Questions

Identify the correct statement $($ s $)$

a$)$ In the regions having relative humidity of $50\%$ or less, corrosive action may be negligible

b$)$ Structures permanently immersed in water exhibit little corrosion of reinforcement

c$)$ Corrosion of reinforcement may lead to deep pitting and a severe loss of cross$-$section of reinforcement

d$)$ For pre$-$stressed concrete the total amount of chloride ions should be limited to $0\mathrm{.}10\%$ by mass of cement

e$)$ For reinforced concrete members submerged in sea$-$water additional cover of $40$ mm should be provided

The corrosion of steel reinforcement can be prevented by the following except

a$)$ The use of corrosion inhibitors, coating on steel or concrete

b$)$ proper design of concrete for the intended environmental exposure

c$)$ use of stainless steel

d$)$ impregnating the pores of concrete by a suitable polymer e$)$ increase thickness of concrete cover over reinforcement

Deterioration of concrete can be prevented by

a$)$ Making a denser concrete b$)$ ensuring efficient alkalinity to provide passive environment against corrosion of reinforcement c$)$ limiting water$-$cement ratio

d$)$ impregnating the pores of concrete with a suitable polymer material e$)$ all of the above

The following are the principal forms of destruction of concrete except

a$)$ Decomposition of concrete due to leaching action

b$)$ chemical reaction between hardened cement constituent of concrete and chemicals of a solution

c$)$ grinding action of sand storms

d$)$ crystallization resulting in the increase of volume of solid phase within the pore structure

e$)$ all the above

Identify the correct statement

a$)$ The durability of concrete is its resistance to the deteriorating influences of both external and internal agencies b$)$ the gradual deterioration of concrete by chemical aggressive agents is called concrete corrosion

c$)$ Corrosion of steel reinforcement results in internal stresses which promote destruction of concrete

d$)$ Micro$-$cracks present at the aggregate$-$cement interface do not affect durability as long as they are small in size and discontinuous

e$)$ none of the above

Identify the correct statement

a$)$ Cracks may represent the total extent of damage or they may point to problems of greater magnitude

b$)$ The cracking in concrete structure is not necessarily a cause for blaming the designer, builder or supplier

c$)$ A crack where movement is observed to continue is termed dormant.

d$)$ Cracks in concrete members usually occur due to incompatible dimensional $($volume$)$ changes

e$)$ None of the above

The most common symptom of distress in a concrete structure is

a$)$ Spalling of concrete

b$)$ cracking of concrete

e$)$ none of the above

c$)$ scaling of concrete

d$)$ surface crazing

Blow$-$holes are caused by

a$)$ Improper design of formwork

b$)$ lack of compaction

water content

e$)$ none of the above

c$)$ inadequate workability

d$)$ excess

The distress in concrete structures may be due to

a$)$ Poor construction practices

b$)$ errors in design and detailing

c$)$ environmental loads exceedin design stipulations

d$)$ shrinkage

e$)$ all of the above

The following compounds may be used as inhibitors of iron corrosion

a$)$ Potassium dichromate, zinc and lead chromates sulphate d$)$ fly ash

e$)$ molasses

b$)$ calcium and sodium chlorides

c$)$

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