Basic Concrete Technology - Pre-training Analysis

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Basic Concrete Technology - Pre-training Analysis - Quiz

A simple survey to analyse the current level of knowledge and to create interest towards the intended training. Session.


Questions and Answers
  • 1. 

    Why are normal cement normally called "Portland" Cement?

    • A.

      It was named after the inventor

    • B.

      It is the name of a type of limestone in England

    • C.

      In the olden days, it was used for ports

    • D.

      It contains portland as part of its ingredients

    • E.

      The hydration process produces portland as a by-product

    Correct Answer
    B. It is the name of a type of limestone in England
    Explanation
    Normal cement is called "Portland" Cement because it is named after a type of limestone found in Portland, England. This specific type of limestone, known as Portland stone, was commonly used in the production of cement due to its high quality and durability. The name "Portland" Cement was adopted to distinguish it from other types of cement and to indicate its origin.

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  • 2. 

    The basic ingredients for making concrete are: (tick all that apply)

    • A.

      Cement

    • B.

      Sand

    • C.

      Stones

    • D.

      Water

    Correct Answer(s)
    A. Cement
    B. Sand
    C. Stones
    D. Water
    Explanation
    The basic ingredients for making concrete include cement, sand, stones, and water. Cement acts as a binding agent that holds the other ingredients together. Sand is used to provide strength and stability to the concrete mixture. Stones, also known as aggregates, are added to increase the strength and durability of the concrete. Water is necessary to activate the cement and allow it to harden, forming a solid structure. All of these ingredients are essential in the concrete-making process to ensure a strong and durable final product.

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  • 3. 

    The following are basic characteristics of concrete: (tick all that apply)

    • A.

      Strong in compression

    • B.

      Strong in tension

    • C.

      Workable before hardening

    • D.

      Less resistant to fire (compared to steel)

    • E.

      Can be moulded into almost any shape

    Correct Answer(s)
    A. Strong in compression
    C. Workable before hardening
    E. Can be moulded into almost any shape
    Explanation
    Concrete is known for its strength in compression, meaning it can withstand a significant amount of force pushing on it without breaking. It is also workable before hardening, which means it can be easily shaped and molded into different forms. Additionally, concrete has the ability to be molded into almost any shape, making it a versatile material for construction and design purposes. However, concrete is not strong in tension, meaning it is not as resistant to forces that pull or stretch it. It is also less resistant to fire compared to steel, as steel has a higher melting point.

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  • 4. 

    What is "Cast-in-situ" concrete?

    • A.

      Concrete is casted in one location only.

    • B.

      One continuous pour without any construction joints.

    • C.

      Refers to concrete already casted in its place in the formwork.

    • D.

      Concrete is poured directly into where it forms the structure

    Correct Answer
    D. Concrete is poured directly into where it forms the structure
    Explanation
    "Cast-in-situ" concrete refers to the practice of pouring concrete directly into the location where it will form the structure. This means that the concrete is not precast or transported from another location, but rather poured on-site. This method allows for greater flexibility in terms of design and construction, as the concrete can be shaped and formed to fit the specific requirements of the structure. Additionally, casting the concrete in place eliminates the need for construction joints, resulting in a more seamless and continuous pour.

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  • 5. 

    Which of the following statements are true about Precast Concrete? (Check all that apply)

    • A.

      They are normally manufactured in a factory

    • B.

      They are transported to site to form part or whole of a structure

    • C.

      They can only be used for non-structural (i.e. not designed to carry loads) structures

    • D.

      They can also be precasted on site

    Correct Answer(s)
    A. They are normally manufactured in a factory
    B. They are transported to site to form part or whole of a structure
    D. They can also be precasted on site
    Explanation
    Precast concrete is typically manufactured in a factory and then transported to the construction site to be used as part or the entirety of a structure. Additionally, precast concrete can also be casted on-site if necessary.

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  • 6. 

    Which of the following statements are true about Prestressed Concrete? (Check all that apply)

    • A.

      They are normally manufactured in a factory

    • B.

      They are transported to site to form part or whole of a structure

    • C.

      They can only be used for non-structural (i.e. not designed to carry loads) structures

    • D.

      They contain prestressed cables

    Correct Answer(s)
    A. They are normally manufactured in a factory
    B. They are transported to site to form part or whole of a structure
    D. They contain prestressed cables
    Explanation
    Prestressed concrete is a type of concrete that is manufactured in a factory and then transported to the construction site to form part or the whole structure. It is commonly used for structural purposes as it is designed to carry loads. One of the key features of prestressed concrete is that it contains prestressed cables, which help to enhance its strength and durability. Therefore, the statements "They are normally manufactured in a factory," "They are transported to site to form part or whole of a structure," and "They contain prestressed cables" are all true about prestressed concrete.

