Freeze and Thaw of Concrete

Question 1

Freezing point of water in pores depends on?

Answer 1

1. size of pores
2. pore size distribution
3. chemistry of pore solution

Question 2

Types of chlorides

Answer 2

1. sodium
2. magnesium
3. calcium
4. potassium

Question 3

ASTM C666 Testing for Freeze Thaw

Answer 3

-concrete prism are made and cured for 14 days
-each cycle is 2-5 hours
- prisms under freeze cycles of 0-40 degrees F
-36 cycles or until failure

Question 4

ASTM C672 Scaling Resistance of Concrete Surface

Answer 4

-sodium chloride solution on concrete surface
-freeze thaw cycles of 18 hours feezing and 8 thawing
-visuual inspection after each 5 cycles
-rate from no scaling to severe scaling

Question 5

Freeze-thaw concrete needs air entraining admixtures

Answer 5

• about 5-8 % air
  -spacing needs to be less than .2 mm
  -surface area is greater than 600 in squared/ in cubed
• low w/c, less than .45
• less than 50% scm
  -proper finish/suitable subgrade (dense)

Question 6

Factors affecting air content in concrete

Answer 6

-fly ash
-pumping
-dirty aggregates
-cement finess
-concrete temperature
-admixture compactibility

Question 7

Identifying Freeze-Thaw damage

Answer 7

-look for cracking around joints(d-cracking)
- look for surface scaling
-look for environment around concrete (moisture/freeze thaw condition)
-look at concrete mix design/proportion( air content/SCM %)