Past Questions

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 governed by the water-cement ratio. 1. Why 'Strength of concrete' is correct: A lower w/c ratio (within workable limits) results in a denser cement paste with fewer capillary pores, leading to higher compressive strength. Conversely, an increase in the w/c ratio increases the porosity of the hardened cement paste, which significantly reduces the strength and durability of the concrete. 2. Why other options are incorrect: - (a) Colour of concrete: The colour is primarily determined by the type of cement, the type of aggregates used, and the presence of admixtures, not the w/c ratio. - (b) Setting time only: While water content can influence the rate of hydration, setting time is more significantly affected by the chemical composition of the cement, temperature, and the use of accelerators or retarders. - (d) Cost: While the amount of cement used affects cost, the specific ratio of water to cement is a technical parameter for quality and strength rather than a primary driver of the overall project cost.

Rural sanitation refers to the provision of facilities and services for the safe disposal of human excreta and wastewater, as well as the maintenance of a clean environment in rural areas. 1. Why 'c' is correct: The primary goal of sanitation is to break the fecal-oral route of disease transmission. By ensuring proper waste disposal and promoting hygiene (such as handwashing), the incidence of waterborne and sanitation-related diseases (like cholera, dysentery, and typhoid) is reduced, thereby protecting public health. 2. Why 'a' is incorrect: While a clean village may look more beautiful, beautification is an aesthetic byproduct, not the primary objective of sanitation engineering. 3. Why 'b' is incorrect: Water saving is the objective of water conservation and management, not sanitation. In fact, some sanitation systems (like pour-flush toilets) actually require a small amount of water to function. 4. Why 'd' is incorrect: While improper waste disposal can lead to soil contamination, the overarching goal of rural sanitation is the well-being of the human population through health and hygiene, not solely the protection of soil.

In the context of sanitation and public health engineering, 'Conservancy' (specifically the Conservancy System) refers to the method of removing human excreta (night soil) and refuse from premises manually or mechanically for disposal elsewhere, rather than using a water-borne sewerage system. - Option (a) Water supply refers to the provision of potable water to consumers. - Option (b) Night soil collection and disposal is the definition of a conservancy system, where waste is collected in pits or buckets and transported to a disposal site. - Option (c) Irrigation refers to the artificial application of water to land for agricultural purposes. - Option (d) Stormwater control refers to the management of runoff from rain and snow to prevent flooding and pollution.

The pH value of water is a measure of its acidity or alkalinity on a scale from 0 to 14, where 7 is neutral. For drinking water, the pH must be maintained within a specific range to ensure it is neither too corrosive nor too scale-forming. According to the World Health Organization (WHO) and the Bureau of Indian Standards (BIS) IS 10500:2012, the acceptable limit for pH in drinking water is 6.5 to 8.5. - Option (a) 5–6: This range is acidic. Acidic water can be corrosive to plumbing and distribution systems, leaching metals like lead and copper into the water. - Option (b) 6.5–8.5: This is the standard acceptable range that ensures water is chemically stable and palatable. - Option (c) 7–9: While mostly acceptable, the upper limit of 9 exceeds the standard guideline of 8.5. - Option (d) 8–10: This range is too alkaline, which can lead to a bitter taste and the formation of scale (calcium carbonate deposits) in pipes.

In hydraulics, a trapezoidal section is one of the most common cross-sections used for open channels (such as irrigation canals and drainage ditches). This is because a trapezoidal shape provides a balance between hydraulic efficiency and structural stability; the sloped sides prevent the banks from collapsing due to soil pressure and erosion, which would happen in a purely rectangular section. Why other options are incorrect: - a. Culverts: While some culverts can be trapezoidal, they are predominantly circular, box (rectangular), or arch-shaped to handle structural loads from the road above. - c. Pipelines: Pipelines are almost exclusively circular to withstand internal hydrostatic pressure uniformly (hoop stress). - d. Wells: Wells are typically circular to ensure structural integrity against external soil/water pressure and to facilitate drilling/sinking processes.

According to IS 456:2000 (the Indian Standard code for Plain and Reinforced Concrete), the nominal cover to reinforcement is specified based on the exposure conditions of the concrete. For footings, which are in direct contact with the soil and groundwater, the environment is typically considered 'Severe' or 'Very Severe' due to the presence of moisture and chemicals in the earth. While the minimum cover for mild exposure is lower, the standard engineering practice and the specific guidelines for foundations (footings) generally mandate a minimum clear cover of 50 mm to protect the reinforcement from corrosion caused by soil chemicals and moisture. - Option (a) 25 mm: This is typically the minimum cover for slabs. - Option (b) 40 mm: This is typically the minimum cover for beams and columns in moderate exposure. - Option (c) 50 mm: This is the standard minimum cover for footings to ensure durability against soil contact. - Option (d) 75 mm: This is usually required for concrete cast against the ground in very aggressive environments or for specific heavy-duty foundations, but 50 mm is the general minimum requirement for standard RCC footings.