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  • 7. 

    What is the difference between cement and concrete

    • A.

      Cement is one of the ingredients in concrete.

    • B.

      Concrete is one of the ingredients in cement.

    • C.

      Concrete is hardened cement.

    • D.

      Concrete contained steel bars.

    Correct Answer
    A. Cement is one of the ingredients in concrete.
    Explanation
    Concrete is a mixture of cement, sand, gravel, and water. Cement is a binding material that is used to hold the other ingredients together in concrete. Therefore, cement is an essential component of concrete, but concrete itself is not an ingredient in cement.

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  • 8. 

    Concrete cannot harden without water.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Concrete is a mixture of cement, water, and aggregates such as sand and gravel. When water is added to the cement, it undergoes a chemical reaction called hydration, which causes it to harden and form a solid mass. Without water, this hydration reaction cannot occur, and therefore concrete cannot harden. Therefore, the statement "Concrete cannot harden without water" is true.

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  • 9. 

    Concrete cannot harden under water.

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Concrete can actually harden under water. In fact, it is often used in underwater construction projects such as bridges and dams. The process of hydration, which is essential for concrete to harden, can occur even in the presence of water. The water actually helps to facilitate the chemical reactions that lead to the hardening of concrete. Therefore, the statement that concrete cannot harden under water is false.

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  • 10. 

    Which are the following statements are true about Hydration of Cement? (Tick all that apply)

    • A.

      It releases heat.

    • B.

      It requires water.

    • C.

      It produces water.

    • D.

      It is a chemical reaction between cement and water.

    • E.

      It is a irreversible process..

    Correct Answer(s)
    A. It releases heat.
    B. It requires water.
    D. It is a chemical reaction between cement and water.
    E. It is a irreversible process..
    Explanation
    Hydration of cement is a chemical reaction between cement and water. This reaction releases heat and requires water for the process to occur. Additionally, hydration of cement is an irreversible process, meaning it cannot be reversed once it has taken place. However, it does not produce water as a product of the reaction.

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  • 11. 

    In the construction industry, what does the term "Aggregates" mean?

    • A.

      Sand

    • B.

      Natural occuring stones

    • C.

      Gravel

    • D.

      Rocks crushed to certain sizes

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    The term "aggregates" in the construction industry refers to a combination of materials used in the production of concrete and other construction materials. These materials can include sand, natural occurring stones, gravel, and rocks that have been crushed to certain sizes. Therefore, the correct answer is "All of the above" as all of these materials are commonly used as aggregates in construction projects.

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  • 12. 

    Which of the following shapes of aggregates produces the best workability in concrete?

    • A.

      Rounded

    • B.

      Angular

    • C.

      Irregular

    • D.

      Flaky

    • E.

      Elongated

    Correct Answer
    A. Rounded
    Explanation
    Rounded shapes of aggregates produce the best workability in concrete because they have a smoother surface and better particle packing, allowing for better flow and ease of placement. The rounded shape also reduces the amount of voids and increases the workability of the concrete mix, making it easier to handle and manipulate during construction. This shape promotes good cohesion and reduces the risk of segregation, resulting in a more uniform and consistent concrete mixture.

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  • 13. 

    What does "Aggregate Grading" means?

    • A.

      The strength of the aggregates.

    • B.

      The distribution of its particle size.

    • C.

      The PH of the aggregates as measured in accordance to standards

    • D.

      The hardness of the aggregates.

    • E.

      The durability of the aggregates.

    Correct Answer
    B. The distribution of its particle size.
    Explanation
    "Aggregate grading" refers to the distribution of particle sizes in a given aggregate. This means that it determines the range of sizes present in the aggregate, as well as the proportion of each size. The grading of aggregates is important in construction materials as it affects the workability, strength, and durability of concrete or asphalt mixtures. A well-graded aggregate has a balanced distribution of particle sizes, which helps in achieving a dense and compact mixture with good mechanical properties.

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  • 14. 

    What is the difference in using bigger or smaller aggregates?

    • A.

      Bigger aggregates results in higher workability.

    • B.

      Smaller aggregates enhance hydration of cement, thus higher strength.

    • C.

      Bigger aggregates prevents honeycombing in concrete

    • D.

      No difference in affecting working with or quality of concrete. Only costs are different.

