30 Questions
What is the typical use of concrete block for basement walls?
To be usually plain faced
Why are coatings often applied to concrete blocks?
To prevent water penetration
What is the key reason why testing of concrete is important according to the text?
To meet manufacturing standards
What makes lightweight concrete units different from normal weight units?
Higher thermal and fire resistance
What does the binding medium in concrete consist of?
A mixture of fine aggregates and coarse aggregates
When should concrete undergo quality tests according to the text?
Before and after completion of casting on site
What is the purpose of measuring the subsidence of concrete in millimeters?
To determine the required slump of the concrete
What type of slump is considered most desirable in concrete testing?
True slump
What does a shear slump indicate about a concrete mix?
Lack of cohesion
What can cause a collapse slump in fresh concrete?
Harsh mix
Which condition represents stiff, consistent, and almost no workability in concrete?
Zero slump
What should be done to the area around the base of the cone before lifting the mould during a concrete slump test?
Cleaned from any accidentally dropped concrete
Why should concrete be placed in uniform layers?
To ensure proper compaction
What happens if water is added to concrete that is setting?
It weakens the concrete
What is the purpose of compacting concrete?
To remove entrapped air voids
Why should each layer of concrete be fully compacted before placing the next one?
To prevent segregation
What is the purpose of using lighting for large, deep sections, walls, and columns?
To aid in correct placing
Why should collision between concrete and formwork or reinforcement be avoided?
To prevent cracking
What happens to the strength of concrete for every 1% of entrapped air?
It decreases by 5-7%
How do air voids affect concrete's permeability?
They increase it
Why is it important to compact concrete fully?
To improve the concrete's strength and durability
What is the consequence of concrete not being dense and impermeable?
It loses strength and is less able to withstand aggressive liquids
How do air voids affect the bond between concrete mix and reinforcement?
They impair the required bond resulting in a weaker reinforced member
What is the purpose of using reinforced walls?
To protect the walls from cracks and strengthen them against natural disasters
Which method is NOT suitable for compacting concrete according to the text?
Pouring water over the mix
In what ways can reinforcement be used in reinforced masonry walls?
Horizontally and vertically
Which category does Reinforced Hollow Unit Masonry belong to?
Confined Masonry
How are solid walls reinforced?
By using metal ties, masonry investments, or collective reinforcement
What are Composite Masonry Walls made of?
A combination of two or more building materials
What is the main advantage of Composite Masonry Walls?
They are cost-effective and optically appealing
Study Notes
Placing Concrete
- To achieve proper placing, concrete should be placed in uniform layers, not in large heaps or sloping layers.
- The thickness of the layer should be compatible with the method of vibration to remove entrapped air.
- The rate of placing and compaction should be equal to avoid mix stiffening or racing ahead of the compacting gang.
Compaction of Concrete
- Compaction is necessary to remove air voids trapped in loose concrete.
- Air voids reduce the strength of concrete, increase permeability, and reduce durability.
- Air voids can cause honeycombing, reduce bond between the mix and reinforcement, and produce blemishes on struck surfaces.
Methods of Compaction
- Vibration is the quickest method of supplying energy to compact concrete.
- Manual techniques like rodding are suitable for smaller projects.
Slump Test
- The slump test measures the workability of concrete by measuring the subsidence of concrete in millimeters.
- The test should be performed on a non-porous surface, with the mould and base moistened, and in a place free of vibration or shocks.
- Types of slump include true slump, shear slump, collapse slump, and zero slump.
Applications of Concrete Masonry Units
- Concrete blocks are used in foundation walls, basement walls, partition walls, and exterior walls.
- Lightweight units have higher thermal and fire resistance properties and lower sound resistance than normal weight units.
Construction Material and Testing
- Testing of concrete is crucial to ensure it meets standards.
- Quality tests are performed on concrete before and after casting on site to determine its quality.
Reinforced Masonry Walls
- Reinforced walls protect against cracks and provide strength against natural disasters.
- Types of reinforced masonry walls include confined masonry, reinforced cavity masonry, reinforced solid masonry, and reinforced grouted masonry.
Composite Masonry Walls
- Composite masonry walls are made with a combination of two or more building materials.
- They reduce the overall cost of construction, improve durability, and provide a superior finish.
Test your knowledge on the typical uses and applications of concrete masonry units. Explore topics such as foundation walls, basement walls, partition walls, exterior walls, and the different coatings applied to concrete blocks.
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