Correct Answer: parapet
Explanation: A guard wall of small height exposed to the weather is called a “parapet.”
Correct Answer: 4 to 6%
Explanation: The allowable clay silt in sand for mortar is typically in the range of 4 to 6%.
Correct Answer: 1:6
Explanation: The preferred cement-sand mortar mix in load-bearing walls is typically 1:6.
Correct Answer: 1:4
Explanation: The preferred cement-sand mortar mix in 1/2 brick walls is typically 1:4.
Correct Answer: 1:3
Explanation: The types of plaster generally used for the ceiling have a cement-sand ratio of 1:3.
Correct Answer: both of the above
Explanation: Lap is the horizontal distance between the vertical joints and is applicable to both stone masonry and brick masonry.
Correct Answer: cornice
Explanation: An ornamental projection from the face of a brick wall is called a “cornice.”
Correct Answer: bull nose
Explanation: Bricks with one or two edges rounded for use in curved corners are called “bull nose” bricks.
Correct Answer: all of the above
Explanation: Horizontal construction joints in concrete walls are generally provided at soffit level, window sill level, and floor level.
Correct Answer: arches
Explanation: The header bond is commonly used in arches.
Correct Answer: flemish bond
Explanation: The bond produced by laying alternate headers and stretchers in each course is known as “flemish bond.”
Correct Answer: english bond
Explanation: In Nepal, the generally used method of bond in masonry wall of brickwork is “english bond.”
Correct Answer: english bond
Explanation: English bond is often used for carrying heavy loads in brick masonry.
Correct Answer: double flemish bond
Explanation: For a uniform face appearance, the desired bond in brick masonry is “double flemish bond.”
Correct Answer: garden wall bond
Explanation: The joint preferred in a single brick wall to save facing bricks is “garden wall bond.”
Correct Answer: half brick
Explanation: The stretcher bond in brick masonry can be used only when the wall is of half brick thickness.
Correct Answer: more compact
Explanation: As compared to english bond, the double flemish bond is more compact.
Correct Answer: stretcher bond
Explanation: The bond in which all courses are laid as stretcher is known as “stretcher bond.”
Correct Answer: facing bond
Explanation: The bond used when bricks are of different thickness is “facing bond.”
Correct Answer: dutch bond
Explanation: The bond filled with 4 bats and 1⁄2 closer with the regular header and stretcher is known as “dutch bond.”
Correct Answer: plinth level
Explanation: In ordinary residential buildings, the damp proofing course (D.P.C.) is generally provided at plinth level to prevent rising dampness.
Correct Answer: damp proof course
Explanation: D.P.C. stands for damp proof course.
Correct Answer: growth of termites
Explanation: Dampness can cause the growth of termites among other issues.
Correct Answer: 4.0 cm
Explanation: In horizontal D.P.C., the thickness of cement concrete (1:2:4) is typically kept at 4.0 cm.
Correct Answer: membrane damp proof
Explanation: The method described is known as membrane damp proofing.
Correct Answer: bitumen sheeting
Explanation: Bitumen sheeting is a flexible material used for damp proofing.
Correct Answer: both of the above
Explanation: D.P.C. can be provided in the form of both horizontal and vertical layers.
Correct Answer: all of the above
Explanation: The D.P.C. should be continued and unbroken through the length and thickness of the wall, sealed with bitumen at lap joints, and even at the source of moisture.
Correct Answer: mastic asphalt
Explanation: When D.P.C. is to be laid over large areas, mastic asphalt is a preferred material.
Correct Answer: horizontal level
Explanation: Generally, D.P.C. is provided at horizontal level.
Correct Answer: horizontal
Explanation: Bituminous asphalt/asphaltic felt is commonly used as D.P.C. on the horizontal surface.
Correct Answer: 10 mm
Explanation: The maximum size of the aggregate used in a damp proof course is typically about 10 mm.