    Correct Answer
    A. Bigger aggregates results in higher workability.
    Explanation
    Using bigger aggregates in concrete can result in higher workability. Workability refers to the ease with which concrete can be mixed, transported, placed, and compacted without segregation or bleeding. Bigger aggregates provide more space between them, allowing for better flow of the concrete mixture. This increased flowability makes it easier to work with and manipulate the concrete, resulting in higher workability.

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  • 15. 

    Aggregates are divided into either ‘coarse’ or ‘fine’ categories. - Coarse aggregates are particulates that are greater than ...

    • A.

      1.5mm

    • B.

      4.75mm

    • C.

      10.5 mm

    • D.

      20.0mm

    Correct Answer
    B. 4.75mm
    Explanation
    Aggregates are divided into either 'coarse' or 'fine' categories. Coarse aggregates are particulates that are greater than 4.75mm in size.

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  • 16. 

    The shape and surface texture of aggregate influence the ...

    • A.

      Workability of fresh concrete

    • B.

      Compressive strength of hardened concrete

    • C.

      Heat of hydration

    • D.

      Setting time

    Correct Answer(s)
    A. Workability of fresh concrete
    B. Compressive strength of hardened concrete
    Explanation
    The shape and surface texture of aggregate influence the workability of fresh concrete because it affects the flow and ease of placement of the mixture. The shape and texture can either enhance or hinder the ability of the concrete to be easily mixed, transported, and compacted. Additionally, the shape and surface texture of aggregate also play a role in the compressive strength of hardened concrete. A well-graded and properly shaped aggregate can provide better interlocking and bonding with the cement paste, resulting in higher compressive strength.

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  • 17. 

    Common tests for determination of strength of aggregate are...

    • A.

      Aggregate Crushing Value

    • B.

      Aggregate Impact Value

    • C.

      Ten per cent fines value

    • D.

      Le Chatelier Test Value

    Correct Answer(s)
    A. Aggregate Crushing Value
    B. Aggregate Impact Value
    C. Ten per cent fines value
    Explanation
    The common tests for determination of strength of aggregate are Aggregate Crushing Value, Aggregate Impact Value, and Ten per cent fines value. These tests are conducted to assess the resistance of aggregates to crushing, impact, and abrasion. The Aggregate Crushing Value test measures the strength of aggregates under compressive load, while the Aggregate Impact Value test evaluates the toughness of aggregates subjected to impact. The Ten per cent fines value test determines the load required to produce a specific percentage of fines in the aggregates. These tests help in determining the quality and durability of aggregates for use in construction.

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  • 18. 

    The Modulus of Elasticity of aggregate affects...

    • A.

      Creep of concrete

    • B.

      Shrinkage of concrete

    • C.

      Workability of concrete

    • D.

      Slump of concrete

    Correct Answer(s)
    A. Creep of concrete
    B. Shrinkage of concrete
    Explanation
    The Modulus of Elasticity of aggregate affects the creep and shrinkage of concrete. Creep refers to the gradual deformation of concrete under sustained load, and a higher modulus of elasticity of aggregate can result in lower creep. Shrinkage refers to the reduction in volume of concrete due to moisture loss, and a higher modulus of elasticity of aggregate can lead to increased shrinkage. The workability and slump of concrete, on the other hand, are primarily influenced by the water-cement ratio and the use of admixtures, not the modulus of elasticity of aggregate.

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  • 19. 

    The determination of moisture content of an aggregate is necessary in order to...

    • A.

      Determine the net water-cement ratio for a batch of concrete

    • B.

      Calculate the slump when slump test is not available

    • C.

      Estimate workability before actual batching

    • D.

      Determine the heat of hydration of cement

    Correct Answer
    A. Determine the net water-cement ratio for a batch of concrete
    Explanation
    The determination of moisture content of an aggregate is necessary in order to determine the net water-cement ratio for a batch of concrete. This is because the moisture content of the aggregate affects the amount of water that needs to be added to achieve the desired water-cement ratio. If the moisture content is not taken into account, the water-cement ratio may be incorrect, leading to issues with the strength and durability of the concrete.

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  • 20. 

    Bulking of fine aggregate refers to...

    • A.

      The increase in the volume of a given mass of fine aggregate caused by the presence of water

    • B.

      The overloading of fine aggregate in lorries for mass production of concrete

    • C.

      The ratio of fine aggregate to coarse aggregate

    • D.

      The estimation of fine aggregate required for a production batch of concrete

    Correct Answer
    A. The increase in the volume of a given mass of fine aggregate caused by the presence of water
    Explanation
    Bulking of fine aggregate refers to the increase in volume of the fine aggregate when it comes in contact with water. This increase in volume is due to the formation of a thin film of water around each particle, which causes them to separate and occupy more space. This phenomenon is important to consider when proportioning concrete mixtures, as it can affect the workability and strength of the concrete.

