Correct Answer: Option ⓐ
Explanation: The amount of insoluble residue and residual retained on the IS90 sieve for Ordinary Portland Cement (OPC) typically ranges around 1.5% and 10%, respectively, reflecting the permissible levels of impurities and residue content in the cement, ensuring its quality and adherence to standard specifications and requirements.
Correct Answer: Option ⓓ
Explanation: All the options are correct. Normally, concreting is done above 20°C, the optimum temperature for concreting is 27°±2°, and the consistency test is indeed done at a temperature of 25°C to 29°C.
Correct Answer: Option ⓒ
Explanation: Gypsum is added to cement to slow down the fast reacting property of tricalcium aluminate, which helps in controlling the setting time of cement and prevents the development of early strength.
Correct Answer: Option ⓒ
Explanation: Limestone is the most commonly used raw material in the manufacture of cement. It is a crucial component that provides the necessary calcium for the chemical reactions that occur during the production of cement.
Correct Answer: Option ⓓ
Explanation: All the options are true. A good quality cement typically has a gray color, feels cool to the touch when thrusting one’s hand in the cement bag, and is smooth when rubbed between fingers.
Correct Answer: Option ⓐ
Explanation: The strength of cement typically remains at 100% up to three months, reflecting its ability to maintain its compressive strength without any significant reduction during this initial period after curing.
Correct Answer: Option ⓑ
Explanation: The strength of cement may reduce by approximately 30% after six months, indicating a gradual decline in its compressive strength over an extended period after the initial curing phase.
Correct Answer: Option ⓐ
Explanation: Water absorption of cement should ideally not be more than 5%, ensuring its resistance to moisture and water penetration, which can otherwise lead to degradation and loss of strength over time.
Correct Answer: Option ⓒ
Explanation: The initial setting of cement is primarily caused by the formation of tricalcium aluminate, which triggers the process of hydration, leading to the initial development of strength and the setting of the cement paste.
Correct Answer: Option ⓑ
Explanation: Cement typically contains the maximum percentage of lime (calcium oxide) among the options listed. Lime is a key ingredient that contributes to the hydration process and the binding properties of cement paste.
Correct Answer: Option ⓑ
Explanation: As per IS specification, the minimum time for the initial setting of ordinary Portland cement is 30 minutes, indicating the standard duration for the cement to attain its initial rigidity after the addition of water.
Correct Answer: Option ⓒ
Explanation: As per IS specification, the maximum final setting time for ordinary Portland cement is 10 hours, reflecting the defined duration for the completion of the setting process and the attainment of its final strength and rigidity after the addition of water.
Correct Answer: Option ⓒ
Explanation: Undesirable properties of cement are often attributed to the formation of tricalcium aluminate, which can lead to the development of certain characteristics that might impact the performance and quality of the cement in various construction applications.
Correct Answer: Option ⓑ
Explanation: The setting and hardening of cement after the addition of water primarily occur due to the hydration and hydrolysis of some constituent compounds of cement, which act as a glue, facilitating the bonding of cement particles and the development of strength and rigidity over time.
Correct Answer: Option ⓐ
Explanation: A type of cement is considered good if it contains a large amount of C3S (tricalcium silicate), as this compound contributes significantly to the development of early strength and the overall strength characteristics of the cement.
Correct Answer: Option ⓐ
Explanation: The constituents of cement that act as binders are typically dicalcium silicate and tricalcium silicate, as these compounds play a crucial role in the binding and cementing process that occurs during the hydration and setting of cement paste.
Correct Answer: Option ⓒ
Explanation: A slow-setting cement often has a higher percentage of dicalcium silicate, which contributes to its delayed setting time and allows for more extended workability and placement time during construction activities.
Correct Answer: Option ⓓ
Explanation: Alite, belite, and celite are the normally bogus compounds found in cement during the burning process. These compounds can impact the quality and properties of the cement, affecting its performance in different applications.
Correct Answer: Option ⓑ
Explanation: When water is added to cement, the cement hydrates, and chemical reactions take place while cement is setting, resulting in an increase in temperature and the generation of a significant quantity of heat. This phenomenon is known as the hydration of cement.
Correct Answer: Option ⓐ
Explanation: The dormant period (2-5hr) is primarily concerned with the hydration of cement, which is the chemical reaction between cement and water leading to the development of strength and rigidity in the cement paste.
