Question 1

Seasoning of timber in building construction: what is the fundamental purpose of seasoning before use? (Select the objective that directly addresses moisture-related dimensional stability and durability.)

Accepted Answer

Introduction / Context: Freshly felled wood contains a significant amount of water that leads to shrinkage, warping, fungal growth, and poor finish. Seasoning is the controlled process of reducing moisture to levels suitable for service. The key goal is moisture reduction, which secondarily improves strength and workability. Given Data / Assumptions: Green timber has high free and bound water. Moisture reduction enhances stability and resistance to decay. Seasoning methods include air and kiln seasoning. Concept / Approach: By driving off free and bound water to near the equilibrium moisture content of the installation environment, timber dimensional changes are minimized in service. Although strength increases as moisture drops, that increase is a consequence of drying rather than the primary goal stated in specifications. Step-by-Step Solution: 1) Identify moisture as the root cause of swelling, checking, and decay.2) Apply controlled drying (seasoning) to lower moisture content to target levels.3) Verify improvements: better finish, lower risk of fungal attack, improved joint performance.4) Conclude that the fundamental objective is decreasing moisture content. Verification / Alternative check: Joinery standards specify moisture ranges (e.g., 8–12% for interiors) precisely to prevent in-service movement and defects. Why Other Options Are Wrong: Increasing moisture: opposite of the requirement. Increasing strength directly: strength improvement is secondary to drying; the process target is moisture reduction. None of these: incorrect since moisture reduction is correct. Common Pitfalls: Over-rapid kiln schedules causing case-hardening; ignoring acclimatization; using unseasoned timber for fine joinery resulting in post-installation warping. Final Answer: Decreasing moisture content

Question 2

Types of pig iron: the pig iron obtained from a blast furnace that is well fired with ample fuel at very high temperature (promoting graphitic carbon) is called what? (Choose the grade commonly preferred for foundry castings.)

Accepted Answer

Introduction / Context: Pig iron is classified by the form in which carbon occurs after solidification, heavily influenced by furnace temperature and chemistry. Foundries prefer a graphitic form of carbon for fluidity and machinability. The question asks which pig iron results from a hot, well-fueled furnace condition. Given Data / Assumptions: High-temperature, well-fueled operation favors graphitization in the solidified iron. Grey pig iron contains carbon mostly as free graphite flakes. White pig iron contains combined carbon as cementite due to relatively rapid solidification/low silicon. Concept / Approach: Ample fuel and high temperature in the furnace, together with sufficient silicon, promote the separation of carbon as graphite during solidification, yielding grey pig iron. This improves fluidity for intricate castings and enhances machinability compared with white iron, which is hard and brittle. Step-by-Step Solution: 1) Map furnace conditions: hot, well-fueled → graphitic carbon formation.2) Associate structure with classification: graphite-rich → grey/foundry pig.3) Exclude white/forge pig: cementite-rich due to different conditions (lower Si/rapid cooling).4) Recognize mottled pig as intermediate; not the target when aiming for foundry fluidity. Verification / Alternative check: Foundry metallurgy texts relate higher silicon and furnace heat to grey iron formation preferred for casting. Why Other Options Are Wrong: Bessemer pig: process label, not directly indicative of carbon form. White or forge pig: combined carbon → poor machinability. Mottled pig: mixed structure; not the ideal foundry grade. Common Pitfalls: Assuming higher hardness (white iron) is always desirable; for casting complexity and machining, grey iron is favored. Final Answer: Grey or foundry pig

Question 3

Durability of building stones in structures is influenced by which factors? (Consider mineral chemistry, texture/fabric, weather resistance, and location/use in the structure.)

