Question 1

Phenol and phenolic resins — key facts Which of the following statements about phenol and phenol–formaldehyde products are correct in basic building-materials practice?

Accepted Answer

Introduction / Context: Phenol and phenolic resins occupy a central place in early polymer chemistry and building materials. Phenolic binders and finishes have been used in laminates, adhesives, and protective coatings for decades due to their heat resistance and durability. Given Data / Assumptions: Nomenclature: “carbolic acid” is the historic name for phenol. Feedstocks: phenol has been produced from coal tar fractions or petrochemical routes (e.g., cumene process from benzene). Resin formation: phenol reacts with formaldehyde to yield thermosetting resins (resols/novolacs). Concept / Approach: All statements trace the pathway from basic phenol sourcing to polymerization chemistry, and finally to practical uses in the built environment. Phenolic resins cure to hard, heat-resistant materials that serve in coatings, moulded parts, and laminates. Step-by-Step Solution: Identify phenol’s identity → carbolic acid is its common name.Recognize industrial sources → coal tar extraction or synthesis from benzene.Note reaction with formaldehyde → formation of phenol–formaldehyde resin.Connect to applications → paints, varnishes, moulded goods (e.g., toilet seats, handles). Verification / Alternative check: Historic materials catalogs and polymer handbooks document phenolic resins under trade names (e.g., Bakelite) with widespread building-related applications. Why Other Options Are Wrong: Since A–D are correct, the best single choice is “All of the above.” Common Pitfalls: Confusing thermosetting phenolics with thermoplastics; once cured, phenolics do not soften on reheating. Also, modern low-VOC coatings may use alternative chemistries, but the fundamentals remain instructive. Final Answer: All of the above.

Question 2

Fibreboards in construction — properties and uses Which statement best summarizes common properties and uses of fibreboard products in building work?

Accepted Answer

Introduction / Context: Fibreboards (e.g., hardboard, medium-density fibreboard, insulating fibreboard) are engineered wood products. They are widely used for interior linings, partitions, and acoustic/thermal applications due to their processability and uniform properties. Given Data / Assumptions: Products include MDF, hardboard, and low-density insulating boards. Manufacture involves wood fibres, resins, and sometimes waxes or fire retardants. Typical uses are non-structural interior applications unless specifically rated. Concept / Approach: Fibreboards derive their performance from the fibre network and resin bonding. Low-density boards offer insulation and sound absorption, while medium/high-density boards provide smooth surfaces for furniture and interior finishes. Step-by-Step Solution: Relate composition (fibres + resin) to properties (stability, machinability).Map densities to uses: low density → acoustic/thermal; higher density → panels and furniture parts.Confirm that these uses are typically non-loadbearing and interior unless treated. Verification / Alternative check: Standards and manufacturers’ datasheets specify density, modulus, and recommended applications aligning with thermal/acoustic control and lightweight partitions. Why Other Options Are Wrong: Since A–C are correct descriptors, “All of the above” (D) is the best single choice. “None of the above” (E) contradicts well-established practice. Common Pitfalls: Using fibreboard in wet areas without moisture-resistant grades; not accounting for fire performance and code compliance; assuming structural capacity without certification. Final Answer: All of the above.

Question 3

Timber pathology — understanding dry rot In timber used for construction, “dry rot” most characteristically causes which outcome over time if unchecked?

Accepted Answer

Introduction / Context: Dry rot is a serious fungal decay of timber. Despite the name, it requires moisture to initiate, but it can continue at relatively low moisture levels once established. Recognizing its hallmark effects is essential for building maintenance and preservation. Given Data / Assumptions: Timber has been exposed to damp conditions sufficient to start fungal growth. Poor ventilation and hidden leaks may be present. No remedial treatment has yet been applied. Concept / Approach: Dry rot fungi digest the cellulose and hemicellulose, leaving weakened, brittle wood. As decay progresses, the timber loses cohesion and can crumble or powder under light pressure. This represents a severe loss of cross-section and mechanical capacity. Step-by-Step Solution: Observe typical signs: cuboidal cracking, mycelium strands, musty odor.Probe with a screwdriver: advanced material disintegrates into powdery crumbs.Diagnose moisture sources and remove them to halt progression.Replace affected members and treat surrounding zones with fungicides and drying protocols. Verification / Alternative check: Laboratory identification of fungal species and moisture mapping confirm diagnosis; structural assessment quantifies residual capacity. Why Other Options Are Wrong: Cracking only (A) and shrinkage only (D) ignore biochemical degradation. Minor strength reduction (B) understates the severity. Surface staining (E) may indicate mildew or superficial mold, not destructive dry rot. Common Pitfalls: Assuming “dry” rot occurs without moisture; failing to remove moisture sources; treating only the surface without replacing severely degraded members. Final Answer: Reduction of timber to a powdery/crumbly mass (severe decay)

