QUIZ 2 FRESH PROPERTIES

Question 1

Workability

Contains two main components

Answer 1

Property determining the effort required to mix, place, compact, and finish concrete.

Consistency and Cohesiveness

Question 2

Workability Factors

Answer 2

Water, time, temperature, admixture type, aggregate, concrete temp

Question 3

Slump Test

Answer 3

1. 3 layers of concrete individually placed and compacted in a steel cone
2. Cone is removed, and downward movement of concrete measured
3. Cone must retain shape to be valid
4. invalid if collapses
5. Normal slump 80 to 120 mm

Question 4

Segregation, how to avoid

Answer 4

• Separation of aggregate from mortar
• Avoid high slump
• Need good placing techniques to avoid segregation, place as close to finishing position as possible

Question 5

Inadequate consolidation leads too…

Answer 5

honeycombing,rock pockets

Question 6

Bleeding Concrete

Answer 6

• bleed water accumulates on surface due to gravity forces
• not an issue but need to wait for bleed

Question 7

Curing Concrete

Answer 7

Maintenace of concrete after placing and finishing to obtain a satisfactory moisture content and temperature in a given time

• time, temp, moisture

Question 8

Curing methods

Answer 8

Fog spray, continuous moist cure, curing compounds

Question 9

Effects of curing on strength Development…. graph

Answer 9

Slide 31 Lcture 7

Question 10

Chemical Admixtures

Answer 10

Air Entrainer, Water Reducer, Retardant, Accelerating

Question 11

Air Entrainer

Answer 11

• causes very small bubbles
• provide durability to freeze/thaw
• improve workability
• lowers compressive strength

Question 12

Water Reducer

Answer 12

Increase workability by not decreasing strength