Accepted Answer

Introduction / Context: Stone selection affects long-term performance of facades, copings, steps, and structural masonry. Durability is a combined outcome of mineralogy, texture, exposure conditions, and detailing. The question addresses which of these parameters matter in practice (answer: all of them). Given Data / Assumptions: Chemical composition governs susceptibility to dissolution, oxidation, or sulphation. Texture (grain size, porosity, bedding) affects water movement and freeze–thaw behavior. Atmospheric exposure dictates wetting–drying, salts, and pollutants. Placement in the structure changes stress and weathering risk. Concept / Approach: Durability is multi-factorial. Even an inherently strong stone can fail if placed with bedding unfavorably or used in an aggressive environment. Good specifications consider both material properties and the service environment, including detail design (drips, falls, sealants). Step-by-Step Solution: 1) Evaluate mineralogy: calcitic stones react with acids; iron-bearing stones may stain.2) Assess texture: high porosity and open bedding increase moisture paths.3) Check environmental resistance: pollution, sea spray, and freeze–thaw cycles accelerate decay.4) Consider location: copings, sills, and parapets see harsher exposure than protected interiors. Verification / Alternative check: Conservation guidelines emphasize matching stone type and orientation to exposure, and selecting low-porosity, chemically compatible stones for severe environments. Why Other Options Are Wrong: Any single-factor choice is incomplete; durability depends on the ensemble of properties and context. Common Pitfalls: Ignoring bedding orientation; choosing stone by appearance only; neglecting salt crystallization risks at splash zones. Final Answer: All of the above

Question 4

Geology for construction: basalt belongs to which rock class based on its origin and mode of formation? (Select the correct category used in engineering geology.)

Accepted Answer

Introduction / Context: Understanding rock origin helps predict engineering properties like strength, durability, and jointing. Basalt is common in many regions and is widely used as aggregate and road metal. The question asks for its geologic classification by origin. Given Data / Assumptions: Igneous rocks form from cooling magma or lava. Extrusive rocks cool at or near the surface; intrusive rocks cool slowly at depth. Basalt is fine-grained and typically forms from lava flows. Concept / Approach: Rapid cooling at the Earth’s surface leads to fine-grained textures. Basalt is the extrusive equivalent of gabbro (its coarse-grained intrusive counterpart). Its mineralogy (mafic) gives it dark color and high specific gravity, making it suitable for aggregates and railway ballast. Step-by-Step Solution: 1) Determine origin: basalt forms from erupted lava.2) Cooling rate: fast at surface → fine-grained matrix.3) Classify accordingly: extrusive igneous rock.4) Rule out sedimentary/metamorphic: different formation mechanisms. Verification / Alternative check: Engineering geology texts list basalt under extrusive igneous rocks alongside andesite and rhyolite, with typical uses in roadwork and concrete aggregate after proper processing. Why Other Options Are Wrong: Sedimentary: requires deposition and lithification of sediments. Metamorphic: requires transformation under heat/pressure of pre-existing rock. Intrusive igneous: slow-cooled coarse-grained rocks like gabbro and granite. Common Pitfalls: Confusing basalt with dolerite (diabase), which is typically medium-grained and often considered hypabyssal/intrusive; basalt is characteristically extrusive. Final Answer: Extrusive igneous rock

Question 5

Water requirement per 50 kg bag of cement: approximately how many litres of water are needed for complete hydration and to fill gel pores (not counting extra water for workability)? (Select the nearest standard value used in mix design concepts.)

Accepted Answer

Introduction / Context: In concrete technology, understanding the theoretical water demand of cement helps distinguish between water needed for chemical hydration and that added for workability. A classic figure is the water-to-cement ratio required to hydrate cement fully and fill gel pores without leaving capillary water. Given Data / Assumptions: Water required for complete hydration is about 0.25 by mass of cement. Water to fill gel pores adds roughly 0.15 by mass of cement. Total theoretical water ≈ 0.25 + 0.15 = 0.40 (often rounded to ≈0.38 to 0.40 depending on reference). One bag of cement = 50 kg. Concept / Approach: Compute the theoretical litres needed using w/c ≈ 0.37–0.40 (commonly taken as ≈0.38). Multiply by bag mass to obtain litres of water (density ≈ 1 kg/L). This yields a value close to 19 L. Among the options, 18.5 L is the nearest standard selection used in many exam problems. Step-by-Step Solution: 1) Take w/c_theoretical ≈ 0.38 (hydration + gel pores).2) For a 50 kg bag: water = 0.38 * 50 = 19.0 kg ≈ 19.0 L.3) Choose the nearest listed value: 18.5 litres.4) Note that extra water above this is usually added for workability, which increases capillary porosity. Verification / Alternative check: Concrete technology texts repeatedly cite ≈0.38 as the theoretical w/c for hydration plus gel pore water; practical mixes use higher water or plasticizers to achieve workability while maintaining strength targets. Why Other Options Are Wrong: 16.5 L: too low for hydration + gel pores. 20.5–25 L: exceed theoretical needs; represent workability additions rather than stoichiometric requirement. Common Pitfalls: Confusing theoretical water with total mix water; assuming more water always improves strength (it reduces it by increasing capillary pores); ignoring admixture use to reduce water demand. Final Answer: 18.5 litres

Question 6

Stone selection for rubble masonry: which property should stones used in rubble masonry primarily possess? (Choose the characteristic that ensures long-term performance under load and weather.)

