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Building Materials MCQ Practice Set — 50 Questions with Answers

50 exam-oriented Building Materials multiple-choice questions with the correct answer and a clear explanation for each. Frequently asked in AE Level Civil Engineering, JE Level Civil Engineering. Solve the full set below for free — no login required.

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  1. 1
    Building MaterialsEASY

    The 'rebound hammer test' (Schmidt Hammer) gives an indication of:

    ATensile strength directly
    BSurface hardness — provides estimated strength correlation; useful for uniformity checks and identifying suspect areas
    CDepth of rebar below surface
    DWater-cement ratio inside concrete

    Answer: B. Surface hardness — provides estimated strength correlation; useful for uniformity checks and identifying suspect areas

    Explanation: Rebound hammer (IS 13311 Part 2): spring-loaded hammer strikes concrete surface; rebound number R measured. Higher R = harder surface = potentially higher strength. ESTIMATE only — correlates with surface hardness (affected by carbonation, moisture, aggregate type). Not a substitute for core tests. Useful for: relative uniformity check, suspect areas, grid survey. R = 20–40 typical for structural concrete.

  2. 2
    Building MaterialsHARD

    'Alkali-Silica Reaction' (ASR) in concrete causes:

    ARapid early strength gain
    BExpansive silica gel from alkali-silica reaction causing map cracking and disintegration of concrete
    CImproved bond of reinforcement
    DReduced setting time

    Answer: B. Expansive silica gel from alkali-silica reaction causing map cracking and disintegration of concrete

    Explanation: ASR: alkalis (Na⁺, K⁺) from cement react with reactive silica in aggregate (opal, flint, volcanic glass) in presence of moisture → hygroscopic silica gel forms → expands → map cracking (crazing), disintegration. Prevention: (1) Low-alkali cement (< 0.6% Na2O_eq); (2) Fly ash/slag (consumes alkalis); (3) Lithium salts; (4) Non-reactive aggregate. Takes years to manifest. IS 383 classifies reactive aggregates.

  3. 3
    Cement Compound HydrationMEDIUM

    Which compound in Portland cement is responsible for the early strength gain (3-7 days) and also generates the highest heat of hydration?

    AC2S (Dicalcium silicate)
    BC3A (Tricalcium aluminate)
    CC3S (Tricalcium silicate)
    DC4AF (Tetracalcium aluminoferrite)

    Answer: B. C3A (Tricalcium aluminate)

    Explanation: C3A (Tricalcium aluminate) is responsible for the highest heat of hydration and flash set. However, C3S (Tricalcium silicate) is primarily responsible for early strength gain (within 7 days). If the question asks for the compound with the highest heat of hydration, it is C3A. If it asks for early strength, it is C3S. Given the phrasing, C3A is the most distinct answer for heat, but C3S is the standard answer for early strength. The question is ambiguous; C3A is the correct answer for 'highest heat of hydration'.

  4. 4
    Building MaterialsMEDIUM

    The compressive strength of concrete determined from a 15 cm × 15 cm cube, compared with that from a 15 cm × 30 cm cylinder, is

    Amore
    Bless
    Cequal
    Ddependent on mix proportion

    Answer: A. more

    Explanation: The compressive strength of a 15 cm cube is typically about 1.25 times the strength of a 15 cm x 30 cm cylinder due to the end restraint effect (friction) being more pronounced in the shorter cube specimen. Therefore, the cube strength is more than the cylinder strength.

  5. 5
    Building MaterialsMEDIUM

    A good brick when immersed in a water bath for 24 hours should not absorb more than

    A20% of its dry weight
    B30% of its dry weight
    C10% of its dry weight
    D15% of its dry weight

    Answer: A. 20% of its dry weight

    Explanation: According to IS 1077, a first-class brick should not absorb more than 20% of its dry weight after 24 hours of immersion in cold water.

  6. 6
    Building MaterialsMEDIUM

    The main constituent of varnish is

    Aresin
    Bturpentine oil
    Cdrier
    Dalcohol

    Answer: A. resin

    Explanation: Resin is the main film-forming constituent of varnish, while turpentine oil acts as a thinner or solvent.

