Question 1

Paint thinners — match common coatings with their usual thinners and identify the correct combined statement. Choose the best option.

Accepted Answer

Introduction / Context: Every coating system has compatible thinners that adjust viscosity and drying characteristics. This question checks practical knowledge of typical thinners used with common paint categories in building works. Given Data / Assumptions: Lacquer paints (nitrocellulose or similar), cellulose paints, oil-based paints, and distemper are considered. We assume standard, widely used thinner pairings. Only one option correctly aggregates all matches. Concept / Approach: Correct thinning ensures proper atomization, leveling, and film formation. The usual pairings are: alcohols for many lacquers, esters/ketones like ethyl acetate for cellulose paints, petroleum distillates (e.g., mineral spirits/naphtha) for oil paints, and plain water for distemper (a water-based paint). Step-by-Step Solution: 1) Lacquer paints: Commonly thinned with alcohols and compatible solvents.2) Cellulose paints: Ethyl acetate and related solvents are standard choices.3) Oil paints: Mineral spirits/naphtha serve as conventional thinners.4) Distemper: A water-borne paint; water is the thinner. Verification / Alternative check: Manufacturer data sheets and trade practice guides confirm these pairings as standard recommendations for application and cleanup. Why Other Options Are Wrong: Each single statement captures only one pairing; the comprehensive, correct grouping is the “All of the above” choice. Common Pitfalls: Using an incompatible thinner can cause poor film formation, slow drying, or surface defects like orange peel and pinholing. Final Answer: All of the above

Question 2

Plastics manufacturing — which statements about common processes are correct? Select the best combined option.

Accepted Answer

Introduction / Context: Industrial plastic forming relies on several foundational processes. This question validates whether you can identify which statements correctly map processes to products and methods. Given Data / Assumptions: Focus on blow moulding, calendering, laminating, and moulding. Common, introductory-level manufacturing knowledge is assumed. No specialized variants (e.g., stretch-blow, twin-screw compounding) are needed. Concept / Approach: Each listed process has a canonical application: blow moulding for hollow articles like bottles; calendering for continuous sheets/films; laminating for resin-bonded composites (paper or fabric); and moulding as the general method of shaping in a cavity. Step-by-Step Solution: 1) Blowing: Expands heated plastic parison/preform against a mould cavity to form bottles and containers.2) Calendering: Passes softened plastic through rollers to produce sheets/films of controlled thickness.3) Laminating: Impregnates or coats sheets (e.g., paper) with thermoset resin, then cures under heat/pressure.4) Moulding: Encompasses compression, injection, transfer, etc., where raw material is shaped in a mould. Verification / Alternative check: Basic manufacturing texts and polymer processing guides match these definitions and typical applications. Why Other Options Are Wrong: Individual process statements are correct but incomplete; the aggregate correctness is captured by “All of the above.” Common Pitfalls: Confusing calendering with extrusion casting; forgetting that blow moulding specifically targets hollow shapes. Final Answer: All of the above

Question 3

Strength properties of hand-moulded bricks — identify the correct set of average values. Choose the most accurate option.

Accepted Answer

Introduction / Context: Brick quality is often summarized by compressive (crushing), tensile, and shear strengths. While compressive strength is the principal criterion, awareness of typical ranges for other strengths helps in design checks and material selection. This question tests recognition of commonly cited average values for hand-moulded bricks in older unit systems. Given Data / Assumptions: Units are given in t/m² (tonnes per square metre). Values asked are “average,” not characteristic minima for high-grade classes. Hand-moulded, fired clay bricks of standard quality. Concept / Approach: Compressive strength of conventional bricks far exceeds their tensile and shear strengths. The listed values represent typical magnitudes referenced in traditional texts, acknowledging variability with raw material, firing, and porosity. Step-by-Step Solution: 1) Crushing (compressive) strength of ~6000 t/m² corresponds to expected ranges for ordinary quality bricks in legacy units.2) Tensile strength is a small fraction of compressive strength; ~200 t/m² as an order-of-magnitude average is reasonable.3) Shearing strength typically lies between tensile and compressive values; ~600 t/m² is a plausible average figure.4) Therefore, the grouped “All of the above” best represents the stated averages together. Verification / Alternative check: Cross-check with standard building materials references that present approximate values and stress the dominance of compressive over tensile capacity in masonry units. Why Other Options Are Wrong: Each single value captures only part of the picture; the comprehensive and correct set is “All of the above.” Common Pitfalls: Comparing these legacy units directly with modern N/mm² without conversion; ignoring wide variability across classes and manufacturing quality. Final Answer: All of the above