Accepted Answer

Introduction / Context: Rubble masonry, comprising irregular or roughly dressed stones, is often used for foundations, retaining walls, and rural structures where economy and durability matter. The principal requirement is that the stones resist crushing and weathering. Hence, hardness and soundness are key selection criteria. Given Data / Assumptions: Rubble units are irregular and rely on interlock and mortar for stability. Exposed faces may encounter cycles of wetting and drying, salts, and frost. Load-bearing performance depends on the stone's compressive strength and abrasion resistance. Concept / Approach: A hard, durable stone minimizes spalling and attrition under service. While density and weight influence handling and dead load, hardness directly addresses strength and abrasion resistance, ensuring longevity even with uneven contact surfaces typical of rubble work. Step-by-Step Solution: 1) Identify functional needs: compressive strength, abrasion/weather resistance.2) Map properties: hardness correlates with these demands.3) Compare alternatives: softness leads to crushing and weathering losses; mere heaviness or lightness does not guarantee durability.4) Select the property most indicative of performance: hardness. Verification / Alternative check: Construction handbooks recommend hard, tough stones (e.g., basalt, granite, quartzite) for rubble masonry, particularly in foundations and water-retaining structures. Why Other Options Are Wrong: Soft: prone to crushing and erosion. Light or heavy: mass alone does not define durability; hard stones may be dense, but density is not the primary criterion here. Common Pitfalls: Selecting stones by appearance or ease of dressing rather than mechanical durability; ignoring bedding orientation in stratified stones. Final Answer: Hard

Question 7

Metallurgy — red-shortness in hot-working of iron/steel: which impurity causes cracking when the metal is bent at red heat? Choose the most appropriate cause.

Accepted Answer

Introduction / Context: When iron or low-alloy steel is worked at red heat (hot-working temperatures), certain impurities can make the metal brittle. This phenomenon is called red shortness (hot shortness). Understanding which element causes this defect helps in specifying proper steelmaking controls and selecting grades for forging and rolling. Given Data / Assumptions: Iron/steel is bent or forged at elevated (red heat) temperatures. Impurities considered: sulphur, carbon, phosphorus, silicon. We focus on hot-working brittleness specifically, not room-temperature effects. Concept / Approach: Sulphur in steel forms iron sulphide (FeS). FeS has a low melting point and concentrates at grain boundaries. At hot-working temperatures, a FeS-rich film becomes weak or partially molten, promoting intergranular tearing and cracking. Manganese is added in steelmaking to combine with sulphur and form MnS, which is less harmful during hot work. Step-by-Step Solution: 1) Identify the defect: red shortness = brittleness during hot work.2) Link impurity to mechanism: sulphur → FeS at grain boundaries, low-melting eutectics.3) Consequence: cracks appear when bending/forging at red heat.4) Mitigation: add manganese to form MnS instead of FeS. Verification / Alternative check: Metallurgy references consistently attribute hot shortness in steels to sulphur (FeS). Process control aims at S reduction and Mn/S balance. Why Other Options Are Wrong: Carbon: Raises strength/hardness; not the primary cause of hot shortness. Phosphorus: Causes cold shortness (brittleness at low temperature), not chiefly hot shortness. Silicon: Deoxidizer; excess may embrittle, but not the classic red-short agent. Common Pitfalls: Confusing red shortness (hot) with cold shortness (phosphorus-dominated) and overlooking the Mn–S control strategy. Final Answer: Sulphur

Question 8

Lime for underwater works — which type of lime is suitable for the construction of structures under water (e.g., foundations, harbors)? Select the best choice.