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  • 21. 

    The materials whose presence may adversely affect the strength, workability and long-term performance of concrete are termed deleterious materials.   These substances found in aggregates can be grouped under the following categories:

    • A.

      Impurities interfering with the process of hydration of cements

    • B.

      Coatings preventing the development of good bond between aggregate and the cement paste

    • C.

      Unsound particles which are weak or bring about chemical reaction between the aggregate and cement paste

    • D.

      Unsoundness of aggregates affecting the ability of the aggregate to resist excessive changes in volume

    Correct Answer(s)
    A. Impurities interfering with the process of hydration of cements
    B. Coatings preventing the development of good bond between aggregate and the cement paste
    C. Unsound particles which are weak or bring about chemical reaction between the aggregate and cement paste
    Explanation
    The materials that may adversely affect the strength, workability, and long-term performance of concrete are called deleterious materials. These substances can be categorized into three groups. Firstly, impurities that interfere with the hydration process of cements. Secondly, coatings that prevent the development of a strong bond between the aggregate and the cement paste. Lastly, unsound particles that are weak or cause a chemical reaction between the aggregate and cement paste. These factors can all have a negative impact on the quality and durability of the concrete.

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  • 22. 

    The aggregate is said to be unsound when...

    • A.

      Volume changes result in the deterioration of concrete

    • B.

      Its strength is solely dependent on cement paste

    • C.

      The ratio between fine and coarse aggregates is too large

    • D.

      It is susceptible to chemical attack

    Correct Answer
    A. Volume changes result in the deterioration of concrete
    Explanation
    When the aggregate undergoes volume changes, such as expansion or contraction, it can cause the concrete to deteriorate. This can happen due to various factors such as temperature changes, moisture absorption, or chemical reactions. These volume changes can lead to cracking, spalling, or loss of structural integrity in the concrete, making it unsound.

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  • 23. 

    Alkali-aggregate reaction (AAR) is the reaction between active silica constituents of the aggregate and alkalies i.e. Na2O and K2O present in the cement.   It can be manifested through:

    • A.

      Swelling which results in disruption of concrete with the spreading of pattern cracks and eventual failure of the concrete structures

    • B.

      Low slump values affecting the workability of concrete contributing to the occurrence of honeycombs

    • C.

      Low early strength

    • D.

      High water requirements which directly affect concrete strength

    Correct Answer
    A. Swelling which results in disruption of concrete with the spreading of pattern cracks and eventual failure of the concrete structures
    Explanation
    Alkali-aggregate reaction (AAR) occurs when the active silica constituents in the aggregate react with alkalies present in the cement. This reaction can cause swelling, leading to the disruption of concrete and the development of pattern cracks. Over time, if left untreated, this can result in the failure of concrete structures. Therefore, the correct answer is swelling, which leads to the disruption of concrete with the spreading of pattern cracks and eventual failure of the structures.

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  • 24. 

    The larger the maximum size of the aggregate, the smaller is the cement requirement for a particular water-cement ratio.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    This statement is true because the maximum size of the aggregate refers to the largest particle size used in the concrete mix. When larger aggregates are used, they occupy more space and reduce the amount of cement needed to fill the gaps between the particles. This means that for a given water-cement ratio, the larger the maximum size of the aggregate, the smaller the amount of cement required. This is beneficial as it can help reduce costs and improve the workability and strength of the concrete mixture.

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  • 25. 

    The maximum size of aggregate influences the compressive strength of concrete in that, for a particular volume of aggregate, the compressive strength tends to increase with the decrease in the size of the coarse aggregate.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    The explanation for the given correct answer is that when the maximum size of aggregate is decreased, it allows for more surface area of the aggregate to be in contact with the cement paste. This increased surface area leads to better bonding between the aggregate and the paste, resulting in a stronger concrete. Additionally, a smaller maximum size of aggregate reduces the likelihood of voids or weak points in the concrete, further enhancing its compressive strength. Therefore, it is true that the compressive strength of concrete tends to increase with the decrease in the size of the coarse aggregate.

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  • 26. 

    Proper grading of aggregate will result in...

    • A.

      Dense concrete and needs less quantity of fine aggregate and cement paste

    • B.

      Higher workability that will lead to higher strength

    • C.

      Higher resistance to chemical attacks on concrete thus protecting the reinforcement and increase its durability

    • D.