Correct Answer: Option ⓒ
Explanation: Flash setting of cement refers to the stiffening of cement without any significant strength development. It is characterized by the rapid stiffening of the cement paste, which can hinder the workability and placement of the cement during construction activities.
Correct Answer: Option ⓑ
Explanation: The strength of Rapid Hardening Portland Cement (RHPC) for one day is generally equivalent to the strength of Ordinary Portland Cement (OPC) for three days. RHPC is known for its early strength development, making it a suitable option for projects that require rapid setting and early load-bearing capacity.
Correct Answer: Option ⓑ
Explanation: An excess quantity of CaCl2 (>2%) and triethanolamine (>0.06%) admixtures behave like a retarder, as they slow down the setting time of cement, providing extended workability and placement time during construction activities.
Correct Answer: Option ⓓ
Explanation: The possibility of bleeding, segregation, and laitance is reduced by the use of air-entraining agents, which create small air bubbles in the concrete, enhancing its workability and resistance to segregation and bleeding during the construction process.
Correct Answer: Option ⓓ
Explanation: Workability is tested by various methods, including the slump test, vee bee test, and compacting factor (C.F.) test, among others. These tests help evaluate the consistency and flow characteristics of the concrete, providing insights into its workability during placement and compaction.
Correct Answer: Option ⓓ
Explanation: The air-entraining agents in concrete are additives that introduce and stabilize microscopic air bubbles in the concrete, enhancing its workability and durability. Common sources of air-entraining agents include animal fats, natural wood resins, and alkali salts, all of which contribute to the improved properties of the concrete.
Correct Answer: Option ⓑ
Explanation: Among the options listed, calcium chloride is the most commonly used accelerator for concreting. It accelerates the setting time of concrete, enabling faster strength development, which is particularly useful in colder temperatures or when a rapid setting is required for construction projects.
Correct Answer: Option ⓓ
Explanation: The workability of concrete is enhanced when there is an excess of cement, water, or round aggregate. These factors contribute to the overall consistency and ease of handling during the concrete placement and finishing processes, ensuring that the concrete remains easy to use and manipulate.
Correct Answer: Option ⓐ
Explanation: Portland pozzolana cement typically contains 20 to 30% of pozzolana, a finely ground material that is used as a partial substitute for Portland cement. This addition enhances the workability and durability of the cement while reducing the amount of cement needed, making it an environmentally friendly choice.
Correct Answer: Option ⓓ
Explanation: All of the statements are correct. Portland pozzolana cement (PPC) generally gains strength at a slower rate than ordinary Portland cement (OPC), but its ultimate strength is often higher. Additionally, PPC exhibits a higher resistance to chemical attacks, making it a popular choice for various construction applications.
Correct Answer: Option ⓐ
Explanation: Quick-setting cement often contains aluminium sulphate as an additive. This compound accelerates the setting time of the cement, enabling faster strength development, which is particularly beneficial when rapid setting is required for construction projects, such as in underwater structures.
Correct Answer: Option ⓒ
Explanation: In low heat cement, the constituent that is kept to a minimum is tricalcium aluminate. This is done to reduce the heat of hydration during the setting process, preventing potential cracking or damage due to the high heat generated by the cement.
Correct Answer: Option ⓐ
Explanation: The raw materials that have more than a 10% proportion in the manufacture of cement are calcium oxide and silica. These materials are essential components in the production of cement, contributing to its overall strength and durability.
Correct Answer: Option ⓐ
Explanation: Tri-calcium silicate is considered the best cementing material in cement. It is responsible for the initial setting and hardening of cement, providing the necessary adhesive properties that contribute to the strength and durability of the final concrete product.
Correct Answer: Option ⓓ
Explanation: The freshness of cement is determined by several factors, including its lack of lumps, its smooth consistency when rubbed between fingers and thumb, and the cool feeling it gives when the hand is inserted in the bag. These characteristics ensure that the cement is in optimal condition for use in construction projects.
Correct Answer: Option ⓐ
Explanation: The consistency test for cement is typically conducted within the temperature range of 25°C to 29°C. This specific temperature range ensures that the test accurately reflects the consistency of the cement, allowing for precise measurements and reliable results.
Correct Answer: Option ⓐ
Explanation: The consistency test for cement is primarily performed to determine the correct water-cement ratio. This ratio is crucial in ensuring the optimal workability and strength of the cement, allowing for efficient and effective use in various construction applications.
