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Past Questions
The factor of safety in slope stability analysis is defined as the ratio of-
A)
Active to passive pressure
B)
Weight to height of slope
C)
Shear strength to shear stress
D)
Cohesion to slope angle
In slope stability analysis, the Factor of Safety (FoS) is a measure of the stability of a soil slope against failure. Failure occurs when the shear stress ($ au$) acting along a potential failure surface exceeds the shear strength ($s$ or $ au_f$) of the soil. Therefore, the Factor of Safety is defined as the ratio of the resisting forces (shear strength) to the driving forces (shear stress). Mathematically: FoS = (Available Shear Strength) / (Mobilized Shear Stress).
Why other options are incorrect:
- Option (a): The ratio of active to passive pressure is used in the design of retaining walls to check for stability against sliding or overturning, but it is not the definition of the factor of safety for slope stability.
- Option (b): Weight and height are parameters used to calculate stresses, but their ratio does not define the stability factor.
- Option (d): Cohesion is a component of shear strength (according to Mohr-Coulomb theory), and the slope angle affects the driving stress, but their direct ratio is not the definition of the factor of safety.
The crushing strength of first-class bricks should not be less than-
A)
3.5 N/mm²
B)
7.0 N/mm²
C)
5.0 N/mm²
D)
10.5 N/mm²
According to Indian Standard (IS) specifications and general civil engineering standards for building materials, bricks are classified based on their quality and compressive strength. For a First-Class Brick, the minimum average crushing strength required is 10.5 N/mm².
Breakdown of brick classes by strength:
1. First Class Bricks: Minimum crushing strength of 10.5 N/mm².
2. Second Class Bricks: Minimum crushing strength of 7.0 N/mm².
3. Third Class Bricks: Minimum crushing strength of 3.5 N/mm².
4. Fourth Class Bricks: These are generally over-burnt or under-burnt bricks used for temporary structures and do not have a strictly defined high strength requirement.
Therefore, option (d) is the correct requirement for first-class bricks, while options (a) and (b) correspond to third and second-class bricks respectively.
The equation representing the hydrological cycle is known as-
A)
Hydrograph equation
B)
Water budget equation
C)
Darey’s law
D)
Continuity equation
The hydrological cycle is governed by the principle of conservation of mass. For a given catchment area or a specific volume of the earth's atmosphere/crust over a specific time interval, the inflow must equal the outflow plus the change in storage. This is mathematically expressed as: (Inflow - Outflow = Change in Storage). This fundamental relationship is known as the Water Budget Equation.
Why other options are incorrect:
- a. Hydrograph equation: A hydrograph is a plot of discharge versus time at a specific point in a river; it is a tool for analysis, not the governing equation of the entire cycle.
- c. Darcy's law: This describes the flow of a fluid through a porous medium (like soil), which is only a small part of the hydrological cycle (infiltration/groundwater flow).
- d. Continuity equation: While the water budget equation is a specific application of the continuity equation (conservation of mass), in the context of Hydrology, the term 'Water Budget Equation' is the standard terminology used to represent the cycle's balance.
The purpose of providing reinforcement in foundation is to-
A)
Reduce dead load
B)
Resist tensile stresses
C)
Prevent shrinkage
D)
Increase soil strength
Step-by-step reasoning: 1. Concrete is a composite material that is very strong in compression but very weak in tension (its tensile strength is typically only 10% of its compressive strength). 2. Foundations are subject to various loads, including vertical loads from the superstructure and differential settlement of the soil. 3. These loads often induce bending moments within the foundation slab or footing. 4. Bending causes one side of the concrete member to be in compression and the opposite side to be in tension. 5. Since concrete cannot effectively resist these tensile stresses, steel reinforcement (which has high tensile strength) is embedded in the tension zone to carry those loads and prevent the concrete from cracking or failing.
Analysis of other options:
- (a) Reduce dead load: Reinforcement (steel) actually increases the dead load because steel is denser than concrete.
- (c) Prevent shrinkage: While specific 'shrinkage reinforcement' exists, the primary structural purpose of reinforcement in foundations is load-bearing (tensile resistance). Shrinkage is primarily controlled by curing and joint design.
- (d) Increase soil strength: Reinforcement is placed within the concrete foundation, not the soil. To increase soil strength, techniques like soil stabilization, compaction, or piling are used, not concrete reinforcement.