Correct Answer: just below the ground floor level
Explanation: The D.P.C. is provided just below the ground floor level for efficiency.
Correct Answer: tricalcium silicate
Explanation: Tricalcium silicate is a compound that helps in obtaining early strength of cement concrete.
Correct Answer: dicalcium silicate
Explanation: Later stage strength of cement is caused by dicalcium silicate.
Correct Answer: high alumina cement
Explanation: High alumina cement is specifically designed to resist chemical attacks, including resistance to acid. This type of cement contains a higher percentage of alumina (Al2O3) compared to ordinary Portland cement, making it suitable for applications where resistance to acidic environments is crucial. High alumina cement is commonly used in construction projects where exposure to acidic conditions is anticipated, such as in chemical plants or areas with high sulfate content in the soil.
Correct Answer: zinc
Explanation: Workability in concrete refers to its ease of handling, placing, and compaction. The addition of certain compounds can enhance workability. Zinc-based compounds, such as zinc stearate or zinc oxide, are often used as workability enhancers in concrete. These compounds act as water-reducing agents, allowing for better dispersion of cement particles and improving the flowability of the concrete mix. As a result, the concrete becomes more manageable during construction.
Correct Answer: increases with an increase in the size of aggregate
Explanation: The density of concrete is influenced by the size and density of its aggregates. Generally, as the size of the aggregate increases, the density of the concrete also increases. This is because larger aggregates occupy more space and result in a higher mass per unit volume. However, other factors such as the mix design, water-cement ratio, and air content can also affect the density of concrete.
Correct Answer: hydration of cement
Explanation: The primary mechanism by which concrete gains strength is through the process of hydration. Hydration is a chemical reaction between cement and water, leading to the formation of crystalline structures that bind the ingredients of concrete together. As the hydration process continues over time, the concrete gradually gains strength and hardness. It is essential to provide adequate curing to allow for proper hydration and achieve the desired strength properties in the concrete.
Correct Answer: curing
Explanation: Curing is the process of maintaining adequate moisture, temperature, and time to ensure the proper hydration of cement in concrete. By keeping the concrete surface moist, the hydration reactions continue, allowing the concrete to harden and gain strength. Curing is a critical step in concrete construction, and its duration is essential for achieving the desired durability and performance of the concrete structure.
Correct Answer: all of the above
Explanation: Curing plays a crucial role in the overall quality of concrete. It serves multiple purposes, including reducing shrinkage, preserving the properties of concrete, and preventing the loss of water by evaporation. Properly cured concrete tends to have fewer cracks, improved strength, and enhanced durability. The curing process involves maintaining a suitable environment, often through the application of water or other curing methods, to ensure optimal conditions for continued hydration.
Correct Answer: ponding method
Explanation: Curing methods can vary based on the type of concrete element. For pavements, floors, roofs, and slabs, the ponding method is commonly employed. In the ponding method, a layer of water is retained on the surface of the concrete by forming a shallow pond or reservoir. This water layer helps in maintaining the moisture content necessary for proper curing. Ponding is particularly effective for large horizontal surfaces where other curing methods, such as covering with wet burlap, may not be as practical.
Correct Answer: all of the above
Explanation: Curing contributes to several desirable properties of concrete. It ensures volume stability and strength development, enhances wear resistance, and improves water tightness and overall durability. Adequate curing is essential for achieving the intended performance and longevity of concrete structures. Insufficient curing can lead to various issues, including reduced strength, cracking, and decreased durability.
Correct Answer: wetting the concrete with water/steam
Explanation: Curing involves maintaining a suitable moisture and temperature environment for the concrete during its early stages of hardening. This can be achieved by wetting the concrete with water through methods like ponding, spraying, or covering with wet materials. In some cases, steam curing may be applied to accelerate the curing process. The goal is to ensure continuous hydration of cement, leading to the development of strength and durability in the concrete.