Question 4

Cement types — identification of white cement Portland cement manufactured from pure white chalk and clay and essentially free from iron oxide pigments is commonly called:

Accepted Answer

Introduction / Context: Different cements are formulated to achieve specific color or performance objectives. When architectural aesthetics call for light or colored finishes, a special low-iron formulation is used to produce a white product. Given Data / Assumptions: Raw materials: very low iron and manganese content to avoid gray coloration. Manufacturing controls to prevent contamination from kiln and grinding media. Application focus: decorative concrete, terrazzo, tiles, and colored mortars. Concept / Approach: The absence of coloring oxides (primarily Fe2O3) yields a white clinker which, when ground with gypsum, becomes white cement. Performance is comparable to ordinary Portland cement, but color control is paramount; white pigments can be added without muddying. Step-by-Step Solution: Select high-purity limestone (chalk) and kaolin with minimal iron.Use kiln refractories and grinding media that do not introduce dark contaminants.Grind clinker with gypsum and test for whiteness index and strength. Verification / Alternative check: Colorimetric tests (whiteness index) and chemical analysis confirm low iron content; compressive strength tests verify structural suitability. Why Other Options Are Wrong: Quick-setting and rapid-hardening cements (A/B): defined by setting/strength characteristics, not color. Low-heat cement (D): formulated for mass concrete to limit temperature rise; again not color-driven. PPC (E): blended with pozzolana, typically gray. Common Pitfalls: Assuming white cement is always weaker or only decorative; it can meet structural grades but is more expensive due to stringent raw materials and processing. Final Answer: White cement

Question 5

Alloys — composition of German silver (nickel silver) German silver, used for decorative and electrical hardware, is an alloy composed of:

Accepted Answer

Introduction / Context: Despite its name, “German silver” (also called nickel silver) contains no elemental silver. It is valued for its silvery appearance, corrosion resistance, and reasonable strength, making it suitable for cutlery, musical instruments, and decorative fittings. Given Data / Assumptions: Typical composition ranges: copper as the base, with significant nickel and zinc. Applications emphasize appearance and tarnish resistance rather than high structural strength. Concept / Approach: Adding nickel to a copper–zinc matrix lightens the color toward a silvery sheen and improves corrosion resistance. The absence of precious-metal silver is the key point to remember. Step-by-Step Solution: Identify base metal: copper.Recognize alloying additions: nickel (for color and corrosion resistance) and zinc (for strength and workability).Confirm that no actual silver is present in the standard alloy family. Verification / Alternative check: Standards (e.g., UNS designations for nickel silver) list compositions like Cu 60–65%, Ni 10–20%, remainder Zn, with no Ag. Why Other Options Are Wrong: Options with silver or gold (B/E) are incorrect; the alloy contains no precious metals. “Copper, brass, and zinc” (D) is inconsistent; brass itself is copper–zinc. “Zinc, lead, and nickel” (A) omits copper, the principal constituent. Common Pitfalls: Assuming the name implies silver content; it refers to appearance only. Do not specify where high conductivity like pure copper is required, as nickel reduces electrical conductivity. Final Answer: Copper, nickel, and zinc

Question 6

Refractories — uses of silica (acid) refractories Silica (acid) refractories are primarily employed for which of the following applications in high-temperature practice?