The efflorescence test for bricks is used to assess the presence of-
A)
Sulphates
B)
Soluble salts
C)
Clay content
D)
Organic impurities
Efflorescence refers to the appearance of a white powdery deposit on the surface of bricks or concrete. This occurs when soluble salts present in the brick material or the mortar react with moisture. As water penetrates the brick and subsequently evaporates, these soluble salts are carried to the surface and crystallize, leaving behind the white powder. The efflorescence test is specifically designed to determine the quantity and nature of these soluble salts to ensure the durability and aesthetic quality of the masonry.
Why other options are incorrect:
- a. Sulphates: While sulphates are a common type of soluble salt that causes efflorescence, the test assesses all soluble salts (including nitrates, chlorides, etc.), not just sulphates.
- c. Clay content: Clay content is determined by the composition analysis of the brick earth, not by an efflorescence test.
- d. Organic impurities: Organic impurities are typically checked through the burning/firing process or specific chemical analysis, as they cause discoloration or holes (bloating) in the brick, not surface powdering.
In a compaction curve, the peak represents-
A)
Maximum moisture content
B)
Maximum dry density and corresponding OMC
C)
Zero air voids
D)
Liquid limit
In soil mechanics, a compaction curve is plotted by graphing the dry density (ρd) of a soil sample against its moisture content (w) for a constant compactive effort. As moisture is added to a dry soil, the water acts as a lubricant, allowing soil particles to slide over each other and pack more densely, causing the dry density to increase. However, beyond a certain point, the water begins to occupy space that would otherwise be filled by soil solids, causing the dry density to decrease. The peak of this bell-shaped curve represents the Maximum Dry Density (MDD). The specific moisture content at which this peak occurs is known as the Optimum Moisture Content (OMC).
Why other options are incorrect:
- Option (a): The peak does not represent the maximum moisture content; moisture content can be increased indefinitely (until saturation), but the density will drop.
- Option (c): The Zero Air Voids (ZAV) line is a theoretical line that the compaction curve approaches but never crosses; it is not the peak itself.
- Option (d): The Liquid Limit is an Atterberg limit related to the consistency of fine-grained soils, not a point on a compaction curve.
Which is a recommended tank material for household rainwater storage?
A)
Asbestos
B)
Lead
C)
HDPE or reinforced concrete
D)
Uncoated iron
In rainwater harvesting systems for household use, the storage tank must be made of materials that are durable, non-toxic, and do not leach harmful chemicals into the water.
1. **HDPE (High-Density Polyethylene)**: This is a food-grade plastic that is corrosion-resistant, lightweight, and does not react with water, making it ideal for potable water storage.
2. **Reinforced Concrete**: This is a traditional and highly durable material for large-scale storage. When properly cured and sealed (often with food-grade liners or waterproof coatings), it provides excellent structural stability and keeps water cool.
Why other options are incorrect:
- **Asbestos (a)**: Asbestos is a known carcinogen and is strictly prohibited for use in drinking water systems due to health risks.
- **Lead (b)**: Lead is a toxic heavy metal that causes lead poisoning; it must never be used for storing drinking water.
- **Uncoated Iron (d)**: Uncoated iron is highly susceptible to corrosion (rusting) when in contact with water, which contaminates the water and leads to structural failure of the tank.
Which soil has the highest permeability?
A)
Silt
B)
Gravel
C)
Clay
D)
Loam
Permeability (hydraulic conductivity) refers to the ease with which a fluid (usually water) can flow through a porous medium. In soil mechanics, permeability is primarily governed by the size of the soil particles and the size of the interconnected voids (pores) between them.
1. **Gravel (Option b):** Consists of the largest particles among the choices. Large particles create large, interconnected pore spaces, offering minimal resistance to water flow. Therefore, gravel has the highest permeability.
2. **Silt (Option a):** Particles are smaller than sand and gravel. The smaller pore spaces increase the frictional resistance to water flow, resulting in lower permeability than gravel.
3. **Clay (Option c):** Consists of the smallest particles (colloidal size). Clay has very small pores and a high specific surface area, which creates strong electrostatic attractions between water molecules and particle surfaces, making it nearly impermeable.
4. **Loam (Option d):** A mixture of sand, silt, and clay. While it has better permeability than pure clay, it is significantly lower than that of pure gravel because the smaller particles (silt/clay) fill the gaps between larger particles, reducing the effective pore size.
In summary, the order of permeability from highest to lowest is: Gravel > Sand > Silt > Clay.