Correct Answer: mass production of precast concrete
Explanation: Steam curing is often employed in the mass production of precast concrete elements. Precast concrete elements, such as beams, columns, and panels, are manufactured in controlled environments, and steam curing is applied to accelerate the curing process. Steam curing can lead to faster strength development, allowing for quicker turnover in precast concrete production. It is particularly useful in achieving high-quality precast elements with consistent properties.
Correct Answer: rapid hardening cement
Explanation: While steam curing can be beneficial for accelerating the curing of concrete, it is typically not used with rapid hardening cement. Rapid hardening cement is designed to achieve high early strength without the need for accelerated curing methods. Steam curing is more commonly applied to ordinary Portland cement or other types of cement to achieve specific strength requirements in a shorter time frame.
Correct Answer: rapid hardening cement
Explanation: Concrete using rapid hardening cement often requires a shorter curing period compared to other types of cement. Rapid hardening cement is formulated to gain strength rapidly, allowing for faster demolding, formwork removal, and earlier use of the concrete structure. However, it’s essential to follow recommended curing practices to ensure that the concrete attains the desired long-term strength and durability.
Correct Answer: compaction factor test
Explanation: The compaction factor test is a method used to assess the workability of concrete mixes with low water-cement ratios. Workability refers to the ease with which concrete can be mixed, placed, and compacted. The compaction factor test involves measuring the degree of compaction achieved by a concrete mix under standardized conditions. A higher compaction factor indicates better workability for the given mix, even with a lower wate cement ratio.
Correct Answer: medium
Explanation: The compaction factor is a dimensionless value that represents the degree of compaction achieved by a concrete mix. A compaction factor of 0.95 suggests a medium level of workability. It indicates that the concrete mix can be easily compacted, but it may not be as fluid or easily flowable as mixes with higher compaction factors. The interpretation of compaction factor values is relative, and the suitability of the workability depends on the specific requirements of the construction project.
Correct Answer: consistency
Explanation: The slump test is a widely used method for assessing the consistency or workability of fresh concrete. During the test, a truncated cone-shaped concrete specimen is molded, and the slumping of the concrete is observed after the removal of the mold. The extent of slumping provides an indication of the consistency of the concrete mix. A higher slump indicates a more workable and fluid mix, while a lower slump suggests a stiffer mix. The slump test is valuable for ensuring that the concrete mix meets the desired consistency for proper placement and compaction during construction.
Correct Answer: 25 times
Explanation: In the slump test, each layer of concrete is compacted by rodding with a steel rod. The standard procedure involves rodding each layer of the concrete specimen 25 times. This helps in achieving proper compaction and ensures consistent results in assessing the workability of the concrete mix.
Correct Answer: medium
Explanation: The slump value is a measure of the workability of concrete. In this context, a slump of 60mm indicates medium workability. Workability refers to the ease with which concrete can be mixed, placed, and compacted. A slump of 60mm suggests that the concrete mix is moderately easy to work with, and it possesses a balance between fluidity and cohesiveness.
Correct Answer: 50-100
Explanation: Different concrete applications require varying degrees of workability. For beam and slab elements in reinforced concrete construction (RCC), a slump range of 50-100mm is commonly recommended. This range ensures that the concrete mix has sufficient fluidity to flow and fill the formwork adequately while maintaining the necessary cohesiveness.
Correct Answer: workability
Explanation: The slump test is primarily used to assess the workability of fresh concrete. It provides information about the consistency and flowability of the concrete mix, helping to ensure that the mix can be easily handled, placed, and compacted during construction. While the test indirectly reflects some aspects of concrete strength, its main purpose is to evaluate workability.
Correct Answer: 40%
Explanation: Concrete typically gains approximately 40% of its ultimate strength at the age of three days. The early strength development is crucial for demolding and formwork removal in construction activities. However, it’s essential to note that the concrete continues to gain strength over an extended period, reaching higher percentages at later ages.