Question 4

Water absorption limit — after immersing a brick for 16 hours, the wet weight should not exceed the dry weight by more than: Choose the correct percentage.

Accepted Answer

Introduction / Context: Water absorption is a key indicator of brick quality and durability. Excessive absorption can lead to frost susceptibility, efflorescence, and reduced strength. Standards specify maximum permissible absorption by weight after immersion for a defined period. Given Data / Assumptions: Immersion period: 16 hours (commonly used test duration). We are considering ordinary good-quality burnt clay bricks. Percentage increase is measured relative to dry weight. Concept / Approach: For general-purpose common bricks, traditional specifications allow up to about one-fifth increase in mass after 16–24 hours immersion. Higher-grade facing bricks may have tighter limits (often 15% or lower), but the typical textbook answer for “good quality” common bricks is 20%. Step-by-Step Solution: 1) Determine dry weight (W_d) and wet weight after immersion (W_w).2) Compute absorption% = ((W_w − W_d) / W_d) * 100.3) For standard good-quality common bricks, the acceptable limit is about 20%.4) Therefore, choose 20% as the maximum permissible increase. Verification / Alternative check: Legacy building codes and materials handbooks frequently cite 20% as the typical limit for ordinary bricks, noting stricter values for higher grades. Why Other Options Are Wrong: 15%: Tighter than typical common-brick limits; applicable to selected grades. 10%: Too stringent for ordinary bricks. None of these: Incorrect because 20% is acceptable for common good-quality bricks. Common Pitfalls: Using limits for special bricks (e.g., engineering bricks) when the question context implies ordinary “good quality” bricks. Final Answer: 20%

Question 5

Seasoned timber — the typical moisture content of well-seasoned wood is approximately: Select the correct range.

Accepted Answer

Introduction / Context: Moisture content directly affects timber strength, dimensional stability, and susceptibility to decay. Proper seasoning lowers moisture to a level compatible with service conditions, minimizing shrinkage and warping after installation. Given Data / Assumptions: “Well-seasoned” refers to properly air- or kiln-seasoned timber for building use. Ambient indoor conditions are assumed (not extreme deserts or humid tropics). We are selecting an indicative range, not an exact single value. Concept / Approach: Equilibrium moisture content (EMC) for indoor service typically lies around 10% to 12% in many climates. Air seasoning often achieves 12%–20%; kiln seasoning can target 10%–12% for internal joinery, flooring, and furniture, providing good dimensional stability. Step-by-Step Solution: 1) Understand EMC: Wood gains/loses moisture until it equilibrates with surrounding humidity.2) For general interior construction, EMC commonly stabilizes near 10%–12%.3) Therefore, well-seasoned timber intended for such use is taken as ~10%–12% moisture content.4) Lower bands like 4%–8% are uncommon except under very dry, controlled conditions. Verification / Alternative check: Timber practice guides recommend kiln-drying targets around 10%–12% for interior applications to balance stability with practicality. Why Other Options Are Wrong: 4%–6% or 6%–8%: Too low for typical indoor service without special conditioning. 8%–10%: Possible in select climates, but 10%–12% is the widely cited band for “well-seasoned.” Common Pitfalls: Confusing “air-seasoned” broader ranges with “well-seasoned” targets for interior service. Final Answer: 10% to 12%

Question 6

Selection of stones for retaining walls — which property is most important for stability against earth pressure? Pick the most appropriate attribute.

