Past Questions — 2026

In highway engineering, the temperature of bitumen is critical for ensuring proper workability, coating of aggregates, and compaction. For Hot Mix Asphalt (HMA), the bitumen must be heated to a temperature that reduces its viscosity enough to allow it to be spread and compacted effectively. According to standard specifications (such as those aligned with IRC or ASTM), the typical temperature range for spreading/laying bitumen-based mixes is generally between 120°C and 160°C. Option (a) 121°C – 163°C most closely aligns with these engineering standards. - Option (b) is too low; at 110°C, the mix may become too stiff to spread and compact properly, leading to voids. - Options (c) and (d) are too high; heating bitumen above 170°C-180°C can lead to 'burning' or oxidative hardening (thermal degradation), which makes the binder brittle and reduces the lifespan of the pavement.

In highway engineering, the side slope of road cuttings is determined based on the stability of the soil to prevent landslides or slope failure. For 'ordinary soils', which include materials like moorum (weathered rock/laterite) and hard clay, the soil possesses moderate cohesive strength. According to standard IRC (Indian Roads Congress) guidelines and general civil engineering practice for road construction in hilly or undulating terrain: 1. Hard Rock is typically cut at 1:0 to 1:0.25. 2. Soft Rock/Hard Soil is typically cut at 1:1 to 1:1.5. 3. Ordinary soils, including moorum and hard clay, require a more gradual slope to ensure stability, typically ranging from 1:1.5 to 1:2 (Vertical:Horizontal). 4. Loose soils or sandy soils require even flatter slopes, such as 1:2 to 1:3. Therefore, for ordinary soils including moorum and hard clay, the recommended slope is 1:1.5 to 1:2.

Option D is correct: Increases.

In the construction of Bituminous Concrete (BC), the rolling process is divided into three stages: initial (breakdown) rolling, intermediate rolling, and final rolling. 1. **Initial/Breakdown Rolling**: This is the first pass of the roller after the mix is laid. The primary objective is to achieve the initial density and stabilize the layer without pushing the material. For Bituminous Concrete, a tandem steel-wheeled roller weighing approximately 8 to 12 tonnes is typically used for this stage to provide the necessary pressure to 'break down' the loose mix. 2. **Intermediate Rolling**: This stage focuses on achieving the required compaction/density. Pneumatic tired rollers (PTR) are often used here because their kneading action helps in closing voids and sealing the surface. 3. **Final Rolling**: This is done to remove any roller marks and provide a smooth finish, usually using a tandem roller. Why other options are incorrect: - **Option a (Fixed wheel pneumatic roller)**: Pneumatic rollers are primarily used for intermediate rolling due to their kneading action; they are not typically used for the initial breakdown of a thick BC layer. - **Option c (Sheep foot roller)**: These are used for compacting cohesive soils (like clay) in embankments, not for bituminous layers, as they would puncture and damage the asphalt surface. - **Option d (Any type of roller)**: Incorrect, as specific rollers are required for different stages of asphalt paving to ensure structural integrity and surface quality.

Bond strength refers to the grip between the reinforcing steel and the surrounding concrete. Let's analyze the options: 1. **Deformed bars (Option a):** Deformed bars (ribbed bars) provide mechanical interlocking with the concrete, which significantly increases bond strength compared to smooth plain bars. Thus, this enhances bond. 2. **Bigger bar diameters (Option b):** Bond strength is fundamentally related to the surface area of the bar in contact with the concrete. For a given cross-sectional area of steel, using one large diameter bar provides less surface area than using multiple smaller diameter bars. Consequently, as the diameter of a single bar increases, the relative bond (bond stress capacity) generally decreases or becomes less efficient per unit area of steel. Therefore, using bigger bar diameters does NOT enhance bond strength. 3. **Higher grade of concrete (Option c):** Higher grade concrete has higher compressive and tensile strength, which increases the friction and the bearing capacity of the concrete ribs/matrix against the steel. This enhances bond strength. 4. **Increased cover (Option d):** Providing adequate concrete cover prevents the concrete from splitting or spalling away from the bar under tension. If the cover is too thin, the concrete can split longitudinally, leading to a premature bond failure. Increasing cover (up to a reasonable limit) ensures the concrete can effectively resist the radial bursting forces, thereby enhancing the effective bond strength. Since the question asks which measure does NOT enhance bond strength, option (b) is the correct answer.

Option B is correct: 476 kgs.

Option D is correct: It improves the life of concrete.