Accepted Answer

Introduction / Context: Lime binders differ in their ability to set and harden in moist or submerged conditions. For underwater or constantly damp structures, the binder must develop strength by hydraulic reactions rather than only by atmospheric carbonation. Given Data / Assumptions: Application: underwater or continuously wet environments. Types considered: hydraulic, fat/pure, and quick lime. Need: setting and hardening without access to air. Concept / Approach: Hydraulic lime contains clayey constituents that form hydraulic compounds (e.g., calcium silicates and aluminates) during burning. These compounds react with water to set and harden even in submerged conditions. Fat/pure lime requires carbon dioxide from air to carbonate and thus is unsuitable underwater. Quick lime is caustic and must be slaked; it is not a finished binder for underwater setting by itself. Step-by-Step Solution: 1) Identify the environment: submerged or saturated.2) Match binder chemistry: hydraulic reactions needed → hydraulic lime.3) Exclude non-hydraulic limes: fat/pure limes rely on carbonation.4) Quick lime is an intermediate (unslaked) form, not a proper underwater-setting binder. Verification / Alternative check: Traditional masonry practice and standards recommend hydraulic lime for wet foundations, retaining walls in damp soil, and underwater works. Why Other Options Are Wrong: Fat/pure lime: Sets slowly in air; fails underwater. Quick lime: Must be slaked; not a hydraulic binder. None of these: Incorrect because hydraulic lime is suitable. Common Pitfalls: Assuming all limes behave similarly; the presence of clayey impurities during burning creates the essential hydraulicity. Final Answer: Hydraulic lime

Question 9

Brick classification — which statement correctly describes second-class bricks as per common building practice? Choose the most accurate description.

Accepted Answer

Introduction / Context: Bricks are graded by their burning quality, strength, and surface finish. First-class bricks are uniformly well-burnt with sharp edges and give a clear metallic ring. Second-class bricks are of moderate quality and often slightly under-burnt, making them suitable for less critical work where a perfect finish is not required. Given Data / Assumptions: We compare acoustic response, burning degree, and shape/finish. Standard building materials terminology is assumed. The choice targets the defining trait of second-class bricks. Concept / Approach: Second-class bricks generally show minor distortions, chips, or surface irregularities and may be slightly under-burnt. They do not usually produce the clear metallic ring of first-class bricks and lack the sharp arrises and uniform colour typical of premium quality. Step-by-Step Solution: 1) First-class benchmark: uniform, well-burnt, metallic ring on impact.2) Second-class: moderate quality, sometimes under-burnt, less uniform.3) Compare statements: the “under-burnt” descriptor aligns with second-class.4) Conclude option D as the correct description. Verification / Alternative check: Textbook definitions highlight slightly under-burnt and less regular geometry for second-class bricks versus first-class quality standards. Why Other Options Are Wrong: Dark brown colour: Not a defining criterion of class. Metallic ring: Characteristic of first-class, not second-class. Well burnt with uniform shape: Again, first-class property. Common Pitfalls: Judging solely by colour; sound test and edge sharpness are stronger indicators of class. Final Answer: They are under-burnt (slightly underfired) and of moderate quality

Question 10

Acrylic (PMMA) sheets — which statements about properties and availability are correct? Select the most comprehensive option.

Accepted Answer

Introduction / Context: Acrylic (polymethyl methacrylate, PMMA) is widely used for glazing, skylights, signage, and protective screens. It combines excellent clarity with high impact resistance relative to ordinary glass, and it can be thermoformed into diverse shapes. Given Data / Assumptions: Comparison is with standard soda-lime glass of equal thickness. Household exposure: soaps/detergents, not strong solvents. Optical transmission evaluated for clear grades. Concept / Approach: Clear acrylic exhibits high visible light transmission (around 92–93%) and better impact resistance than ordinary glass (often quoted in the 10–17× range). It resists mild chemicals like household detergents but is sensitive to strong solvents and abrasives. Acrylic can be cast or extruded in sheets, then fabricated by machining or thermoforming into different shapes. Step-by-Step Solution: 1) Impact & durability: acrylic outperforms glass in breakage resistance in common handling scenarios.2) Chemical resistance: generally fine with soaps/detergents; avoid aggressive solvents.3) Optical clarity: top-tier transmission near 93% contributes to glass-like transparency.4) Formability: available as flat sheets, rods, tubes; thermoformable into complex shapes. Verification / Alternative check: Manufacturer datasheets for PMMA list high light transmission, significant impact improvement over glass, and common cleaning guidance with mild detergents. Why Other Options Are Wrong: Each single property is correct but incomplete; only the aggregate answer captures the full attribute set. Common Pitfalls: Cleaning with solvents or abrasive pads that craze/scratch acrylic; confusing acrylic with polycarbonate (which has even higher impact strength). Final Answer: All of the above

Question 11

Stone for sculpture — the typical colour preferred for statuary marble used in fine sculptor’s work is: Choose the correct colour.

