Question 1

Classification of rocks by composition: Rocks in which argil (clay) predominates are termed as which class of rocks?

Accepted Answer

Introduction / Context: In building materials, rock classification by dominant constituents influences strength, durability, and weathering behavior. Civil engineers often classify sedimentary rocks into calcareous, siliceous, and argillaceous groups based on predominant minerals. Given Data / Assumptions: “Argil” is clay-rich constituent (alumino-silicates). We must pick the class where clay dominates. Concept / Approach: Argillaceous rocks are clay-rich (e.g., shale, slate as a metamorphosed derivative). Siliceous rocks are silica-rich (quartzites, sandstones), calcareous rocks are rich in calcium carbonate (limestones, marbles), and igneous is a genetic, not compositional, term in this context. The name “argillaceous” derives from “argilla,” Latin for clay. Step-by-Step Solution: Identify the predominant constituent: clay.Map to classifications: argillaceous ↔ clay rich.Conclude: argillaceous rocks is the correct class. Verification / Alternative check: Standard materials texts list shale and claystones as argillaceous; their engineering behavior (low permeability, potential for swelling if montmorillonite is present) follows clay mineralogy. Why Other Options Are Wrong: Siliceous: dominated by silica; not clay. Calcareous: dominated by calcium carbonate; not clay. Igneous: origin-based term (formed from magma), not a clay-dominance descriptor here. Common Pitfalls: Confusing genetic (igneous, sedimentary, metamorphic) with compositional (siliceous, calcareous, argillaceous) classifications. Final Answer: argillaceous rocks

Question 2

Selecting building stones for different uses: Which of the following statements together best describe appropriate stone selection for carving, arches, and high-pressure applications?

Accepted Answer

Introduction / Context: Stone selection depends on application: ornamentation, arch construction, and load-bearing conditions require different combinations of weight, strength, and workability. This conceptual question checks your ability to match stone properties to use-cases. Given Data / Assumptions: Carving requires ease of tooling. Arches benefit from reduced self-weight in some designs. High pressure or heavy loads demand strong, hard stones. Concept / Approach: Soft, fine-grained stones (e.g., some limestones, soft sandstones) carve readily for intricate details. Lightweight stones (e.g., some tuffs or lighter density stones) reduce dead load, which can be beneficial in arches where self-weight influences thrust. Hard stones (e.g., granites, dense basalts) resist crushing and are appropriate for high-pressure zones like columns and foundations. Step-by-Step Solution: Match property to function: softness → carving (tooling ease).Reduce dead load: lighter stones can be advantageous in arches, subject to structural design.Require strength: hardness correlates with compressive strength for high-pressure regions. Verification / Alternative check: Historic architecture illustrates soft limestones for ornamentation, lighter stones in some arch rings, and strong igneous rocks for columns and bearing elements. Modern codes also emphasize compressive strength for load-bearing masonry units. Why Other Options Are Wrong: Each individual statement is correct on its own, but the best comprehensive choice is the combination acknowledging all three principles; hence “All of the above.” Common Pitfalls: Assuming “light stones” are always inferior; in arches, dead load matters, but stone must still meet strength requirements. Equating “hard” solely with wear resistance; here compressive strength is central. Final Answer: All of the above

Question 3

Roofing stones in building construction: Which rock is most commonly used for roofing slabs because it naturally splits into thin, durable sheets?