Accepted Answer

Introduction / Context: Silica refractories are “acid” in character and maintain strength at elevated temperatures with excellent load-bearing capability and resistance to silica-rich slags. They play a crucial role in metallurgical coke production and glass manufacture. Given Data / Assumptions: High silica content (typically > 93% SiO2) with controlled mineral phases. Service environment features high temperatures and specific slag chemistries. Thermal cycling and dimensional stability are important. Concept / Approach: Silica bricks soften at very high temperatures and show good creep resistance in hot conditions. Their acid nature makes them compatible with acidic slags and glass melts. This suitability spans coke oven walls, checkerwork, and glass tank crowns. Step-by-Step Solution: Match chemistry: acid refractory → compatible with silica-rich environments.Identify industries: coke ovens (metallurgy) and glass furnaces.Relate product form: silica bricks are the standard shape for these linings. Verification / Alternative check: Industrial practice and refractory handbooks document silica brick use in coke oven batteries, glass tank superstructures, and some hot-blast stoves. Why Other Options Are Wrong: Options A, B, C list individual uses; the best comprehensive answer is the inclusive option D. “None of these” (E) contradicts well-established applications. Common Pitfalls: Using acid refractories where basic slags (high in CaO/MgO) are present; chemical incompatibility will cause rapid degradation. Select refractory class to match slag chemistry. Final Answer: All of these (silica bricks, coke ovens, and glass-furnace linings)

Question 7

Curing practice in building construction: For traditional lime mortar used in masonry or plastering, what is the typical (normal) period over which the work should be kept moist and protected to ensure proper setting and strength gain?

Accepted Answer

Introduction / Context: Curing is the controlled maintenance of moisture and temperature after laying mortar or concrete. For lime mortar, adequate curing is vital because setting occurs primarily by carbonation and, in hydraulic limes, by hydration reactions. This question asks the normal period recommended to keep lime mortar moist so that it achieves intended bond, density, and durability. Given Data / Assumptions: Lime mortars may be fat (non-hydraulic) or hydraulic, but routine site guidance specifies a minimum curing period. Ambient conditions are typical (not extremely hot/windy). Objective: select the commonly accepted “normal” curing period used in practice and standard MCQs. Concept / Approach: Lime mortars gain strength slower than neat cement mortars. A practical site norm is to keep the work damp for about one week to avoid early drying and shrinkage, allowing hydration (if hydraulic lime) and carbonation to proceed. Prolonged gentle moisture helps prevent cracking and dusting, especially in plaster. Step-by-Step Solution: Identify the binding mechanism: hydration (hydraulic lime) and carbonation (fat lime).Prevent premature drying: maintain moisture by sprinkling/covering.Adopt standard on-site practice: provide curing for approximately 7 days as the normal period.Result: adequate early strength and minimized surface defects. Verification / Alternative check: Construction handbooks and traditional specifications for lime mortars cite keeping the work damp for about a week under moderate climate; hotter or windy weather may need longer curing, while cool-humid conditions may suffice with similar or slightly shorter periods. Why Other Options Are Wrong: One day / 3 days: too short; risk of shrinkage and poor strength. 10 days / 14 days: sometimes used in harsh climates, but the common “normal” site practice is 7 days for typical conditions. Common Pitfalls: Confusing cement-mortar curing guidance with lime mortar; lime often benefits from equal or longer moist protection. Allowing surfaces to dry out quickly due to sun or wind exposure. Final Answer: 7 days

Question 8

Lime classification and manufacture: Given the statements S1–S3 below, which option correctly identifies the set of true statements about types of lime used in construction? S1. Quick lime is obtained by burning (calcining) relatively pure limestone…