In India, most of the annual precipitation occurs due to:
A)
Cyclones
B)
Monsoon rains
C)
Snowfall
D)
Convection storms
India's climate is dominated by the monsoon system. The vast majority of the annual precipitation (approximately 75% to 90% in many regions) occurs during the Southwest Monsoon season, which typically lasts from June to September. This is caused by the seasonal reversal of winds, where moisture-laden winds blow from the Indian Ocean toward the landmass.
Why other options are incorrect:
- a. Cyclones: While cyclones cause heavy rainfall in coastal regions (like Odisha, Andhra Pradesh, and West Bengal), they are episodic and do not contribute the bulk of the total annual precipitation for the entire country.
- c. Snowfall: Snowfall is restricted to the Himalayan regions and high-altitude areas; it represents a very small fraction of India's total precipitation.
- d. Convection storms: These occur locally (such as pre-monsoon showers or 'Mango Showers'), but they are not the primary driver of the annual precipitation volume compared to the monsoon.
Which component prevents leakage at construction joints in water tanks?
A)
Steel bar
B)
Water bar (PVC or rubber)
C)
Formwork
D)
Lining
In the construction of water-retaining structures like water tanks, construction joints are inevitable due to the pouring of concrete in stages. These joints are potential paths for water leakage. To prevent this, a 'Water bar' (also known as a waterstop) is used. A water bar is a flexible strip made of PVC or rubber that is embedded halfway into one concrete pour and halfway into the next. It creates a physical barrier that blocks the flow of water through the joint.
Why other options are incorrect:
- a. Steel bars: These provide structural strength and reinforcement against tension but do not create a watertight seal.
- c. Formwork: This is the temporary mold used to shape the concrete; it is removed after the concrete sets and does not prevent leakage.
- d. Lining: While lining (like epoxy or membranes) can be applied to the interior surface of a tank to reduce permeability, it is a surface treatment rather than a specific component designed to seal construction joints.
Which of the following types of cement is suitable for use in cold weather concreting?
A)
Ordinary Portland Cement
B)
Low Heat Cement
C)
Rapid Hardening Cement
D)
Sulphate Resisting Cement
In cold weather concreting, the primary challenge is the slow rate of hydration of cement due to low temperatures. This leads to a delayed setting time and a slow gain in early strength, which can increase the risk of freezing and structural failure. Rapid Hardening Cement (RHC) is specifically designed to gain strength quickly. It achieves this through a higher tricalcium silicate (C3S) content and a finer grinding of the clinker, which accelerates the hydration process and generates more heat of hydration. This internal heat helps maintain the temperature of the concrete mix, ensuring that the concrete sets and gains sufficient strength rapidly even in cold environments.
Analysis of other options:
- Ordinary Portland Cement (OPC): Its hydration rate slows down significantly in cold weather, making it less ideal than RHC for rapid strength gain.
- Low Heat Cement: This cement is designed to minimize the heat of hydration to prevent thermal cracking in mass concrete (like dams). Using it in cold weather would be counterproductive as it would further slow down the setting process.
- Sulphate Resisting Cement: This is used in environments with high sulphate concentrations (like coastal areas or certain soils) to prevent chemical attack; it does not specifically address cold weather hydration issues.
Which type of wall provides protection against erosion along riverbanks?
A)
Toe wall
B)
Revetment wall
C)
Breast wall
D)
Anchor wall
Step-by-step reasoning:
1. **Analysis of the Requirement**: The question asks for a structure specifically designed to protect riverbanks from erosion caused by the flow of water.
2. **Evaluating Option (b) Revetment wall**: A revetment is a facing of stone, concrete, or other materials placed on a bank or shoreline to protect it from erosion caused by wave action or currents. It acts as a protective layer (armoring) that prevents the soil from being washed away by the river flow. This directly matches the question's requirement.
3. **Evaluating Option (a) Toe wall**: A toe wall is a wall constructed at the base (toe) of a slope or a larger retaining wall to prevent the sliding or scouring of the base. While it helps in stability, it is not the primary structure used for overall bank erosion protection.
4. **Evaluating Option (c) Breast wall**: A breast wall is a retaining wall built across a slope or at the edge of a road/embankment to prevent the soil from sliding down. It is typically used for slope stability rather than protecting against hydraulic erosion from a river.
5. **Evaluating Option (d) Anchor wall**: An anchor wall is a type of retaining wall that uses anchors (cables or rods) driven into the ground to provide additional stability against overturning. It is a structural design for stability, not a specific erosion protection measure for riverbanks.
Conclusion: The revetment wall is the correct technical term for a structure providing protection against erosion along riverbanks.