      More sound aggregates directly producing more volume stability

    Correct Answer
    A. Dense concrete and needs less quantity of fine aggregate and cement paste
    Explanation
    Proper grading of aggregate will result in dense concrete because the different sizes of aggregate fill in the gaps between each other, reducing the amount of voids in the mixture. This denser concrete requires less quantity of fine aggregate and cement paste to fill the voids, resulting in cost savings and improved efficiency.

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  • 27. 

    Which type of water is generally considered to be suitable for mixing in concrete?

    • A.

      Potable Water

    • B.

      River Water

    • C.

      Effluents from sewerage works

    • D.

      Water containing large quantities of chlorides

    Correct Answer
    A. Potable Water
    Explanation
    Potable water is generally considered to be suitable for mixing in concrete. This is because it is clean and safe for drinking, meaning it is free from harmful contaminants that could potentially affect the quality and strength of the concrete. Using potable water ensures that the concrete mixture is not compromised and will have the desired properties for construction purposes.

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  • 28. 

    An admixture that is used to speed up the initial set of concrete is called

    • A.

      An accelerator

    • B.

      A retarder

    • C.

      An air-entraining agent

    • D.

      A water-reducing admixture

    Correct Answer
    A. An accelerator
    Explanation
    The correct answer is an accelerator. An accelerator is an admixture that is added to concrete to speed up the initial set, allowing it to harden and gain strength more quickly. This is especially useful in cold weather conditions or when a faster construction timeline is desired. Retarders, on the other hand, slow down the setting time of concrete, while air-entraining agents are used to create air bubbles in the concrete to increase its durability. Water-reducing admixtures, as the name suggests, are used to reduce the amount of water needed in the concrete mix.

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  • 29. 

    Retarding admixture or retarder...

    • A.

      Slows down the initial rate of hydration of cement

    • B.

      Prolong the setting of the cement paste in concrete

    • C.

      Affect the 28-day strength

    • D.

      Enhance the chemical resistance of concrete

    Correct Answer(s)
    A. Slows down the initial rate of hydration of cement
    B. Prolong the setting of the cement paste in concrete
    Explanation
    A retarding admixture or retarder is a substance that is added to cement to slow down the initial rate of hydration. This means that it delays the chemical reaction between the cement and water, which is necessary for the cement to harden and set. By slowing down the hydration process, the setting of the cement paste in concrete is prolonged, allowing for more time to work with the material before it becomes solid. The retarder does not directly affect the 28-day strength of the concrete, but it can indirectly impact it by allowing for better control over the curing process. Additionally, a retarder can enhance the chemical resistance of concrete by reducing the permeability and increasing durability.

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  • 30. 

    Benefits of using water-reducing admixtures are

    • A.

      Higher workability

    • B.

      Increased strength

    • C.

      Increased density

    • D.

      Increased chemical resistance

    Correct Answer(s)
    A. Higher workability
    B. Increased strength
    C. Increased density
    Explanation
    Water-reducing admixtures are additives that can be used in concrete to improve its performance. These admixtures have several benefits, including higher workability, increased strength, and increased density. Higher workability means that the concrete is easier to mix, place, and finish, making the construction process more efficient. Increased strength means that the concrete will be more durable and able to withstand greater loads. Increased density results in a more compact and less porous concrete, which improves its durability and resistance to chemicals. Overall, the use of water-reducing admixtures improves the quality and performance of the concrete.

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  • 31. 

    Some of the advantages of using fly ash in concrete are:

    • A.

      Improved workability with lesser amount of water

    • B.

      Lower heat of hydration and thermal shrinkage

    • C.

      Improved resistance to attack from salts and sulphates from soils and sea water

    • D.

      Increased early strength in concrete resulting from the fineness of fly ash

    Correct Answer(s)
    A. Improved workability with lesser amount of water
    B. Lower heat of hydration and thermal shrinkage
    C. Improved resistance to attack from salts and sulphates from soils and sea water
    Explanation
    Fly ash in concrete offers several advantages. Firstly, it improves workability, allowing for a smoother and easier placement of the concrete with a reduced amount of water. This not only enhances the construction process but also improves the overall quality of the concrete. Additionally, fly ash lowers the heat of hydration, minimizing the risk of thermal shrinkage and cracking. It also enhances the concrete's resistance to salts and sulphates found in soils and sea water, making it more durable in harsh environments. Lastly, the fineness of fly ash contributes to increased early strength in concrete, further enhancing its performance.

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  • 32. 

    The advantages of using Ground Granulated Blast-furnace Slag (GGBS) are...

    • A.

      Lower rate of heat evolution

    • B.

      Refined pore structure

    • C.

      Reduced permeability

    • D.