DI pipes stands for Ductile Iron pipes. Ductile iron is a strong, tough form of cast iron widely used for water supply and sewer pipelines because it has good strength, durability, and resistance to pressure. The other options are incorrect because 'Dull Iron', 'Double Iron', and 'Durable Iron' are not standard engineering terms used for DI pipes.

Storm water drainage is a specialized system designed to manage and divert water that originates from precipitation (rain, snowmelt). The primary goal is to prevent flooding in urban areas by collecting rainwater runoff from impervious surfaces (like roads, roofs, and parking lots) and transporting it to a safe discharge point, such as a river, lake, or infiltration basin. Why other options are incorrect: - a. Domestic sewage: This is handled by the 'Sanitary Sewerage System'. - b. Industrial effluents: These are chemical or process wastes handled by 'Industrial Drainage' or specialized treatment plants. - d. Septic discharge: This refers to the effluent from a septic tank, which is part of an 'On-site Sewage Facility' (OSSF), not storm drainage.

Masonry is defined as the building of structures from individual units, which are often laid in and bound together by mortar. 1. **Brick (Option b):** Bricks are the most common and traditional units used in masonry work (Brick Masonry). Other common masonry units include stone, concrete blocks, and adobe. Therefore, this is the correct answer. 2. **Concrete (Option a):** While concrete is used in 'concrete masonry units' (CMUs), concrete itself is typically categorized as a cast-in-place material or a composite material rather than a masonry unit. Masonry refers to the assembly of discrete units. 3. **Steel (Option c):** Steel is a structural metal used for framing, reinforcement, or cladding, but it is not a masonry material. 4. **Aluminium (Option d):** Aluminium is a non-ferrous metal used for window frames, doors, and cladding, but it cannot be used for masonry work.

Step-by-step reasoning: 1. **Sedimentation**: This is a physical water treatment process that uses gravity to remove suspended particles (solids) from water. Heavier particles settle to the bottom of a tank over time, forming a sludge layer, which is then removed. This is the primary unit designed specifically for the removal of suspended solids. 2. **Filtration (Option a)**: While filtration also removes particles, it is typically used as a secondary polishing step to remove *smaller* suspended particles and colloidal matter that did not settle during sedimentation. Sedimentation is the primary unit for bulk suspended particle removal. 3. **Disinfection (Option b)**: This is a chemical or physical process (e.g., chlorination, UV) used to kill or inactivate pathogenic microorganisms. It does not remove physical suspended particles. 4. **Aeration (Option d)**: This process involves bringing water and air into close contact to remove dissolved gases (like CO2 or H2S) and oxidize dissolved metals (like Iron and Manganese). It is not used for the removal of suspended particles. Therefore, Sedimentation is the most accurate answer for the unit that removes suspended particles via gravity.

In water supply engineering, water demand is categorized based on the end-use of the water. 1. **Institutional Demand (Correct):** This refers to the water required for public institutions such as schools, colleges, hospitals, government offices, prisons, and libraries. These facilities have specific water requirements for sanitation, drinking, and specialized services (like sterilization in hospitals). 2. **Domestic Demand (Incorrect):** This refers to water used in residential households for activities such as drinking, cooking, bathing, and flushing toilets. 3. **Industrial Demand (Incorrect):** This refers to water used in manufacturing processes, cooling systems, and power plants (e.g., textile mills, chemical plants). 4. **Fire Demand (Incorrect):** This is the quantity of water required to extinguish a fire in a specific area, calculated based on formulas like the Kuichling or Freeman formulas, and is separate from daily consumption needs.

To determine which pipe has the highest corrosion resistance, we must analyze the material properties of each option: 1. **GI (Galvanized Iron):** These are steel pipes coated with a layer of zinc. While the zinc provides initial protection, once the galvanization layer is breached or worn away, the underlying steel is highly susceptible to oxidation (rusting) and corrosion. 2. **DI (Ductile Iron):** DI pipes are stronger than cast iron and often have internal cement mortar linings and external coatings to prevent corrosion. However, being metallic, they are still fundamentally susceptible to electrochemical corrosion over time if the protective coatings fail. 3. **CI (Cast Iron):** CI pipes are prone to graphitization and corrosion, especially in acidic soils or water, leading to pitting and eventual failure. 4. **PVC (Polyvinyl Chloride):** PVC is a synthetic plastic polymer. Unlike metals, plastics do not undergo electrochemical corrosion (rusting). They are chemically inert to most acids, bases, and salts found in soil and water. Therefore, PVC is inherently immune to the types of corrosion that affect GI, DI, and CI pipes. Conclusion: Because PVC is a non-metallic material, it possesses the highest corrosion resistance among the given options.