Accepted Answer

Introduction / Context: Lime used in building is commonly classified as fat (quick) lime, hydraulic lime, and poor (lean) lime based on the proportion of clayey and other impurities in the parent limestone and the resulting setting behavior. Recognizing these definitions is essential for selecting materials for mortar, plaster, or stabilization works. Given Data / Assumptions: S1: Quick lime from relatively pure limestone. S2: Hydraulic lime from limestone containing 5%–30% clay. S3: Poor lime from limestone with impurities > 30% (very high impurities impair lime quality). Concept / Approach: Quick (fat) lime results from calcination of nearly pure calcium carbonate; it slakes vigorously and sets slowly (mainly by carbonation). Hydraulic lime contains reactive silica/alumina (from clay), enabling hydraulic set in damp or underwater conditions. When impurities become excessive (well beyond about 30%), the product is weak and is classed as poor/lean lime; however, many elementary question banks consider S3 as indicative but not universally standardized, so MCQs often mark S1 and S2 as the assured correct pair. Step-by-Step Solution: Check S1 against definition → correct.Check S2 against standard range (5%–30% clay) → correct.S3: some texts define poor lime for very high impurities (around or exceeding 30%); due to variability, many exams accept S1+S2 as the strictly correct core set.Therefore, choose “Only S1 and S2 are correct.” Verification / Alternative check: Classical materials texts present the 5%–30% clay range for hydraulic lime; quick lime demands near-pure limestone. Poor lime descriptions vary among sources, hence conservative marking retains S1 and S2 as the reliable pair. Why Other Options Are Wrong: Only S2 and S3 / Only S1: omit a definitely correct statement. All S1, S2, S3: treats S3 as universally fixed; exam keys often avoid this. Common Pitfalls: Confusing “poor” with “hydraulic.” Assuming any impurity automatically equals hydraulic behavior; the chemistry matters. Final Answer: Only S1 and S2 are correct

Question 9

Corrugated sheet iron in roofing: Which statements about manufacture, properties, protection, and typical use of corrugated iron sheets are correct?

Accepted Answer

Introduction / Context: Corrugated iron (or steel) sheets are ubiquitous in roofing and cladding. Corrugations increase structural efficiency, and galvanising mitigates corrosion. Understanding how they are made and why they are used helps in material selection for lightweight roofing systems. Given Data / Assumptions: Manufacturing uses mechanical corrugating rollers. The structural role is primarily roofing on pitched structures. Protection is via zinc galvanising in most common products. Concept / Approach: Corrugation is a geometric stiffening method. The sinusoidal/trapezoidal profile increases section modulus and moment of inertia without adding thickness, thus improving resistance to bending and buckling. Zinc galvanising provides sacrificial protection against corrosion, extending service life in outdoor exposure. Sloping roofs shed rain effectively and suit lapped, lightweight sheets. Step-by-Step Solution: Manufacture: pass flat sheets through matched corrugating rollers.Property: corrugation increases stiffness/strength per unit weight.Protection: galvanising coats steel with zinc, resisting rust.Application: installed on pitched roofs with overlaps for watertightness. Verification / Alternative check: Product datasheets and roofing handbooks confirm improved structural performance and standard galvanised finishes, with typical use on industrial, agricultural, and residential lean-to or pitched roofs. Why Other Options Are Wrong: Options A–D are each correct; thus the comprehensive and most accurate choice is “All of the above.” Common Pitfalls: Assuming strength gain requires thicker metal; shape alone contributes significantly. Ignoring the need for corrosion protection in coastal/industrial atmospheres. Final Answer: All of the above

Question 10

Puddling (historic refining of pig iron to wrought iron): During the puddling process in a reverberatory furnace, which of the following statements are true regarding the metal–fuel separation, oxidation of impurities, and heating method?

Accepted Answer

Introduction / Context: Puddling is a classic, now largely obsolete, furnace process used to refine pig iron into wrought iron. It relies on oxidation of impurities and furnace design that separates fuel from the molten bath. This question reviews core features of the process. Given Data / Assumptions: Reverberatory furnace used (flame and hot gases sweep over the charge). Objective is to reduce carbon and remove other impurities by oxidation and slagging. Concept / Approach: In a reverberatory furnace, fuel burns on the grate, and hot products of combustion heat the metal bath indirectly. Stirring exposes fresh metal to oxidising conditions. Carbon oxidises predominantly to CO and CO2; silicon oxidises to silica and enters slag; phosphorus and other impurities also react and partition to slag under suitable conditions. Step-by-Step Solution: Confirm metal–fuel separation: yes, the bath is not in contact with solid fuel.Oxidation: carbon is oxidised (to CO/CO2), lowering carbon content.Slag formation: oxidised silicon forms silica-rich slag with fluxes.Heating mode: radiant/convection from hot gases provides the heat. Verification / Alternative check: Metallurgy texts describe puddling as an indirect-fired process, emphasising oxidation of carbon and slagging of silicon, sulfur, and phosphorus to produce malleable wrought iron blooms. Why Other Options Are Wrong: All individual statements A–D are correct descriptions, so the collective answer is “All of the above.” Common Pitfalls: Confusing puddling with Bessemer blowing (which uses air blown through molten metal). Assuming fuel contacts the bath directly; it does not in reverberatory puddling. Final Answer: All of the above