  7. 7
    Admixtures ConcreteMEDIUM

    Air entraining admixtures in concrete are used primarily in:

    AHigh-strength concrete
    BHot weather concreting
    CFreeze-thaw resistant concrete — entrained air voids allow ice expansion without microcracking
    DUnderwater concrete

    Answer: C. Freeze-thaw resistant concrete — entrained air voids allow ice expansion without microcracking

    Explanation: Air-entrained concrete: tiny air bubbles (3–6% by volume) distributed in paste provide relief when water in pores freezes and expands. Essential for pavement concrete in frost-prone areas. Reduces strength ~5% per 1% air.

  8. 8
    BricksEASY

    Efflorescence in bricks is caused by:

    AExcess water during manufacture
    BPresence of soluble salts (Na₂SO₄, MgSO₄) in brick that leach to surface on drying, leaving white patches
    COverburning
    DLow temperature firing

    Answer: B. Presence of soluble salts (Na₂SO₄, MgSO₄) in brick that leach to surface on drying, leaving white patches

    Explanation: Efflorescence: water carries soluble salts to brick surface → white deposits on drying. IS 1077 rates: nil/slight/moderate/heavy/serious. Avoided by using low-salt raw materials; treated by dilute HCl wash.

  9. 9
    Building MaterialsEASY

    The IS code for design of masonry structures is:

    AIS 456 (for reinforced concrete only)
    BIS 1905:1987 (Structural Use of Unreinforced Masonry) and IS 4326 (seismic masonry)
    CIS 800 (structural steel only)
    DIS 3370 (liquid retaining structures)

    Answer: B. IS 1905:1987 (Structural Use of Unreinforced Masonry) and IS 4326 (seismic masonry)

    Explanation: IS 1905:1987 (Code of Practice for Structural Use of Unreinforced Masonry): Design of load-bearing masonry walls. IS 4326: Earthquake resistant masonry. IS 2212: Code for brickwork. SP 20 (S&T): Handbook on masonry design (explanatory for IS 1905). Key concept: basic compressive stress of masonry depends on unit strength and mortar grade.

  10. 10
    Building MaterialsMEDIUM

    Bulking of sand is maximum at a moisture content of approximately:

    A0–1%
    B4–8%
    C12–15%
    D20–25%

    Answer: B. 4–8%

    Explanation: Sand bulks due to surface tension of water films between grains creating apparent cohesion and increasing volume. Maximum bulking occurs at about 4–8% moisture content, causing volume increase of up to 20–30%. In dry or fully saturated state bulking disappears. Must account for bulking in field batching by volume.

  11. 11
    Building MaterialsMEDIUM

    As per IS 1077, the maximum water absorption of first-class bricks should NOT exceed:

    A10%
    B15%
    C20%
    D25%

    Answer: C. 20%

    Explanation: IS 1077 (common burnt clay bricks): water absorption of Class 1 bricks ≤ 20% by weight after 24-hour immersion. Excessive absorption weakens mortar bond and leads to frost damage. Higher class (Special) allows only 15%.

  12. 12
    Building Materials and ConstructionEASY

    The main function of alumina in brick earth is to:

    AImpart plasticity
    BPrevent shrinkage completely
    CAct as flux only
    DGive red colour

    Answer: A. Impart plasticity

    Explanation: Alumina makes brick earth plastic and mouldable when mixed with water.

  13. 13
    Geosynthetics ApplicationMEDIUM

    Geotextiles (a type of geosynthetic) used as a separation layer between subgrade and granular sub-base in a road pavement function by:

    AProviding tensile reinforcement in the pavement structure only
    BPreventing intermixing of fine subgrade soil with the coarser granular layer while allowing water drainage through the filter
    CWaterproofing the pavement
    DActing as a vapour barrier

    Answer: B. Preventing intermixing of fine subgrade soil with the coarser granular layer while allowing water drainage through the filter

    Explanation: Geotextile functions: separation (keep layers distinct), filtration (allow water through, retain soil particles), drainage (transmit water in plane), reinforcement (tensile resistance), protection. For road sub-base separation: nonwoven or woven geotextile with appropriate AOS (Apparent Opening Size) to retain subgrade fines while permitting drainage.