In environmental engineering and waste management, different terms are used to categorize waste based on its physical state and origin: 1. **Refuse (Correct Answer):** This is the general term used for solid waste generated from residential, commercial, and institutional sources. It includes garbage (organic waste), rubbish (non-organic waste like plastics, glass, metals), and ashes. 2. **Sludge:** This refers to the semi-solid material that settles out during the treatment of sewage or industrial wastewater. It is a byproduct of liquid waste treatment, not the primary solid waste from houses. 3. **Sewage:** This is a broad term for wastewater, which is a mixture of water carried by sewers, containing human excreta, soap, oils, and other waste. It is primarily liquid waste. 4. **Sullage:** This is a specific type of sewage known as 'greywater'. It is wastewater from bathrooms, kitchens, and laundries that does not contain human excreta (unlike 'blackwater').

A septic tank is an on-site wastewater treatment unit used to receive domestic sewage, allow solids to settle as sludge, and partially decompose organic matter by anaerobic action. Hence its function is sewage treatment. Option (a) is incorrect because a septic tank is not meant for water storage. Option (b) is incorrect because it does not work as a filtration unit; it mainly relies on sedimentation and anaerobic digestion. Option (d) is incorrect because sludge is not burned in a septic tank; it is only collected and later removed for disposal.

In India, the standards for water supply are governed by the Manual on Water Supply and Sanitation (CPHEEO) and the Ministry of Urban Development. For urban areas, the normal per capita water supply is specified as 135 liters per capita per day (lpcd). This value is based on the assumption of a piped water supply system with a functional sewerage system. Breakdown of options: - 70 lpcd: This is generally considered the minimum requirement for basic survival and hygiene in rural areas or very small settlements without full sewerage. - 100 lpcd: While some smaller towns may target this, it is not the national standard for urban areas. - 135 lpcd: This is the official standard for urban areas with full sewerage systems in India. - 200 lpcd: This value is typically seen in high-income metropolitan cities or specific luxury developments, but it is not the 'normal' standard for general urban planning.

Reinforced Cement Concrete (RCC) is a composite material designed to leverage the strengths of two different materials: concrete and steel. 1. Concrete is naturally very strong in compression but very weak in tension (it cracks easily when pulled). 2. Steel is exceptionally strong in both tension and compression. 3. By embedding steel reinforcement bars (rebars) into the concrete, the steel carries the tensile loads while the concrete carries the compressive loads. Therefore, the resulting RCC structure is strong in both tension and compression, making it ideal for beams, slabs, and columns in buildings. Why other options are incorrect: - Option (a): RCC is not 'always' cheap; costs vary based on material prices and labor compared to timber or steel structures. - Option (b): RCC is specifically designed to be strong in bending (flexure) because bending involves a combination of compression (top) and tension (bottom). - Option (d): RCC is heavy due to the density of concrete; it is certainly not 'lightweight always'.

Rainwater harvesting collects and stores rainwater so it can be used directly or allowed to percolate into the ground, thereby increasing groundwater recharge. This is the main benefit of the practice. The other options are incorrect because rainwater harvesting does not waste water; it conserves it. It does not cause pollution; in fact, it can reduce runoff and contamination. It also does not promote corrosion; corrosion is unrelated to the purpose of harvesting rainwater.

RCC stands for Reinforced Cement Concrete, which is concrete strengthened with steel reinforcement bars to improve tensile strength. Option c is correct. The other options are incorrect because 'Reinforced Clay Concrete' is not a standard construction term, 'Ready Cement Concrete' is not the meaning of RCC, and 'Rapid Cement Concrete' is also not a recognized expansion of RCC.

Masonry consists of individual units (bricks, stones, or concrete blocks) bonded together with mortar. The materials used in masonry are inherently strong in compression but very weak in tension. 1. Compression (Correct): Masonry walls are designed to carry vertical loads (such as the weight of the roof and upper floors) which push the materials together. This is the primary structural function of a load-bearing masonry wall. 2. Tension (Incorrect): Masonry has negligible tensile strength. When subjected to tension, the bond between the mortar and the unit fails quickly, leading to cracking. 3. Torsion (Incorrect): Torsion involves twisting. Masonry is brittle and cannot resist twisting forces effectively without reinforcement (like steel). 4. Impact (Incorrect): While masonry has some mass, it is brittle and prone to cracking or shattering under high-velocity impact loads compared to ductile materials like steel.