In highway engineering, specifically during the construction of Bituminous Concrete (BC) or Dense Bituminous Macadam (DBM), the rolling process is critical to achieve the required density and avoid surface irregularities. According to standard specifications (such as MORTH - Ministry of Road Transport and Highways), the rolling speed must be kept low to ensure proper compaction and to prevent the displacement of the mix. The recommended maximum speed for the rollers during the compaction of bituminous layers is typically specified as not more than 7 km/hr. Rolling at higher speeds can lead to 'shoving' (lateral movement of the mix) or uneven compaction, while excessively slow speeds may cause overheating of the mix in certain conditions. Therefore, option (d) is the standard technical requirement.

In highway engineering, cross drainage works (such as culverts) are designed to facilitate the flow of water from one side of the road to the other. To ensure that water flows efficiently by gravity and to prevent the accumulation of silt or debris (self-cleansing velocity), a longitudinal slope (gradient) is provided to the floor of the culvert. According to standard IRC (Indian Roads Congress) guidelines and general civil engineering practice for cross drains, a longitudinal slope of 1 in 20 is typically recommended to maintain an adequate velocity of flow. Slopes like 1 in 5, 1 in 7, or 1 in 10 are generally too steep for standard culvert floors and could lead to excessive erosion of the bed material or structural instability, whereas 1 in 20 provides a balanced hydraulic gradient.

Soundness of aggregate is the property that indicates its resistance to disintegration due to weathering actions such as alternate wetting and drying, freezing and thawing, and salt crystallization. Hence, it is intended to study the resistance of aggregate to weathering action. Option (d) is incorrect because frost resistance is only one part of soundness, not the full definition. Option (c) refers to abrasion resistance, which is a different property measured by abrasion tests. Option (b) refers to load-carrying durability/strength, which is not what soundness measures.

In bridge engineering, the selection of a bridge site is critical for the structural stability, longevity, and cost-effectiveness of the bridge. 1. **Straight reach of the river**: A straight reach is preferred because it ensures that the flow of water is perpendicular to the bridge axis, minimizing the risk of scouring and reducing the complexity of the hydraulic design. In contrast, meandering portions (Option b) are prone to shifting channels and high erosion on the outer banks. 2. **High banks above HFL (High Flood Level)**: Banks that are naturally high above the HFL provide natural protection against flooding and reduce the need for extensive embankment work or expensive floodwalls. 3. **Hard inerodible strata close to bed level**: The presence of rock or hard strata near the river bed is highly desirable because it provides a strong foundation for the piers and abutments, reducing the depth of foundation required and preventing settlement or failure due to scouring. Why other options are incorrect: - **Option b**: Meandering portions are unstable; the river may change its course over time, potentially leaving the bridge 'high and dry' or causing severe erosion. - **Option c**: While shallow water might seem easier for construction, it is not a primary 'desirable characteristic' for the overall stability and longevity of the bridge structure compared to the foundation strata. - **Option d**: A wide channel increases the total cost of the bridge (longer span), and while slow currents are generally better, they are not as critical as the stability of the banks and the foundation strata.

In Highway Engineering, cross drainage (CD) structures are categorized based on their span length to manage the flow of water across a road embankment. 1. **Culverts**: These are small cross-drainage structures. According to standard engineering specifications (such as IRC - Indian Roads Congress), a culvert is generally defined as a structure with a clear span of less than 6 meters. Culverts can be pipe, box, arch, or slab culverts. 2. **Bridges**: When the span of the structure exceeds 6 meters, it is classified as a bridge (Minor Bridge, Major Bridge, or Long Span Bridge). Evaluating the options: - Option (a) 'Less than 6m' aligns with the standard technical definition of a culvert. - Options (b), (c), and (d) provide ranges or limits that are either too restrictive or do not cover the full standard definition of culverts.

In highway engineering, the side slope of road cuttings depends on the nature of the material being excavated to ensure the stability of the slope and prevent landslides. For soft rock and shale, the material is more stable than soil but less stable than hard rock. The standard recommended slope for soft rock/shale is typically expressed as a ratio of vertical to horizontal. A slope of 1:1/5 to 1:1/9 means that for every 1 unit of vertical height, the horizontal distance is 1/5 to 1/9 of that height (which is equivalent to a steep slope of 5:1 to 9:1 vertical:horizontal). This steepness is permissible in soft rock compared to the much flatter slopes (like 1:1 or 1:2) required for loose soil or soft clay. Option (a) and (d) are typical for soil/earthwork, and option (c) is generally reserved for harder rock formations.

