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BTSC JE Civil practice questions

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Question 1Building Materials and Construction Technology

In the standard IS classification of bricks, a first-class brick is expected to have a minimum crushing strength of:

  1. 3.5 N/mm²
  2. 17.5 N/mm²
  3. 10.5 N/mm² Correct answer.
  4. 7.0 N/mm²

Explanation

IS 1077 classifies common burnt clay bricks by compressive strength, and the minimum average strength for a first-class (Class 10) brick is 10.5 N/mm², with no individual brick falling below 85 percent of that value. Lower values such as 3.5 or 7.0 N/mm² correspond to lower classes and are used only in less demanding situations.

Question 2Building Materials and Construction Technology

The main purpose of adding gypsum to Portland cement clinker during grinding is to:

  1. reduce the heat of hydration of the cement
  2. increase the long-term strength of concrete
  3. accelerate the setting of the cement
  4. retard the setting of the cement Correct answer.

Explanation

Clinker ground without gypsum sets very rapidly because tricalcium aluminate reacts quickly with water, making the concrete unworkable. Gypsum is interground in small quantities (about 3 to 5 percent) to control this reaction and provide adequate setting time for placing and finishing.

Question 3Building Materials and Construction Technology

A timber specimen shows a distinct central core of darker, denser wood surrounded by a lighter outer band. The darker inner portion is best described as:

  1. sapwood
  2. inner bark
  3. heartwood Correct answer.
  4. cambium layer

Explanation

Heartwood is the inner, older wood whose cells have become filled with extractives and no longer conduct sap; it is darker, denser and more durable. Sapwood is the lighter outer zone that is still active in sap conduction and is more permeable and less durable.

Question 4Building Materials and Construction Technology

In a standard test for the initial setting time of cement, the Vicat plunger is considered to have reached the initial set when it penetrates the paste to a depth of:

  1. 5 to 7 mm Correct answer.
  2. 33 to 35 mm
  3. 10 to 12 mm
  4. 25 to 27 mm

Explanation

The initial setting time is the interval from adding water until the Vicat plunger, when released, fails to penetrate beyond 5 to 7 mm from the bottom of the mould. The 33 to 35 mm penetration corresponds to the standard consistency test, which is a different measurement.

Question 5Building Materials and Construction Technology

A mortar mix of 1:6 (cement:sand by volume) is specified for brickwork. If the bulking of the sand is 20 percent, the field volume of sand to be measured per unit volume of cement is:

  1. 5.0
  2. 6.0
  3. 4.8
  4. 7.2 Correct answer.

Explanation

Bulking increases the loose volume of damp sand for the same dry mass, so the measured field volume must be increased in proportion. For a nominal 1:6 mix with 20 percent bulking, the sand volume becomes 6 × 1.20 = 7.2 per unit volume of cement.

Question 6Building Materials and Construction Technology

A concrete cube of 150 mm side fails at a load of 540 kN. The compressive strength of the concrete is:

  1. 36 N/mm²
  2. 12 N/mm²
  3. 18 N/mm²
  4. 24 N/mm² Correct answer.

Explanation

Compressive strength equals the failure load divided by the loaded area. The area is 150 × 150 = 22,500 mm², so 540,000 N ÷ 22,500 mm² gives 24 N/mm².

Question 7Building Materials and Construction Technology

In the slump test on a concrete sample, the slump is measured as:

  1. the angle of the conical heap formed after removal of the mould
  2. the vertical settlement of the concrete from the top of the mould Correct answer.
  3. the time taken for the concrete to collapse completely
  4. the horizontal spread of concrete after the mould is lifted

Explanation

The slump is the vertical distance between the top of the mould and the displaced top of the concrete after the mould is lifted, measured with the mould still standing beside the sample. It is a measure of consistency and workability, not of spread or flow time.

Question 8Building Materials and Construction Technology

A burnt clay brick is found to absorb 22 percent of its dry mass when soaked for 24 hours. According to common IS acceptance practice for building bricks, this brick is:

  1. rejected, since absorption exceeds the usual 15 percent limit
  2. acceptable, since absorption is below 25 percent
  3. acceptable, since absorption is below 20 percent
  4. rejected, since absorption exceeds the usual 20 percent limit Correct answer.

Explanation

For common burnt clay building bricks, the usual acceptance limit on 24-hour water absorption is about 20 percent for higher classes, with slightly relaxed values for the lowest class. A brick absorbing 22 percent exceeds the general 20 percent limit and would normally be rejected or downgraded.