HDPE is a thermoplastic polymer produced from the monomer ethylene. In the context of piping materials for Public Health Engineering (PHE), it is widely used due to its high strength-to-density ratio, corrosion resistance, and flexibility. Breakdown of the acronym: - High Density: Refers to the molecular structure where there is minimal branching, allowing the polymer chains to pack closely together, increasing density and strength. - Poly: Short for polymer. - Ethylene: The chemical building block (monomer) used to create the plastic. Analysis of other options: - Option (a) 'Pipe Element' is incorrect as 'E' stands for Ethylene. - Option (b) 'Durable Pipe Equipment' is incorrect; while HDPE is durable, the acronym does not stand for this. - Option (d) 'Ductile Poly Element' is incorrect; 'Ductile' is a property often associated with cast iron (Ductile Iron), not the name of the HDPE polymer.

Step-by-step reasoning: 1. Analysis of Brick Types: Bricks are categorized based on their manufacturing process and quality. Burnt clay bricks (First class, Second class, Engineering) undergo a firing process in a kiln, which gives them high compressive strength and durability. 2. Sun-dried Bricks: These are bricks that are molded and dried in the sun without being fired in a kiln. Because they are not burnt, they have very low strength, poor durability, and are highly susceptible to water damage. 3. Application: Due to their low cost and low strength, sun-dried bricks are unsuitable for permanent structures but are ideal for temporary constructions, such as temporary sheds, boundary walls for short-term use, or low-cost rural housing. 4. Evaluation of other options: (a) First class bricks are used for permanent, high-quality load-bearing structures. (b) Second class bricks are used for permanent structures where a plaster coat is applied. (d) Engineering bricks are high-density, low-absorbency bricks used for heavy-duty permanent works like sewers and bridge abutments.

According to IS 456:2000 (the Indian Standard code of practice for Plain and Reinforced Concrete), the minimum grade of concrete for Reinforced Cement Concrete (RCC) work depends on the exposure conditions. For 'Mild' exposure conditions, the minimum grade of concrete specified for RCC is M20. Grades below M20 (such as M10 and M15) are generally used for Plain Cement Concrete (PCC) or lean concrete work and are not permitted for structural RCC elements because they do not provide sufficient strength and durability to protect the reinforcement from corrosion. While higher grades like M25 are used for more severe exposure conditions, M20 remains the absolute baseline minimum for any RCC work under standard conditions.

Step-by-step reasoning: 1. **Disinfection** is the process of killing pathogenic microorganisms (bacteria, viruses, and protozoa) in water to make it safe for human consumption. 2. **Chlorine (Option c)** is the most widely used chemical for disinfection globally. It acts as a powerful oxidizing agent that penetrates the cell walls of microorganisms, disrupting their enzymatic activity and killing them. It also provides a 'residual effect,' meaning it continues to protect the water from re-contamination as it travels through the distribution system. 3. **Alum (Option a)**, or Aluminum Sulfate, is used as a 'coagulant' in water treatment. It helps in removing turbidity by clumping small particles together into larger flocs, but it does not disinfect the water. 4. **Lime (Option b)**, or Calcium Hydroxide, is primarily used for 'water softening' (removing hardness) and pH adjustment to prevent corrosion in pipes. 5. **Soda (Option d)**, usually referring to Soda Ash (Sodium Carbonate), is also used for water softening and pH stabilization, not for disinfection.

Safe Bearing Capacity (SBC) of soil is defined as the maximum intensity of pressure that can be applied to the soil such that the shear stress developed in the soil does not exceed the safe shear strength of the soil, and the settlement remains within permissible limits. Since it is a measure of 'pressure' or 'stress', it must be expressed in units of Force per unit Area. 1. Analysis of Options: - Option (a) m³: This is a unit of volume, not pressure. - Option (b) kg: This is a unit of mass, not pressure. - Option (c) kN/m²: This is a unit of pressure (Kilo-Newton per square meter), which is equivalent to the kilo-Pascal (kPa). This is the standard unit for bearing capacity. - Option (d) kN: This is a unit of force, not pressure. Therefore, the correct unit for expressing the safe bearing capacity of soil is kN/m².

In road construction, stones used for aggregates (soling, WMM, and bituminous layers) must possess high compressive strength, high toughness, and resistance to wear and abrasion. 1. Basalt: This is an igneous rock known for its extreme hardness, density, and durability. It has high crushing strength and low water absorption, making it ideal for road surfaces and heavy-duty pavements where it must withstand constant traffic loads and weathering. 2. Marble: This is a metamorphic rock primarily used for ornamental and decorative purposes. It is too soft and susceptible to chemical weathering (acid rain) for road works. 3. Sandstone: While used in some building constructions, sandstone is generally too porous and lacks the necessary toughness and abrasion resistance required for high-traffic road surfaces. 4. Limestone: Although used in some road bases or as a filler, limestone is generally softer than basalt and can be prone to wear and chemical degradation over time compared to igneous rocks.