In foundation and geotechnical engineering, stone masonry retaining walls are gravity walls that rely on their own weight to resist the lateral earth pressure. Due to the inherent limitations of stone masonry (such as the lack of tensile strength and the risk of sliding or overturning as height increases), there is a practical limit to their height. According to standard engineering practice and various building codes (including those often referenced in PWD manuals), the recommended maximum height for a stone masonry retaining wall is typically 6 meters. Beyond this height, the base width required to maintain stability becomes economically unfeasible and structurally risky, making reinforced concrete (RCC) cantilever walls a more appropriate choice. Therefore, option (d) 6m is the standard recommended maximum height.

Option B is correct: N/m (Pascal).

The California Bearing Ratio (CBR) is a penetration test used to evaluate the subgrade strength of roads and pavements. It is defined as the ratio of the load pressure required to penetrate a soil sample with a standard piston to the load pressure required to penetrate a standard high-quality crushed stone material (standard CBR material) to the same depth. Mathematically, it is expressed as: CBR (%) = (Load pressure of soil / Load pressure of standard crushed stone) × 100 Because it is a ratio of two pressures (stress values) multiplied by 100, the resulting value is dimensionless and expressed as a percentage. Analysis of other options: - a. mm: This is a unit of length/penetration depth, not the CBR value itself. - b. cm: This is also a unit of length. - d. N/mm²: This is a unit of pressure (MPa). While the loads used to calculate CBR are measured in pressure units, the final CBR value is the ratio of these pressures, making it a percentage.

Step-by-step reasoning: 1. Definition: A catch water drain (also known as an interceptor drain) is a drainage channel constructed on the hillside, above the road embankment or cutting, specifically in hilly terrains. 2. Purpose: Its primary function is to intercept surface runoff flowing down the slope from the hillside before it reaches the road cutting or the pavement surface. 3. Mechanism: By capturing this water and diverting it safely into natural streams or designated outlets, it prevents the pavement from being flooded and protects the road slope from erosion and landslides caused by uncontrolled water flow. Analysis of other options: - Option (a) is incorrect because draining water from the pavement surface is the function of 'Camber' and 'Side drains'. - Option (b) is incorrect because catch water drains are surface drains, not subsurface drains. - Option (d) is incorrect because water from weep holes (found in retaining walls) is handled by the wall's internal drainage system and the side drains at the base, not by catch water drains located uphill.

According to Hooke's Law, within the elastic limit of a material, the stress induced in the material is directly proportional to the strain produced. Mathematically, this is expressed as Stress (σ) ∝ Strain (ε), or σ = Eε, where 'E' is the Modulus of Elasticity (Young's Modulus). This means that if the stress is increased, the strain increases linearly in the same proportion. - Option (b) is incorrect because an indirect (inverse) proportion would imply that strain decreases as stress increases, which is physically incorrect for standard materials. - Option (c) is incorrect because proportionality exists up to the proportional limit. - Option (d) is incorrect because stress and strain are fundamentally related by the material's stiffness properties.

Cement concrete is a rigid material with a low coefficient of thermal expansion, but over long stretches of highway, temperature variations cause significant expansion and contraction. 1. **Why Option (d) is correct:** When the temperature increases, the concrete slab expands. If there is no space for this expansion, internal compressive stresses build up, leading to 'buckling' or 'blow-ups'. Conversely, when temperatures drop, the slab contracts, creating tensile stresses that lead to uncontrolled cracking. Joints (Expansion, Contraction, and Longitudinal joints) are provided to create controlled gaps or weak planes, thereby relieving these temperature-induced stresses and preventing random cracking. 2. **Why other options are incorrect:** - **Option (a):** Curing is the process of maintaining moisture to ensure hydration of cement; joints do not facilitate this process. - **Option (b):** Friction (skid resistance) is improved by surface texturing (like grooving or tining), not by providing joints. - **Option (c):** While construction joints are used to mark the end of a day's work, the primary engineering purpose of the overall jointing system in rigid pavements is stress management, not merely the 'ease' of construction.

Biodegradable waste refers to organic materials that can be broken down (decomposed) into simpler organic matter by the action of microorganisms such as bacteria and fungi. 1. Food waste (Option c) consists of organic matter (carbohydrates, proteins, fats) which is readily decomposed by microbes, making it biodegradable. 2. Plastic (Option a) is a synthetic polymer derived from petroleum; it is non-biodegradable because microorganisms lack the enzymes to break its strong carbon-carbon bonds. 3. Glass (Option b) is an inorganic material made primarily of silica; it is chemically inert and does not decompose biologically. 4. Metal (Option d) is an inorganic element/alloy; while it may corrode or oxidize (chemical change), it is not broken down by biological organisms.