Question 11

Steelmaking route identification: The process in which pig iron is first decarbonised (oxidised) and then recarburised by adding a measured quantity of carbon (for example via spiegeleisen) to obtain steel of desired composition is called:

Accepted Answer

Introduction / Context: Classical steelmaking routes include Bessemer, open hearth, crucible, and cementation. The Bessemer converter famously uses a blowing step to oxidise carbon and impurities, followed by controlled recarburisation to achieve the target carbon content in steel. Given Data / Assumptions: Pig iron is the starting material. Process includes decarbonisation then measured addition of carbon. Concept / Approach: In the Bessemer process, air is blown through molten pig iron. Carbon, silicon, and manganese are oxidised; the heat of oxidation keeps the bath molten. After the blow, a recarburiser such as spiegeleisen or ferromanganese is added to adjust composition, providing the desired carbon and manganese levels for the final steel. Step-by-Step Solution: Identify key cue: air blow decarbonises → characteristic of Bessemer.Adjustment step: add spiegeleisen to recarburise and deoxidise.Conclude the named process is the Bessemer process. Verification / Alternative check: Historic practice documents the decarburisation–recarburisation sequence as central to Bessemer steelmaking prior to basic oxygen and open-hearth dominance. Why Other Options Are Wrong: Cementation: solid-state carburising of wrought iron to produce blister steel, not decarbonising. Crucible: batch melting; not defined by blowing and recarburisation from pig iron. Open hearth: refinery furnace with longer heat and different control steps. Common Pitfalls: Assuming all historical routes recarburise in the same way; the air-blown decarburisation is Bessemer’s hallmark. Final Answer: Bessemer process

Question 12

Brick strength classification: According to common building materials standards, what is the minimum compressive strength specified for second-class (II class) burnt clay bricks?

Accepted Answer

Introduction / Context: Bricks are graded by compressive strength, dimensional tolerances, and appearance. Knowing the minimum strength helps designers specify appropriate classes for load-bearing or non-load-bearing masonry. Given Data / Assumptions: Question refers to typical textbook/MCQ values for second-class bricks. Units are in kg/cm² (1 MPa ≈ 10.197 kg/cm²). Concept / Approach: Common exam references state that first-class bricks have a compressive strength around 100–105 kg/cm² or higher, while second-class bricks are typically specified at about 70–75 kg/cm² minimum. Hence among the given choices, 75 kg/cm² is the accepted minimum for II class bricks. Step-by-Step Solution: Recall standard values: I class ≈ 100 kg/cm²+, II class ≈ 70–75 kg/cm².Match options to the conventional minimum → 75 kg/cm².Select 75 kg/cm² as the minimum for II class bricks. Verification / Alternative check: Many handbooks and solved question banks align II class bricks near 7 MPa (≈ 71–75 kg/cm²), confirming the choice. Why Other Options Are Wrong: 90/100/120/150 kg/cm²: these values correspond to first-class or special bricks; too high for the minimum of II class. Common Pitfalls: Mixing up MPa and kg/cm² leading to numerical mis-selection. Assuming the same minimum for both I and II class bricks. Final Answer: 75 kg/cm²

Question 13

Fibre (fiber) boards in interior works: With reference to finishing, what can be done to fibre boards used for partitions, ceilings, and panels?

