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All questions of Construction Materials for Civil Engineering (CE) Exam
The role of superplasticizer in a cement paste is to- a)disperse the particles, remove air bubbles and to retard setting
- b)disperse the particles and to remove air bubbles
- c)disperse the particles
- d)retard setting
Correct answer is option 'A'. Can you explain this answer?
The role of superplasticizer in a cement paste is to
a)
disperse the particles, remove air bubbles and to retard setting
b)
disperse the particles and to remove air bubbles
c)
disperse the particles
d)
retard setting
 | Gate Gurus answered |
Super plasticizers are improved version of plasticizers and they interact with cement both physically and chemically. They are anionic in nature and impart negative charge on cement particles causing them to disperse and release the entrapped air and water. This makes the mix more workable with less amount of water.
Below figure shows the effect of super plasticizer.
For good bonding in bricks uniform in size- a)all bricks need not be uniform in size .
- b)bats must be used in alternate course only
- c)the vertical joints in alternate course should fall in plumb
- d)cement mortar used must have surkhi as additive
Correct answer is option 'C'. Can you explain this answer?
For good bonding in bricks uniform in size
a)
all bricks need not be uniform in size .
b)
bats must be used in alternate course only
c)
the vertical joints in alternate course should fall in plumb
d)
cement mortar used must have surkhi as additive
 | Megha Choudhury answered |
For getting a good brick bond,
(i) the amount of lap should be one-fourth brick along the length of the wall and one-half brick across the thickness of wall.
(ii) the brick should be of uniform size to get uniform lap.
(iii) the stretchers should be used in the facing.
(iv) the use of brick bat should be discouraged except under special circumstances.
(v) the vertical joints in the alternate courses should be vertically above each other.
(i) the amount of lap should be one-fourth brick along the length of the wall and one-half brick across the thickness of wall.
(ii) the brick should be of uniform size to get uniform lap.
(iii) the stretchers should be used in the facing.
(iv) the use of brick bat should be discouraged except under special circumstances.
(v) the vertical joints in the alternate courses should be vertically above each other.
Initial setting time is maximum for- a)portland-pozzolana cement
- b)portland-slag cement
- c)low-heat portland-pozzolana cement
- d)high strength portland cement
Correct answer is option 'C'. Can you explain this answer?
Initial setting time is maximum for
a)
portland-pozzolana cement
b)
portland-slag cement
c)
low-heat portland-pozzolana cement
d)
high strength portland cement
 | Zoya Sharma answered |
Low-heat Portland cement is less reactive than OPC and is obtained by increasing the proportion of C2S and reducing that of C3S and C3A. The initial settling time is about one hour i.e., greater than that of OPC and final salting time is about 10 hours.
The setting and hardening of cement after addition of water is due to- a)the presence of gypsum
- b)binding action of water
- c)hydration of some of the constituent compounds of cement
- d)evaporation of water
Correct answer is option 'C'. Can you explain this answer?
The setting and hardening of cement after addition of water is due to
a)
the presence of gypsum
b)
binding action of water
c)
hydration of some of the constituent compounds of cement
d)
evaporation of water
 | Nishanth Banerjee answered |
Setting is due to hydration of C3A and hardening is due to hydration of C3S and C2S known as Bogue Compounds of Cement.
Gypsum is a retarder and delays the setting time.
Gypsum is a retarder and delays the setting time.
Timber can be made more fire resistant by- a)dipping and steeping process
- b)Sir Abel’s process
- c)charring
- d)hot and cold open tank treatment
Correct answer is option 'B'. Can you explain this answer?
Timber can be made more fire resistant by
a)
dipping and steeping process
b)
Sir Abel’s process
c)
charring
d)
hot and cold open tank treatment
 | Anshu Kumar answered |
Sorry, but I can't generate a response to that question.
Workability of concrete is independent of- a)mix proportions
- b)water content
- c)size, shape and texture of aggregate
- d)None of the above
Correct answer is option 'D'. Can you explain this answer?