Accepted Answer

Introduction / Context: Traditional roofing in many regions uses natural stone slabs. The suitability of a rock for roofing depends on its ability to split into thin, strong, weather-resistant sheets with a pleasant appearance and adequate durability. Given Data / Assumptions: Roofing requires thin, flat, strong panels. The stone should have good cleavage for splitting and good weather resistance. Concept / Approach: Slate, a metamorphic rock derived from shale, exhibits slaty cleavage, allowing it to be split into thin, uniform slabs. It is durable, resists water penetration, and provides long service life. Granite and basalt are strong but do not split as cleanly into thin roofing slabs; pumice is too porous and weak for structural roofing sheets. Step-by-Step Solution: Identify key property: slaty cleavage → easy splitting into thin sheets.Filter rocks: slate fits; granite and basalt lack suitable cleavage; pumice is lightweight and weak.Select slate as the roofing rock of choice. Verification / Alternative check: Historic and modern slate roofs worldwide (Wales, Spain, India, USA) confirm slate’s ubiquitous use where available, due to its cleavage and weathering performance. Why Other Options Are Wrong: Granite/Basalt: very strong but unsuitable for thin splitting; machining to thin slabs is expensive and impractical for roofing. Pumice: too soft and porous; not a structural roofing sheet material. Common Pitfalls: Confusing decorative stone facings with roofing slabs; cladding has different thickness and attachment. Final Answer: slate

Question 4

Geological classification of marble: From a geological standpoint, marble belongs to which category of rocks?

Accepted Answer

Introduction / Context: Accurate rock classification affects expectations about durability, weathering, and workability. Marble is widely used in architecture and sculpture; recognizing its origin informs selection and maintenance decisions. Given Data / Assumptions: Marble results from the transformation of pre-existing rock. Recrystallization implies metamorphism. Concept / Approach: Marble forms when limestone (a calcareous sedimentary rock) undergoes metamorphism under heat and pressure, causing calcite crystals to recrystallize. Thus, marble is classified as a metamorphic rock, not sedimentary or igneous. “Stratified rock” refers to layered structure typical of many sedimentary rocks; metamorphism often obliterates original bedding. Step-by-Step Solution: Identify parent rock: limestone (sedimentary).Apply metamorphic conditions: elevated temperature and pressure.Resultant rock: marble (recrystallized calcite), hence metamorphic. Verification / Alternative check: Petrology texts describe coarse interlocking calcite crystals in marble and the loss of fossils/strata typical of limestone due to metamorphism, confirming the metamorphic classification. Why Other Options Are Wrong: Sedimentary: describes limestone, not its metamorphosed form. Igneous: formed from magma; not applicable here. Stratified: a structural descriptor of many sedimentary rocks, not a metamorphic category. Common Pitfalls: Using commercial trade names (“marble”) for any polishable carbonate rock; geologically, true marble is metamorphic. Final Answer: metamorphic rock

Question 5

Bituminous road materials: In producing plastic bitumen (plasticized or mastic-type bitumen mixes), which of the following has historically been used as a fine filler to modify consistency and performance?

Accepted Answer

Introduction / Context: Bituminous mixes often include mineral fillers to adjust viscosity, stiffness, and durability. In older formulations of plastic or mastic-type bitumen, a fine fibrous filler was sometimes employed to improve stability and workability for waterproofing and paving applications. Given Data / Assumptions: Question refers to traditional practice (“plastic bitumen”) used in legacy specifications. We are selecting the typical fine filler cited in classical construction-materials references. Concept / Approach: Classical plastic/mastic bitumen mixes used asbestos powder as a filler to increase cohesiveness, reduce temperature susceptibility, and improve deformation resistance. While modern practice may avoid asbestos due to health hazards, many traditional questions reflect earlier materials technology where asbestos filler was common in mastics and plastic bitumen. Step-by-Step Solution: Identify historical fillers: asbestos, mineral dust, limestone powder.Match “plastic bitumen” context: asbestos powder widely cited.Select asbestos powder as the classical answer. Verification / Alternative check: Legacy textbooks and specifications mention asbestos-filled mastics for roofing and paving; contemporary standards now specify safer alternatives, but the exam context typically expects “asbestos powder.” Why Other Options Are Wrong: Shale or talc powders: used in some fillers but not the standard association for plastic bitumen in older references. Plastic powder: not a conventional filler in bitumen mastics; modern “plastic roads” use waste plastics differently (as modifiers), not as fine mineral fillers. None of these: incorrect because asbestos powder is classically cited. Common Pitfalls: Confusing modern modified bitumen technology with historical exam content. Assuming health restrictions retroactively change classical answers; exams often retain legacy terminology. Final Answer: asbestos powder

Question 6

Metallurgy of steels: Cast steel (steel solidified from the molten state in molds) is classically produced by which manufacturing process in traditional practice?