Accepted Answer

Introduction / Context: Fibre boards (hardboard, medium-density fibreboard, insulating fibre board) are common in interior applications. Understanding their finish compatibility helps specify decorative treatments and maintenance schedules. Given Data / Assumptions: Fibre boards are used as wall/ceiling panels, partitions, and backing boards. Finishes include distemper, emulsion paints, and enamels when properly primed. Concept / Approach: Because fibre boards present a uniform surface, they can accept a variety of coatings. With appropriate sealing/priming, they can be distempered or painted. Heavy structural furniture frames are typically not made from insulating or low-density fibre boards; MDF can be used for cabinetry panels but the option presented emphasizes “structural frames,” which is not their main use compared to solid wood or engineered lumber. Step-by-Step Solution: Identify finish compatibility: both distemper and paint are suitable with primer.Eliminate options that are too restrictive (only one finish).Eliminate structural furniture assertion; fibre boards are more for panels than primary frames. Verification / Alternative check: Manufacturers’ datasheets recommend sealing/priming fibre boards, after which a wide range of coatings (including distemper and paint) can be applied for interior use. Why Other Options Are Wrong: Only distemper / only paint: both are possible; limiting to one is incomplete. Mainly for structural furniture frames: misleading; boards are primarily panel products, not high-strength frames. Common Pitfalls: Skipping primer and getting poor adhesion or raised fibres. Using exterior exposure without weatherproof grades or coatings. Final Answer: They can be both painted and distempered

Question 14

Basic properties of plastics in building applications: Identify the incorrect statement among the following general properties of plastics.

Accepted Answer

Introduction / Context: Plastics (thermoplastics and thermosets) are widely used because they resist many chemicals, are lightweight, and are good electrical insulators. However, their mechanical behavior differs from metals; specifically, their ductility in the metallurgical sense is limited. Given Data / Assumptions: General property statements typical of civil/building materials exams. We look for the statement that is not generally true for plastics. Concept / Approach: Many plastics are resistant to water and numerous chemicals, exhibit long service life in benign environments, and are excellent electrical insulators due to high resistivity. “Ductility,” defined as the ability to undergo significant plastic deformation in tension before fracture (like mild steel), is typically not a defining property of most engineering plastics in structural contexts; many are relatively brittle at room or low temperatures or display limited elongation-to-failure compared with metals. Step-by-Step Solution: Evaluate chemical resistance: generally true for many plastics (with exceptions).Durability: many plastics are durable in non-UV/controlled environments.Electrical insulation: widely true; plastics are commonly used as insulators.Ductility: not a universal property; often limited compared to metals, thus the incorrect generalization. Verification / Alternative check: Materials handbooks report high volume resistivity and corrosion resistance of plastics, but variable and often modest tensile ductility; some thermosets are distinctly brittle. Why Other Options Are Wrong: Chemical resistant/durable/insulators: broadly correct, acknowledging environmental limits (UV, solvents, temperature). Common Pitfalls: Overgeneralizing from one plastic to all; properties vary widely across families. Confusing impact toughness with tensile ductility. Final Answer: Plastics are ductile

Question 15

Water–cement ratio calculation in mix design: If 1 standard bag of cement (50 kg) requires 30 litres of water for a particular mix, what is the water–cement ratio (by mass)?

Accepted Answer

Introduction / Context: The water–cement ratio (w/c) is a key parameter controlling strength, durability, and workability of cement-based materials. It is defined as the mass of water divided by the mass of cement in the mix. This numerical question checks basic calculation and unit interpretation. Given Data / Assumptions: Mass of cement in one bag = 50 kg. Water added = 30 litres. Assume density of water ≈ 1 kg per litre, so 30 litres ≈ 30 kg of water. Concept / Approach: Compute w/c = mass of water / mass of cement. Using consistent mass units yields a dimensionless ratio. Accurate unit handling avoids common mistakes (e.g., dividing by volume of cement rather than mass). Step-by-Step Solution: Convert water volume to mass: 30 litres → 30 kg.Cement mass: 50 kg per bag.Compute ratio: w/c = 30 / 50 = 0.60.Select the matching option 0.60. Verification / Alternative check: Cross-check: 0.6 is a common w/c for moderate workability mixes; lower w/c (0.4–0.5) is used for higher strength/durability with plasticizers. Why Other Options Are Wrong: 0.40 / 0.50: would correspond to 20 kg or 25 kg of water for 50 kg cement, not the given 30 kg. None of these: incorrect because 0.60 matches the calculation. Common Pitfalls: Using litres directly without converting to mass for w/c. Assuming a 40 kg cement bag (some markets) instead of 50 kg; always confirm bag mass. Final Answer: 0.60

Question 16

Condensation polymers in building materials and plastics: Which of the following resins are formed by condensation polymerisation reactions?

