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Past Questions
Define Deposit Works. What are the conditions for taking up of Deposit works?
Explain ‘Test checking of measurement by the Assistant Engineer’.
What are the General principles of Leave Rules?
What is the procedure to award work without call of Tender?
Differentiate between Performance Gurantee and Security Deposit
Explain the process of preparation & checking of Comparative Statement.
Plasticizer in cement concrete mix is added to
A)
increase workability without an increase in water content
B)
increase workability with corresponding increase in water content
C)
increase workability with corresponding decrease in water content
D)
None of these
Plasticizers, also known as water-reducers, are chemical admixtures added to concrete to improve its fluidity and workability. In a standard concrete mix, increasing workability usually requires adding more water; however, adding more water increases the water-cement ratio, which leads to higher porosity and lower compressive strength. Plasticizers work by dispersing cement particles (reducing flocculation), which allows the mix to flow more easily. This enables the engineer to either: 1) Increase workability while keeping the water content constant, or 2) Maintain the same workability while reducing the water content to increase the strength of the concrete. Therefore, the primary purpose of adding a plasticizer is to increase workability without needing to increase the water content. Option (b) is incorrect because adding water is what plasticizers are designed to avoid. Option (c) is incorrect because while plasticizers allow for a decrease in water, the 'increase in workability' is the result of the chemical action, not a result of decreasing water (decreasing water alone would decrease workability).
To avoid Alkali-Aggregate reaction in cement concrete work, the aggregates used should not contain
A)
Sodium oxide
B)
Potassium oxide
C)
Ferrous minerals
D)
Siliceous minerals
Alkali-Aggregate Reaction (AAR), specifically Alkali-Silica Reaction (ASR), is a chemical reaction between the hydroxyl ions of the alkali hydroxides (sodium and potassium) present in the cement and the reactive silica found in certain aggregates.
1. **Mechanism**: When cement is hydrated, it releases sodium oxide (Na2O) and potassium oxide (K2O). If the aggregates contain 'reactive silica' (found in certain siliceous minerals like opal, chalcedony, or volcanic glass), these alkalis react with the silica to form an alkali-silica gel.
2. **Effect**: This gel absorbs water and expands, creating internal pressure that leads to characteristic 'map cracking' and structural deterioration of the concrete.
3. **Prevention**: To avoid this reaction, one must either use low-alkali cement or ensure that the aggregates used do not contain reactive siliceous minerals.
Why other options are incorrect:
- **Options a and b (Sodium and Potassium oxide)**: These are the alkalis typically provided by the cement itself. While reducing them helps, the question asks what the *aggregates* should not contain. Aggregates are generally not the primary source of these oxides compared to the cement.
- **Option c (Ferrous minerals)**: Iron-based minerals do not participate in the alkali-silica reaction and do not cause the expansive gel formation associated with AAR.
The Indian standard codes and provisions prescribed for designing water retaining structures is/are
A)
IS:3370
B)
IS:456-2000
C)
IS:3370 & IS:456-2000
D)
IS:1893-2002 & IS:456-2000
Designing water retaining structures requires a combination of general reinforced concrete principles and specialized requirements to prevent leakage and cracking.
1. **IS 3370**: This is the specific Indian Standard code dedicated to the 'Code of Practice for Concrete Structures for Storage of Liquids'. It provides specialized guidelines on limiting crack widths, durability requirements, and design methods specifically for water tanks and reservoirs.
2. **IS 456-2000**: This is the general 'Plain and Reinforced Concrete - Code of Practice'. Since water retaining structures are made of reinforced concrete, the fundamental rules for material properties, reinforcement detailing, and general structural design provided in IS 456 must be followed.
Therefore, a designer must refer to both IS 3370 (for liquid-retaining specifics) and IS 456 (for general RCC design).
Other options are incorrect because:
- Option (a) is incomplete as IS 3370 relies on the general provisions of IS 456.
- Option (b) is insufficient as it lacks the specific requirements for liquid tightness.
