Applications of Concrete Masonry Units Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the typical use of concrete block for basement walls?

To be covered with stucco

To provide high thermal resistance

To be usually plain faced (correct)

To act as a back-up material

Why are coatings often applied to concrete blocks?

To increase water penetration

To enhance sound resistance

To decrease thermal resistance

To prevent water penetration (correct)

What is the key reason why testing of concrete is important according to the text?

To improve fire resistance properties

To enhance sound resistance

To reduce thermal properties

To meet manufacturing standards (correct)

What makes lightweight concrete units different from normal weight units?

Higher thermal and fire resistance Signup and view all the answers

What does the binding medium in concrete consist of?

A mixture of fine aggregates and coarse aggregates Signup and view all the answers

When should concrete undergo quality tests according to the text?

Before and after completion of casting on site Signup and view all the answers

What is the purpose of measuring the subsidence of concrete in millimeters?

To determine the required slump of the concrete Signup and view all the answers

What type of slump is considered most desirable in concrete testing?

True slump Signup and view all the answers

What does a shear slump indicate about a concrete mix?

Lack of cohesion Signup and view all the answers

What can cause a collapse slump in fresh concrete?

Harsh mix Signup and view all the answers

Which condition represents stiff, consistent, and almost no workability in concrete?

Zero slump Signup and view all the answers

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 Signup and view all the answers

Why should concrete be placed in uniform layers?

To ensure proper compaction Signup and view all the answers

What happens if water is added to concrete that is setting?

It weakens the concrete Signup and view all the answers

What is the purpose of compacting concrete?

To remove entrapped air voids Signup and view all the answers

Why should each layer of concrete be fully compacted before placing the next one?

To prevent segregation Signup and view all the answers

What is the purpose of using lighting for large, deep sections, walls, and columns?

To aid in correct placing Signup and view all the answers

Why should collision between concrete and formwork or reinforcement be avoided?

To prevent cracking Signup and view all the answers

What happens to the strength of concrete for every 1% of entrapped air?

It decreases by 5-7% Signup and view all the answers

How do air voids affect concrete's permeability?

They increase it Signup and view all the answers

Why is it important to compact concrete fully?

To improve the concrete's strength and durability Signup and view all the answers

What is the consequence of concrete not being dense and impermeable?

It loses strength and is less able to withstand aggressive liquids Signup and view all the answers

How do air voids affect the bond between concrete mix and reinforcement?

They impair the required bond resulting in a weaker reinforced member Signup and view all the answers

What is the purpose of using reinforced walls?

To protect the walls from cracks and strengthen them against natural disasters Signup and view all the answers

Which method is NOT suitable for compacting concrete according to the text?

Pouring water over the mix Signup and view all the answers

In what ways can reinforcement be used in reinforced masonry walls?

Horizontally and vertically Signup and view all the answers

Which category does Reinforced Hollow Unit Masonry belong to?

Confined Masonry Signup and view all the answers

How are solid walls reinforced?

By using metal ties, masonry investments, or collective reinforcement Signup and view all the answers

What are Composite Masonry Walls made of?

A combination of two or more building materials Signup and view all the answers

What is the main advantage of Composite Masonry Walls?

They are cost-effective and optically appealing Signup and view all the answers

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.