Question 9Building Materials and Construction Technology

The workability of a concrete mix is improved mainly by increasing which of the following, while keeping the water-cement ratio unchanged?

  1. the curing period
  2. the maximum size of coarse aggregate Correct answer.
  3. the proportion of flaky aggregate
  4. the cement content

Explanation

For a given water-cement ratio, a larger maximum size of coarse aggregate reduces the specific surface area to be wetted and allows a leaner, more workable mix. Cement content changes the water-cement ratio if water is not adjusted, and flaky aggregate reduces workability.

Question 10Building Materials and Construction Technology

In a compression test on a standard timber specimen, the load at proportional limit is 45 kN and the cross-sectional area is 7,500 mm². The stress at the proportional limit is:

  1. 6 N/mm² Correct answer.
  2. 12 N/mm²
  3. 9 N/mm²
  4. 3 N/mm²

Explanation

Stress is force divided by area, so 45,000 N ÷ 7,500 mm² equals 6 N/mm². This stress marks the end of the linear elastic range and is used along with the ultimate stress in timber grading.

Question 11Building Materials and Construction Technology

Which constituent of ordinary Portland cement contributes most to the early strength development of concrete?

  1. Tricalcium silicate (C3S) Correct answer.
  2. Tetracalcium aluminoferrite (C4AF)
  3. Dicalcium silicate (C2S)
  4. Tricalcium aluminate (C3A)

Explanation

Tricalcium silicate hydrates rapidly and is chiefly responsible for early strength gain, typically within the first 28 days. Dicalcium silicate hydrates slowly and governs long-term strength, while the aluminate and ferrite phases contribute little to strength and mainly affect setting and heat.

Question 12Building Materials and Construction Technology

A masonry wall of 230 mm thickness is to be built with modular bricks of nominal size 200 × 100 × 100 mm including mortar joints. The number of bricks required per square metre of wall face, ignoring wastage, is approximately:

  1. 100
  2. 25
  3. 75
  4. 50 Correct answer.

Explanation

With a nominal brick face of 200 × 100 mm including the joint, each brick covers 0.02 m² of wall face. One square metre therefore needs 1 ÷ 0.02 = 50 bricks, before adding an allowance for breakage and wastage.

Question 13Building Materials and Construction Technology

Lime putty used for whitewashing and mortar preparation is obtained by:

  1. calcining dolomite at low temperature without slaking
  2. burning limestone in a kiln and grinding the clinker directly
  3. slaking quicklime with excess water and storing it under water Correct answer.
  4. mixing hydrated lime with sand and allowing it to air-dry

Explanation

Quicklime is slaked with an excess of water and the resulting paste is kept submerged to mature into a plastic putty free of unslaked particles. This fat lime putty is then used for whitewashing and for fine finishing mortars.

Question 14Building Materials and Construction Technology

In a bituminous mix, the penetration test is primarily used to:

  1. assess the flash point of the binder
  2. measure the ductility of the binder at low temperature
  3. determine the softening point of the binder
  4. grade the binder by hardness at a standard temperature Correct answer.

Explanation

The penetration test measures how far a standard needle sinks into a bitumen sample under specified conditions of load, time and temperature, giving a grading of hardness. Lower penetration values indicate harder binders suitable for hotter climates.

Question 15Building Materials and Construction Technology

A concrete mix has a water-cement ratio of 0.5 by mass and a cement content of 400 kg per cubic metre. If 25 percent of the mixing water is lost by evaporation before curing begins, the effective water available for hydration per cubic metre is:

  1. 200 kg
  2. 150 kg Correct answer.
  3. 100 kg
  4. 250 kg

Explanation

The total mixing water is 0.5 × 400 = 200 kg per cubic metre. Losing 25 percent leaves 75 percent of that water, so 200 × 0.75 = 150 kg remains available for hydration and pore solution.

Question 16Building Materials and Construction Technology

Which of the following is the most appropriate test to assess the soundness of cement, that is, its tendency to undergo undesirable volume change after setting?

  1. Blaine air permeability test
  2. Le Chatelier apparatus test Correct answer.
  3. Vicat apparatus test
  4. Compressive strength test on mortar cubes

Explanation

The Le Chatelier test measures the expansion of a cement paste specimen caused by uncombined lime or magnesia, indicating unsoundness. Vicat tests measure consistency and setting time, Blaine measures fineness, and cube tests measure strength.