A retaining wall is primarily used to-
A)
Support roofing
B)
Resist lateral earth pressure
C)
Anchor piles
D)
Store water
A retaining wall is a structure designed to hold back soil or other materials that would otherwise move due to gravity. The primary engineering purpose of a retaining wall is to resist the 'lateral earth pressure' exerted by the soil behind it, preventing slope failure or landslides and allowing for the creation of level terraces in hilly terrain.
Analysis of other options:
- Option (a) 'Support roofing' is the function of beams, columns, or load-bearing walls, not retaining walls.
- Option (c) 'Anchor piles' refers to a foundation technique; while some retaining walls use anchors (anchored walls), the wall's primary purpose is not to anchor the piles themselves.
- Option (d) 'Store water' is the function of tanks, reservoirs, or dams. While some retaining walls may be designed for hydrostatic pressure, their primary definition relates to earth retention.
The initial setting time of Ordinary Portland Cement (OPC) should not be less than-
A)
15 minutes
B)
20 minutes
C)
30 minutes
D)
60 minutes
According to the Indian Standard (IS) specifications for Ordinary Portland Cement (OPC), the setting time is divided into two stages: Initial Setting Time and Final Setting Time.
1. Initial Setting Time: This is the time elapsed between the moment water is added to the cement and the time when the paste starts losing its plasticity. For OPC, the standard requirement is that the initial setting time should not be less than 30 minutes. This ensures that the concrete remains workable long enough for mixing, transporting, placing, and compacting.
2. Final Setting Time: This is the time when the cement paste has completely lost its plasticity and has attained sufficient firmness to resist a certain amount of pressure. For OPC, the final setting time should not exceed 600 minutes (10 hours).
Comparing the options:
- Option (a) 15 minutes: Too short; does not meet IS standards.
- Option (b) 20 minutes: Too short; does not meet IS standards.
- Option (c) 30 minutes: Correct as per IS specifications.
- Option (d) 60 minutes: While 60 minutes is greater than 30, the minimum requirement (the threshold) specified by the code is 30 minutes.
A water tank develops hairline cracks soon after construction. Which factor is most likely responsible?
A)
Low cement grade
B)
Improper curing and high water-cement ratio
C)
Use of reinforcement
D)
Rapid shuttering removal
Hairline cracks appearing soon after construction in concrete structures, especially water tanks, are typically 'plastic shrinkage cracks' or 'drying shrinkage cracks'.
1. **High Water-Cement (w/c) Ratio**: A high w/c ratio increases the amount of evaporable water in the concrete mix. As this excess water evaporates, the volume of the concrete decreases, leading to shrinkage. Since the structure is restrained, this shrinkage manifests as hairline cracks.
2. **Improper Curing**: Curing is essential to maintain moisture for the hydration of cement. If curing is inadequate, the surface dries out rapidly, leading to differential shrinkage between the surface and the core of the concrete, which triggers cracking.
Why other options are incorrect:
- **Option a (Low cement grade)**: While cement grade affects strength, it is not the primary driver of immediate hairline shrinkage cracks; shrinkage is more closely tied to the water content and curing process.
- **Option c (Use of reinforcement)**: Reinforcement is intended to control cracking and provide tensile strength. Its presence generally reduces the width of cracks rather than causing them.
- **Option d (Rapid shuttering removal)**: Removing formwork too early typically leads to structural sagging, deflection, or large structural cracks due to the concrete not having reached sufficient strength to support its own weight, rather than widespread hairline shrinkage cracks.
The specific gravity of soil solids is usually determined using-
A)
Triaxial apparatus
B)
Pycnometer
C)
Casagrande apparatus
D)
Plate load test
The specific gravity (G) of soil solids is defined as the ratio of the unit weight of the soil solids to the unit weight of distilled water. To determine this, a device that can accurately measure the mass of a known volume of liquid and the mass of soil solids displaced by that liquid is required. A Pycnometer (or a density bottle) is specifically designed for this purpose.
Why other options are incorrect:
- a. Triaxial apparatus: Used to determine the shear strength parameters (cohesion and angle of internal friction) of soil under controlled drainage and pressure conditions.
- c. Casagrande apparatus: Used to determine the Liquid Limit (LL) of a soil sample as part of Atterberg limits testing.
- d. Plate load test: A field test used to determine the ultimate bearing capacity of soil and the settlement characteristics of the ground.
Which component is essential in a rooftop rainwater harvesting system?