Correct Answer: Option ⓑ
Explanation: In the Vicat apparatus test, for normal consistency, the penetration should typically be between 30 to 35 mm. This range indicates the appropriate water content required to achieve the desired consistency of the cement, ensuring optimal workability during the construction process.
Correct Answer: Option ⓑ
Explanation: Le-Chatelier’s apparatus is primarily used to conduct the soundness test of cement. This test assesses the potential volume change of the cement due to the presence of uncombined lime, which can lead to disruptive and damaging effects, particularly in large structures or under certain environmental conditions.
Correct Answer: Option ⓐ
Explanation: The soundness test of cement primarily determines the quantity of free lime present in the cement. Free lime can have detrimental effects on the performance and durability of cement, leading to potential cracks or damage in the structure over time.
Correct Answer: Option ⓒ
Explanation: In the briquette test, the minimum acceptable seven-day tensile strength of good Portland cement should not be less than 25 kg/cm^2. This ensures the cement’s durability and reliability, indicating its suitability for various construction applications.
Correct Answer: Option ⓒ
Explanation: The seven-day compressive strength of good Portland cement, as determined from the compressive test on cement-sand mortar cubes, should not be less than 175 kg/cm^2. This strength requirement ensures the stability and structural integrity of the cement, making it suitable for various construction projects.
Correct Answer: Option ⓐ
Explanation: The presence of excessive free lime and magnesia in the cement can render the cement unsound, leading to potential cracking or disruption in the structure over time. It is crucial to control the proportion of these components to ensure the overall quality and durability of the cement.
Correct Answer: Option ⓓ
Explanation: The dry process of manufacturing cement has become obsolete primarily because it is slow and costly, results in the production of inferior quality cement, and is challenging to maintain the correct proportions of the constituents. These factors have contributed to the prevalence of the wet process, which is more efficient and effective in producing high-quality cement.
Correct Answer: Option ⓐ
Explanation: Rapid hardening cement achieves early strength primarily due to a larger proportion of lime that is ground finer than in ordinary cement. This characteristic enables the rapid hardening of the cement, ensuring quick strength development and setting, which is beneficial for time-sensitive construction projects.
Correct Answer: Option ⓒ
Explanation: Portland cement manufactured from pure white chalk and clay without any iron oxide content is commonly referred to as white cement. It is primarily used in architectural applications where aesthetic appeal and color consistency are crucial, ensuring a visually appealing and high-quality finish.
Correct Answer: Option ⓑ
Explanation: Tri-calcium aluminate is the constituent of the cement that sets and hardens first upon the addition of water. This property is essential for the initial setting process of the cement, contributing to its adhesive and structural properties, ensuring its stability and durability over time.
Correct Answer: Option ⓐ
Explanation: The moisture content of cement is a critical factor in determining its effectiveness and durability. If the absorbed moisture content of cement exceeds 5%, it can render the cement useless, leading to potential degradation, reduced strength, and compromised performance, particularly in construction applications.
Correct Answer: Option ⓒ
Explanation: In the sieve analysis of the fineness test, the residue on the IS sieve No. 90μ after 15 minutes of sieving should not exceed 10%. This ensures that the cement is finely ground and does not contain excessive coarse particles, ensuring its optimal performance and consistency in various construction applications.
Correct Answer: Option ⓐ
Explanation: Quick setting cement is particularly useful for construction projects involving structures that need to be set quickly, especially in underwater applications where rapid hardening is crucial.
Correct Answer: Option ⓐ
Explanation: The initial and final setting times of ordinary Portland cement are typically 30 minutes and 10 hours, respectively, which are crucial time frames in construction operations.
Correct Answer: Option ⓒ
Explanation: Quick setting cement has considerably shorter initial and final setting times, making it a preferred choice for projects requiring rapid completion and early strength development.
Correct Answer: Option ⓑ
Explanation: Expansive cement is often employed for patching pavement works, primarily due to its ability to counteract the potential cracking and damage caused by temperature fluctuations and seasonal changes.
Correct Answer: Option ⓒ
Explanation: Pozzolana Portland cement generally takes more time than ordinary Portland cement to gain strength, often necessitating careful planning and scheduling during construction activities.
Correct Answer: Option ⓑ
Explanation: Pozzolana Portland cement typically exhibits higher ultimate strength compared to ordinary Portland cement, making it a favorable option for projects where enhanced strength characteristics are desired.