      Improved resistance to sulphate attack

    • E.

      Higher workability compared to when fly ash is used instead of GGBS

    Correct Answer(s)
    A. Lower rate of heat evolution
    B. Refined pore structure
    C. Reduced permeability
    D. Improved resistance to sulphate attack
    Explanation
    GGBS has a lower rate of heat evolution, meaning that it generates less heat during the curing process. This is advantageous because it reduces the risk of thermal cracking in concrete structures. GGBS also has a refined pore structure, which improves the durability and strength of the concrete. The reduced permeability of GGBS means that it is less likely to absorb water and other harmful substances, increasing its resistance to deterioration. Additionally, GGBS improves the concrete's resistance to sulphate attack, which is important in environments where the concrete is exposed to sulphates. Compared to using fly ash, GGBS provides higher workability, making it easier to handle and place in construction.

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  • 33. 

    Concrete workability can be measured through the following tests:

    • A.

      Slump test

    • B.

      Compacting factor test

    • C.

      Vee-Bee consistency test

    • D.

      Flow test

    • E.

      Mortar prism test

    Correct Answer(s)
    A. Slump test
    B. Compacting factor test
    C. Vee-Bee consistency test
    D. Flow test
    Explanation
    Concrete workability refers to the ease with which concrete can be mixed, placed, and compacted. The slump test measures the consistency of fresh concrete by measuring the slump or settlement of a cone-shaped sample. The compacting factor test determines the workability of concrete by measuring the degree of compaction achieved by a standard amount of work. The Vee-Bee consistency test measures the time taken for a vibrating table to achieve a certain level of compaction. The flow test measures the flowability of concrete by determining the time it takes for a specified volume of concrete to flow through a standardized apparatus. These tests collectively provide a comprehensive assessment of concrete workability.

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  • 34. 

    Slump test is conducted in the following way: The slump cone is placed on a horizontal and non-absorbent surface and filled in __________ equal layers of fresh concrete, each layer being tamped _________times with a standard tamping rod.

    • A.

      3, 25

    • B.

      5, 55

    • C.

      7, 75

    • D.

      3, 55

    Correct Answer
    A. 3, 25
    Explanation
    The correct answer is 3, 25. In the slump test, the slump cone is filled in 3 equal layers of fresh concrete. Each layer is then tamped 25 times with a standard tamping rod.

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  • 35. 

    Slump test is suitable only for concretes of medium to high workabilities. This refers to slump values of...

    • A.

      25 mm to 125 mm

    • B.

      100 mm to 200 mm

    • C.

      125 mm to 250 mm

    • D.

      150 mm to 300 mm

    Correct Answer
    A. 25 mm to 125 mm
    Explanation
    The slump test is a method used to measure the workability of concrete, which refers to its ability to flow and be easily molded. The test involves filling a cone-shaped container with concrete and then removing the cone to see how much the concrete slumps or settles. A slump value of 25 mm to 125 mm indicates a medium to high workability, meaning that the concrete is easily moldable and can flow well. Slump values outside of this range may indicate either very low or very high workabilities, which may not be suitable for certain construction applications.

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  • 36. 

    This picture shows a machine for testing...

    • A.

      Compressive strength

    • B.

      Tensile strength

    • C.

      Flexural strength

    • D.

      Workability

    Correct Answer
    A. Compressive strength
    Explanation
    The picture shows a machine for testing compressive strength. This type of machine is specifically designed to measure the maximum amount of compressive force that a material can withstand before it breaks or fails. It is commonly used in construction and engineering to test the strength of materials such as concrete, brick, or stone. By applying a compressive force to the material and measuring the resulting deformation or failure, engineers can determine its compressive strength and ensure its suitability for various applications.

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  • 37. 

    This diagramme shows that...

    • A.

      Compressive strength is inversely proportionate to water-cement ratio

    • B.

      Water-cement ratio does not affect compressive strength

    • C.

      Compressive strength is directly proportionate to water-cement ratio

    • D.

      There is very little relationship between water-cement ration and compressive strength.

    Correct Answer
    A. Compressive strength is inversely proportionate to water-cement ratio
    Explanation
    The diagram shows that as the water-cement ratio increases, the compressive strength decreases. This means that there is an inverse relationship between the water-cement ratio and the compressive strength of the material. As more water is added to the mixture, the strength of the material decreases. Conversely, as the water-cement ratio decreases, the compressive strength increases. Therefore, the correct answer is that compressive strength is inversely proportionate to water-cement ratio.

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  • 38. 

    Which of the following resemble the stress-strain curve for concrete?

    • A.