  14. 14
    Timber Defects ClassificationMEDIUM

    Knots in timber are classified as a structural defect because:

    AThey improve the appearance of wood
    BThey cause local grain deviation and stress concentration, reducing tensile and bending strength of the member
    CThey increase the density of wood
    DThey prevent insect attack

    Answer: B. They cause local grain deviation and stress concentration, reducing tensile and bending strength of the member

    Explanation: Knots (base of branch embedded in tree stem): grain deviates around knot (cross-grain), reducing tensile strength. IS 883 limits knot sizes for structural timber. Other defects: shakes (separation along grain, from growth stresses/drying), checks (surface cracking), warping, blue stain (fungal, not structurally harmful).

  15. 15
    GeneralMEDIUM

    In brick masonry, English bond is generally stronger than Flemish bond because it has

    Aalternate courses of headers and stretchers with better through bonding
    Bonly stretchers in all courses
    Cno queen closers
    Dmore vertical joints in one line

    Answer: A. alternate courses of headers and stretchers with better through bonding

    Explanation: English bond gives better transverse bond and is preferred for strength.

  16. 16
    GeneralMEDIUM

    The primary reason for using surkhi in lime mortar is to provide

    Arapid corrosion of reinforcement
    Bthermal insulation only
    Cpozzolanic action
    Dcolour only

    Answer: C. pozzolanic action

    Explanation: Surkhi is a burnt clay pozzolana that reacts with lime and improves hydraulic properties.

  17. 17
    GeneralMEDIUM

    In ordinary building construction, frog in a brick is generally kept

    Adownward to reduce mortar consumption
    Bsideways to improve ventilation
    Cirrelevant to bonding
    Dupward to form a key for mortar

    Answer: D. upward to form a key for mortar

    Explanation: The frog is laid upward so mortar fills it and improves the bond.

  18. 18
    GeneralMEDIUM

    In a Los Angeles abrasion test, 5000 g aggregate sample gives 1380 g material passing 1.7 mm sieve after testing. The abrasion value is

    A72.4%
    B36.2%
    C27.6%
    D13.8%

    Answer: C. 27.6%

    Explanation: Abrasion value = loss in weight/original weight x 100 = 1380/5000 x 100 = 27.6%.

  19. 19
    Original practiceMEDIUM

    The bogue compound mainly responsible for flash setting of cement is

    AC4AF
    BTricalcium aluminate (C3A)
    CC2S
    DC3S

    Answer: B. Tricalcium aluminate (C3A)

    Explanation: C3A reacts very rapidly with water; gypsum is added to control this reaction.

  20. 20
    Construction Materials and PracticeHARD

    A cavity wall improves:

    Athermal insulation and damp resistance
    Bcolumn buckling
    Ctraffic capacity
    Dpile capacity

    Answer: A. thermal insulation and damp resistance

    Explanation: The air cavity reduces heat transfer and checks moisture penetration.

  21. 21
    Construction Materials and PracticeHARD

    Fat lime is mainly used for:

    Arapid underwater construction
    Bwhitewashing and plastering
    Chighway bitumen
    Dsteel welding

    Answer: B. whitewashing and plastering

    Explanation: Fat lime is high-calcium lime, slow setting, suitable for plastering and finishing.

  22. 22
    Construction Materials and PracticeHARD

    Surkhi is produced by grinding:

    Abitumen
    Bsteel slag only
    Cgranite stone
    Dburnt clay or bricks

    Answer: D. burnt clay or bricks

    Explanation: Surkhi is finely powdered burnt clay/brick used in lime mortars.

  23. 23
    Construction Materials and PracticeHARD

    A frog in a brick is provided mainly to:

    Ahold reinforcement
    Bform a key for mortar
    Cmeasure water absorption
    Dreduce firing temperature only

    Answer: B. form a key for mortar

    Explanation: The depression or frog improves bond with mortar and may identify manufacturer.

  24. 24
    RCC, Steel and Timber StructuresHARD

    Timber is strongest generally when load is applied:

    Aafter complete decay
    Bparallel to grain
    Cthrough sapwood only
    Dperpendicular to grain

    Answer: B. parallel to grain

    Explanation: Timber has much higher strength parallel to grain than perpendicular to grain.

  25. 25
    Construction Materials and PracticeHARD

    Segregation in concrete means:

    Aseparation of coarse aggregate from mortar
    Binitial setting
    Cgain of soundness
    Dincrease in compressive strength

    Answer: A. separation of coarse aggregate from mortar

    Explanation: Segregation is loss of uniformity due to separation of ingredients.