Efficiency (η) of any mechanical system, including a pump, is defined as the ratio of the useful work performed (output) to the total energy supplied to the system (input). 1. In the context of a pump, the 'Output Power' is known as the Water Horsepower (WHP), which is the power actually delivered to the fluid to increase its pressure or lift it to a certain height. 2. The 'Input Power' is known as the Brake Horsepower (BHP), which is the power supplied to the pump shaft by the motor or engine. Formula: Efficiency (η) = (Output Power / Input Power) × 100% Analysis of other options: - Option (a) is the inverse of efficiency; input power is always greater than output power due to losses (friction, leakage), so this ratio would be > 1. - Option (b) Speed to torque is not a definition of efficiency; their product (Speed × Torque) is actually proportional to power. - Option (c) Head to discharge is a characteristic of the pump's performance curve, not a measure of efficiency.

In welding, flux is a chemical cleaning agent, flowing agent, or purifying agent. Its primary function is to protect the weld pool from atmospheric contamination. When flux melts, it forms a protective layer (slag) over the molten metal, which prevents oxygen and nitrogen from the air from reacting with the molten metal (oxidation). This prevents the formation of porosity and inclusions, ensuring a strong, clean weld. Analysis of other options: - (a) Welding speed is primarily determined by the current, voltage, and the skill of the operator, not the flux. - (b) Hardness is generally controlled by the base metal composition, filler metal chemistry, and the cooling rate (heat treatment), not the flux itself. - (c) Power consumption is a function of the electrical parameters of the welding machine and the material thickness, and is not reduced by the use of flux.

Step-by-step reasoning: 1. The objective is to identify the structure specifically designed to collect or withdraw water from a raw water source (like a river) for treatment and distribution. 2. An 'Intake' structure is specifically engineered to draw water from a river, lake, or reservoir while preventing debris and fish from entering the pumping system. 3. Analysis of other options: (a) A Reservoir is a large natural or artificial lake used for storage, not the specific collection structure. (b) An Aqueduct is a conduit or bridge-like structure used to transport water from one location to another. (d) A Weir is a low dam built across a river to raise the water level or measure flow, which may facilitate an intake, but the weir itself is not the collection structure. Therefore, 'Intake' is the correct technical term.

To understand this, we must look at the relationship between Water Power (Hydraulic Power) and Brake Power (Shaft Power). 1. Water Power (P_w) is the theoretical power required to lift a certain volume of fluid to a specific height: P_w = ρ * g * Q * H (where ρ is density, g is gravity, Q is flow rate, and H is head). 2. Brake Power (P_b) is the actual power input required from the motor to drive the pump. 3. Pump Efficiency (η) is defined as the ratio of Water Power to Brake Power: η = P_w / P_b. Rearranging the formula to find the required power (Brake Power): P_b = P_w / η. Since the Water Power (P_w) remains constant for a given flow and head, the Brake Power (P_b) is inversely proportional to the efficiency (η). Therefore, if the efficiency decreases (η ↓), the required input power must increase (P_b ↑) to maintain the same output. - Option (a) is incorrect because a decrease in efficiency means more energy is lost (as heat or vibration), requiring more input, not less. - Option (b) is incorrect because power input must change to compensate for efficiency losses. - Option (d) is incorrect because zero power would mean the pump is not operating.

In water supply and pumping systems, the velocity of flow in pumping mains is determined by balancing two competing factors: the cost of the pipe (capital cost) and the cost of energy to overcome friction (operational cost). 1. If the velocity is too low (e.g., 0.1 – 0.3 m/s), the pipe diameter must be very large to carry the required discharge, leading to excessively high material and installation costs. 2. If the velocity is too high (e.g., above 2.5 m/s), the head loss due to friction increases exponentially (since head loss is proportional to the square of the velocity, hf ∝ v²). This leads to high pumping costs and increases the risk of water hammer (hydraulic transients) which can burst the pipes. Therefore, the economically and technically optimal velocity range for pumping mains is generally accepted to be between 0.6 m/s and 1.5 m/s. This range ensures that the pipes are not oversized while keeping friction losses and energy consumption within reasonable limits.