A)
Drain valve
B)
Well casing
C)
First flush diverter
D)
Overflow pipe only
In a rooftop rainwater harvesting system, the first rain of the season or the first few minutes of a rainfall event typically carry accumulated pollutants, dust, bird droppings, and organic debris from the roof surface. A 'First Flush Diverter' is an essential component designed to divert this initial contaminated water away from the storage tank, ensuring that only clean water is collected.
Analysis of other options:
- a. Drain valve: While useful for maintenance, it is not a defining essential component for the harvesting process itself.
- b. Well casing: This is a component of groundwater wells (borewells), not specifically a rooftop harvesting system.
- d. Overflow pipe only: While an overflow pipe is necessary to prevent tank flooding, the word 'only' makes this option incorrect, and it is less critical for water quality than the first flush diverter.
Crib walls are generally made from-
A)
Timber or precast concrete units
B)
Masonry only
C)
Steel reinforcement
D)
Plastic cells
A crib wall is a type of retaining structure consisting of an open-work framework of interlocking members. These members are typically laid in a criss-cross pattern to form a 'crib' or cage, which is then filled with granular material (like crushed stone or gravel) to provide stability through gravity.
1. **Materials**: Historically, timber was the primary material used for crib walls due to its availability and ease of assembly. In modern engineering, precast concrete units are widely used because they offer greater durability and resistance to decay compared to timber.
2. **Why other options are incorrect**:
- **Masonry only (b)**: Masonry is used for gravity walls or cantilever walls, but a 'crib' specifically refers to the open-frame structure, which is not the characteristic of solid masonry.
- **Steel reinforcement (c)**: While steel may be used in some specialized reinforced earth walls, a standard crib wall is defined by its modular frame (timber/concrete) rather than internal steel reinforcement.
- **Plastic cells (d)**: While geocells exist for soil stabilization, traditional crib walls are defined as being constructed from timber or concrete units.
Which retaining structure is most suitable for steep terrains and quick installations?
A)
Gravity wall
B)
Cantilever wall
C)
Crib wall
D)
Counterfort wall
A Crib wall is a prefabricated cellular structure made of interlocking precast concrete or timber units, which are then filled with granular material (like crushed stone or gravel).
1. Why it is suitable for steep terrains: Crib walls are flexible and permeable. Their ability to drain water freely prevents the buildup of hydrostatic pressure, which is a critical failure mode in steep, mountainous terrains with high rainfall.
2. Why it is suitable for quick installation: Because they are composed of prefabricated modular units, they can be assembled rapidly on-site without the need for extensive formwork, curing time for cast-in-situ concrete, or heavy machinery required for massive gravity walls.
Comparison with other options:
- Gravity walls (a): Require massive amounts of material and extensive site preparation, making them slow to install and difficult to transport to steep terrains.
- Cantilever walls (b) and Counterfort walls (d): These are reinforced concrete structures that require significant formwork, steel reinforcement placement, and curing time, making them slower to install than modular crib walls.
Which property is most affected when aggregate with high water absorption is used without accounting for it?
A)
Initial setting time
B)
Workability
C)
Compressive strength
D)
Durability
Step-by-step reasoning: 1. Water absorption refers to the ability of an aggregate to absorb water into its internal pore structure. 2. In a concrete mix, the 'effective water' is the water available to lubricate the aggregates and hydrate the cement paste, which directly determines the workability (slump) of the mix. 3. If aggregates with high water absorption are used without adjusting the mix design (i.e., without adding extra water to compensate for what the aggregate absorbs), the aggregates will soak up a portion of the mixing water. 4. This reduction in free water leads to a drier mix, significantly reducing the workability of the concrete, making it difficult to place and compact. 5. While compressive strength and durability can be affected indirectly if the mix is poorly compacted due to low workability, the most immediate and direct property affected by the absorption of mixing water is the workability. 6. Initial setting time is primarily a property of the cement and chemical admixtures, not the water absorption of the aggregate.
The partial safety factor for concrete in LSM is typically taken as-
A)
1.0
B)
1.5
C)
1.25
D)
2.0
In Limit State Method (LSM) for reinforced concrete design, the partial safety factor for concrete is typically taken as 1.5 (for concrete strength in design). Hence option b is correct. Option c (1.25) is not the standard value for concrete in LSM; it is sometimes associated with other materials or specific code contexts, but not the usual concrete factor. Option a (1.0) would mean no safety reduction, which is not used for design strength. Option d (2.0) is too high and not the prescribed partial safety factor for concrete in standard LSM design.