Correct Answer: Option ⓑ
Explanation: The ultimate strength of cement is primarily provided by dicalcium silicate, an essential constituent that contributes significantly to the overall strength development of the cement matrix.
Correct Answer: Option ⓓ
Explanation: In the test for loss on ignition, the cement is subjected to a temperature of 1000°C to determine the precise amount of combustible substances present in it.
Correct Answer: Option ⓑ
Explanation: Loss on ignition in cement should ideally be limited to 4% to ensure the absence of excessive combustible materials that might compromise the overall quality and performance of the cement.
Correct Answer: Option ⓓ
Explanation: The presence of insoluble residues in good cement should be less than 1.5%, indicating the purity and high quality of the cement composition.
Correct Answer: Option ⓑ
Explanation: The volume of one bag of cement weighing 50 kg is typically 0.0347 cubic meters, which is a crucial factor to consider during transportation and storage.
Correct Answer: Option ⓒ
Explanation: Slag cement usually contains a significant amount of sulphate, contributing to its unique properties and performance characteristics, especially in terms of durability and strength.
Correct Answer: Option ⓓ
Explanation: For the determination of the initial setting time, the water to be added is 0.85 times the percentage of water required for normal consistency (P).
Correct Answer: Option ⓒ
Explanation: Poorly mixed cement concrete often leads to the formation of honeycombs, resulting in compromised structural integrity and durability of the concrete.
Correct Answer: Option ⓑ
Explanation: The strength of cement generally decreases with prolonged storage, emphasizing the importance of using fresh cement for ensuring optimal performance and durability of concrete structures.
Correct Answer: Option ⓑ
Explanation: Cement should ideally be stored on a dry platform to prevent the absorption of moisture, which can adversely affect its quality and performance in concrete.
Correct Answer: Option ⓐ
Explanation: The fineness of cement is primarily determined by the air permeability method, which measures the specific surface area of the cement particles.
Correct Answer: Option ⓒ
Explanation: Sand reaches its minimum volume when it is in either an absolutely dry state or an absolutely wet state, highlighting the importance of considering its moisture content during construction.
Correct Answer: Option ⓐ
Explanation: The main constituents of Portland cement include lime, silica, and alumina, which play crucial roles in the overall properties and behavior of the cement.
Correct Answer: Option ⓑ
Explanation: Portland cement is the most commonly used type of cement in general construction due to its versatile properties and widespread availability.
Correct Answer: Option ⓓ
Explanation: The chemical reaction between cement and water, resulting in the formation of a solid matrix, is known as hydration, which is a fundamental process in concrete formation and hardening.
Correct Answer: Option ⓐ
Explanation: Gypsum is the most commonly used retarder in cement, helping to regulate the setting time of the concrete to ensure workability and proper placement during construction.
Correct Answer: Option ⓐ
Explanation: Clay soil, which typically contains silica and alumina, is considered ideal for making bricks due to its plasticity and binding properties when mixed with water.
Correct Answer: Option ⓒ
Explanation: Alkali and kankar are both impurities that are not desirable in soil used for brick formation as they can significantly affect the quality and structural integrity of the resulting bricks.
Correct Answer: Option ⓑ
Explanation: Low porosity in bricks typically indicates high strength, which is a desirable characteristic for ensuring the durability and long-term performance of the brick structures.
Correct Answer: Option ⓑ
Explanation: Silica is the key ingredient in brick earth that enables the brick to retain its shape during the firing process, contributing to the overall strength and stability of the brick.
Correct Answer: Option ⓒ
Explanation: Good brick earth typically contains a percentage of silica ranging between 50% and 60%, contributing to the favorable properties and characteristics of the resulting bricks.
Correct Answer: Option ⓐ
Explanation: The red color of the brick is primarily due to the presence of iron oxide, which gives the brick its characteristic reddish appearance.
Correct Answer: Option ⓑ
Explanation: As per the Nepal Standard (NBC205:2013), the standard size of a brick is 230x115x57 mm³, which is an essential specification for ensuring uniformity and compatibility in construction projects.
Correct Answer: Option ⓒ
Explanation: During the testing of compressive strength, the load is typically applied at the rate of 14 N/mm² per minute to evaluate the structural integrity and load-bearing capacity of the bricks.
Correct Answer: Option ⓑ
Explanation: Good brick earth generally contains a percentage of alumina ranging between 20% and 30%, contributing to the overall plasticity and workability of the brick material during the manufacturing process.
