Special Types of Concrete

Question 1

What are the typical ranges of density and 28 day compressive strength of structural lightweight concrete?

Answer 1

The common designed strength is 3000 to 5000psi

density?

Question 2

What is the difference between an all light weight concrete and a sanded lightweight concrete?

Answer 2

Lightweight concretes use both lightweight coarse and lightweight fine aggregate. Sanded lightweight concrete uses natural sand and lightweight coarse aggregates.

Question 3

What are some aggregates that are commonly used in making lightweight concretes

Answer 3

expanded clay, expanded shales, expanded slates, expanded slags

Question 4

How is structural lightweight concrete difference from a normal concrete in terms of the most important factor affecting its strength

Answer 4

Lightweight concrete and normal concretes are similar except for the fact that lightweight concretes use lightweight aggregates

Question 5

Are there any difference between the slump requirement for lightweight concrete and normal concrete to obtain the same workability during placement

Answer 5

A lightweight concrete with a slump of 50-75mm has a similar workability to a normal concrete with a slump of 100 to 125mm. (lower slump required for lightweight concrete)

Question 6

What are the possible advantages of using a structural lightweight concrete as compared with normal concrete?

Answer 6

Reduction in dead weight of structure (better resistance to earthquake loading), savings in steel reinforcement, and reduced handling, transportation & construction costs for precast concrete elements

Question 7

What is the typical usage of heavyweight concrete?

Answer 7

Radiation shielding, low initial and maintenance cost

Question 8

What is the typical density of high strength concrete? How is it produced?

Answer 8

Typically 210 to 240 pcf. It is produced by using natural heavyweight aggregates

Question 9

What is the typical range of 28 day compressive strength of high strength concrete?

Answer 9

40MPa

Question 10

What are the usages of high strength concrete

Answer 10

.

Question 11

What is roller compacted concrete? What is its compressive strength?

Answer 11

No slump almost dry concrete moisture which is finished by compacting with a vibratory roller. Compressive strength of up to 10000 psi can be achieved

Question 12

What are possible usages and advantages of roller compacted concrete?

Answer 12

Advantages include low cement content, lower formwork cost, lower transport cost due to ease of handling, higher rate of concrete placement and higher rate of utilization, along with lower unit cost

Question 13

What are disadvantages of using roller compacted concrete?

Answer 13

Difficulty bonding fresh roller compacted concrete to other concrete surfaces due to dry consistency

Question 14

What is latex modified concrete?

Answer 14

Mix where materials and production method is similar to normal portland cement except a latex is used as an admixture

Question 15

What are properties of latex modified concrete? What are possible usages?

Answer 15

Compressive strength is similar to that of normal concrete
Tensile and flexural strengths are significantly higher than those of normal concrete
Good bonding with old concrete, used for rehabilitation of deteriorated floors, pavements, and bridge decks

Question 16

What is fiber reinforced concrete?

Answer 16

Concrete containing discontinuous discrete fibers. Fibers of various shapes and sizes produced from steel, plastic, glass, and natural materials can be used.

Question 17

What are properties of fiber reinforced concrete? What are possible usages?

Answer 17

Higher tensile strain, higher toughness and resistance to impact, increased ultimate tensile strength, reduced workability, increased fatigue life, similar elastic modulus, similar drying shrinkage, similar compressive creep.
Can be used for parking garage slabs, airport runways, overlay on pavement, shotcrete for tunnel lining, and repair work.