A normally consolidated clay will exhibit-
A)
High compressibility
B)
Very low permeability
C)
Low compressibility
D)
High shear strength
A normally consolidated (NC) clay is a soil that has never been subjected to a vertical effective stress greater than the current existing vertical effective stress. In soil mechanics, NC clays are characterized by the following:
1. **Compressibility**: Because the soil has not been 'pre-compressed' by higher historical loads, it is highly susceptible to volume reduction (consolidation) when additional loads are applied. This results in high compressibility compared to over-consolidated (OC) clays.
2. **Permeability**: While clays generally have low permeability, 'very low permeability' is a general characteristic of all clays, not a specific distinguishing feature of 'normally consolidated' clay versus 'over-consolidated' clay.
3. **Shear Strength**: NC clays typically have lower shear strength compared to over-consolidated clays of the same current stress level, as OC clays have a denser structure and higher internal friction/cohesion due to their loading history.
Therefore, the most defining characteristic of a normally consolidated clay among the given options is its high compressibility.
Toe walls are constructed at-
A)
Top of hill slopes
B)
Below foundation
C)
Bottom of slopes to prevent scouring
D)
On bridges
A toe wall is a structural component used in civil engineering, specifically in the design of retaining walls and slope stabilization. Its primary purpose is to provide stability at the base (the 'toe') of a slope or a retaining wall.
1. **Function**: The toe wall acts as a protective barrier at the bottom of the slope to prevent 'scouring' (the erosion of soil caused by the flow of water) and to prevent the slope from sliding or 'kicking out' at the base.
2. **Placement**: It is strategically placed at the bottom of the embankment or slope where the risk of erosion and instability is highest.
Analysis of other options:
- **Option a (Top of hill slopes)**: Structures at the top are typically called 'crest walls' or 'coping walls', used to prevent surface water from entering the backfill.
- **Option b (Below foundation)**: While foundations are below ground, a 'toe wall' specifically refers to the base of a slope/retaining structure, not a general foundation layer.
- **Option d (On bridges)**: While bridges have abutments (which are types of retaining walls), toe walls are a specific feature of slope protection and retaining structures, not a general bridge component.
The water-cement ratio for general construction work should be approximately-
A)
0.3
B)
0.5
C)
0.7
D)
0.9
The water-cement (w/c) ratio is the ratio of the weight of water to the weight of cement used in a concrete mix. According to Abram's Law, the strength of concrete is primarily dependent on the w/c ratio; as the ratio increases, the strength decreases due to the formation of more capillary pores.
1. **General Construction Range:** For most general construction purposes, a w/c ratio between 0.40 and 0.60 is typically used to balance workability and strength. A value of 0.5 is considered the standard representative average for general-purpose concrete.
2. **Analysis of Options:**
- **0.3 (Option a):** This is a very low ratio, typically reserved for high-strength concrete or specialized pre-cast elements. It often requires the use of superplasticizers to ensure the mix is workable.
- **0.5 (Option b):** This is the ideal balance for general construction, providing sufficient strength and adequate workability without excessive shrinkage.
- **0.7 (Option c):** This is too high for structural concrete. It leads to high porosity, increased permeability, and significantly reduced compressive strength.
- **0.9 (Option d):** This ratio is excessively high and would result in very weak concrete prone to severe segregation and shrinkage cracks.
Which test is used to check the durability of aggregates?
A)
Fineness Modulus Test
B)
Soundness Test
C)
Shape Test
D)
Water Absorption Test
The durability of aggregates refers to their ability to resist volume changes due to environmental factors such as freeze-thaw cycles or chemical reactions.
1. **Soundness Test (Correct):** This test is specifically designed to evaluate the resistance of aggregates to weathering actions. It involves immersing the aggregate in a solution of sodium sulfate or magnesium sulfate. If the aggregate disintegrates or expands significantly, it is considered 'unsound,' meaning it lacks durability.
2. **Fineness Modulus Test (Incorrect):** This is a measure of the average particle size of the aggregate (primarily for fine aggregates) and is used for grading purposes, not durability.
3. **Shape Test (Incorrect):** This test (e.g., Flakiness and Elongation Index) determines the geometric shape of the particles. While shape affects workability and strength, it does not measure the chemical or physical durability against weathering.
4. **Water Absorption Test (Incorrect):** This test measures the amount of water an aggregate can absorb into its pores. While high absorption can be an indicator of potential durability issues (like frost damage), the test itself measures porosity/absorption, not the overall durability/soundness of the material.