Durability Exam Questions

Question 1

A reinforced concrete structure was constructed approximately 50 m from the ocean in 1970. A w/c ratio of 0.45 was used with a GP cement and a cover depth of 50mm. There are now some visible but isolated signs of cracking and rust staining. What are the two most likely causes of deterioration given the limited information available

Answer 1

• corrosion

Question 2

Examples of Micro Defects

Answer 2

• ITZ

- gel pores

Question 3

Examples of Meso Defects

Answer 3

• capillary porosity

Question 4

Examples of Macro Defects

Answer 4

• cracking

- delamination

Question 5

what are three issues/events that occur while concrete is still in the fresh state that can affect long term durability

Answer 5

• poor compaction = excessive voids
• poor handling = segregation
• temperature of concrete =

Question 6

what are three issues/events that occur while concrete is still in the fresh state that can affect long term durability

Answer 6

• poor compaction = excessive voids
• poor handling = segregation
• temperature of concrete =

Question 7

T/F: Capillary voids and gel pores are equally affected by the selection of w/c in the mix design

Answer 7

F

Question 8

T/F: The interfacial transition zone (ITZ) is generally considered to be meso-defect

Answer 8

F

Question 9

What are the three requirements of Alkali Silica reaction

Answer 9

• alkali conditions
• reactive silica aggregate
• moisture

Question 10

silica material causing ASR

Answer 10

• Waikato River Sands

- Taranaki andesite