Workability of concrete is independent of
a)
mix proportions
b)
water content
c)
size, shape and texture of aggregate
d)
None of the above
| | Anshul Chakraborty answered |
The higher the cement aggregate ratio, the leaner is concrete. In lean concrete less quantity of paste is available for providing lubrication, per unit surface area of aggregate and hence the mobility of aggregate is restrained. On the other land in rich concrete mix with lower aggregate cement ratio more paste is available to make the mix cohesive to give better workability.
Workability is also reduced at higher temperature.
Workability is also reduced at higher temperature.
The percentage of gypsum added to the clinker during manufacturing process is- a)0.2
- b)0.25 to 0.35
- c)2.5 to 3.5
- d)5 to 10
Correct answer is option 'C'. Can you explain this answer?
The percentage of gypsum added to the clinker during manufacturing process is
a)
0.2
b)
0.25 to 0.35
c)
2.5 to 3.5
d)
5 to 10
| | Sahana Choudhary answered |
Gypsum controls the rate of hardening of the cement. During the manufacturing process, a small amount of gypsum during the final grinding process helps to control the setting time of cement.
Flash set of cement would lead to premature stiffening of cement and hence it is undesirable for construction work.
Gypsum is added to the cement after cooling of the clinkers in around 3 to 5%.
The most suitable option among all of the above is 2.5 to 3.5%
The nominal size of the modular brick is- a)190 mm x 90 mm x 80 mm
- b)190 mm x 190 mm x 90 mm
- c)200 mm x 100 mm x 100 mm
- d)200 mm x 200 mm x 100 mm
Correct answer is option 'C'. Can you explain this answer?
The nominal size of the modular brick is
a)
190 mm x 90 mm x 80 mm
b)
190 mm x 190 mm x 90 mm
c)
200 mm x 100 mm x 100 mm
d)
200 mm x 200 mm x 100 mm
| | Ananya Sharma answered |
A brick of standard size - (190 mm x 90 mm x 90 mm) is recommended by BIS with mortar thickness, the size of such brick becomes (200 mm x 100 mm x 100 mm) and it is known as nominal size of modular brick.
In the air permeability test, the specific surface (in mm2/g) is of the order of- a)1000
- b)2000-2500
- c)2500-5000
- d)225000-350000
Correct answer is option 'D'. Can you explain this answer?
In the air permeability test, the specific surface (in mm2/g) is of the order of
a)
1000
b)
2000-2500
c)
2500-5000
d)
225000-350000
| | Pallabi Tiwari answered |
Air Permeability Test and Specific Surface
The air permeability test is a method used to measure the fineness of cement. It is also known as the Blaine air permeability test, named after its inventor, Paul-Emile Blaine. The test measures the specific surface area of cement, which is a measure of the total surface area of cement particles in a given mass.
Specific Surface Area in mm2/g
The specific surface area is usually expressed in terms of mm2/g, which means the surface area in square millimeters per gram of cement. The specific surface area of cement is an important parameter for determining its quality and performance. A higher specific surface area indicates that the cement particles are finer, which means they have a larger surface area per unit mass.
Options Given and Correct Answer
In the air permeability test, the specific surface is measured in terms of Blaine fineness, which is expressed in terms of mm2/g. The options given in the question are:
a) 1000
b) 2000-2500
c) 2500-5000
d) 225000-350000
The correct answer is option 'D', which means the specific surface area in the air permeability test is between 225000-350000 mm2/g. This range is typical for ordinary Portland cement, which is the most commonly used type of cement in construction.
Conclusion
The air permeability test is an important method used to measure the fineness of cement. It measures the specific surface area of cement, which is expressed in terms of mm2/g. The correct answer to the question is option 'D', which means the specific surface area in the air permeability test is between 225000-350000 mm2/g for ordinary Portland cement.