Accepted Answer

Introduction / Context: Retaining walls resist lateral earth pressure through a combination of weight, geometry, and structural action. When using masonry or random rubble, the self-weight of the stones plays a critical role in preventing sliding and overturning. Given Data / Assumptions: Traditional gravity or semi-gravity retaining wall using stone masonry. Primary concern is global stability under lateral soil loads. Material choices influence unit weight and durability. Concept / Approach: For gravity action, higher unit weight provides larger stabilizing moments and frictional resistance. While hardness relates to durability and abrasion resistance, “heavy” directly targets the wall's self-weight, which is the main stabilizing factor against overturning and sliding in gravity-type walls. Step-by-Step Solution: 1) Identify governing failure modes: overturning and sliding due to earth pressure.2) Stabilizing actions depend on wall weight and base friction; heavier stones increase both.3) Soft vs hard: Hardness affects wear and long-term durability but not weight-based stability as directly as density.4) Light stones reduce stabilizing weight and are undesirable for gravity walls. Verification / Alternative check: Design handbooks emphasize unit weight for gravity walls, often using dense stones or concrete to attain needed resisting moments. Why Other Options Are Wrong: Soft: Suggests lower strength/durability; not preferred. Hard: Desirable for durability but secondary to unit weight for stability in this context. Light: Reduces self-weight; unfavorable. Common Pitfalls: Equating surface hardness with structural stability; forgetting that gravity walls primarily rely on mass. Final Answer: Heavy

Question 7

Building Materials – Trade Names and Types In civil engineering construction, “Snowcrete” is widely referenced in specifications for architectural finishes and decorative concrete. Which generic material does the trade name “Snowcrete” denote?

Accepted Answer

Introduction: Snowcrete is a well-known trade name in building materials used on sites and in BOQ specifications. This question checks whether you can distinguish between proprietary trade names and the underlying generic material category, a common source of confusion in exams and practice. Given Data / Assumptions: Snowcrete is a registered or proprietary name. Context is architectural finishes and decorative concrete/plaster. We must map the trade name to a generic material (cement vs paints). Concept / Approach: Trade names often look similar (Snowcrete vs Snowcem). The approach is to recall that Snowcrete refers to white Portland cement, whereas Snowcem refers to waterproof cement paints. Mixing them up is a classic pitfall. Step-by-Step Solution: 1) Identify whether the item is a cement or paint. Snowcrete suggests a cementitious product.2) Recall standard usage: Snowcrete is specified for aesthetic, light-colored concrete, terrazzo, and precast facade units.3) White cement is produced with low iron/ manganese raw mix and fuels giving high reflectance.4) Therefore, the correct generic class is white Portland cement. Verification / Alternative check: Check typical applications: tile grouts, terrazzo, GRC/architectural precast, fair-faced concrete needing high brightness—all align with white cement, not paints. Why Other Options Are Wrong: Waterproof cement paint: That maps to Snowcem, not Snowcrete. Enamel paint, cellulose paint, and distemper are film-forming coatings unrelated to hydraulic cement chemistry. Common Pitfalls: Confusing Snowcrete with Snowcem due to similar spelling; assuming any 'snow'-named product is a paint. Final Answer: White Portland cement (white cement)

Question 8

Lime Technology – Slaking Process Slaking (hydration) of quicklime to form lime putty or hydrated lime primarily occurs under which action or condition?

Accepted Answer

Introduction: Slaking of lime is the chemical hydration of quicklime (calcium oxide) to produce hydrated lime (calcium hydroxide). The question tests understanding of the practical condition that drives slaking on site and in materials processing. Given Data / Assumptions: Material: quicklime (CaO) to be converted to hydrated lime (Ca(OH)2). We compare typical field conditions: air exposure, immersion in water, mechanical crushing. Goal: identify which action actually causes slaking. Concept / Approach: The hydration reaction is CaO + H2O → Ca(OH)2 with heat release. Without water, slaking cannot proceed substantially. Therefore, options involving water contact will be correct. Step-by-Step Solution: 1) Recognize that slaking is a chemical reaction requiring water.2) Immersion or carefully controlled addition of water provides the reactant directly to CaO.3) Crushing only reduces size; it does not supply water.4) Air exposure may cause slow carbonation (CaCO3 formation), not proper slaking. Verification / Alternative check: Observe field practice: pits or drums are used for slaking by controlled water addition to avoid violent reaction and ensure complete hydration. Why Other Options Are Wrong: Air exposure: leads to carbonation, not hydration. Crushing: physical process only. Dry sand: inert and does not hydrate lime. 'None of these': incorrect because immersion in water is correct. Common Pitfalls: Adding too much water too quickly (violent reaction), confusing carbonation with hydration, and assuming size reduction equals slaking. Final Answer: Immersing the quicklime in water (controlled hydration)