Accepted Answer

Introduction / Context: Historically, producing high-quality cast steel involved melting refined steel and pouring it into molds. Multiple processes exist in steelmaking; understanding which is traditionally associated with “cast steel” is a common materials question. Given Data / Assumptions: Question targets classical terminology from standard materials textbooks. “Cast steel” emphasizes fully molten steel poured into molds rather than wrought processing. Concept / Approach: The crucible process (Huntsman process) melted blister steel or refined steel in sealed clay crucibles to produce homogeneous, high-quality molten steel, which was then cast—hence “cast steel.” The cementation process carburizes wrought iron to make blister steel (not direct casting). Bessemer and open-hearth are bulk steelmaking processes; they can produce ingots, but the exam-classical pairing for “cast steel” is specifically the crucible method. Step-by-Step Solution: Identify process used to melt and cast high-quality steel in small batches → crucible process.Differentiate from cementation (solid-state carburizing) and conversion processes (Bessemer, open-hearth).Select “Crucible process.” Verification / Alternative check: Historical references describe “crucible cast steel” as a premium product for tools and springs prior to widespread basic oxygen/electric furnace technologies. Why Other Options Are Wrong: Cementation: does not melt/cast; produces blister steel. Bessemer/Open hearth: large-scale refining routes; while they yield ingots, the term “cast steel” in classical MCQs points to crucible cast steel. Common Pitfalls: Assuming any ingot route equals “cast steel”; the question is about the historically named process. Final Answer: Crucible process

Question 7

Plywood raw materials: Commercial plywood panels used in construction and furniture are typically manufactured from which source material?

Accepted Answer

Introduction / Context: Plywood is a versatile wood product made by bonding veneers peeled from logs. Understanding its feedstock helps in material selection, sustainability considerations, and cost analysis in construction and furniture applications. Given Data / Assumptions: Plywood is an engineered product relying on wood veneers. Species selection varies by region and grade; there is no single mandatory species. Concept / Approach: Manufacturers use a wide range of common timbers (e.g., poplar, eucalyptus, birch, pine, gurjan) to produce veneers for plywood. The essential criterion is veneer quality, bond, and layup, not a single species. Bamboo-based panels do exist (e.g., bamboo plywood), but that is a distinct product. Teak plywood is a premium decorative option, not the exclusive norm. Asbestos has no role in plywood manufacture. Step-by-Step Solution: Identify typical source: logs of common commercial timbers → peeled into veneers.Bond veneers with adhesives (UF, PF, MF depending on grade) and hot press.Conclude “common timber” is the general, correct answer. Verification / Alternative check: Product standards (e.g., IS/EN/ASTM) list multiple species suitable for structural and non-structural plywood; teak is optional as a face veneer for appearance, not a requirement. Why Other Options Are Wrong: Bamboo fibre: used in separate bamboo panels, not standard timber plywood. Teak wood only: too restrictive; many species are used. Asbestos sheets: unrelated mineral product. Common Pitfalls: Equating decorative face veneer species with the entire panel composition. Confusing bamboo-based products with wood-based plywood. Final Answer: common timber

Question 8

Metallurgy — flux selection in iron making If iron ore contains clay (siliceous) as the main impurity, which flux should be added during calcination to promote slag formation?