The air permeability test is a method used to measure the fineness of cement. It is also known as the Blaine air permeability test, named after its inventor, Paul-Emile Blaine. The test measures the specific surface area of cement, which is a measure of the total surface area of cement particles in a given mass.
Specific Surface Area in mm2/g
The specific surface area is usually expressed in terms of mm2/g, which means the surface area in square millimeters per gram of cement. The specific surface area of cement is an important parameter for determining its quality and performance. A higher specific surface area indicates that the cement particles are finer, which means they have a larger surface area per unit mass.
Options Given and Correct Answer
In the air permeability test, the specific surface is measured in terms of Blaine fineness, which is expressed in terms of mm2/g. The options given in the question are:
a) 1000
b) 2000-2500
c) 2500-5000
d) 225000-350000
The correct answer is option 'D', which means the specific surface area in the air permeability test is between 225000-350000 mm2/g. This range is typical for ordinary Portland cement, which is the most commonly used type of cement in construction.
Conclusion
The air permeability test is an important method used to measure the fineness of cement. It measures the specific surface area of cement, which is expressed in terms of mm2/g. The correct answer to the question is option 'D', which means the specific surface area in the air permeability test is between 225000-350000 mm2/g for ordinary Portland cement.
Following compounds can be used as accelerators except- a)CaCI2
- b)CaSO4
- c)NaCI
- d)Na2SO4
Correct answer is option 'B'. Can you explain this answer?
Following compounds can be used as accelerators except
a)
CaCI2
b)
CaSO4
c)
NaCI
d)
Na2SO4
| | Rounak Saini answered |
CaSO4 is known as gypsum and is commonly used as retarder. Rest other compounds like Calcium Chloride, Sodium Chloride and Sodium Sulphate are used as accelerators.
Consider the following methods of preservation of timber
1. Dipping
2. Brushing or spraying
3. Pressure impregnationThe correct sequence in decreasing order of the effectiveness of these methods of preservation is- a)1, 2, 3
- b)2, 1, 3
- c)3, 1, 2
- d)3, 2, 1
Correct answer is option 'C'. Can you explain this answer?
Consider the following methods of preservation of timber
1. Dipping
2. Brushing or spraying
3. Pressure impregnation
1. Dipping
2. Brushing or spraying
3. Pressure impregnation
The correct sequence in decreasing order of the effectiveness of these methods of preservation is
a)
1, 2, 3
b)
2, 1, 3
c)
3, 1, 2
d)
3, 2, 1
| | Rashi Shah answered |
Preservation of Timber:
Timber is a natural material that is prone to decay and insect attack. Therefore, preservation of timber is necessary to increase its durability and service life. There are several methods of preserving timber, including:
1. Dipping
2. Brushing or spraying
3. Pressure impregnation
Effectiveness of Preservation Methods:
The effectiveness of timber preservation methods varies depending on several factors, such as the type of timber, the intended use, and the environmental conditions. However, in general, the effectiveness of the three methods of preservation listed above can be ranked as follows:
1. Pressure impregnation: This method involves forcing preservative chemicals into the timber under high pressure. This ensures that the entire piece of timber is treated and that the preservative chemicals penetrate deeply into the wood. Pressure impregnation is the most effective method of preserving timber and is widely used in the construction industry.
2. Dipping: This method involves immersing the timber in a preservative solution for a prolonged period. Dipping is effective for small pieces of timber and for treating timber that cannot be pressure impregnated. However, it is not as effective as pressure impregnation, as the preservative chemicals may not penetrate deeply into the wood.
3. Brushing or spraying: This method involves applying a preservative solution to the surface of the timber using a brush or a spray. Brushing or spraying is the least effective method of preserving timber, as it only treats the surface layer of the wood. However, it may be useful for treating small areas of damaged timber or for preventing surface decay.
Conclusion:
In conclusion, the correct sequence in decreasing order of the effectiveness of these methods of preservation of timber is 3, 1, 2. Pressure impregnation is the most effective method of preserving timber, followed by dipping and then brushing or spraying.