Question 9

Cast Iron – Typical Engineering Uses Among the following, which application is the most appropriate and common use of cast iron in civil/mechanical services?

Accepted Answer

Introduction: Cast iron is an iron–carbon alloy with high carbon and silicon content. The question evaluates practical knowledge of where cast iron is preferred versus where steel or other materials perform better. Given Data / Assumptions: Material: gray or ductile cast iron products. We compare uses across pipes, beams, columns, and tension members. We assume typical modern practice and safety considerations. Concept / Approach: Cast iron offers good compressive strength, damping, machinability, and corrosion resistance (with proper lining). It is brittle in tension and shows low ductility, which constrains structural use in bending/tension. Step-by-Step Solution: 1) Identify applications demanding ductility (beams, tension members) → not ideal for cast iron.2) Pipes for water and sewer benefit from corrosion resistance, mass, and castability of iron.3) Historically, some columns were cast iron, but modern practice favors steel due to brittleness concerns.4) Therefore, the consistent, safe, and common application is water/drainage pipes. Verification / Alternative check: Field catalogs list cast iron/ductile iron pipes with pressure ratings, coatings (cement mortar lining), and standard joints—reinforcing this choice. Why Other Options Are Wrong: Beams need ductility and toughness; columns and long struts risk brittle failure; tension members are unsuitable; reinforcement must bond and yield—cast iron is inappropriate. Common Pitfalls: Assuming compressive strength alone makes cast iron good for columns; overlooking brittleness and notch sensitivity. Final Answer: Small to medium diameter water pipes and drainage pipes

Question 10

Stainless Steel – Reason for Corrosion Resistance Which element in stainless steel produces the protective passive film that gives the alloy its characteristic corrosion resistance?

Accepted Answer

Introduction: Stainless steels are defined by their ability to resist rusting in many environments. This capability is tied to alloy chemistry. The question examines knowledge of the key element behind passivation. Given Data / Assumptions: Typical stainless steels contain iron, chromium, and may include nickel, molybdenum, etc. Passivity arises from a very thin, adherent oxide film. We must identify the element primarily responsible. Concept / Approach: Chromium at around 10.5 percent or more enables formation of a stable chromium oxide film (Cr2O3) on the surface that self-repairs in the presence of oxygen, drastically reducing corrosion rates. Step-by-Step Solution: 1) Recall the passivation threshold: chromium content ≥ about 10.5 percent.2) The passive film is thin, adherent, and self-healing when damaged.3) Other elements (Ni, Mo) optimize toughness or crevice/pitting resistance, but chromium is the fundamental enabler. Verification / Alternative check: Compare ferritic, austenitic, and martensitic grades: they all share chromium as the common backbone for corrosion resistance. Why Other Options Are Wrong: Carbon affects hardness but too much reduces corrosion resistance; sulphur promotes machinability but can harm corrosion behavior; vanadium and manganese play secondary roles unrelated to the primary passive film. Common Pitfalls: Confusing nickel's role (austenite stabilization) with the primary passivation role of chromium. Final Answer: Chromium

Question 11

Mastic Asphalt – Key Material Property Which statement best describes mastic asphalt as used for roofs, terraces, bridge decks, and damp-proofing layers?