- Option (d) includes IS 1893, which is the code for Earthquake Resistant Design, and while it may be used for seismic zones, it is not the primary code for water retaining structures.
Which of the following sources of water will have the least turbidity?
A)
Ground water
B)
Lake water
C)
Stream in dry water
D)
Stream in flood
Turbidity is caused by the presence of suspended particles (such as clay, silt, organic matter, and microscopic organisms) in water.
1. **Ground water (Option a):** As water percolates through layers of soil, sand, and rock to reach an aquifer, the earth acts as a natural filter. This process removes the vast majority of suspended solids, resulting in water with very low turbidity.
2. **Lake water (Option b):** Lakes can contain suspended algae, organic debris, and sediment stirred up from the bottom, leading to higher turbidity than groundwater.
3. **Stream in dry weather (Option c):** While clearer than during a flood, streams still carry suspended sediments and organic matter from the surrounding terrain.
4. **Stream in flood (Option d):** During floods, high-velocity water causes significant erosion and runoff, carrying large amounts of silt, clay, and debris, resulting in the highest turbidity among all the options.
Therefore, ground water typically has the least turbidity due to natural filtration.
Which of the following types of roof would be most desirable for harvesting rainwater?
A)
Unpainted and uncoated roofs
B)
Thatched roofs such as Palms and Grasses
C)
Mud roofs
D)
Acrylic painted roofs
In rainwater harvesting, the 'catchment area' (the roof) must be non-porous, smooth, and chemically inert to ensure that the collected water is clean and the runoff coefficient is high.
1. **Acrylic painted roofs (Option d):** These are the most desirable because acrylic coatings provide a smooth, impermeable surface that prevents water seepage and protects the underlying material from corrosion. They are generally non-toxic and ensure a high percentage of rainfall is collected (high runoff coefficient) while minimizing contamination.
2. **Unpainted and uncoated roofs (Option a):** Depending on the material (like galvanized iron or concrete), uncoated roofs can leach metals, rust, or absorb water, leading to lower quality water and lower collection efficiency.
3. **Thatched roofs (Option b):** Materials like palms and grasses are highly porous. They absorb a significant amount of water and introduce organic debris and contaminants into the runoff, making them unsuitable for harvesting potable water.
4. **Mud roofs (Option c):** Mud is highly permeable and will absorb most of the rainwater. Furthermore, mud will dissolve and wash into the collection system, resulting in highly turbid and contaminated water.
The design period of a sewer system should be
A)
10 years
B)
15 to 20 years
C)
20 to 40 years
D)
Indefinite
The correct answer is **20 to 40 years**. In sewerage engineering, the design period is the expected service life for which the sewer system is planned, and major sewer components are generally designed for a long life, typically around **20–40 years**, because replacement is difficult and costly.
Why the others are incorrect:
- **a) 10 years**: too short for a sewer system; this is more typical of some short-life appurtenances, not the main sewer network.
- **b) 15 to 20 years**: still on the lower side; sewer systems are usually designed for a longer horizon.
- **d) Indefinite**: not correct because all infrastructure is designed for a finite planning period based on population growth, flow estimates, and economic considerations.
The grade of cement not to be used in the construction of RCC water tank is
A)
53 Grade
B)
43 Grade
C)
33 Grade
D)
None of these
In the construction of RCC water tanks, the primary concern is not just the compressive strength, but the durability and the prevention of cracking. 53 Grade cement is a high-strength cement that generates a higher amount of heat during the hydration process (heat of hydration) compared to 33 or 43 grade cements. In mass concrete structures like water tanks, high heat of hydration can lead to thermal cracking and shrinkage cracks. These cracks compromise the water-tightness of the tank, leading to leakages. Therefore, for water-retaining structures, lower or moderate grade cements (like 33 or 43 grade) are preferred because they are less prone to thermal cracking and provide better long-term durability and impermeability. While 53 grade is excellent for high-rise buildings or pre-cast elements where early strength is needed, it is generally avoided in water tanks to ensure structural integrity against leakage.