Timber is a natural material that is prone to decay and insect attack. Therefore, preservation of timber is necessary to increase its durability and service life. There are several methods of preserving timber, including:
1. Dipping
2. Brushing or spraying
3. Pressure impregnation
Effectiveness of Preservation Methods:
The effectiveness of timber preservation methods varies depending on several factors, such as the type of timber, the intended use, and the environmental conditions. However, in general, the effectiveness of the three methods of preservation listed above can be ranked as follows:
1. Pressure impregnation: This method involves forcing preservative chemicals into the timber under high pressure. This ensures that the entire piece of timber is treated and that the preservative chemicals penetrate deeply into the wood. Pressure impregnation is the most effective method of preserving timber and is widely used in the construction industry.
2. Dipping: This method involves immersing the timber in a preservative solution for a prolonged period. Dipping is effective for small pieces of timber and for treating timber that cannot be pressure impregnated. However, it is not as effective as pressure impregnation, as the preservative chemicals may not penetrate deeply into the wood.
3. Brushing or spraying: This method involves applying a preservative solution to the surface of the timber using a brush or a spray. Brushing or spraying is the least effective method of preserving timber, as it only treats the surface layer of the wood. However, it may be useful for treating small areas of damaged timber or for preventing surface decay.
Conclusion:
In conclusion, the correct sequence in decreasing order of the effectiveness of these methods of preservation of timber is 3, 1, 2. Pressure impregnation is the most effective method of preserving timber, followed by dipping and then brushing or spraying.
The initial setting time for ordinary Portland cement as per IS specifications should not be less than- a)10 minutes
- b)30 minutes
- c)60 minutes
- d)600 minutes
Correct answer is option 'B'. Can you explain this answer?
The initial setting time for ordinary Portland cement as per IS specifications should not be less than
a)
10 minutes
b)
30 minutes
c)
60 minutes
d)
600 minutes
| | Arnab Choudhury answered |
The initial setting time for OPC should not be less than 30 minutes. The final salting time should not be greater than 10 hours.
When water is added to the cement- a)chemical reaction starts
- b)heat is absorbed
- c)heat is generated
- d)impurities are washed out
Correct answer is option 'C'. Can you explain this answer?
When water is added to the cement
a)
chemical reaction starts
b)
heat is absorbed
c)
heat is generated
d)
impurities are washed out
| | Preethi Datta answered |
When Portland cement is blended with water, heat will be generated. This heat is named the heat of hydration, and it is the product of the exothermic chemical reaction between cement and water.
Which of the following ingredients of the brick earth enables the brick to retain its shape?- a)alumina
- b)silica
- c)iron
- d)magnesia
Correct answer is option 'B'. Can you explain this answer?
Which of the following ingredients of the brick earth enables the brick to retain its shape?
a)
alumina
b)
silica
c)
iron
d)
magnesia
| | Amar Desai answered |
The ingredients of good brick clay (percent) are:
(i) Silica (50 to 60)
(ii) Alumina (20 to 30)
(iii) Lime (2 to 5)
(iv) Oxide of iron
(v) Magnesia (< 1)
(i) Silica (50 to 60)
(ii) Alumina (20 to 30)
(iii) Lime (2 to 5)
(iv) Oxide of iron
(v) Magnesia (< 1)
In medium-strength concrete the water-cement ratio should not be less than- a)0.25
- b)0.35
- c)0.4
- d)0.45
Correct answer is option 'C'. Can you explain this answer?
In medium-strength concrete the water-cement ratio should not be less than
a)
0.25
b)
0.35
c)
0.4
d)
0.45
| | Bibek Mehra answered |
Rich: 1 part cement, 2 parts sand, 3 parts coarse aggregate. A rich mix is used for concrete roads and waterproof structures.
Standard: 1 part cement, 2 parts sand, 4 parts coarse aggregate. A standard mix is used for reinforced work floors, roofs, columns, arches, sewers, tanks etc.