Accepted Answer

Introduction / Context: Statuary marble is prized for sculpture due to its purity, fine grain, and ability to take a high polish. Colour and translucency significantly influence the visual impact and detail rendering of the finished work. Given Data / Assumptions: Considering classical and contemporary sculptural practice. Marble quality relates to low impurity content and uniform texture. Question focuses on typical/standard colour selection. Concept / Approach: White marble (e.g., Carrara, Makrana) offers uniformity, high reflectance, and slight translucency that imparts lifelike depth to sculpted forms. Pigmented marbles exist but are less common for fine statuary where detail and neutral colour are desired. Step-by-Step Solution: 1) Identify visual requirements: neutrality and ability to show fine detail.2) Match to material: white, fine-grained marble has minimal veining and impurities.3) Evaluate alternatives: colored marbles are decorative but less standard for statuary.4) Conclude: white is the typical colour for statuary marble. Verification / Alternative check: Historic masterpieces and architectural sculptures predominantly use white statuary marbles for clarity and classical aesthetics. Why Other Options Are Wrong: Red/blue/green/yellow marbles are used decoratively but are not the typical choice for statuary. Common Pitfalls: Equating decorative marble choices with sculptural standards; veins and colours can distract from form. Final Answer: White

Question 12

Plywood availability — what is the typical lower-end thickness range in which commercial plywood sheets are normally supplied? Pick the most appropriate range.

Accepted Answer

Introduction / Context: Plywood is manufactured by cross-laminating veneers to produce sheets with improved dimensional stability and strength. Commercial availability spans a range of standardized thicknesses depending on grade and application (furniture, paneling, shuttering, etc.). Given Data / Assumptions: Considering common commercial plywood (not specialty veneer or aircraft-grade exceptions). Focus is on the typical lower-end sheet thickness readily available. Regional standards may vary slightly, but common practice applies. Concept / Approach: In many markets, the thinnest widely available plywood sheets start around 3 mm to 4 mm for general use. Ultra-thin 1–2 mm sheets are usually veneers or specialty products, not standard plywood stock for typical building/furniture work. Step-by-Step Solution: 1) Identify standard thickness series (e.g., ~3, 4, 6, 9, 12, 16/18 mm etc.).2) Exclude ultra-thin veneers that are not typical plywood sheets.3) Select the common lower-end range: 3–4 mm.4) Conclude option D as the best answer. Verification / Alternative check: Supplier catalogues and building material standards commonly list 3–4 mm as the thinnest routine plywood options. Why Other Options Are Wrong: 1 mm, 2 mm, 2–3 mm: These are veneer/specialty ranges, not standard plywood sheets for general distribution. Common Pitfalls: Confusing veneer thickness with plywood sheet thickness; plywood is multiple veneers cross-laminated. Final Answer: 3 mm to 4 mm thick

Question 13

Corrosion tendencies — which combined statement correctly summarizes oxidation/rusting behavior among common ferrous materials? Choose the best option.

Accepted Answer

Introduction / Context: Rusting of ferrous materials involves oxidation in the presence of moisture and oxygen. The microstructure and composition (carbon, alloying, slag inclusions) influence how quickly different iron-based materials corrode in typical atmospheres. Given Data / Assumptions: Ordinary atmospheric exposure is considered. Materials: cast iron, steel, wrought iron. Qualitative comparison of relative oxidation tendencies. Concept / Approach: Rust (hydrated iron oxides) forms readily on steel. Cast iron, with higher carbon and graphite, often corrodes more slowly in uniform exposure due to graphitic layers acting as a partial barrier. Wrought iron, containing slag stringers, shows moderate corrosion behavior compared to the other two. All statements A–D are thus concurrently valid as a general qualitative summary. Step-by-Step Solution: 1) Define rust: hydrated iron oxides formed during atmospheric corrosion.2) Compare materials: steel > wrought iron > cast iron in typical oxidation rate.3) Confirm that cast iron often shows better general corrosion resistance than mild steel.4) Synthesize: all listed statements align with the qualitative hierarchy. Verification / Alternative check: Materials engineering texts describe cast iron’s graphitic corrosion and steel’s higher rusting rate in many environments, with wrought iron intermediate. Why Other Options Are Wrong: Any single-statement option omits the correctness of the remaining true assertions; only the aggregate option captures the complete, commonly taught comparison. Common Pitfalls: Assuming one rule fits all corrosive environments; chloride-rich or acidic conditions can change relative performance, but the general trend holds for typical atmospheres. Final Answer: All of the above

