week 6 Flashcards
(20 cards)
What are the main types of bricks used in construction?
Common bricks, facing bricks, special performance bricks, and engineering bricks.
What determines whether a brick meets dimensional tolerance standards?
Bricks are tested by laying 20 bricks end-to-end and checking total length against specified tolerances (e.g., 230 mm ± 2 mm for DW1 grade).
Why must expansion joints be considered in brickwork?
Clay bricks expand permanently (up to 0.25%), which can lead to cracking if joints are not included.
What is the typical compressive strength range for clay bricks in Australia?
between 20 MPa and 80 MPa, as per AS/NZS 4456.4:2003.
How is flexural strength increased in brick construction?
By inserting reinforcement steel bars inside the holes of bricks or blocks, especially in cyclone-prone areas.
How does brick absorption affect mortar performance?
High absorption can draw water from mortar, weakening hydration; bricks are often wetted before use to control this
What are the three primary materials bricks are made from?
Clay, calcium silicate (sand-lime), and concrete.
What are the main properties of calcium silicate bricks?
Smooth texture, good strength, fire resistance, shrink on drying, not suitable in acidic or salty environments.
How do concrete blocks contribute to thermal insulation?
Their air-filled aggregates and cellular structure help provide insulation, but they shrink and may crack when drying.
What are the visual and practical differences between extruded and pressed bricks?
Extruded bricks are generally stronger than pressed bricks and often used where strength is more critical
What is the purpose of DPC and DPM in wall construction?
DPC (Damp Proof Course) stops rising damp above ground level, while DPM (Damp Proof Membrane) blocks moisture from below slabs or floors. Both must overlap to ensure continuous moisture protection.
What are the differences between double brick and brick veneer walls?
Double brick uses two brick layers with a cavity and is load-bearing; brick veneer has a single brick skin on a timber/steel frame, making it lighter and cheaper but less thermally efficient.
When are concrete block walls preferred, and what types exist?
Preferred for speed and cost-efficiency. Dense blocks are strong (load-bearing), while lightweight blocks are better for thermal performance (non-load bearing).
What is the role of wall ties and mortar jointing in masonry walls?
Wall ties (to AS/NZS 2699.1) connect masonry layers, while proper mortar jointing (e.g., ironed joints) improves strength and water resistance, especially in exposed walls.
What materials are used for lintels, and how are they selected?
Lintels can be made from concrete (precast/in-situ), prestressed concrete, or steel. Material choice depends on span, load, and exposure, with steel being common and galvanised for corrosion resistance.
What structural roles and standards must walls comply with in Australia?
Walls can be load-bearing or non-load-bearing, and interior or exterior. All must meet NCC and Australian Standards for durability, fire resistance, serviceability, strength, and stability, with specific codes for masonry (AS 3700), timber (AS 1720), and steel (AS 3623, AS 4600).
What is slenderness ratio, and how does it affect wall stiffness?
Slenderness ratio (SR = effective height ÷ effective thickness) indicates wall stiffness. A lower SR means greater resistance to buckling. SR can be improved by adding lateral supports or increasing wall thickness with piers or buttresses.
How is wall robustness ensured in design?
Robustness prevents wall failure under accidental lateral loads. AS 3700 provides max height/length limits based on wall thickness and restraint types. Graphs help determine required thickness for given dimensions and restraints
What does Fire Resistance Level (FRL) mean for walls?
FRL covers: Structural Adequacy (e.g., 120 mins), Integrity (e.g., 60 mins), and Insulation (e.g., 90 mins). Graphs and tables from AS 3700 help select correct wall thickness for the desired FRL performance.
How do walls meet durability and weatherproofing standards?
Durability is achieved by using proper mortar classes and brick grades (e.g., M3 for general, M4 for marine). Weatherproofing uses DPCs, flashings, and membranes to protect from rain and water ingress, especially in external single-skin or cavity walls.