Accepted Answer

Introduction / Context: In extractive metallurgy, choosing the correct flux is essential for removing gangue from iron ore. When the impurity is clay (largely silica), the furnace must be provided with a basic flux so that a fluid, separable slag forms, improving metal quality and furnace efficiency. Given Data / Assumptions: Ore contains clay (siliceous gangue, mainly SiO2 and aluminosilicates). Objective: convert acidic gangue into a basic slag that can be tapped off. Standard ironmaking practice using limestone as a basic flux. Concept / Approach: Silica (acidic) requires a basic flux. Limestone (CaCO3) decomposes to CaO and CO2 on heating. The calcium oxide then reacts with silica to form calcium silicate slag. This slag is fluid at furnace temperature and separates from molten iron due to density differences. Step-by-Step Solution: Thermal decomposition: CaCO3 → CaO + CO2.Acid–base reaction: CaO + SiO2 → CaSiO3 (slag).Slag floats above iron and is removed, taking siliceous impurities with it.Therefore, add limestone when the gangue is clay/silica rich. Verification / Alternative check: Basic slag formation is standard in blast furnace practice; basic fluxes neutralize acidic gangue. Process flow sheets and slag analyses confirm predominance of calcium silicates when limestone is used. Why Other Options Are Wrong: Clay is the impurity itself; adding more does not help. Argillaceous iron ore adds further silica/alumina, worsening slagging. “All of the above” cannot be correct since basic–acid pairing is required. Dolomite provides CaO and MgO and can be used, but limestone is the conventional first choice for siliceous gangue in the context of the question. Common Pitfalls: Confusing acidic and basic slags; attempting to remove silica with acidic flux; ignoring the decomposition of limestone and slag fluidity requirements. Final Answer: limestone (CaCO3)

Question 9

Cement technology — characteristics and uses of low-heat cement Which statements correctly describe low-heat Portland cement with respect to strength gain, setting times, and applications?

Accepted Answer

Introduction / Context: Low-heat Portland cement (LHC) is formulated to reduce the rate of heat evolution during hydration. This is critical in large pours such as dams and massive foundations, where thermal gradients can lead to cracking. Understanding its properties ensures the right cement is used for durability. Given Data / Assumptions: LHC has reduced C3S and C3A contents compared to ordinary Portland cement. Target is lower peak temperature and slower heat release. Standard setting time windows: initial ≥ 60 minutes; final often within about 10 hours (may vary with standards and admixtures). Concept / Approach: Lower C3S and C3A reduce early strength gain and heat of hydration. Longer setting times help dissipate heat over a longer period, minimizing temperature rise and thermal stresses in mass concrete. The application focus is on massive elements where temperature control outweighs rapid strength development. Step-by-Step Solution: Relate composition to performance: lower C3S/C3A → slower, cooler hydration → lower early strength.Check setting time criteria: initial setting around 60 minutes is typical for LHC; final setting often around 10 hours depending on conditions.Match application: mass concrete benefits from reduced thermal cracking risk → use LHC.Therefore, all listed statements correctly describe LHC. Verification / Alternative check: Thermal monitoring in dam construction shows lower temperature gradients with LHC vs. OPC. Specification documents list increased initial set and reduced heat evolution. Why Other Options Are Wrong: Each individual statement is accurate; the comprehensive choice “All of the above” best captures LHC’s characteristics and use cases. Common Pitfalls: Assuming LHC achieves the same early strength as OPC; neglecting ambient temperature effects; ignoring admixture impacts on set times. Final Answer: All of the above

Question 10

Lime chemistry — theoretical water for slaking quicklime For slaking 10 kg of CaO (quicklime), what is the theoretical mass of water required to form Ca(OH)2?

Accepted Answer

Introduction / Context: Slaking of quicklime is a fundamental reaction in building materials and environmental engineering. Correct water dosage is important for efficient hydration, heat control, and achieving desired workability in lime mortars and stabilization works. Given Data / Assumptions: Chemical reaction: CaO + H2O → Ca(OH)2. Molar masses: CaO = 56 kg/kmol, H2O = 18 kg/kmol. Target quicklime mass: 10 kg. Concept / Approach: The stoichiometric water requirement follows directly from molar mass ratios in the balanced equation. One mole of water reacts with one mole of CaO. Compute water mass per mass of CaO and scale to 10 kg. Step-by-Step Solution: Required water per kg CaO = 18 / 56 kg/kg.For 10 kg CaO: water = (18 / 56) * 10.Calculate: 18 / 56 = 0.321428…Water needed = 0.321428… * 10 = 3.21428… kg ≈ 3.2 kg. Verification / Alternative check: Cross-check by proportionality: 56 kg CaO requires 18 kg H2O; 10 kg CaO requires (10 * 18 / 56) = 3.214 kg. Why Other Options Are Wrong: 2.2 kg and 1.5 kg understate the stoichiometric need and would leave unreacted CaO. 4.0 kg exceeds the theoretical requirement; extra water may be used in practice for workability but is not the theoretical stoichiometric amount. “None of these” is incorrect because 3.2 kg is available and correct. Common Pitfalls: Confusing theoretical water with practical water addition; ignoring heat of hydration which can cause flash setting and safety hazards; not accounting for lime purity in real projects. Final Answer: 3.2 kg