Correct Answer: 0.65
Explanation: The approximate ratio of the strength of cement concrete at 7 days to that at 28 days is around 0.65. This means that concrete gains a significant portion of its strength within the first 7 days, and the strength continues to increase up to 28 days of curing. The specific ratio may vary based on mix proportions and curing conditions.
Correct Answer: 100%
Explanation: Concrete is generally considered to have achieved its full strength potential at the age of twenty-eight days. The strength gained by concrete at this stage is often used as a reference point for assessing the quality and performance of the concrete mix. While further strength development may occur beyond twenty-eight days, the rate of gain diminishes.
Correct Answer: 1.15
Explanation: The approximate ratio of the strength of cement concrete at 3 months to that at 28 days is around 1.15. This ratio reflects the continued strength development of concrete beyond the initial 28 days of curing. Concrete structures often experience ongoing improvement in strength and durability over extended periods.
Correct Answer: 1.10
Explanation: The approximate ratio of the strength of a larger concrete cube (30 cm) to that of a smaller cube (15 cm) is around 1.10. This ratio is influenced by factors such as the size effect and the distribution of aggregate particles within the concrete mix. Generally, larger concrete specimens tend to exhibit slightly higher strengths compared to smaller specimens.
Correct Answer: 1.2
Explanation: The approximate ratio of the strength of cement concrete at 6 months to that at 28 days is around 1.2. This indicates that concrete continues to gain strength beyond the initial 28 days of curing. The specific ratio can vary based on factors such as mix design, curing conditions, and the type of cement used.
Correct Answer: 1.30
Explanation: The approximate ratio of the strength of cement concrete at 1 year to that at 28 days is around 1.30. This signifies the continued long-term development of strength in concrete. The ratio may vary based on several factors, and the specific requirements of a project determine the importance of the strength achieved at different ages.
Correct Answer: 4.75 mm
Explanation: The size of fine aggregates in concrete is typically specified based on the maximum particle size. The commonly accepted maximum size for fine aggregates is 4.75 mm (or No. 4 sieve size). This ensures that the fine aggregates are suitable for various concrete applications, providing a balance between workability and strength.
Correct Answer: one year
Explanation: Concrete experiences shrinkage as it dries and loses moisture over time. The maximum shrinkage takes place after drying for an extended period, typically around one year. This long-term shrinkage is attributed to the continued moisture loss and structural adjustments within the concrete matrix.
Correct Answer: removal of moisture
Explanation: Shrinkage in cement concrete is influenced by factors such as moisture content. The shrinkage decreases when moisture is added or when the concrete is kept in a moist environment. Adequate curing and moisture retention during the early stages of concrete development can help minimize shrinkage and enhance the overall durability of the structure.
Correct Answer: rounded aggregate
Explanation: Rounded aggregates generally have fewer voids when compacted compared to irregular, angular, or flaky aggregates. The shape of aggregates can influence the workability and density of concrete. Rounded aggregates facilitate better compaction and result in concrete with reduced voids, contributing to improved overall performance.
Correct Answer: rounded aggregate
Explanation: Workability of concrete is influenced by the shape of aggregates. Rounded aggregates provide better workability for a given water content. The smooth surfaces of rounded aggregates allow them to move more freely, resulting in a more fluid and workable concrete mix.
Correct Answer: all of the above
Explanation: An excess of flaky particles in concrete aggregates can have several adverse effects. It may increase the quantity of water and sand needed in the mix, negatively impact the durability of concrete, and concentrations exceeding a certain percentage (commonly more than 15%) are generally considered undesirable.
Correct Answer: nine-fifths of the mean size
Explanation: An aggregate is considered elongated if its greatest dimension (length) is greater than nine-fifths of the mean size. Elongated particles can adversely affect the workability and strength of concrete and may lead to issues such as poor compaction.
Correct Answer: 3/5 mean dimension
Explanation: An aggregate is classified as flaky if its least dimension is less than three-fifths (3/5) of the mean dimension. Flaky particles are undesirable in concrete as they can result in a less workable mix and contribute to weaknesses in the hardened concrete.