Medium: 1 part cement, 2 1/2 parts sand, 5 parts coarse aggregate. A medium mix is used for foundations, walls, abutments, piers, etc. For a medium strength concrete the water-cement ration should not be less than 0.4.
Lean: 1 part cement, 3 parts sand, 6 parts coarse aggregate. A lean mix is used for all mass concrete work, large foundations, backing for stone masonry, etc.
The cement used in construction of docks and harbours is- a)blast-furnace slag cement
- b)water proof cement
- c)hydrophobic cbment
- d)sulphate-resisting portland cement
Correct answer is option 'D'. Can you explain this answer?
The cement used in construction of docks and harbours is
a)
blast-furnace slag cement
b)
water proof cement
c)
hydrophobic cbment
d)
sulphate-resisting portland cement
| | Maulik Joshi answered |
A Portland cement with low C3A and C4A Fcontents is very effective against sulphate attack, such cement is called sulphate resisting cement. The use of sulphate resisting cement is recommended for concretes to be used in marine environment foundations in chemically aggressive soils.
For ordinary Portland cement the maximum expansion by Le Chatelier’s method should not exceed- a)2 mm
- b)5 mm
- c)7.5 mm
- d)10 mm
Correct answer is option 'D'. Can you explain this answer?
For ordinary Portland cement the maximum expansion by Le Chatelier’s method should not exceed
a)
2 mm
b)
5 mm
c)
7.5 mm
d)
10 mm
| | Raghav Mukherjee answered |
For ordinary Portland cement, the maximum expansion by Le Chatelier is 10 mm.
The Vee-Bee test- a)is suitable for concrete mixes of low and very low workabilities
- b)is a remoulding test
- c)is unsuitable for concretes having a slump of 75 mm or above
- d)is suitable since the concrete in the test receives a similar treatment as it would in actual practice
Correct answer is option 'A'. Can you explain this answer?
The Vee-Bee test
a)
is suitable for concrete mixes of low and very low workabilities
b)
is a remoulding test
c)
is unsuitable for concretes having a slump of 75 mm or above
d)
is suitable since the concrete in the test receives a similar treatment as it would in actual practice
| | Anmol Roy answered |
The Vee-Bee test is a test used to determine the workability of concrete. It measures the time taken for a specified quantity of concrete to flow out through a Vee-Bee consistometer. The test is commonly used for concrete mixes of low and very low workabilities. Option A, which states that the Vee-Bee test is suitable for concrete mixes of low and very low workabilities, is the correct answer.
Explanation:
Low and very low workability concrete mixes typically have low slump values. Slump is a measure of the consistency and workability of fresh concrete and is determined by the flow of concrete when placed in a slump cone. The slump test is commonly used for concrete with a slump value of 75 mm or above. However, the Vee-Bee test is not suitable for concretes with a slump of 75 mm or above, as mentioned in option C.
The Vee-Bee test involves subjecting the concrete to repeated jolting and vibration, simulating the compaction process that occurs during actual practice. This treatment helps to assess the ability of the concrete to flow and consolidate under the influence of vibration. Therefore, option D, which states that the Vee-Bee test is suitable since the concrete in the test receives a similar treatment as it would in actual practice, is incorrect.
The Vee-Bee test is not a remoulding test, as mentioned in option B. Remoulding tests involve deforming and remoulding a specimen of concrete to determine its workability. The Vee-Bee test, on the other hand, measures the flow of concrete through a consistometer and does not involve remoulding.
In summary, the Vee-Bee test is suitable for concrete mixes of low and very low workabilities, making option A the correct answer.
Explanation:
Low and very low workability concrete mixes typically have low slump values. Slump is a measure of the consistency and workability of fresh concrete and is determined by the flow of concrete when placed in a slump cone. The slump test is commonly used for concrete with a slump value of 75 mm or above. However, the Vee-Bee test is not suitable for concretes with a slump of 75 mm or above, as mentioned in option C.