Accepted Answer

Introduction: Mastic asphalt is a dense, void-free asphaltic material used where watertightness and durability are essential. The question probes recognition of its defining performance characteristic in construction waterproofing. Given Data / Assumptions: Application areas: roofs, terraces, podiums, bridge decks, damp-proof courses. Composition: bitumen binder with graded mineral aggregates and fillers. Service condition: compacted, cooled layer forming an impermeable sheet. Concept / Approach: The hallmark of mastic asphalt is impermeability to liquid water when properly laid at specified thickness and falls. Elasticity is limited compared with membranes; vapour permeability is also low. Step-by-Step Solution: 1) Identify the primary design attribute demanded in these applications: waterproofing.2) Mastic asphalt is placed hot, then cools to a dense, void-free layer that blocks water ingress.3) It is not highly elastic; flexibility is limited and temperature dependent.4) Therefore, the statement emphasizing waterproof and non-porous behavior is correct. Verification / Alternative check: Engineering manuals specify mastic asphalt for zero-permeability details (e.g., upstands, gutters) confirming its non-porous nature. Why Other Options Are Wrong: Highly elastic: incorrect; that describes rubber/modified membranes. Allows percolation: opposite of design intent. Combustible surface: laid asphalt has acceptable fire performance in rated systems; the key property asked is impermeability. Vapor-open: false—mastic asphalt is typically vapour-tight. Common Pitfalls: Confusing mastic asphalt with polymeric membranes; assuming all asphaltic products are elastic; overlooking the need for movement joints and proper detailing. Final Answer: It is waterproof and non-porous under service conditions

Question 12

Ceramic Drainage and Chemical Stoneware – Glazing Choice For sanitary pipes and chemical stoneware articles used in sewers, effluent lines, and acid-bearing services, which glazing treatment is most appropriate to obtain a dense, smooth, and durable…

Accepted Answer

Introduction: This question checks practical knowledge of glazing used for stoneware sanitary pipes and chemical stoneware, where durability, smoothness, and chemical tolerance are needed to reduce abrasion, abrasion driven head losses, and fouling. Given Data / Assumptions: Product: vitrified stoneware pipes and chemical stoneware fittings. Service: sanitary sewage, industrial effluents, and chemically aggressive liquids. Objective: select a glazing that forms a strong, smooth, and durable skin. Concept / Approach: During firing, common practice for stoneware pipes is salt glazing. Common salt reacts with silica at high temperature to form a thin, glassy sodium alumino-silicate film that is adherent, hard, and smooth, improving resistance to abrasion and many chemicals. Step-by-Step Solution: 1) Identify that the body is stoneware fired to vitrification.2) Recall that salt is introduced during firing to create an in-situ glaze.3) The resulting glaze reduces porosity and surface roughness, which limits fouling and facilitates flow.4) Hence, salt glazing is the appropriate choice for sanitary and chemical stoneware. Verification / Alternative check: Standards and catalogs for vitrified stoneware sewer pipes describe salt-glazed internal and external surfaces, confirming long service in harsh drainage conditions. Why Other Options Are Wrong: Lead glazing: not preferred for sanitary effluent lines and chemical stoneware due to toxicity and chemical limitations. Opaque or tin glazes are decorative and not the industry norm for sewer stoneware. None of these: incorrect because salt glazing is correct. Common Pitfalls: Assuming any glossy glaze is suitable; ignoring process integrated salt glazing used specifically for stoneware pipe manufacture. Final Answer: Salt glazing for stoneware pipes

Question 13

Protective Coatings – Anti-Corrosive Pigment in Primers When specifying a primer to inhibit corrosion on steel, which pigment has been traditionally used for strong anti-corrosive performance (historically in metal primers)?