Correct Answer: all of the above
Explanation: An excess of thin, flat, or elongated particles in concrete aggregates can reduce workability. Thin particles may increase the water demand, flat particles can lead to segregation, and elongated particles may hinder proper compaction. Therefore, a balanced aggregate shape is crucial for achieving good workability.
Correct Answer: all of the above
Explanation: The grading of sand, which refers to the distribution of particle sizes, can significantly impact various properties of concrete. It influences workability, strength, and durability. Properly graded sand helps achieve a well-balanced concrete mix with desirable properties.
Correct Answer: a horizontal line
Explanation: Gap grading in a grading curve is represented by a horizontal line. Gap grading occurs when certain particle sizes are absent or sparsely represented in the aggregate gradation. This can affect the workability and stability of the concrete mix.
Correct Answer: in single size aggregates, bulk density is maximum
Explanation: The correct statement is that in single size aggregates, bulk density is least. Properly graded aggregates with a mix of different particle sizes tend to have higher bulk density. Single size aggregates, where all particles are of the same size, have lower bulk density due to increased void spaces.
Correct Answer: all of the above
Explanation: The bulk density of aggregates depends on various factors, including the shape of particles, the grading (distribution of particle sizes), and the compaction method. The arrangement and packing of particles influence the overall bulk density of the aggregate.
Correct Answer: kg/liter
Explanation: The bulk density of aggregates is commonly expressed in kilograms per liter (kg/liter). It represents the mass of aggregates per unit volume. The specific units may vary, and other common expressions include kilograms per cubic meter (kg/m³) or grams per cubic centimeter (g/cm³).
Correct Answer: all of the above
Explanation: The risk of segregation in concrete is influenced by various factors, including a wet mix, coarse grading of aggregates, and a larger proportion of the maximum size aggregate. A wet mix can lead to bleeding, and an uneven distribution of coarse aggregates may result in segregation during transportation and placement.
Correct Answer: rounded spherical
Explanation: Rounded spherical aggregates, by their nature, tend to have fewer voids when compacted compared to irregular or flaky aggregates. The shape of aggregates plays a crucial role in the packing density and overall performance of concrete.
Correct Answer: 12.5%
Explanation: The coefficient of variation (CV) is calculated as the ratio of the standard deviation to the mean (average) compressive strength, expressed as a percentage. In this case, (500/4000) * 100 equals 12.5%. The coefficient of variation provides a measure of the relative variability or dispersion of the compressive strength values.
Correct Answer: all of the above
Explanation: Batching error refers to inaccuracies in the quantity of various ingredients in the concrete mix. It can involve errors in measuring aggregates, cement, water, or any other components. Accurate batching is crucial to ensure the desired properties and performance of the concrete.
Correct Answer: swelling of sand when wetted
Explanation: Bulking of sand refers to the increase in volume or swelling of sand particles when they are saturated with water. The presence of moisture causes the sand particles to separate and occupy a larger volume, affecting the accurate measurement of sand in a moist condition. This phenomenon is important to consider during concrete mix design to account for the bulking effect when determining the correct proportions.
Correct Answer: graded aggregates
Explanation: Graded aggregates, where the sizes of particles are distributed in a well-graded manner, are commonly used to ensure the quality of concrete. Proper grading helps in achieving a dense and workable concrete mix with improved strength and durability.
Correct Answer: shear strength
Explanation: The allowable shear stress of concrete depends upon its shear strength. Shear strength is an important property of concrete in resisting forces acting parallel to the surface. It is influenced by factors such as concrete mix design, curing conditions, and the presence of reinforcement.
Correct Answer: 150 kg/cm2
Explanation: The permissible compressive strength of M 150 concrete grade is 150 kg/cm2. Concrete grades are specified based on their compressive strength, and M 150 indicates a mix design with a characteristic compressive strength of 150 kg/cm2.