Question 14

Cement manufacture — which raw material is most commonly used as the principal source of calcium in Portland cement production? Select the correct rock.

Accepted Answer

Introduction / Context: Portland cement clinker is produced by sintering a precisely proportioned raw mix dominated by calcium oxide, along with silica, alumina, and iron oxides. The main calcium source is a decisive choice for plant location and quarrying strategy. Given Data / Assumptions: We consider standard Portland cement manufacture. Primary requirement: CaCO3-rich feedstock. Auxiliary sources supply silica, alumina, and iron. Concept / Approach: Limestone (calcium carbonate) is the principal raw material supplying CaO upon calcination. It is abundant, quarried easily, and blends well with shale/clay/iron correctives to achieve kiln feed chemistry. Slate, sandstone, and basalt lack the necessary high CaCO3 content to serve as the main calcium source in typical cement plants. Step-by-Step Solution: 1) Identify dominant oxide in clinker: CaO ~ 60–67%.2) Map to raw rock: limestone provides CaCO3 for CaO after calcination.3) Evaluate alternatives: slate/sandstone/basalt are silica/alumina-rich or mafic; not primary Ca source.4) Conclude: limestone is the correct answer. Verification / Alternative check: All major cement plants are co-located with limestone quarries to secure long-term, high-CaCO3 feed. Why Other Options Are Wrong: Slate/Sandstone/Basalt: Do not provide the high calcium carbonate content required. Common Pitfalls: Confusing corrective additives with the principal calcium-bearing raw rock. Final Answer: Limestone

Question 15

Electrical porcelain — which preparation method is correctly matched with the voltage class of porcelain insulators? Choose the correct statement.

Accepted Answer

Introduction / Context: Porcelain electrical insulators are produced using either wet (plastic) processes or dry pressing, depending on the required geometry, density, and electrical performance. The voltage class often dictates the forming route and firing schedule for optimal dielectric properties and mechanical strength. Given Data / Assumptions: Two broad forming routes: wet (plastic forming, slip casting) and dry pressing. Low- vs high-voltage applications require different densities and microstructures. Statement matching is about typical practice. Concept / Approach: Low-voltage porcelain components (e.g., switches, small insulators) are commonly produced by dry pressing, which yields consistent shapes at high production rates. High-voltage, complex shapes are more often made by wet plastic forming or slip casting to achieve the required density and uniformity with fewer flaws. Step-by-Step Solution: 1) Identify LV needs: high throughput, simpler shapes → dry press.2) Identify HV needs: larger/complex shapes, stringent dielectric integrity → wet processes.3) Match statements: LV ↔ dry process is the correct pairing.4) Conclude option C as correct; A and B reverse the common practice. Verification / Alternative check: Industry practice and ceramics texts note dry pressing for small/LV porcelain parts and wet/slip processes for larger/HV insulators. Why Other Options Are Wrong: A: Reverses the typical assignment. B: Also reversed; HV usually uses wet/slip processes. D: Incorrect since C is correct. Common Pitfalls: Assuming one process fits all; geometry and voltage class drive the forming choice. Final Answer: Low-voltage porcelain is prepared by dry process

Question 16

Wood finishing — in building and furniture work, “French polish” refers to which type of finish? Select the correct classification.