Accepted Answer

Introduction: Corrosion control on steel often begins with a primer pigmented to inhibit rust. This question verifies recognition of the classic anti-corrosive pigment historically used in heavy duty primers and shop coats for ferrous substrates. Given Data / Assumptions: Substrate: steel or cast iron components. Coating: primer layer requiring active inhibition. Pigment choices: several common white and filler pigments plus one anti-corrosive pigment. Concept / Approach: Red lead (minium) has been widely used in traditional primers for steel due to its inhibitive action. Although modern health and environmental regulations encourage alternative systems, the conceptual answer in materials engineering remains red lead as the classic inhibitor. Step-by-Step Solution: 1) Identify which pigment provides an inhibitive mechanism rather than mere opacity or body.2) Red lead historically passivates steel surfaces, minimizing underfilm corrosion.3) Zinc white and gypsum mainly provide opacity and body; white lead is a general pigment with toxicity concerns but not the classic inhibitor for steel.4) Therefore, choose red lead as the anti-corrosive pigment. Verification / Alternative check: Old bridge maintenance manuals and shop primer specifications cite red lead primer systems before the shift to zinc rich primers and epoxy technologies. Why Other Options Are Wrong: Zinc white: primarily a white pigment. Gypsum: extender/filler. White lead: general purpose with toxicity issues, not the standard corrosion inhibitor for steel. Ferrous oxide as listed is not the standard inhibitive choice. Common Pitfalls: Confusing any oxide pigment with inhibitive pigments; overlooking historical context versus modern alternatives like zinc rich primers. Final Answer: Red lead (minium) for anti-corrosion priming

Question 14

Bricks and Clays – Effect of Constituents on Drying and Burning In the composition of good brick earth, excess of which constituent leads to undue shrinkage and warping of raw bricks during drying and burning?

Accepted Answer

Introduction: Understanding how each constituent of brick earth affects behavior during drying and firing is crucial for quality bricks. This question focuses on warping and shrinkage defects that appear when the clay fraction is not balanced properly. Given Data / Assumptions: Typical constituents: alumina (clay), silica (sand), lime, iron oxide, magnesia. Observation: shrinkage and warping during drying and burning are being linked to a specific excess constituent. We assume standard kiln practices and controlled firing curves. Concept / Approach: Alumina imparts plasticity and workability, but too much plastic clay causes large drying shrinkage. Without sufficient sand (silica) as a non plastic temper, bricks deform and warp as water leaves and during sintering. Step-by-Step Solution: 1) Identify the role of each constituent in green strength and firing behavior.2) Recognize that alumina rich mixtures show high plasticity and high shrinkage.3) Balance with silica to control shrinkage; otherwise warpage occurs.4) Thus, excess alumina is the cause of shrinkage and warping noted in the question. Verification / Alternative check: Standard brickmaking texts note that silica reduces shrinkage and helps maintain shape, while alumina increases plasticity and shrinkage. Why Other Options Are Wrong: Lime excess risks cracking or melting but is not the primary shrinkage driver. Iron oxide influences color and vitrification. Magnesia can improve color and reduce warpage at small amounts. Sand in excess reduces shrinkage rather than causing it. Common Pitfalls: Confusing the role of lime or iron oxide with the plasticity controlled by alumina and silica balance. Final Answer: Alumina (clay fraction) in excess

Question 15

Asbestos Types – Acid Resistance of Fibers Among the common commercial asbestos types, which one is generally considered the least resistant to acids in service conditions?

Accepted Answer

Introduction: Different asbestos mineral families show different chemical resistances. This question tests recognition that serpentine and amphibole asbestos behave differently in acidic environments relevant to legacy industrial materials selection. Given Data / Assumptions: Comparison across chrysotile (serpentine) and amphibole types such as amosite, tremolite, and anthophyllite. Service environment involves potential acid exposure. We are asked to identify the fiber that is less acid resistant. Concept / Approach: Chrysotile has a sheet silicate structure with brucite like layers, making it more susceptible to acid attack, which readily dissolves magnesium from the structure. Amphibole fibers tend to show better acid resistance under comparable conditions. Step-by-Step Solution: 1) Distinguish serpentine (chrysotile) from amphiboles (amosite, tremolite, anthophyllite).2) Recall that acids preferentially leach magnesium from chrysotile layers.3) Amphiboles are generally more acid resistant than chrysotile.4) Therefore, chrysotile is the least acid resistant among the listed fibers. Verification / Alternative check: Materials references on asbestos chemistry report faster acid dissolution rates for chrysotile relative to amphibole asbestos under similar temperatures and concentrations. Why Other Options Are Wrong: Tremolite, amosite, and anthophyllite are amphiboles with comparatively higher acid resistance than chrysotile. 'None of these' is incorrect since a valid least resistant fiber has been identified. Common Pitfalls: Assuming all asbestos types behave the same; confusing mechanical heat resistance with chemical acid resistance. Final Answer: Chrysotile asbestos (serpentine group)

Question 16

Refractory Bricks – Service Characteristics in Furnaces and Kilns Refractory bricks used in furnace linings and kilns are selected for their ability to resist which of the following service conditions?