Question 17Building Materials and Construction Technology

A simply supported timber beam of span 4 m carries a uniformly distributed load of 5 kN/m. The maximum bending moment in the beam is:

  1. 10 kN·m Correct answer.
  2. 20 kN·m
  3. 40 kN·m
  4. 5 kN·m

Explanation

For a simply supported beam under a uniformly distributed load, the maximum bending moment is wL²/8. Substituting w = 5 kN/m and L = 4 m gives 5 × 16 ÷ 8 = 10 kN·m at midspan.

Question 18Building Materials and Construction Technology

In a concrete mix design, the use of angular crushed aggregate instead of rounded river gravel, with all other parameters unchanged, will generally:

  1. increase workability and reduce the water demand
  2. reduce the compressive strength of the hardened concrete
  3. reduce workability and increase the water demand Correct answer.
  4. leave workability unchanged because grading is the same

Explanation

Angular crushed particles have more interlocking and a higher surface area per unit volume than rounded gravel, so internal friction rises and more water is needed for the same workability. Rounded aggregate gives better workability at the same water content.

Question 19Building Materials and Construction Technology

A brick masonry wall shows fine, random hairline cracks and a whitish efflorescence on the surface after the monsoon. The most probable cause is:

  1. use of flaky coarse aggregate in the mortar
  2. insufficient curing of the plaster only
  3. soluble salts in the bricks or mortar drawn to the surface with moisture Correct answer.
  4. excessive cement content in the mortar

Explanation

Efflorescence occurs when soluble salts present in bricks, sand or cement dissolve in water and migrate to the surface, where they crystallise as a white deposit after evaporation. The associated hairline cracking points to moisture movement and volume change rather than to mix richness alone.

Question 20Building Materials and Construction Technology

The standard consistency of a cement paste is defined as the water content at which the Vicat plunger:

  1. penetrates to a depth of 5 to 7 mm from the bottom
  2. penetrates exactly half the depth of the mould
  3. settles 33 to 35 mm from the top of the mould Correct answer.
  4. fails to penetrate the paste at all

Explanation

Standard consistency is the water content, expressed as a percentage of the cement mass, at which the Vicat plunger settles 33 to 35 mm from the top of the mould. This value is fixed before setting time tests are conducted.

Question 21Strength of Materials and Structural Analysis

A simply supported beam of span 6 m carries a central point load of 40 kN. What is the maximum bending moment in the beam?

  1. 30 kN·m
  2. 120 kN·m
  3. 240 kN·m
  4. 60 kN·m Correct answer.

Explanation

For a simply supported beam with a central point load W over span L, the maximum bending moment occurs at midspan and equals WL/4. Here W = 40 kN and L = 6 m, so M = 40 × 6 / 4 = 60 kN·m.

Question 22Strength of Materials and Structural Analysis

For a beam cross-section, the shear stress is zero at which location?

  1. At one-quarter depth from the top fibre
  2. At the neutral axis
  3. At the centroid of the compression zone only
  4. At the extreme fibres (top and bottom surfaces) Correct answer.

Explanation

Shear stress in a beam is given by τ = VQ/(Ib), where Q is the first moment of area beyond the level considered. At the extreme fibres Q is zero, so the shear stress vanishes there; it reaches its maximum at the neutral axis for a rectangular section.

Question 23Strength of Materials and Structural Analysis

A steel bar of length 2 m, area 500 mm² and modulus 200 GPa carries an axial tensile load of 100 kN. Its elongation is:

  1. 2.0 mm Correct answer.
  2. 4.0 mm
  3. 0.5 mm
  4. 1.0 mm

Explanation

Axial elongation is δ = PL/(AE). Substituting P = 100,000 N, L = 2000 mm, A = 500 mm² and E = 200,000 N/mm² gives δ = (100000 × 2000)/(500 × 200000) = 2.0 mm.

Question 24Strength of Materials and Structural Analysis

The maximum shear stress in a solid circular shaft of diameter d transmitting torque T occurs at the surface and equals:

  1. 32T/(πd³)
  2. 4T/(πd³)
  3. 8T/(πd³)
  4. 16T/(πd³) Correct answer.

Explanation

Torsion theory gives τ = Tr/J, and for a solid circular shaft J = πd⁴/32 with r = d/2. Substituting gives τ_max = 16T/(πd³), which is the standard torsion formula for a solid shaft.

Question 25Strength of Materials and Structural Analysis

A column of length L with both ends hinged has an effective length of:

  1. 0.7L
  2. 2L
  3. 0.5L
  4. L Correct answer.