Question 11

Timber technology — anatomical zones In a timber log, what is the inner, mature region surrounding the pith commonly called?

Accepted Answer

Introduction / Context: Timber is composed of distinct anatomical zones, each with unique properties affecting durability, strength, and treatment response. Identifying heartwood versus sapwood is crucial for selection in structural and finishing applications. Given Data / Assumptions: Pith occupies the very center. Heartwood surrounds the pith and is typically darker, denser, and less permeable. Sapwood forms the outer, lighter band that conducts sap. Cambium is a thin growth layer under the bark. Concept / Approach: As trees mature, older xylem becomes heartwood, a reservoir of extractives that enhance natural durability. Sapwood remains physiologically active, transporting water and nutrients. The cambium is responsible for radial growth but is not a bulk wood zone. Step-by-Step Solution: Identify the region immediately around the pith: mature xylem.This region is typically darker and called heartwood.Therefore, the correct term is heartwood. Verification / Alternative check: Examine any cross section: central pith, then a ring of darker heartwood, then lighter sapwood, then cambium and bark. Why Other Options Are Wrong: Sapwood is outer, active xylem, not the inner mature zone. Cambium is a thin cell-generating layer, not the bulk wood surrounding pith. Bast (phloem) lies outside cambium and is unrelated to the inner wood. Common Pitfalls: Assuming heartwood is always stronger; species and defects matter. Confusing color differences due to staining versus true heartwood boundaries. Final Answer: heartwood

Question 12

Lime materials — properties of quicklime (CaO) Which statements correctly describe quicklime used in construction materials and chemical processes?

Accepted Answer

Introduction / Context: Quicklime (calcium oxide) is a key material for soil stabilization, mortar production, and environmental applications. Knowing its origin and behavior is crucial for safe handling and effective use at site. Given Data / Assumptions: Limestone is primarily CaCO3. Calcination occurs in kilns at elevated temperatures. Quicklime reacts exothermically with water to form slaked lime (Ca(OH)2). Concept / Approach: Calcination drives CO2 off limestone, producing CaO. The product is highly reactive with water and atmospheric moisture, which is why storage must be dry and airtight. Quicklime is generally non-crystalline (amorphous) as produced industrially, contributing to its reactivity. Step-by-Step Solution: Calcination: CaCO3 → CaO + CO2 (endothermic decomposition).Hygroscopic behavior: CaO readily hydrates → Ca(OH)2 with substantial heat release.Material structure: commonly amorphous/finely crystalline, aiding rapid reaction.Therefore, all three statements are correct. Verification / Alternative check: Industrial datasheets list loss on ignition, free CaO content, and storage precautions due to moisture affinity. Why Other Options Are Wrong: The extra option claiming pre-hydrated and non-reactive contradicts the very definition of quicklime; pre-hydrated material is slaked lime, not quicklime. Common Pitfalls: Exposing quicklime to ambient humidity leading to unsafe heat release; mistaking hydrated lime for quicklime in mix designs; ignoring purity effects on performance. Final Answer: All of the above

Question 13

Bricks — minimum clay and silt content in good brick earth For a good brick earth mix, what should be the minimum combined percentage of clay and silt in the raw material?