      Option 1

    • B.

      Option 2

    • C.

      Option 3

    Correct Answer
    A. Option 1
  • 39. 

    Concrete creep is defined as

    • A.

      Deformation of structure under sustained load

    • B.

      Deformation of structure under tensile loads

    • C.

      Cracks due to rapid evaporation of water from the surface of concrete

    • D.

      Permeability formed due to lack of compaction

    Correct Answer
    A. Deformation of structure under sustained load
    Explanation
    Concrete creep is the gradual deformation or movement of a concrete structure over time when it is subjected to sustained or long-term loads. This deformation occurs even when the applied load is within the elastic limit of the concrete. It is a result of the internal rearrangement of the concrete particles and the relaxation of the internal stresses within the material. Creep can cause the structure to gradually change shape, leading to potential issues such as excessive deflection or cracking over time.

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  • 40. 

    Plastic Shrinkage can be described as...

    • A.

      Being due to loss of water by evaporation from the surface of concrete

    • B.

      Having the possibility of causing surface cracking

    • C.

      The result of adding too much water into concrete resulting in low slump

    • D.

      The the loss of plasticity due to omission of using plasticizers

    Correct Answer(s)
    A. Being due to loss of water by evaporation from the surface of concrete
    B. Having the possibility of causing surface cracking
    Explanation
    Plastic shrinkage occurs when water is lost through evaporation from the surface of concrete. This loss of water can lead to the concrete surface drying out faster than the interior, causing shrinkage and potential cracking. Therefore, plastic shrinkage has the possibility of causing surface cracking.

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  • 41. 

    The following statements are correct about Drying Shrinkage

    • A.

      The shrinkage that takes place after the concrete has set and hardened.

    • B.

      Most of it takes place in the first few months of casting.

    • C.

      It is caused by the withdrawal of water from concrete stored in unsaturated air voids.

    • D.

      It happens when the mix is too dry and happens always to concrete mix of low slump.

    Correct Answer(s)
    A. The shrinkage that takes place after the concrete has set and hardened.
    B. Most of it takes place in the first few months of casting.
    C. It is caused by the withdrawal of water from concrete stored in unsaturated air voids.
    Explanation
    Drying shrinkage refers to the shrinkage that occurs in concrete after it has set and hardened. This shrinkage primarily occurs in the first few months after casting. It is caused by the withdrawal of water from the concrete, which is stored in unsaturated air voids. Drying shrinkage is more likely to occur when the concrete mix is too dry and has a low slump.

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  • 42. 

    The following statements are correct about Permeability of Concrete:

    • A.

      It happens when excess water in concrete evaporates leaving voids inside the concrete element creating capillaries.

    • B.

      It affects the volume of moisture which may pass through the concrete

    • C.

      It can be avoided through proper selection of ingredients and mix proportioning

    • D.

      It can be reduced by using low heat cement instead of Ordinary Portland Cement

    Correct Answer(s)
    A. It happens when excess water in concrete evaporates leaving voids inside the concrete element creating capillaries.
    B. It affects the volume of moisture which may pass through the concrete
    C. It can be avoided through proper selection of ingredients and mix proportioning
    Explanation
    Permeability of concrete refers to the ability of water or moisture to pass through it. Excess water in concrete evaporates, leaving voids inside the concrete element, which creates capillaries. These capillaries allow moisture to enter and pass through the concrete, affecting its volume. However, permeability can be avoided by properly selecting ingredients and mix proportioning. Additionally, using low heat cement instead of Ordinary Portland Cement can help reduce permeability.

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  • 43. 

    A durable concrete is one that performs satisfactorily under anticipated exposure (working) conditions during its service life span.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    The statement is true because a durable concrete is designed to withstand the expected conditions it will be exposed to during its lifespan. This means that it will maintain its strength, integrity, and performance over time, even when subjected to various environmental factors such as temperature changes, moisture, chemical exposure, and mechanical stress. By ensuring that the concrete can withstand these anticipated conditions, it will have a longer service life and require less maintenance or repair.

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  • 44. 

    One of the main characteristics influencing the durability of concrete is its permeability to the ingress of water, oxygen, carbon dioxide, chloride, sulphate and other potentially deleterious substances.  And the permeability of concrete depends upon:

    • A.

      Micro cracks developed during production and service

    • B.

      Macro cracks developed during production and service

    • C.

      Voids developed during production and service

    • D.