Explanation

The effective length depends on end conditions through the effective length factor K. For a column hinged at both ends the ends are free to rotate but not translate, so K = 1 and the effective length equals the actual length L.

Question 26Strength of Materials and Structural Analysis

A body is subjected to two mutually perpendicular direct stresses of equal magnitude σ (both tensile) with no shear stress on those planes. The maximum shear stress in the material is:

  1. 0
  2. σ/2 Correct answer.
  3. 2σ
  4. σ

Explanation

For a biaxial state with principal stresses σ and σ, the Mohr circle reduces to a point for the normal stress but the maximum shear stress is (σ1 − σ2)/2. With σ1 = σ2 = σ, this gives σ/2, though the radius of the circle is zero only when the stresses are equal and opposite in sign analysis confusion; here the correct magnitude is σ/2.

Question 27Strength of Materials and Structural Analysis

The point of contraflexure in a beam is the location where:

  1. The shear force is maximum
  2. The shear force changes sign
  3. The deflection is maximum
  4. The bending moment changes sign Correct answer.

Explanation

A point of contraflexure is where the bending moment diagram crosses zero and changes sign, meaning the curvature reverses from sagging to hogging. It is a property of the bending moment distribution, not of shear or deflection.

Question 28Strength of Materials and Structural Analysis

A simply supported beam of span 4 m carries a uniformly distributed load of 10 kN/m over its entire length. The maximum shear force is:

  1. 40 kN
  2. 80 kN
  3. 10 kN
  4. 20 kN Correct answer.

Explanation

The total load is wL = 10 × 4 = 40 kN, shared equally by the two supports. The maximum shear force at each support is therefore 40/2 = 20 kN, decreasing linearly to zero at midspan.

Question 29Strength of Materials and Structural Analysis

A cantilever of length 3 m carries a point load of 20 kN at its free end. The bending moment at the fixed support is:

  1. 20 kN·m (hogging)
  2. 60 kN·m (sagging)
  3. 30 kN·m (hogging)
  4. 60 kN·m (hogging) Correct answer.

Explanation

For a cantilever with an end point load P, the fixed-end moment is PL and it produces tension at the top fibre, i.e. hogging. Here M = 20 × 3 = 60 kN·m hogging.

Question 30Strength of Materials and Structural Analysis

The section modulus of a rectangular section of width b and depth d, bent about its centroidal axis parallel to the width, is:

  1. bd/6
  2. bd²/6 Correct answer.
  3. bd²/3
  4. bd³/12

Explanation

Section modulus is Z = I/y_max. For a rectangle, I = bd³/12 and y_max = d/2, giving Z = (bd³/12)/(d/2) = bd²/6.

Question 31Strength of Materials and Structural Analysis

For a simply supported beam carrying a concentrated load not at midspan, the deflection under the load is obtained using which principle?

  1. Superposition of shear flows
  2. Unit load method (virtual work) Correct answer.
  3. Lami's theorem
  4. Parallel axis theorem

Explanation

The unit load method applies a virtual unit load at the point where deflection is required and integrates the product of real and virtual moments over the span, giving the displacement. It handles unsymmetrical loading directly, unlike standard closed-form midspan formulas.

Question 32Strength of Materials and Structural Analysis

A material has a modulus of elasticity of 200 GPa and a Poisson's ratio of 0.3. Its modulus of rigidity is approximately:

  1. 154 GPa
  2. 100 GPa
  3. 77 GPa Correct answer.
  4. 60 GPa

Explanation

The relation between elastic constants is G = E/[2(1 + ν)]. Substituting E = 200 GPa and ν = 0.3 gives G = 200/(2 × 1.3) ≈ 76.9 GPa, i.e. about 77 GPa.

Question 33Strength of Materials and Structural Analysis

The principal tensile stress at a point has magnitude 80 MPa and the principal compressive stress is 40 MPa, with directions mutually perpendicular. The maximum shear stress is:

  1. 20 MPa
  2. 120 MPa
  3. 40 MPa
  4. 60 MPa Correct answer.

Explanation

Maximum shear stress is (σ1 − σ2)/2 where σ1 and σ2 are principal stresses taken with sign. With σ1 = +80 MPa and σ2 = −40 MPa, τ_max = (80 + 40)/2 = 60 MPa.

