**1. As per IS 456:2000, Minimum grade of concrete for plain concrete exposed to seacoast is _____.**

[A] M20

[B] M30

[D] M25

[C] M40

**Answer: Option A**

**2. Flexural strength (in N/mm²) of concrete is computed by ______.**

[A] 5000√f_{ck}

[B] 7000√f_{ck}

[C] 0.7√f_{ck}

[D] 0.5√f_{ck}

**Answer: Option A**

**3. If creep coefficient for concrete at 7 days is K _{1} and 28 days is K_{2} then ______.**

[A] K_{1} > K_{2}

[B] K_{1} < K_{2}

[D] K_{1} <= K_{2}

[C] K_{1} = K_{2}

**Answer: Option A**

**4. An ordinary mild steel bar has been prestressed to a working stress of 200 MPa. If the Young’s modules of steel is 200 GPa and permanent negative strain due to shrinkage and creep is 0.0008, what is the effective stress left in the steel?**

[A] 190 MPa

[C] 85 MPa

[B] 170 MPa

[D] 40 MPa

**Answer: Option D**

**Solution:**

Initial prestress = 200MPa

Shrinkage Strain (ϵ_{s}) = 8 * 10^-4

Modulus elasticity of steel (E_{s}) = 200GPa = 200 * 10^3 MPa

Now, loss of prestress = ϵ_{s} * E_{s }= 8 * 10^-4 * 200 * 10 ^ 3 = 160MPa

Stress left in steel = 200 – 160 = 40MPa

**5. The modulus of elasticity E = 5000 where f _{ck} is the characteristic compressive strength of concrete specified in IS:456-2000 is based on ______.**

[A] Tangent modulus

[B] Initial tangent modulus

[C] Secant modulus

[D] Chord modulus

**Answer: Option B**