Correct Answer: controlling setting time
Explanation: Gypsum is added to cement during the manufacturing process to control the setting time. It acts as a retarder, slowing down the setting of cement. This is important for providing sufficient time for concrete placement and finishing.
Correct Answer: 5%
Explanation: The cement becomes compromised and less effective if its absorbed moisture content exceeds 5%. Excessive moisture can lead to clumping and affect the performance of the cement in concrete applications.
Correct Answer: decreases
Explanation: The strength of cement tends to decrease with the passage of time. This is particularly true if cement is improperly stored, exposed to moisture, or if it ages over an extended period.
Correct Answer: increases
Explanation: The strength of concrete generally increases with the passage of time due to the ongoing hydration process. Proper curing and adequate time allow the concrete to gain strength and achieve its design compressive strength.
Correct Answer: 75 mm
Explanation: An aggregate is known as a cyclopean aggregate if its size is more than 75 mm. Cyclopean aggregates are larger-sized aggregates commonly used in mass concrete constructions.
Correct Answer: saturated surface dry aggregate
Explanation: Saturated surface dry (SSD) aggregate refers to aggregates that have absorbed moisture into their pores but have a dry surface. SSD condition is commonly used in concrete mix design to account for the water content absorbed by aggregates.
Correct Answer: abrasion resistance
Explanation: The Los Angeles machine is used to test the abrasion resistance of aggregates. The test involves subjecting aggregates to abrasion, impact, and grinding actions to determine their resistance to wear and tear.
Correct Answer: fine sand
Explanation: The fineness modulus (FM) is a measure of the fineness or coarseness of sand. A fineness modulus of 2.5 indicates fine sand. The classification ranges from very fine sand (lower FM) to coarse sand (higher FM).
Correct Answer: 50%
Explanation: To obtain aggregates with a fineness modulus (FM) of 5.4, a combination of aggregates with different FM is required. In this case, the percentage of aggregate with FM 2.6 to be combined with coarse aggregate (FM 6.8) is 50%.
Correct Answer: both of the above
Explanation: The moisture content of aggregates can be determined by both the displacement method and the drying method. The displacement method involves measuring the volume of water displaced by the aggregate, while the drying method involves drying the aggregate and measuring the loss of weight.
Correct Answer: both (a) and (b) of the above
Explanation: The water-cement ratio can be expressed either as the volume of water to the volume of cement or as the weight of water to the weight of cement. Both expressions are commonly used to specify the water-cement ratio in concrete mix design.
Correct Answer: 50 kg
Explanation: The water-cement ratio is generally expressed as the volume of water required per unit weight of cement. A common convention is to express it in terms of the volume of water required for 50 kg of cement.
Correct Answer: Lean mix of concrete possesses higher strength than that of a rich mix of concrete
Explanation: The statement is incorrect. In concrete, a rich mix (higher cement content) generally possesses higher strength than a lean mix. The strength of concrete is influenced by factors such as the water-cement ratio, curing conditions, and the quality of materials.
Correct Answer: -11.7°C
Explanation: The datum temperature for maturity by Plowman is -11.7°C. Maturity in concrete refers to the total exposure to a combination of time and temperature. It is an indicator of the concrete’s progress towards achieving its ultimate strength.
Correct Answer: Maturity of concrete
Explanation: The summation of the product of time and temperature of concrete is referred to as the maturity of concrete. Maturity is a measure that considers the effect of both time and temperature on the development of concrete strength.
Correct Answer: Thick and heavily reinforced
Explanation: Higher workability is generally required for concrete structures that are thick and heavily reinforced. Adequate workability ensures that the concrete can flow easily and be properly placed around densely packed reinforcement, reducing the likelihood of voids and achieving good compaction.
Correct Answer: Hardness
Explanation: A concrete mix that causes difficulty in obtaining a smooth finish is known to possess hardness. Hard concrete mixes can be challenging to finish and may require special techniques or additives to improve workability and finishability.
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