Question 34Strength of Materials and Structural Analysis

A simply supported beam of span L has a uniformly distributed load w. The maximum deflection at midspan is:

  1. 5wL⁴/(384EI) Correct answer.
  2. wL⁴/(8EI)
  3. wL⁴/(185EI)
  4. wL³/(48EI)

Explanation

The standard result for a simply supported beam under uniform load is δ_max = 5wL⁴/(384EI) at midspan. It follows from double integration of the moment expression with the boundary conditions of zero deflection at both supports.

Question 35Strength of Materials and Structural Analysis

In a three-hinged arch, the horizontal thrust H for a parabolic arch carrying a uniformly distributed load w over span L with rise h is:

  1. wL²/(8h) Correct answer.
  2. wL²/(4h)
  3. wL/(8h)
  4. wh²/(8L)

Explanation

Taking moments about the crown hinge for half the arch gives H = wL²/(8h) for a three-hinged parabolic arch under uniform horizontal load. The same expression arises from equating the bending moment at the crown to zero.

Question 36Strength of Materials and Structural Analysis

The degree of static indeterminacy of a continuous beam with three spans and four simple supports, with no internal hinges, is:

  1. 3
  2. 1
  3. 2 Correct answer.
  4. 4

Explanation

For a continuous beam, the degree of static indeterminacy equals the number of redundant reactions beyond the three equilibrium equations. Four simple supports give four vertical reactions, so the redundancy is 4 − 3 = 1? Careful: with four supports and no horizontal restraint counted, the vertical redundancy is 4 − 2 = 2 when horizontal reactions are ignored. Using the standard formula, D_s = 2 for a three-span continuous beam on four supports.

Question 37Strength of Materials and Structural Analysis

Which method is most suitable for analysing a rigid portal frame with many members and sway, using slope and deflection relationships at joints?

  1. Conjugate beam method
  2. Moment distribution method Correct answer.
  3. Maxwell's reciprocal theorem
  4. Unit load method

Explanation

The moment distribution method iteratively balances fixed-end moments at joints using stiffness-based distribution factors and carry-over factors, and it handles sway frames through a sway correction. It is a standard hand method for rigid jointed frames.

Question 38Strength of Materials and Structural Analysis

A two-hinged arch is statically indeterminate to the first degree. Its horizontal thrust is commonly determined by which condition?

  1. Zero shear at the springings
  2. Zero bending moment at the crown
  3. Zero vertical reaction at one hinge
  4. Zero relative horizontal displacement between the two hinges Correct answer.

Explanation

In a two-hinged arch the horizontal thrust is the single redundant, and it is found by requiring that the relative horizontal movement of the hinge points be zero. This compatibility condition is applied through the unit load or energy method.

Question 39Strength of Materials and Structural Analysis

The strain energy stored in an axially loaded bar of length L, area A, modulus E under axial force P is:

  1. P²L/(2AE) Correct answer.
  2. PL²/(2AE)
  3. PL/(AE)
  4. P²L/(AE)

Explanation

Strain energy for axial loading is U = ∫P²/(2AE) dx, which for constant P and A over length L gives P²L/(2AE). It equals one-half the load times the elongation.

Question 40Strength of Materials and Structural Analysis

A point on a stressed body has σx = 100 MPa, σy = 0 and τxy = 50 MPa. The major principal stress is:

  1. 120.7 MPa Correct answer.
  2. 100 MPa
  3. 50 MPa
  4. 150 MPa

Explanation

Principal stresses are given by σ1,2 = (σx + σy)/2 ± √[((σx − σy)/2)² + τxy²]. Substituting gives 50 ± √(50² + 50²) = 50 ± 70.7, so σ1 ≈ 120.7 MPa.

Question 41Strength of Materials and Structural Analysis

The shape factor of a rectangular section in plastic bending about its centroidal axis is:

  1. 1.5 Correct answer.
  2. 1.15
  3. 1.0
  4. 2.0

Explanation

Shape factor is the ratio of plastic moment to yield moment, Zp/Ze. For a rectangle, Zp = bd²/4 and Ze = bd²/6, giving a ratio of 1.5.

Question 42Strength of Materials and Structural Analysis

A simply supported beam of span 8 m carries a point load of 30 kN at 2 m from the left support. The reaction at the right support is:

  1. 30 kN
  2. 22.5 kN
  3. 15 kN
  4. 7.5 kN Correct answer.

Explanation

Taking moments about the left support gives R_right × 8 = 30 × 2, so R_right = 60/8 = 7.5 kN. The left reaction takes the remainder, 22.5 kN, confirming vertical equilibrium.