Accepted Answer

Introduction / Context: Condensation polymerisation involves step-growth reactions where small molecules (often water or methanol) are eliminated as monomers react. Many resins in wood products and laminates are condensation polymers, important for adhesives and decorative laminates in construction and furniture. Given Data / Assumptions: Phenol–formaldehyde (PF), urea–formaldehyde (UF), and melamine–formaldehyde (MF) systems are listed. We must identify which are condensation polymers. Concept / Approach: PF, UF, and MF resins form through step-growth reactions between monomers (phenol/urea/melamine with formaldehyde), eliminating small molecules during curing. These resins are widely used as binders in plywood, particleboard, MDF, and high-pressure laminates due to good bonding and heat resistance (especially PF and MF). Step-by-Step Solution: Phenol–formaldehyde: classic condensation resin, water released during polymer growth and cure.Urea–formaldehyde: step-growth polymerisation yielding methylene/ether linkages and releasing water.Melamine–formaldehyde: thermosetting condensation resin used in laminates and tableware.Therefore, all listed are condensation polymers. Verification / Alternative check: Polymer chemistry references classify PF, UF, MF as thermosetting condensation polymers, in contrast to addition polymers like polyethylene and polystyrene formed by chain-growth without by-product elimination. Why Other Options Are Wrong: Each individual resin listed is indeed a condensation polymer; hence the only comprehensive correct option is “All of these.” Common Pitfalls: Confusing “condensation” with “addition” polymerisation; note the elimination of small molecules in condensation systems. Assuming all thermosets are condensation polymers; epoxies cure differently. Final Answer: All of these

Question 17

Building materials — bituminous felts in building construction Bituminous felts (bituminous membranes) are commonly specified for which application on buildings?

Accepted Answer

Introduction / Context: Bituminous felts (also called bituminous membranes or roofing felts) are factory-made sheets impregnated or coated with bitumen. They are widely used in civil engineering works to resist water ingress. Knowing their correct application helps designers and site engineers select the right material for damp-proofing and waterproofing. Given Data / Assumptions: Bituminous felt is flexible, water-resistant, and usually laid in one or more plies with hot or cold bitumen bonding. Applications include damp-proof courses (D.P.C.) in walls and floors, and membrane waterproofing on terraces and basements. The question asks for the most appropriate/common building application. Concept / Approach: A D.P.C. is a barrier against capillary rise of moisture from substructure into superstructure. Bituminous felts provide an effective impermeable barrier when properly lapped and bonded. While felts may be used on some roof build-ups, they are not intended just to “cover” A.C. sheets for appearance, and they are not typically the primary outermost layer on steep sloping roofs without a full roofing system. Step-by-Step Solution: Identify the property: bituminous felts are waterproof and flexible.Map property to use: ideal for D.P.C. and membrane waterproofing (horizontal and vertical).Evaluate distractors: aesthetic covering of A.C. sheets is not a standard specification; sloping roofs typically use tiles/sheets/shingles, with felts as underlays only.Hence, the correct, textbook use is D.P.C. and waterproofing layers. Verification / Alternative check: Standard building codes and specifications list bituminous felt as an approved D.P.C. material alongside PVC membranes and polymer-modified bituminous sheets. Why Other Options Are Wrong: Covering A.C. sheets: not a normal or recommended application; does not address jointing/fastener penetrations properly. Covering sloping roofs: felts alone are not used as the outer weathering surface on steep roofs; they may be an underlayment only. None of these and temporary shuttering: incorrect; felts are not shuttering materials. Common Pitfalls: Using felts without proper laps/primers; laying on dusty or damp substrates; inadequate upturns/flashings at edges; ignoring UV protection where exposed. Final Answer: Providing a damp-proof course (D.P.C.) and waterproofing layers

Question 18

Engineering geology — properties of quartzite (a metamorphic rock) Which set of descriptors best matches quartzite, a metamorphic stone derived from sandstone?