Construction of temporary structure to support temporarily an unsafe structure in a civil engineering works is called
A)
Formwork
B)
Shoring
C)
Scaffolding
D)
Underpinning
Step-by-step reasoning:
1. **Shoring** is defined as the process of providing temporary support to an existing structure (such as a wall or a building) that has become unstable or unsafe, or to prevent it from collapsing during nearby excavation or repair work. It is essentially a temporary structural support system.
2. **Formwork** (Option a) refers to the temporary molds (usually made of timber, steel, or aluminum) into which concrete is poured to give it a specific shape until it hardens.
3. **Scaffolding** (Option c) is a temporary platform used to support workers and materials during the construction, repair, or cleaning of a building. Unlike shoring, its primary purpose is access and safety for workers, not the structural support of an unsafe building.
4. **Underpinning** (Option d) is a permanent method of strengthening and stabilizing the foundation of an existing building by extending the foundation in depth or breadth.
Since the question specifically asks for the temporary support of an unsafe structure, 'Shoring' is the correct technical term.
According to the International standards for drinking water, 3rd edition, WHO, Geneva, 1971, the highest desirable pH level is
A)
6.0 to 6.5
B)
6.5 to 7.0
C)
7.0 to 8.0
D)
7.5 to 8.5
According to the historical guidelines set by the WHO (World Health Organization) in the 1971 standards for drinking water, the pH of water is monitored primarily for its effect on the distribution system (corrosivity) and taste, rather than direct health risks. While pure water has a pH of 7.0, drinking water is generally preferred to be slightly alkaline to prevent the corrosion of metal pipes (which occurs in acidic water). The range of 7.5 to 8.5 is considered the highest desirable range because it minimizes the leaching of metals like lead and copper from plumbing while remaining well within the acceptable taste and safety limits for human consumption. Options a and b are too acidic (increasing corrosion risk), and option c is neutral to slightly alkaline but does not represent the 'highest desirable' upper limit specified in these specific historical standards.
The most common evaporation system of sewage disposal is
A)
Oxidation pond
B)
Stream disposal
C)
Rapid infiltration
D)
Ocean discharge
Step-by-step reasoning: 1. The question asks for the most common 'evaporation system' of sewage disposal. 2. Oxidation ponds (also known as stabilization ponds) are shallow basins where sewage is treated through the interaction of sunlight, bacteria, and algae. 3. In these ponds, a significant portion of the liquid waste is removed through evaporation and transpiration, especially in warm climates, making them a primary example of an evaporation-based disposal/treatment system. 4. Analyzing other options: (b) Stream disposal and (d) Ocean discharge are methods of direct discharge into water bodies, relying on dilution rather than evaporation. (c) Rapid infiltration relies on the percolation of sewage into the soil (infiltration), not evaporation. Therefore, the oxidation pond is the only system among the choices that utilizes evaporation as a key mechanism for volume reduction and disposal.
The chemical reaction of cement with water, by virtue of which cement becomes a bonding agent is known as
A)
Incineration
B)
Oxidation
C)
Hydration
D)
Hardening
The process described is the chemical reaction between cement and water.
1. **Hydration (Correct):** When water is added to cement, a chemical reaction occurs between the water and the cementitious compounds (primarily tricalcium silicate and dicalcium silicate). This process is called 'hydration'. It results in the formation of a calcium silicate hydrate (C-S-H) gel, which binds the aggregates together and gives the concrete its strength and hardness.
2. **Incineration (Incorrect):** This is a waste treatment process that involves the combustion of organic substances contained in waste materials.
3. **Oxidation (Incorrect):** This is a chemical reaction that involves the loss of electrons or the addition of oxygen to a substance; it is not the primary mechanism by which cement sets.
4. **Hardening (Incorrect):** While hardening is the *result* of the process, it is a physical state change. The specific *chemical reaction* that leads to hardening is called hydration.
