loading.
- This slippage helps to dissipate energy during earthquakes.
Common Types of Wall Construction
- Brick Veneer Walls: Non-structural cladding dependent on a supporting frame. The frame transfers building forces to the footings. Wall ties connect the veneer to the frame to resist local wind and earthquake loads.
- Cavity Walls: Two leaves of masonry separated by a drained cavity (typically 50mm) to prevent water ingress. They offer good thermal and strength properties and do not require external coatings. Resistance to lateral loads relies on the interaction between the leaves via wall ties.
Construction and Compliance Considerations
- Bedding must be as specified, either full or face-shell bedding.
Common Construction Faults
- Poorly filled joints: Weakens the bond and reduces structural strength.
- Poor bonding at joints: Affects structural integrity and leads to potential failure.
- Clogged weephole and control joint: Prevents drainage and moisture management, leading to deterioration.
- Excessive cavity and inadequate embedment: Reduces structural integrity and affects proper load transfer.
- Mortar on wall ties: Interferes with proper load transfer and can lead to corrosion issues.
- Ties bent up and not engaged: Reduces the effectiveness of the ties and compromises structural stability.
Master Level of Craftsmanship
- Malbork Castle (Poland) showcases the high level of craftsmanship achievable in masonry construction. It is the world's largest brick gothic castle and a testament to the enduring strength and beauty of masonry.
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Description
Explore the various masonry units including clay, concrete, and calcium silicate. Understand important terminology such as stretcher, header, and soldier, which are essential for masonry construction. This quiz will enhance your grasp of masonry practices and their applications.