Accepted Answer

Introduction / Context: Quartzite is a metamorphic rock formed when quartz-rich sandstone is subjected to heat and pressure, causing recrystallization and interlocking of quartz grains. Understanding its mechanical and physical properties is critical for its use in construction, flooring, and as aggregate. Given Data / Assumptions: Parent rock: sandstone composed predominantly of quartz. Metamorphism leads to interlocking crystalline texture. Typical engineering descriptors: hardness, brittleness, compactness. Concept / Approach: During metamorphism, silica cements and quartz grains fuse, producing a dense, crystalline mass with high hardness (quartz hardness ~7 on Mohs scale). The strong interlocking texture makes quartzite hard and compact, but like many strong rocks, it tends to fail with limited plastic deformation, so it is described as brittle under load. Step-by-Step Solution: Identify mineralogy: largely quartz → high hardness.Identify texture: recrystallized, interlocking grains → crystalline and compact.Relate mechanics: strong and stiff but with limited ductility → brittle behavior.Therefore, all descriptors (hard, brittle, crystalline, compact) apply. Verification / Alternative check: Hand specimens show sugary to glassy luster and conchoidal fracture; density and rebound hammer readings reflect compactness and hardness. Why Other Options Are Wrong: Any single descriptor alone is incomplete; quartzite typically exhibits all listed properties, hence “All of the above” is correct. Common Pitfalls: Confusing quartzite with quartz-rich sandstone (less compact, clastic); misidentifying foliated metamorphic rocks (e.g., schist) as quartzite; assuming hardness implies toughness (brittle rocks can chip under impact). Final Answer: All of the above

Question 19

Timber defects and features — identification of waney edge In sawn timber, the visible remnant of the original rounded tree surface on a manufactured piece is called:

Accepted Answer

Introduction / Context: Recognizing surface features and defects in timber helps in grading, pricing, and specifying wood for structural or finish applications. A common feature is the presence of the original rounded tree surface on an edge or corner after sawing. Given Data / Assumptions: The piece has an unplaned, rounded, bark-adjacent edge or surface remnant. The term sought is a standard timber trade term. The alternatives include other surface defects unrelated to the original tree curvature. Concept / Approach: When a log is converted to boards, outer pieces may retain part of the curved surface; this is termed wane or waney edge. It reduces the full rectangular cross-section and may be unacceptable in structural members where full bearing or planeness is required. Step-by-Step Solution: Identify cue: presence of rounded, natural surface on an otherwise sawn piece.Match with terminology: wane/waney edge.Exclude other defects: torn grain (machining tear-out), diagonal grain (grain not parallel to edge), chip marks (tooling marks). Verification / Alternative check: Grading rules in lumber standards classify wane and specify allowable limits for structural grades. Why Other Options Are Wrong: Torn grain is a machining defect from planing; diagonal grain is a grain orientation issue; chip marks are minor machining blemishes; honeycombing is internal checking, not an outer rounded surface. Common Pitfalls: Accepting excessive wane in load-bearing edges; painting over waney edges without proper trimming; confusing bark inclusions with simple wane. Final Answer: Wane (waney edge)

Question 20

Rock textures — foliation occurrence by rock class Foliated structure (planar alignment of minerals) is most commonly associated with which class of rocks?

Accepted Answer

Introduction / Context: Foliation is a planar fabric resulting from differential stress that aligns platy or elongate minerals. Recognizing foliation helps engineers and geologists anticipate anisotropic behavior such as preferred failure planes and directional permeability. Given Data / Assumptions: Foliation develops during solid-state deformation and metamorphism. Common foliated rocks: slate, phyllite, schist, gneiss. Sedimentary bedding is a different planar feature and should not be confused with foliation. Concept / Approach: Under regional metamorphism, pressure solution and recrystallization align mica and other minerals perpendicular to maximum compressive stress, producing foliation. Igneous rocks may show flow banding but that is not foliation; sedimentary rocks show bedding/lamination formed by deposition, not metamorphic alignment. Step-by-Step Solution: Define foliation: planar fabric from metamorphic processes.Map to rock class: metamorphic rocks commonly exhibit foliation.Exclude other classes: sedimentary → bedding; igneous → massive or flow structures. Verification / Alternative check: Field mapping uses foliation strike and dip to evaluate slope stability and excavation directions. Why Other Options Are Wrong: Sedimentary rocks have bedding, not foliation. Igneous rocks are generally non-foliated; any banding is not metamorphic foliation. “None of these” contradicts standard metamorphic petrology. Common Pitfalls: Confusing bedding cleavage with slaty cleavage; ignoring anisotropy in stability analysis; equating flow banding with foliation. Final Answer: Metamorphic rocks

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