Accepted Answer

Introduction / Context: Brick earth composition controls plasticity, drying behavior, firing shrinkage, and final strength. Understanding the minimum clay/silt content ensures adequate plasticity for moulding while avoiding excessive shrinkage and cracking. Given Data / Assumptions: Typical good brick earth ranges: silica (sand) 50–60%, alumina (clay) 20–30%, lime 5–10%, iron oxide 5–7%, and small alkalis. Clay and silt contribute plasticity and binding during moulding. Excess clay leads to higher shrinkage; too little clay leads to poor cohesion. Concept / Approach: A minimum threshold of fine fraction (clay and silt) around 20% is widely cited to secure workable plasticity without excessive drying defects. While optimal mixes often use 20–30% clay, the question asks for the minimum acceptable percentage, which is 20%. Step-by-Step Solution: Identify required roles: clay/silt provide plasticity and green strength.Balance with silica to control shrinkage and warping.From standard composition ranges, the minimum combined clay/silt lies at about 20%. Verification / Alternative check: Pilot mixes with clay below 20% show poor workability and cracking; specifications for good brick earth list alumina content not less than about 20%. Why Other Options Are Wrong: 25–50% may be suitable in some cases but are not the minimum threshold; the question asks for the least acceptable value. Common Pitfalls: Confusing optimum with minimum; overlooking the role of tempering water and aging; ignoring that silt behaves differently from true clay minerals during firing. Final Answer: 20%

Question 14

Cement testing — purpose of the soundness test The soundness test of cement primarily assesses which aspect of cement quality?

Accepted Answer

Introduction / Context: Unsound cement expands excessively after setting, leading to cracking and failure in concrete. The soundness test is designed to detect potential late expansion due to undesirable constituents, protecting long-term durability. Given Data / Assumptions: Problematic constituents: excess free CaO and MgO that hydrate slowly and expand. Common test methods: Le Chatelier and autoclave expansion tests. Objective: ensure volume stability of hardened cement paste. Concept / Approach: Free lime and periclase (MgO) can hydrate after setting, causing volumetric instability. Soundness tests accelerate conditions to reveal such expansion risk. They do not measure strength or set times; those are separate standardized tests. Step-by-Step Solution: Recognize the property measured: freedom from excessive expansion.Link expansion to free CaO/MgO content and their late hydration.Therefore, soundness testing primarily assesses the presence/effect of these expansive components. Verification / Alternative check: Compare acceptable expansion limits in standards; cements failing soundness often show higher free CaO or MgO in chemical analysis. Why Other Options Are Wrong: Ultimate strength, setting time, and fresh workability are measured by different tests (compressive strength cubes, Vicat, and slump/flow tests), not by soundness procedures. Common Pitfalls: Assuming sulfate resistance equals soundness; confusing autoclave expansion (soundness) with sulfate expansion tests on mortar bars. Final Answer: quality of free lime (and magnesia) causing excessive expansion

Question 15

Petrology — rock classification by origin Rocks formed by alteration of existing rocks due to heat and/or high pressure (without melting) are called:

Accepted Answer

Introduction / Context: Engineering geology classifies rocks based on their origin: igneous, sedimentary, and metamorphic. This classification informs strength, anisotropy, weathering, and suitability for construction and aggregates. Given Data / Assumptions: Metamorphism alters mineralogy and texture in the solid state. Agents: heat, pressure, chemically active fluids. No bulk melting; otherwise the product would be igneous. Concept / Approach: When pre-existing rocks (igneous or sedimentary) are subjected to elevated temperature and pressure, new minerals grow and original textures are reconstituted. The resulting rocks are called metamorphic (e.g., gneiss, schist, marble, quartzite). Step-by-Step Solution: Identify process: solid-state recrystallization under T–P conditions.Relate to products: foliation, banding, increased density and strength.Therefore, the correct class is metamorphic rocks. Verification / Alternative check: Field features like schistosity or gneissic banding confirm metamorphic processes; lab thin-sections show neoblastic minerals. Why Other Options Are Wrong: Sedimentary rocks form by deposition and lithification; igneous rocks form by crystallization from melt; “extrusive” is a subset of igneous, not a separate origin. Common Pitfalls: Confusing contact metamorphism near intrusions with partial melting; mislabeling metasomatic alterations as igneous. Final Answer: metamorphic rocks

Question 16

Igneous petrology — plutonic vs. volcanic examples Which of the following is a plutonic (intrusive) igneous rock formed by slow cooling at depth?