Accepted Answer

Introduction: Refractory bricks are engineered ceramics placed in the hottest and harshest parts of furnaces and kilns. This question checks whether you recognize that refractories must withstand multiple simultaneous degradations rather than a single factor in isolation. Given Data / Assumptions: Applications: furnace crowns, burner blocks, kilns, stoves, regenerators. Exposure: extreme heat, corrosive slags and gases, and possible moisture or steam during heat-up or shutdown. Requirement: structural integrity and minimal chemical interaction. Concept / Approach: Proper refractory selection balances refractoriness under load, thermal shock resistance, chemical compatibility with slags/gases, and resistance to moisture related spalling. Therefore the correct choice acknowledges the combined challenges encountered in service. Step-by-Step Solution: 1) Identify that refractory duty is not just temperature; chemistry and moisture also matter.2) Note that alkali vapors, acidic or basic slags, and condensates can attack refractory bonds.3) Design and selection use phase diagrams and compatibility tests to ensure stability under all factors.4) Hence, resistance to high temperature, chemical action, and dampness together is required. Verification / Alternative check: Manufacturer data sheets specify refractoriness under load, corrosion indices against slags, and guidance for drying out to manage dampness and steam pressure. Why Other Options Are Wrong: Choosing only one stressor ignores the real world combined exposure. Abrasion only is insufficient without thermal and chemical resistance. Common Pitfalls: Over focusing on maximum temperature rating while overlooking chemical compatibility and moisture management during commissioning and shutdown. Final Answer: All of the above (combined severe service)

Question 17

In building materials and construction engineering, identify the source from which good-quality sand is never obtained. Choose the best single answer based on salt content, grain shape, and cleanliness standards used at site inspections.

Accepted Answer

Introduction / Context: Sand quality strongly influences mortar and concrete performance. This question tests your understanding of permissible sources of fine aggregates for construction and why some sources are rejected in practice. Given Data / Assumptions: We are evaluating typical field sources: river, nala (seasonal stream), sea, and crushed gravel fines. Standards require sand to be clean, hard, chemically inert, and with limited harmful salts and organic matter. Concept / Approach: Sea sand contains soluble salts (notably chlorides and sulfates) that cause corrosion of embedded steel and disrupt cement hydration. Unless it undergoes rigorous desalination and grading (rare at small sites), sea sand is rejected for structural work. River or well-graded stream sands are usually acceptable after washing and sieving. Manufactured fines (from gravel) can be used if they meet grading, shape, and dust limits. Step-by-Step Solution: 1) Evaluate each source for salts and impurities.2) Sea sand: high chloride content → promotes reinforcement corrosion → unacceptable.3) River/nala sands: typically rounded to sub-rounded; may need washing but generally suitable.4) Gravel powder: can be used as manufactured sand if properly graded and with low stone dust percentage. Verification / Alternative check: Field tests (salt taste, silver nitrate check) and lab tests (chloride content limits) confirm sea sand’s unacceptability without treatment. Why Other Options Are Wrong: River: commonly acceptable after washing. Nala: similar to river source if clean. Gravel powder: acceptable as manufactured sand when it meets grading and dust limits. Common Pitfalls: Assuming sun-drying removes salts—it does not. Confusing “clean appearance” with chemical suitability. Final Answer: sea

Question 18

For manufacturing fly-ash building bricks used in walls and partitions, select the standard mix proportion (by parts) of fly ash, sand (or stone dust), and lime adopted in common practice. Choose one best ratio.