Accepted Answer

Introduction / Context: French polishing is a traditional finishing technique that produces a deep, high-gloss finish on wood. It is common in fine furniture and musical instruments and relies on a specific binder and solvent system for rapid film build and clarity. Given Data / Assumptions: Finish applied by pad/rubber in repeated thin coats. Binder is shellac flakes dissolved in alcohol. Not a paint or distemper; it is a clear/amber transparent finish. Concept / Approach: French polish uses a spirit varnish—shellac dissolved in alcohol (typically ethanol or methylated spirits). The alcohol flashes quickly, allowing rapid layering and a lustrous, chatoyant finish. Distemper is a water-based paint; oil paint is pigment-in-oil film-forming—neither matches French polish. Step-by-Step Solution: 1) Identify system: shellac (resin) + alcohol (solvent) → spirit varnish.2) Application: many thin coats with padding and lubrication (often mineral oil) to avoid tearing.3) Result: high-gloss, transparent finish enhancing grain depth.4) Classification: spirit varnish, not paint or distemper. Verification / Alternative check: Wood finishing guides consistently classify French polish as shellac-based spirit varnish applied by rubbing. Why Other Options Are Wrong: Oil paint: Opaque pigmented coating; unrelated technique. Distemper: Water-based paint with chalk/glue; not a varnish. None of these: Incorrect because spirit varnish is correct. Common Pitfalls: Confusing shellac spirit varnish with polyurethane or lacquer; the application method and solvent system are distinct. Final Answer: Spirit varnish (shellac-based)

Question 17

Brick Manufacturing – Terminology for Mixing Clay to a Uniform, Workable Mass In brickmaking practice, what is the correct term for the harmonious mixing and kneading of clay ingredients (often with water) to obtain a uniform, plastic, and workable …

Accepted Answer

Introduction: Brick manufacturing involves several preparatory steps applied to raw clay before moulding and burning. This question checks whether you can correctly name the process in which clay ingredients are mixed and kneaded with water to achieve a uniform and plastic mass that can be shaped reliably into bricks without cracking. Given Data / Assumptions: Clay may contain silt, sand, and additives that must be homogenized. Water is added to reach a plastic, workable consistency. The objective is uniformity, plasticity, and removal of air pockets before moulding. Concept / Approach: In standard terminology, 'tempering' refers to mixing and thorough kneading of prepared clay with water until the mass becomes plastic and homogeneous. It often uses manual methods, pug mills, or mechanical mixers. 'Blending' means mixing different clay types to adjust composition, while 'weathering' is an earlier stage in which dug clay is left exposed to the atmosphere so that lumps disintegrate and soluble salts leach out. Step-by-Step Solution: 1) Identify the target outcome: a cohesive, plastic clay mass suitable for moulding.2) Recognize that this is achieved by mixing with water and kneading—defining traits of tempering.3) Distinguish from blending (composition adjustment) and weathering (atmospheric action).4) Conclude that the correct technical term for harmonious mixing and kneading is 'tempering'. Verification / Alternative check: Brickwork handbooks describe the sequence: winning → weathering → blending (if required) → tempering (with water) → moulding → drying → burning. The step explicitly associated with water addition and thorough kneading is tempering. Why Other Options Are Wrong: Weathering: exposure to sun/rain; not active kneading. Blending: mixing clays or additives to tune properties, may be dry. 'None of these': incorrect because a standard term exists. 'Pugging without water': pugging is a means to perform tempering, but tempering intrinsically involves appropriate moisture addition for plasticity. Common Pitfalls: Using 'blending' and 'tempering' interchangeably; ignoring the key role of added water and kneading energy in tempering. Final Answer: Tempering

Question 18

Glass and Daylighting – Understanding Ground (Frosted) Glass in Building Use Which statements about ground (frosted) glass used in windows/partitions are correct with respect to manufacture and function?

Accepted Answer

Introduction: Ground (frosted) glass is specified in buildings when designers want ambient daylight while controlling privacy or glare. The question checks understanding of how such glass is produced and why it is chosen over clear glazing in certain rooms like bathrooms, stairwells, and office partitions. Given Data / Assumptions: 'Ground' means the surface is roughened to diffuse light. Multiple production methods exist: grinding, sandblasting, acid etching. The functional goal is light diffusion with visual obscurity, not opacity. Concept / Approach: Roughening a glass surface creates microfacets that scatter incident light. This diffusion maintains overall illuminance yet prevents clear imaging through the pane. Manufacturing routes vary, but the optical effect is similar: a matte, privacy-preserving finish that still transmits a substantial fraction of visible light. Step-by-Step Solution: 1) Recognize that mechanical grinding/etching alters the surface finish.2) Note that sandblasting and acid-etching are standard industrial processes producing a frosted texture.3) Link the texture to function: transmit light, obscure detail.4) Therefore, all listed manufacturing and functional statements hold true for ground glass. Verification / Alternative check: Product datasheets specify light transmission percentages for frosted glass types, confirming that they are translucent (not opaque) and commonly used for privacy and glare control. Why Other Options Are Wrong: Option (e) claims complete blocking of light—this is false; opaque panels are different products (e.g., enamelled/vision-block panels). Ground glass is translucent, not opaque. Common Pitfalls: Confusing translucency with opacity; assuming frosted glass is a coating instead of a modified surface that can be on one side only. Final Answer: All of the above