Question 43Strength of Materials and Structural Analysis

In the analysis of a fixed beam of uniform section carrying a central point load, the fixed-end moment at each support is:

  1. WL/16
  2. WL/4
  3. WL/8 Correct answer.
  4. WL/2

Explanation

For a fixed beam with a central point load W over span L, the fixed-end moment is WL/8, which is hogging at both supports. The midspan sagging moment is WL/8 as well, giving a total moment diagram with zero slope at the ends.

Question 44Strength of Materials and Structural Analysis

A thin cylindrical pressure vessel of diameter 1 m and wall thickness 10 mm is subjected to an internal pressure of 2 MPa. The hoop stress is:

  1. 200 MPa
  2. 10 MPa
  3. 50 MPa
  4. 100 MPa Correct answer.

Explanation

Hoop stress in a thin cylinder is σ_h = pd/(2t). With p = 2 MPa, d = 1000 mm and t = 10 mm, σ_h = 2 × 1000/(2 × 10) = 100 MPa.

Question 45Concrete Technology and Reinforced Concrete Design

As per IS 10262 guidelines, the target mean strength of concrete for mix design is obtained by adding which quantity to the characteristic compressive strength?

  1. The coefficient of variation multiplied by 1.65
  2. The standard deviation multiplied by 1.65 Correct answer.
  3. The standard deviation multiplied by 2.33
  4. The standard deviation multiplied by 1.00

Explanation

Target mean strength equals characteristic strength plus 1.65 times the assumed standard deviation, because 1.65 corresponds to the 5 percent failure probability permitted for Grade M15 and above. This margin ensures no more than 5 percent of test results fall below the characteristic value.

Question 46Concrete Technology and Reinforced Concrete Design

In a reinforced concrete beam, the lever arm used in the working stress method is measured between which two resultants?

  1. The neutral axis and the extreme compression fibre
  2. The centroid of the tensile steel and the extreme tension fibre
  3. The centroid of the compressive steel and the neutral axis
  4. The centroid of the tensile steel and the centroid of the compressive stress block Correct answer.

Explanation

The resisting moment in the working stress method is the couple formed by the compressive force in concrete and the tensile force in steel, so the lever arm is the distance between their centroids. For a singly reinforced section the compressive centroid lies at one-third of the neutral axis depth from the top.

Question 47Concrete Technology and Reinforced Concrete Design

Which compound of Portland cement is chiefly responsible for the early strength gain of concrete within the first few days?

  1. Tricalcium aluminate
  2. Dicalcium silicate
  3. Tricalcium silicate Correct answer.
  4. Tetracalcium aluminoferrite

Explanation

Tricalcium silicate hydrates rapidly and contributes most of the strength developed in the first week, which is why it dominates early strength. Dicalcium silicate hydrates slowly and governs long-term strength instead.

Question 48Concrete Technology and Reinforced Concrete Design

A concrete cube of 150 mm side is tested and fails at a load of 540 kN. What is the compressive strength of the concrete?

  1. 18 N/mm²
  2. 24 N/mm² Correct answer.
  3. 36 N/mm²
  4. 27 N/mm²

Explanation

The loaded area of a 150 mm cube is 22500 mm², so strength equals 540000 divided by 22500, giving 24 N/mm². Cube strength is always reported as load divided by the plane area of the loaded face.

Question 49Concrete Technology and Reinforced Concrete Design

Which test is used to assess the resistance of concrete to freezing and thawing cycles in the laboratory?

  1. The Vebe consistometer test
  2. The split tensile test
  3. The rebound hammer test
  4. Repeated freeze-thaw cycling of saturated specimens with measurement of dynamic modulus or mass loss Correct answer.

Explanation

Durability against frost action is judged by subjecting saturated specimens to repeated freezing and thawing and monitoring deterioration through dynamic modulus, length change or mass loss. Saturation is essential because frost damage requires water in the pores.

Question 50Concrete Technology and Reinforced Concrete Design

In limit state design of a reinforced concrete flexural member, the partial safety factor for concrete material strength is taken as:

  1. 1.5 Correct answer.
  2. 0.87
  3. 1.0
  4. 1.15

Explanation

IS 456 adopts a partial safety factor of 1.5 on the characteristic compressive strength of concrete for the ultimate limit state, giving the design strength 0.67 fck divided by 1.5. The factor accounts for material variability and the difference between cube and in-situ strength.