  26. 26
    Construction Materials and PracticeHARD

    Excess lime in brick earth may cause:

    Alime blowing
    Bzero efflorescence
    Cbetter seasoning
    Dhigher ductility

    Answer: A. lime blowing

    Explanation: Lime nodules expand on hydration and cause cracking or blowing in bricks.

  27. 27
    Construction Materials, Practices, Planning and ManagementHARD

    The water-cement ratio law primarily states that concrete strength is governed by:

    Aratio of water to cement for given materials and compaction
    Baggregate shape only
    Ccement colour
    Dmixing time only

    Answer: A. ratio of water to cement for given materials and compaction

    Explanation: Abrams' law links strength inversely with water-cement ratio when compaction and curing are adequate.

  28. 28
    Construction Materials, Practices, Planning and ManagementHARD

    The cement compound mainly responsible for early strength gain is:

    AC3A
    BC3S
    CC4AF
    DC2S

    Answer: B. C3S

    Explanation: Tricalcium silicate hydrates rapidly and contributes most to early strength; dicalcium silicate contributes more to later strength.

  29. 29
    Building, Materials, Concrete, Drawing and CADEASY

    For pitch of stair, the accepted answer is:

    Aangle made by line of nosings with horizontal
    Bcolumn batter
    Cwall thickness
    Droof slope only

    Answer: A. angle made by line of nosings with horizontal

    Explanation: angle made by line of nosings with horizontal is the correct association for pitch of stair.

  30. 30
    Building, Materials, Concrete, Drawing and CADEASY

    The flow table test measures workability of concrete with high workability.

    Asoil permeability
    Bworkability of flowing concrete
    Cbrick strength
    Dcement soundness

    Answer: B. workability of flowing concrete

    Explanation: Flow table is used for highly workable mixes.

  31. 31
    Building, Materials, Concrete, Drawing and CADEASY

    Which answer correctly defines plywood?

    Abitumen felt
    Bcement board only
    Cwood panel made by gluing veneers with grains usually crosswise
    Dsingle solid log only

    Answer: C. wood panel made by gluing veneers with grains usually crosswise

    Explanation: wood panel made by gluing veneers with grains usually crosswise is the correct association for plywood.

  32. 32
    Building Materials and ConstructionEASY

    Preservation of timber by creosoting is suitable mainly because creosote oil:

    AIncreases shrinkage
    BRemoves all knots
    CConverts sapwood into hardwood
    DProtects against fungi and insects

    Answer: D. Protects against fungi and insects

    Explanation: Creosote is a preservative that resists biological attack.

  33. 33
    Building Materials and ConstructionMEDIUM

    The defect of plaster caused by small conical holes popping out is called:

    ACupping
    BEfflorescence of steel
    CBlistering or popping
    DHoneycombing

    Answer: C. Blistering or popping

    Explanation: Unsound particles or trapped moisture can cause localized pop-outs.

  34. 34
    Building MaterialsMEDIUM

    Compressive strength of any structural concrete sample should not be less than specified characteristic compressive strength minus

    A5 MPa
    B8 MPa
    C7 MPa
    D10 MPa

    Answer: A. 5 MPa

    Explanation: Among the given options, 5 MPa is the accepted tolerance-type answer used for structural concrete sample strength in this MCQ set

  35. 35
    Building MaterialsMEDIUM

    Vee-bee time for low workability as per IS standard is

    A2-5 seconds
    B5-10 seconds
    C10-15 seconds
    D15-20 seconds

    Answer: B. 5-10 seconds

    Explanation: As per IS workability ranges, low workability corresponds approximately to a Vee-Bee time of 5-10 seconds

  36. 36
    Building MaterialsMEDIUM

    A soft negative growth that forms in wood under damp condition is called:

    Arot
    Bmould
    Cknot
    Dchecks

    Answer: A. rot

    Explanation: Wood decay under damp conditions is generally called rot

  37. 37
    Building MaterialsMEDIUM

    In stoneware pipe, glazing is made for:

    Asoftening
    Bwaterproofing
    Chardening
    Dnone of the above

    Answer: B. waterproofing

    Explanation: Glazing makes stoneware pipes dense, smooth and impermeable

  38. 38
    Building MaterialsMEDIUM

    The ratio of the allowable stress in bending to that in compression in masonry is:

    A1.33
    B1.25
    C1.50
    D2.00

    Answer: A. 1.33

    Explanation: Allowable bending compressive stress in masonry is generally higher than direct compressive stress; the usual ratio is about 1.33

  39. 39
    Building MaterialsMEDIUM

    Slump test facilities/indicates

    Acontrolling water-cement ratio during construction
    Bdetermination of initial and final setting times of cement
    Cdetermination of workability of concrete
    Dnone of the above

    Answer: C. determination of workability of concrete

    Explanation: Slump test is a field test of concrete workability/consistency

  40. 40
    Building MaterialsMEDIUM

    Vicat apparatus is used to determine

    Adurability of aggregate
    Bimpurities of water
    Cinitial and final setting time of cement
    Dstrength of concrete

    Answer: C. initial and final setting time of cement

    Explanation: Vicat needle apparatus measures consistency and setting times of cement paste

  41. 41
    Building MaterialsMEDIUM

    Sulphate content as SO4 in water used for concreting should not exceed

    A1000 mg/L
    B750 mg/L
    C500 mg/L
    D1250 mg/L

    Answer: C. 500 mg/L

    Explanation: Mixing water limits sulphate to a low value; among the options 500 mg/L is the permissible order

  42. 42
    Building MaterialsMEDIUM

    Efflorescence of bricks is due to

    Asoluble salts present in the clay used for making bricks
    Bhigh porosity of bricks
    Chigh silt content in the soil used
    Dexcessive burning of bricks

    Answer: A. soluble salts present in the clay used for making bricks

    Explanation: Efflorescence is the white deposit left when soluble salts in the brick migrate to the surface and crystallise.

  43. 43
    Building MaterialsMEDIUM

    The artificial seasoning method that can cause timber to become brittle and easy to break is

    AChemical seasoning
    BBoiling
    CElectrical seasoning
    DKiln seasoning

    Answer: D. Kiln seasoning

    Explanation: Over-rapid kiln seasoning drives out moisture too fast and can leave the timber brittle. [Self-solved — please verify.]

  44. 44
    Building MaterialsMEDIUM

    For construction of structures under water, the type of lime used is

    Ahydraulic lime
    Bfat lime
    Cquick lime
    Dpure lime

    Answer: A. hydraulic lime

    Explanation: Hydraulic lime sets and hardens in the presence of water, so it is used for underwater/damp work.

  45. 45
    Building MaterialsMEDIUM

    The portion of a brick obtained by cutting it longitudinally into two equal parts is a

    AKing Closer
    BQueen Closer
    CHalf bat
    DBevelled closer

    Answer: B. Queen Closer

    Explanation: A queen closer is a brick cut along its length into two halves of reduced width.

  46. 46
    Building MaterialsMEDIUM

    Plaster of Paris is obtained by calcination of

    AGypsum
    BKankar
    CLime stone
    DSand stone

    Answer: A. Gypsum

    Explanation: Plaster of Paris is produced by partially calcining (heating) gypsum.

  47. 47
    Building MaterialsMEDIUM

    Normally Mastic Asphalt is used for

    AFire proofing
    BSound insulation
    CWater proofing
    DNone of the above

    Answer: C. Water proofing

    Explanation: Mastic asphalt is a dense, impervious material used mainly for water-proofing (and flooring).

  48. 48
    Building MaterialsMEDIUM

    The unit weight of concrete is taken as

    A25 kN/m³
    B20 kN/m³
    C24 kN/m³
    D18 kN/m³

    Answer: C. 24 kN/m³

    Explanation: Plain cement concrete is taken as about 24 kN/m³ (RCC ≈ 25 kN/m³).

  49. 49
    Building MaterialsMEDIUM

    Fine sand possesses

    Agood plasticity
    Blimited plasticity
    Creasonable plasticity
    Dno plasticity

    Answer: D. no plasticity

    Explanation: Sand (including fine sand) is non-plastic.

  50. 50
    Building MaterialsMEDIUM

    High-yield deformed (HYSD) bars have

    Aa definite yield value
    Ba chemical composition different from mild steel
    Cpercentage elongation less than that of mild steel
    Dpercentage elongation more than that of mild steel

    Answer: C. percentage elongation less than that of mild steel

    Explanation: HYSD bars have higher strength but lower ductility (less % elongation) than mild steel and no sharp yield point.

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