Concrete degradation

Proper moisture curing leads to formation of more C-S-H crystals (not expansive) in the pores of the hardened cement paste. Will it be harmful (cause cracking) to concrete?

• Yes

• No

Sulfate attack leads to the formation of more ettringite crystals (expansive/size grow) in the pores of the hardened cement paste. Will it be harmful (cause cracking) to concrete?

• Yes

• No

The use of sea sand with a high concentration of salt can lead to the degradation of reinforced concrete. What is the main reason?

• Salt damage the cement paste structure

• Ettringite formation

• Corrosion of steel (leads to formation of expansive crytsal)

• Decrease the pH value in concrete

What is the natural pH environment of concrete?

• acidic (pH <7)

• alkaline (pH >7)

• neutral (pH = 7)

• I don't know

Cement hydration is a heat-releasing reaction. Which one of the following methods cannot prevent thermal cracking in mass concrete construction?

• Use ice water

• Low heat cement (with cement partially replaced by pozzolans)

• Use retarder (reduce the reaction rate and make the setting time longer)

• Cover the concrete surface with a plastic film