Concrete Durability

Question 1

Concrete durability refers to:

Answer 1

It’s ability to resist weathering action, chemical attack, abrasion, or any other process of deterioration that limits its service life.

Question 2

The four exposure classes:

Answer 2

(F) Freezing & Thawing
(S) Sulfate
(W) In Contact w/ Water
(C) Corrosion Protection of Reinforcement

Question 3

Why is Freezing & Thawing a category class?

Answer 3

Moisture can permeate and accumulate inside concrete, and as water freezes—it expands. This expansion will damage concrete.

Question 4

What is the importance of air entrainment to combat Freeze/ Thaw (F).

Answer 4

More air means more voids for the moisture to fill. If freezing temps cause it to expand, it has more places to go.

Question 5

Air content required for mixes is based on two variables:

Answer 5

1. Exposure class.
2. Maximum nominal aggregate size.
   ( the larger the aggregate, the less air content required.)

Question 6

What does air content do to the concrete’s compressive strength?

Answer 6

A reduction to its compressive strength.

Question 7

How does concrete increase its air content?

Answer 7

Concrete naturally has air entrapped in it. This is usually between about .5% and 2%. To increase the air content, Air Entraining Admixtures are added to the mix.

Question 8

Why is In Contact with Water (W) a class exposure?

Answer 8

Water permeates concrete over time, especially since all concrete has at least some air content. Problematic for example, concrete water tanks.

Question 9

Why is Corrosion Protection of Reinforcement an exposure class?

Answer 9

For concrete that can be exposed to moisture as well as chloride’s, like deicing chemicals, salt, seawater. Water and chloride can damage reinforcing steels.

Question 10

Aside from concrete being exposed to high compressive loads, what else is it exposed to that affects its durability?

Answer 10

• freezing weather
• de-icing chemicals
• seawater
• rain