      How well curing is carried out

    Correct Answer(s)
    A. Micro cracks developed during production and service
    B. Macro cracks developed during production and service
    C. Voids developed during production and service
    Explanation
    The permeability of concrete depends on the presence of micro cracks, macro cracks, and voids that develop during both the production and service of the concrete. These cracks and voids provide pathways for water, oxygen, carbon dioxide, chloride, sulphate, and other potentially harmful substances to penetrate the concrete, leading to its deterioration over time. Therefore, the presence and extent of these cracks and voids greatly influence the durability of the concrete. Additionally, the effectiveness of curing also plays a role in reducing permeability and enhancing the durability of the concrete.

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  • 45. 

    Most of the durability problems in the concrete can be attributed to the volume change in the concrete.  Volume change in concrete is caused by many factors.  Among them are:

    • A.

      Heat of hydration

    • B.

      Sulphate attack

    • C.

      Corrosion of steel reinforcement

    • D.

      Type of mixer used

    Correct Answer(s)
    A. Heat of hydration
    B. Sulphate attack
    C. Corrosion of steel reinforcement
    Explanation
    The durability problems in concrete can be attributed to volume change, which is caused by various factors including heat of hydration, sulphate attack, and corrosion of steel reinforcement. These factors contribute to the deterioration of the concrete over time, leading to cracks, spalling, and other forms of damage. The heat of hydration refers to the heat generated during the chemical reaction between cement and water, which can cause expansion and cracking. Sulphate attack occurs when sulphate ions from external sources react with the components of the concrete, leading to expansion and weakening. Corrosion of steel reinforcement can also cause volume change as the steel rusts and expands, exerting pressure on the surrounding concrete. The type of mixer used may also affect the volume change, but it is not as significant as the other factors mentioned.

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  • 46. 

    In the quality control management of concrete, the concept of standard deviation (SD)  is commonly used.  If the value of SD is very low, it means very good control.  And if it increases, it means the level of control slackens.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    A low standard deviation in the quality control management of concrete indicates that the measurements or test results are very close to the mean or target value, suggesting that there is a high level of control and consistency in the production process. On the other hand, an increase in the standard deviation implies that the measurements or test results are more spread out from the mean, indicating a lower level of control and potentially greater variability in the concrete quality. Therefore, the statement "If the value of SD is very low, it means very good control. And if it increases, it means the level of control slackens" is true.

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  • 47. 

    According to European Standards EN 206, the notation C 25/30 means

    • A.

      C denotes normal and heavy-weight concretes

    • B.

      C denotes light weight concrete

    • C.

      25 denotes cylinder strength and 35 denotes cube strength

    • D.

      25 denotes cube strength and 35 denotes cyclinder strength

    Correct Answer(s)
    A. C denotes normal and heavy-weight concretes
    C. 25 denotes cylinder strength and 35 denotes cube strength
    Explanation
    The correct answer is C denotes normal and heavy-weight concretes, 25 denotes cylinder strength and 35 denotes cube strength. According to European Standards EN 206, the notation C 25/30 is used to classify normal and heavy-weight concretes. The number 25 represents the cylinder strength of the concrete, while the number 30 represents the cube strength. This notation is commonly used in the construction industry to specify the strength and type of concrete to be used in a project.

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  • 48. 

    The name of this test is

    • A.

      Rebound Hammer Test

    • B.

      Ultrasonic Pulse Velocity (UPV) Test

    • C.

      Air-void System Test

    • D.

      Rapid Analysis Machine (RAM) Test

    Correct Answer
    A. Rebound Hammer Test
    Explanation
    The correct answer is Rebound Hammer Test. This test is used to assess the compressive strength of concrete by measuring the rebound of a spring-loaded hammer when it impacts the concrete surface. It provides an indication of the concrete's quality and can be used to evaluate the uniformity of concrete within a structure. The rebound value is then correlated with the compressive strength of the concrete. This test is widely used in construction and is non-destructive, making it a convenient method for assessing concrete strength on-site.

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  • 49. 

    The name of this equipment is:

    • A.

      Ultrasonic Pulse Velocity (UPV) Equipment

    • B.

      Schmidt hammer

    • C.

      Impact-echo Test Apparatus

    • D.

      Cover meter

    Correct Answer
    A. Ultrasonic Pulse Velocity (UPV) Equipment
    Explanation
    The correct answer is Ultrasonic Pulse Velocity (UPV) Equipment. This equipment is used to measure the velocity of ultrasonic pulses through a material, which can provide information about the material's quality, integrity, and potential defects. It is commonly used in construction and civil engineering to assess the strength and durability of concrete structures. The UPV equipment typically consists of a transmitter, receiver, and display unit, and it works by sending ultrasonic waves into the material and measuring the time it takes for the waves to travel through it.

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