Accepted Answer

Introduction / Context: Igneous rocks are categorized by cooling environment: intrusive (plutonic) rocks crystallize slowly underground, producing coarse grains; extrusive (volcanic) rocks cool rapidly at the surface, yielding fine grains or glassy textures. Recognizing these helps predict engineering behavior. Given Data / Assumptions: Plutonic examples: granite, gabbro. Hypabyssal (shallow intrusive): dolerite/diabase, with medium grain. Extrusive examples: basalt, rhyolite. Concept / Approach: Granite is the classic plutonic rock: coarse-grained quartz-feldspar-mica texture from slow cooling at depth. Dolerite is typically hypabyssal and medium-grained; basalt is fine-grained extrusive. Step-by-Step Solution: Identify cooling environment: deep and slow → plutonic.Match example: granite fits plutonic; dolerite is subvolcanic; basalt is volcanic.Therefore, the plutonic rock among options is granite. Verification / Alternative check: Hand specimen reveals coarse interlocking grains in granite; basalt shows fine matrix; dolerite displays medium ophitic textures. Why Other Options Are Wrong: Dolerite is not fully plutonic; it is hypabyssal. Basalt is extrusive; rapid cooling at the surface. “All of the above” cannot be correct because basalt is not plutonic. Rhyolite is extrusive, felsic equivalent of granite. Common Pitfalls: Grouping all igneous rocks without regard to cooling depth; assuming grain size solely indicates mineral composition rather than cooling rate. Final Answer: Granite

Question 17

Construction materials — expanded metal Expanded metal used in civil works (e.g., pavements and plaster reinforcement) is characterized by which statements?

Accepted Answer

Introduction / Context: Expanded metal is a versatile mesh product created from solid sheet, offering high strength-to-weight ratio, excellent bond with concrete and plaster, and efficient use of material. It is common in pavements, stucco, and light reinforcement applications. Given Data / Assumptions: Manufacturing involves slitting and stretching a sheet to form diamond-shaped openings. Common materials include low-carbon steel; coatings like galvanizing improve durability. Dimensions are standardized as SWM (short way mesh) and LWM (long way mesh). Concept / Approach: Because the mesh is produced from a single piece without welds, it maintains continuity and structural integrity, providing good anchorage in cementitious matrices. Its geometry improves crack control and distribution of tensile stresses in thin sections. Step-by-Step Solution: Identify the process: slit-and-stretch from steel sheet → expanded mesh.Identify uses: secondary reinforcement in pavements, toppings, and plaster lath.Identify measurement: mesh openings are defined by SWM and LWM along with strand width and thickness.Therefore, all listed statements correctly describe expanded metal. Verification / Alternative check: Manufacturers’ catalogs specify SWM/LWM and typical civil applications; design guides provide crack control benefits and lap requirements. Why Other Options Are Wrong: The extra option claiming “only from aluminum foil” is incorrect; steel is the most common base metal in construction uses. Common Pitfalls: Confusing expanded metal with welded wire mesh; misinterpreting SWM/LWM as strand dimensions; poor corrosion protection in aggressive environments. Final Answer: all of the above

Question 18

Timber conversion methods in civil engineering and carpentry Pick the correct statement(s) about sawing methods used to convert logs into boards:

Accepted Answer

Introduction / Context: Sawing methods determine board appearance, dimensional stability, and structural behavior. Civil engineering materials and building construction syllabi commonly test recognition of tangential (plain), quarter, and radial (rift) sawing. Understanding how the cut intersects growth rings and medullary rays explains performance differences in use. Given Data / Assumptions: Boards are cut from sound logs of typical softwood or hardwood species. Annual rings are the visible growth rings; medullary rays are radial cellular structures. Standard woodworking nomenclature is applied. Concept / Approach: Tangential (plain) sawing cuts boards roughly parallel to annual rings, maximizing yield and speed but increasing tendency to cup. Quarter sawing first quarters the log; boards are then sawn so that ring angles are typically 45° to 90°, improving dimensional stability and revealing ray fleck in some species. Radial (rift) sawing aims perpendicular to growth rings (parallel to rays), producing very stable, uniform grain, though with lower yield and higher cost. Step-by-Step Solution: Relate each named method to the orientation between the saw kerf and annual rings.Match definitions: tangential ≈ parallel to rings; quarter sawn ≈ 45°–90° ring angle after quartering; radial ≈ perpendicular to rings, parallel to rays.Conclude that all three statements accurately describe their respective methods. Verification / Alternative check: Dimensional changes occur mainly tangential to rings; the more perpendicular a board is to rings (quarter/radial), the more stable it will be—consistent with the definitions above. Why Other Options Are Wrong: Since each individual statement is correct, selecting only one would ignore the completeness of the methods; therefore the combined choice is best. Common Pitfalls: Confusing quarter sawing with pure radial sawing; quarter sawn boards span a range of ring angles, not solely 90°. Assuming tangential boards are inferior in all cases—while economical, they are appropriate when aesthetics and cost dominate. Final Answer: All of the above.

Question 19

Building materials — chemical classification of marble Chemically, marble belongs to which rock class?

Accepted Answer

Introduction / Context: Construction materials are often classified both by origin and by dominant chemistry. Marble is widely used for cladding, flooring, and sculptures. Identifying its chemical family supports decisions on durability, weathering, and compatibility with mortars and cleaning agents. Given Data / Assumptions: Marble forms by metamorphism of limestone. Limestone is primarily calcium carbonate (CaCO3). Chemical families: calcareous (lime-rich), siliceous (silica-rich), and argillaceous (clay-rich). Concept / Approach: Although marble is a metamorphic rock by origin, its chemistry remains dominated by calcium carbonate, making it calcareous. Chemical classification addresses susceptibility to acids and salts—key for maintenance and restoration. Step-by-Step Solution: Recognize marble's parent rock: limestone.Identify main constituent: CaCO3 (calcite), a lime-rich material.Select the chemical class: calcareous. Verification / Alternative check: Effervescence when a drop of dilute acid is applied confirms calcareous nature due to CO2 release from CaCO3. Why Other Options Are Wrong: Metamorphic describes genesis, not chemistry for this question. Argillaceous implies clay minerals dominate. Siliceous implies silica-rich minerals (e.g., quartz, sandstone), which is not the case. Common Pitfalls: Confusing geological classification (metamorphic) with chemical classification (calcareous). Field tests often blur the distinction unless the question is read carefully. Final Answer: Calcareous rock

Question 20

Brickwork — standard modular size used in masonry (India) What is the standard size of a modular masonry brick (without mortar joint)?

Accepted Answer

Introduction / Context: Standardization of brick size ensures uniform bonding, predictable mortar consumption, and reliable estimates. In Indian practice, the modular brick size is widely examined in construction materials courses and is fundamental to drafting wall details and calculating quantities. Given Data / Assumptions: Modular brick size excludes mortar (dry size). Nominal dimensions with mortar differ by approximately 10 mm in length and width. All dimensions are in centimetres. Concept / Approach: For modular bricks, the standard dry size is 19 × 9 × 9 cm. When laid with a 10 mm mortar joint, the nominal size becomes 20 × 10 × 10 cm, aiding module-based design and coursing rules. Step-by-Step Solution: Recall the modular dry size used in IS specifications: 19 × 9 × 9 cm.Differentiate it from nominal size with mortar: 20 × 10 × 10 cm.Choose the correct dry (standard) size from the options. Verification / Alternative check: Brick coursing in elevation drawings confirms that adding a 10 mm joint yields the nominal module of 20 × 10 × 10 cm, matching design grids. Why Other Options Are Wrong: 18 × 8 × 8 and 21 × 11 × 11 are non-standard. 20 × 10 × 10 cm corresponds to nominal size with mortar, not the dry modular brick size asked. Common Pitfalls: Mixing up dry and nominal sizes, leading to quantity errors in procurement and estimation. Final Answer: 19 cm × 9 cm × 9 cm

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