Accepted Answer

Introduction / Context: Fly-ash bricks are made by proportioning fly ash with sand/stone dust and lime (often with a small gypsum additive). This tests recall of a widely used baseline proportion used in production lines and quality control. Given Data / Assumptions: Three constituents: fly ash, sand (or stone dust), and lime. We want a typical production mix yielding adequate early strength and dimensional stability. Concept / Approach: Industrial practice commonly targets a high fly-ash fraction for pozzolanic reaction with lime, with sand providing skeleton and workability. A representative proportion accepted in many plants is 70:20:10 (fly ash : sand : lime) by parts, sometimes with 1–2 parts gypsum as a setting regulator. Step-by-Step Solution: 1) Compare options against common practice: fly ash usually 60–75%, sand 20–30%, lime 8–12%.2) The ratio 70:20:10 fits the typical window for strength and curing behavior.3) Alternatives such as 80:13:7 may under-supply sand for particle packing; 60:35:5 may under-supply lime for pozzolanic reaction. Verification / Alternative check: Plant trials and compressive strength testing (e.g., 7/28-day) confirm that 70:20:10 consistently meets performance, subject to curing and gypsum addition. Why Other Options Are Wrong: 80:13:7: sand too low; workability and packing issues. 60:35:5: lime too low; slower strength gain. None of these: incorrect because 70:20:10 is a valid standard mix. Common Pitfalls: Ignoring gypsum role; skipping curing humidity; assuming one ratio covers all fly-ash qualities. Final Answer: 70 : 20 : 10

Question 19

In geology and engineering geology, rocks formed by cooling and solidification of magma at relatively shallow depth (subvolcanic level) are called what? Choose the most accurate term.

Accepted Answer

Introduction / Context: Igneous rocks are classified by their depth of emplacement: deep-seated, shallow intrusive, or surface extrusive. The question checks your knowledge of the specific term for shallow intrusive bodies. Given Data / Assumptions: Cooling occurs below the surface but not at great depth. Textures are typically medium to fine due to faster cooling than plutonic bodies. Concept / Approach: Shallow intrusive rocks formed at subvolcanic levels are termed hypabyssal. Plutonic refers to very deep and slow cooling (coarse texture), whereas volcanic refers to surface lava flows and pyroclastics (very rapid cooling, fine to glassy). “Igneous rocks” is a broad category, not a specific depth term. Step-by-Step Solution: 1) Identify emplacement depth: shallow subsurface → subvolcanic.2) The precise nomenclature for subvolcanic intrusions is “hypabyssal”.3) Therefore, hypabyssal rocks is the correct specific term. Verification / Alternative check: Examples include dykes and sills showing porphyritic to fine crystalline textures consistent with intermediate cooling rates. Why Other Options Are Wrong: Plutonic: too deep. Volcanic: extrusive at surface. Igneous (generic): not a depth-based subclass. Common Pitfalls: Confusing hypabyssal with volcanic due to fine grains; overlooking intrusive vs extrusive context. Final Answer: Hypabyssal rocks

Question 20

In the classification of building stones, what name is given to rocks having alumina (clay) as the major constituent? Select one correct category used in civil engineering.

Accepted Answer

Introduction / Context: Civil engineers classify stones by dominant chemistry and mineralogy to predict durability and behavior. This question asks for the term applied when alumina/clay predominates. Given Data / Assumptions: Major constituent is alumina-bearing clay minerals. We need the standard petrographic category used in construction texts. Concept / Approach: Argillaceous rocks contain significant clay (aluminosilicate) content. This affects strength, water absorption, and weathering. Siliceous rocks are silica-rich (e.g., quartz), calcareous are calcium carbonate-rich (e.g., limestone). “Sedimentary” and “igneous” are process-based, not chemistry-specific labels. Step-by-Step Solution: 1) Identify major chemical constituent: alumina/clay.2) The correct chemical family term is “argillaceous”.3) Therefore, argillaceous rocks is the required answer. Verification / Alternative check: Examples include shales and mudstones that soften on wetting, confirming clay dominance. Why Other Options Are Wrong: Siliceous: silica-rich, not clay-rich. Calcareous: calcium carbonate dominant. Sedimentary/igneous: genetic classes, not specific to alumina content. Common Pitfalls: Equating “sedimentary” with “argillaceous”—many argillaceous rocks are sedimentary, but not all sedimentary rocks are clay-rich. Final Answer: argillaceous rocks

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