The minimum cement content for M20 grade concrete is
A)
250 kg/cum
B)
300 kg/cum
C)
400 kg/cum
D)
450 kg/cum
For nominal M20 concrete, the commonly specified minimum cement content is about 300 kg per cubic metre (as per standard practice/IS 456 durability requirements for ordinary exposure). Hence option **b (300 kg/cum)** is correct. The other options are incorrect because **250 kg/cum** is generally too low for M20, while **400 kg/cum** and **450 kg/cum** are higher than the usual minimum cement content for M20 and are not the standard minimum value asked here.
Which of the following is provided in water tank for easy feeding of water into the pipe?
A)
Puddle piece with collar
B)
Duck foot bend
C)
Ventilator
D)
Bell mouth
In water storage tanks, a 'Bell mouth' (also known as a bell-mouth inlet or outlet) is a flared, funnel-shaped fitting provided at the end of the pipe. Its primary purpose is to reduce turbulence, minimize head loss, and prevent the formation of vortices (whirlpools) as water enters the pipe from the tank, thereby ensuring a smooth and efficient feeding of water.
Why other options are incorrect:
- a. Puddle piece with collar: This is a cast-iron pipe fitting used to provide a watertight seal where a pipe passes through a concrete wall or floor to prevent leakage.
- b. Duck foot bend: This is a specific type of bend used to connect a vertical pipe to a horizontal one, typically used in water distribution mains to connect a service pipe to a valve.
- c. Ventilator: This is used to allow air to enter or escape the system to prevent vacuum formation or pressure buildup; it does not facilitate the feeding of water into a pipe.
The pitch of lateral ties in RCC columns should not exceed
A)
300 mm
B)
350 mm
C)
400 mm
D)
450 mm
In the design of Reinforced Concrete (RCC) columns, lateral ties (transverse reinforcement) are provided to prevent the longitudinal bars from buckling outwards and to provide confinement to the concrete core. According to standard RCC design codes (such as IS 456:2000), the pitch (spacing) of these lateral ties is restricted to ensure stability. While the specific spacing depends on the diameter of the longitudinal bars and the column dimensions, the general maximum limit for the pitch of lateral ties in standard column design is typically 300 mm. Spacings greater than this (such as 350mm, 400mm, or 450mm) would fail to provide adequate lateral support to the main reinforcement, increasing the risk of buckling under axial loads.
The standard size of Brick including mortar thickness is
A)
19cm×9cm×9cm
B)
20cm×10cm×10cm
C)
19cm×10cm×10cm
D)
20cm×9cm×9cm
In civil engineering and building materials, it is important to distinguish between the 'Modular size' and the 'Nominal size' of a brick:
1. **Modular Size (Standard Size):** The standard size of a modular brick is 19 cm × 9 cm × 9 cm. This is the actual size of the brick without any mortar.
2. **Nominal Size:** The nominal size is the size of the brick including the thickness of the mortar joints (usually 10 mm or 1 cm).
Calculation for Nominal Size:
- Length: 19 cm + 1 cm (mortar) = 20 cm
- Width: 9 cm + 1 cm (mortar) = 10 cm
- Height: 9 cm + 1 cm (mortar) = 10 cm
Therefore, the size of the brick including mortar thickness is 20 cm × 10 cm × 10 cm.
- Option (a) represents the modular size (without mortar).
- Option (b) represents the nominal size (with mortar).
- Options (c) and (d) are incorrect combinations of modular and nominal dimensions.
Turbidity in water supply may be removed by
A)
Chlorination
B)
Sedimentation with or without chemical coagulant and filtration
C)
Cation-exchange method
D)
Radio-isotope removal
Turbidity is caused by the presence of suspended particles (such as clay, silt, organic matter, and microscopic organisms) in water. To remove these particles, the following processes are used:
1. Sedimentation: Allowing heavier particles to settle at the bottom of a tank due to gravity.
2. Coagulation/Flocculation: Adding chemical coagulants (like Alum) to neutralize the charges on colloidal particles, causing them to clump together into larger 'flocs' that settle more easily.