Correct Answer: Option ⓓ
Explanation: Excess silica in brick earth can lead to brittleness, which can compromise the structural integrity and overall performance of the bricks, making them more prone to breakage and damage.
Correct Answer: Option ⓒ
Explanation: Excess alumina in brick earth can lead to cracking and warping during the drying process, affecting the overall shape and structural stability of the bricks, leading to potential defects and performance issues.
Correct Answer: Option ⓐ
Explanation: Alumina in brick earth primarily serves the function of imparting plasticity, making it easier to shape and mold the bricks during the manufacturing process.
Correct Answer: Option ⓑ
Explanation: The process of kneading clay, water, and other ingredients to make a brick is referred to as tempering, which is a crucial step in ensuring the proper consistency and workability of the brick material before molding.
Correct Answer: Option ⓓ
Explanation: The process of mixing sand with the powdered natural soil to enhance the quality and properties of the resulting bricks is commonly known as blending, an important step in achieving the desired characteristics and performance of the bricks.
Correct Answer: Option ⓒ
Explanation: Excessive iron oxide in brick earth can lead to a color change, causing the brick color to shift from red to dark blue, which can impact the overall aesthetic appeal and market value of the bricks.
Correct Answer: Option ⓒ
Explanation: Lime is mixed with brick earth to help prevent shrinkage, ensuring that the bricks maintain their shape and structural integrity during the drying and firing process, minimizing potential defects and deformities.
Correct Answer: Option ⓑ
Explanation: The maximum percentage of water absorption of 1st class bricks in 24 hours should be limited to 15% to ensure that the bricks maintain their structural stability and durability when exposed to moisture.
Correct Answer: Option ⓒ
Explanation: The maximum percentage of water absorption of 2nd class bricks in 24 hours should be limited to 20% to maintain their overall structural integrity and prevent potential damage or degradation caused by excessive moisture absorption.
Correct Answer: Option ⓒ
Explanation: The crushing strength of 1st class bricks should not be less than 105 kg/cm², ensuring that they can withstand the applied load and pressure without undergoing deformation or failure, demonstrating their high load-bearing capacity and durability.
Correct Answer: Option ⓑ
Explanation: The minimum compressive strength of 2nd class bricks should be 70 kg/cm², ensuring that they possess sufficient strength to withstand the expected loads and pressures experienced in construction projects.
Correct Answer: Option ⓑ
Explanation: Bricks are typically burnt at temperatures ranging from 700°C to 1000°C when low melting clay is used, ensuring proper vitrification and structural integrity of the bricks during the firing process.
Correct Answer: Option ⓒ
Explanation: During the burning of dried bricks, the sequence of chemical changes that occur involves dehydration, followed by oxidation and vitrification, ensuring the proper fusion of the clay particles and the formation of a durable and strong brick structure.
Correct Answer: Option ⓒ
Explanation: For burning clay products like sewer pipes, the necessary chemical change that occurs is vitrification, where the clay particles are fused together to form a dense and impermeable structure, ensuring the required strength and durability for the intended application.
Correct Answer: Option ⓑ
Explanation: As per the NS (Nepal Standard), for one cubic meter of brick masonry, the number of machine-made bricks required is 530, providing a standard guideline for the efficient and accurate estimation of material quantities in construction projects.
Correct Answer: Option ⓑ
Explanation: According to the IS (Indian Standard) standard, the number of standard bricks required for one cubic meter of brick masonry is 500, serving as a key reference for ensuring the proper calculation and utilization of bricks in construction activities.
Correct Answer: Option ⓓ
Explanation: The red color obtained by the bricks is primarily due to the presence of iron oxide, which imparts the characteristic reddish hue to the bricks, making them visually appealing and widely used in various construction applications.
Correct Answer: Option ⓑ
Explanation: The soil used for the manufacture of bricks should preferably not contain pebbles, as their presence can negatively impact the structural integrity and overall quality of the bricks, leading to potential defects and performance issues.
Correct Answer: Option ⓒ
Explanation: Tiles are commonly used for covering roofs and flooring as well as for making drains, serving as versatile construction materials that offer durability, aesthetic appeal, and effective water management solutions.
Correct Answer: Option ⓒ
Explanation: As per the NS (Nepal Standard) norms, the amount of local brick required for one cubic meter of masonry is 560, providing a standardized measure for estimating material quantities and ensuring accurate calculations in construction projects.
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