Question 19

Bulking of Sand – Identify the Incorrect Statement About Moisture Effects on Volume With reference to bulking behavior of fine aggregates, which one of the following statements is NOT correct under typical field conditions?

Accepted Answer

Introduction: Bulking refers to the temporary increase in the apparent volume of sand at low moisture contents because thin water films create surface tension forces that separate particles. Understanding this effect is crucial in volumetric batching of mortar and concrete to avoid under-sanded mixes and strength loss. Given Data / Assumptions: Fine sand shows greater bulking than coarse sand at the same moisture content. Peak bulking typically occurs around 4%–6% moisture by weight. At saturation, bulking disappears because water floods voids and eliminates the capillary tension effect. Concept / Approach: At low moisture, a meniscus forms between grains, increasing apparent volume. As moisture increases beyond the peak, the meniscus effect is lost and the volume contracts back toward the dry volume. Therefore, any statement implying increasing bulking at higher moisture (toward saturation) is incorrect. Step-by-Step Solution: 1) Recall typical bulking curve: increases from 0% moisture to a peak near 4%–6%, then decreases toward zero at saturation.2) Evaluate each statement against the curve.3) Statement (c) contradicts the known decrease beyond about 8%–10% moisture.4) Hence, (c) is the incorrect statement; the others are consistent with field observations. Verification / Alternative check: Site tests (e.g., bulking jar test) and standard texts show maximum bulking of fine sands may be in the 20%–35% range near 4%–6% moisture and reduce to ~0% at full saturation. Why Other Options Are Wrong: They are not wrong: (a) states a commonly observed range; (b) notes fine sand bulks more; (d) correctly states saturation removes bulking; (e) accurately explains the surface tension mechanism. Common Pitfalls: Assuming constant bulking increase with moisture; ignoring that volumetric batching must be corrected for bulking to avoid lean mixes. Final Answer: If moisture content exceeds about 10%, bulking begins to increase again and becomes greater at full saturation

Question 20

Protective Coatings – Appropriate Primer for Steelwork For new fabricated steelwork on site or in the shop, which primer is commonly specified to provide initial corrosion protection and good adhesion for subsequent coats?

Accepted Answer

Introduction: Steel exposed to the atmosphere rapidly oxidizes. A primer formulated to inhibit corrosion and promote adhesion is essential before applying intermediate and finishing coats. This question tests recognition of the standard primer type used for general steelwork in many specifications and schedules of rates. Given Data / Assumptions: Substrate: structural steel sections and fabricated assemblies. Objective: early corrosion protection and a sound base for topcoats. Environment: typical building and light industrial exposure (non-specialty). Concept / Approach: Red oxide of iron primers are traditional shop/field primers that provide a compatible, adherent base for alkyd or other coating systems. While modern zinc-rich/epoxy systems are common for severe duty, red oxide primer remains a widely referenced baseline for general environments. Step-by-Step Solution: 1) Identify that primers for steel must address corrosion and adhesion.2) Recognize that cement or casein paints are not designed for metal substrates.3) Using only a finishing paint without primer compromises system performance.4) Therefore, choose oxide of iron (red oxide) primer as the standard solution. Verification / Alternative check: Public works specifications and product datasheets list red oxide primers for structural steel in normal exposures; specialty primers are selected based on corrosivity category. Why Other Options Are Wrong: White lead mixes are obsolete/toxic and not standard primers today; cement and casein paints lack metal adhesion and corrosion inhibition; skipping primer is poor practice. Common Pitfalls: Assuming masonry primers or finish coats alone suffice on bare steel; ignoring surface preparation requirements (e.g., cleaning to standard). Final Answer: Oxide of iron (red oxide) primer

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