3. Filtration: Passing the water through a porous medium (like sand or anthracite) to trap the remaining fine suspended particles.
Why other options are incorrect:
- Chlorination (a) is a disinfection process used to kill pathogens (bacteria/viruses), not to remove physical turbidity.
- Cation-exchange method (c) is primarily used for water softening (removing hardness ions like Ca2+ and Mg2+) or removing specific dissolved ions.
- Radio-isotope removal (d) is a specialized process for removing radioactive contaminants, which is not the standard treatment for general turbidity.
The electrode used in the standard method of measuring pH value is
A)
Glass
B)
Hydrogen
C)
Nickel
D)
Mica
The standard method for measuring the pH value of a solution in environmental engineering and chemistry is the use of a pH meter, which utilizes a Glass Electrode.
1. **How it works**: The glass electrode consists of a thin, pH-sensitive glass membrane. When immersed in a solution, an ion exchange occurs between the hydrogen ions (H+) in the solution and the ions in the glass membrane, creating a potential difference (voltage) proportional to the pH of the solution.
2. **Reference Electrode**: The glass electrode is typically used in conjunction with a reference electrode (like a Calomel or Silver/Silver Chloride electrode) to complete the electrical circuit.
3. **Why other options are incorrect**:
- **Hydrogen electrode (b)**: While the Standard Hydrogen Electrode (SHE) is the theoretical reference for all electrode potentials, it is impractical for routine pH measurement because it requires a constant stream of pure hydrogen gas and is difficult to maintain.
- **Nickel (c)** and **Mica (d)**: These materials do not possess the specific ion-selective properties required to measure the activity of hydrogen ions in a solution and are not used as pH-sensing electrodes.
The minimum gross pressure intensity at the base of the foundation at which the soil fails in shear is called
A)
Safe bearing capacity
B)
Net safe bearing capacity
C)
Net ultimate bearing capacity
D)
Ultimate bearing capacity
In foundation engineering, bearing capacity is defined based on the failure mode of the soil.
1. **Ultimate Bearing Capacity (UBC):** This is defined as the minimum gross pressure intensity at the base of the foundation at which the soil fails in shear. It represents the maximum load the soil can support before catastrophic failure occurs.
2. **Net Ultimate Bearing Capacity:** This is the ultimate bearing capacity minus the pressure exerted by the soil (overburden pressure) at the foundation level. It represents the additional pressure the soil can take beyond its existing state.
3. **Safe Bearing Capacity (SBC):** This is the maximum pressure that can be applied to the soil such that the shear stress developed is not more than the allowable shear stress (usually UBC divided by a factor of safety). It ensures that the soil does not fail and that settlements are within permissible limits.
4. **Net Safe Bearing Capacity:** This is the safe bearing capacity minus the overburden pressure.
Since the question specifically asks for the pressure intensity at which the soil 'fails in shear', it is referring to the ultimate limit state, which is the Ultimate Bearing Capacity.
Amoebic dysentery is an infection of waterborne communicable disease due to the presence of
A)
Bacteria
B)
Viruses
C)
Protozoan
D)
None of these
Amoebic dysentery (also known as amoebiasis) is caused by the parasite Entamoeba histolytica. In biological classification, Entamoeba histolytica is a protozoan—a single-celled eukaryotic organism. It is typically transmitted through the fecal-oral route, often via contaminated water or food containing the cysts of the protozoan.
Why other options are incorrect:
- a. Bacteria: While bacillary dysentery (shigellosis) is caused by bacteria, amoebic dysentery specifically is caused by a protozoan.
- b. Viruses: Waterborne viral diseases include Hepatitis A or Polio, but not amoebic dysentery.
- d. None of these: This is incorrect as option 'c' is the scientifically accurate answer.