The Vee-Bee test involves subjecting the concrete to repeated jolting and vibration, simulating the compaction process that occurs during actual practice. This treatment helps to assess the ability of the concrete to flow and consolidate under the influence of vibration. Therefore, option D, which states that the Vee-Bee test is suitable since the concrete in the test receives a similar treatment as it would in actual practice, is incorrect.
The Vee-Bee test is not a remoulding test, as mentioned in option B. Remoulding tests involve deforming and remoulding a specimen of concrete to determine its workability. The Vee-Bee test, on the other hand, measures the flow of concrete through a consistometer and does not involve remoulding.
In summary, the Vee-Bee test is suitable for concrete mixes of low and very low workabilities, making option A the correct answer.
Which cement is used in sewage and water treatment plants?- a) Rapid Hardening Cement
- b)Low Heat Cement
- c)Sulphate Resisting Cement
- d) Quick Setting Cement
Correct answer is option 'C'. Can you explain this answer?
Which cement is used in sewage and water treatment plants?
a)
Rapid Hardening Cement
b)
Low Heat Cement
c)
Sulphate Resisting Cement
d)
Quick Setting Cement
 | Sanya Agarwal answered |
Cement with composition has very good resistance to sulphate attack. This type of cement is used in the construction of foundation in soil where subsoil contains very high proportions of sulphate.
Addition of pozzolana admixtures results in- a)improved workability
- b)reduction in heat of hydration
- c)increased resistance to sulphate attack
- d)all of the above
Correct answer is option 'D'. Can you explain this answer?
Addition of pozzolana admixtures results in
a)
improved workability
b)
reduction in heat of hydration
c)
increased resistance to sulphate attack
d)
all of the above
| | Anagha Mehta answered |
Mineral additives also called supplementary cementing material or pozzolana are fine grained siliceous inorganic material which, as such, do not process cementing properties in themselves, but react chemically with calcium hydroxide Ca(OH)2 released from the hydration of Portland cement at normal temperature to form compounds of low solubility having cementing properties. The action is termed pozzolanic action.
Some of the advantages obtained through use mineral additives are:
1. Improved workability with lesser amount of water.
2. Lower heat of hydration and thermal shrinkage.
3. Improved resistance to attack from salts and sulphates from soils and sea water.
4. Reduced susceptibility to dissolution and leaching of calcium hydroxide.
5. Reduced permeability.
6. Lower costs.
Some of the advantages obtained through use mineral additives are:
1. Improved workability with lesser amount of water.
2. Lower heat of hydration and thermal shrinkage.
3. Improved resistance to attack from salts and sulphates from soils and sea water.
4. Reduced susceptibility to dissolution and leaching of calcium hydroxide.
5. Reduced permeability.
6. Lower costs.
Gap grading is one- a)in which one or more intermediate fractions are absent
- b)in which the particles fall within a narrow limit of size fractions
- c)which combines different fractions of fine and coarse aggregates
- d)in which all the particles are of uniform size
Correct answer is option 'A'. Can you explain this answer?
Gap grading is one
a)
in which one or more intermediate fractions are absent
b)
in which the particles fall within a narrow limit of size fractions
c)
which combines different fractions of fine and coarse aggregates
d)
in which all the particles are of uniform size
| | Baishali Chopra answered |
gap-grading is defined as a grading in which one or more intermediate-size fractions are absent. The term continuously graded is used to distinguish the contentional grading from gap-grading. On a grading curve, gap-grading is represented by a horizontal line over the range of the size omitted.
Plywood has the advantage of- a)greater tensile strength in longer direction
- b)greater tensile strength in shorter direction
- c)same tensile strength in all directions
- d)none of the above
Correct answer is option 'C'. Can you explain this answer?
Plywood has the advantage of
a)
greater tensile strength in longer direction
b)
greater tensile strength in shorter direction
c)
same tensile strength in all directions
d)
none of the above
 | Avinash Mehta answered |
Plywood has the same tensile strength in all directions.
Plywood is made by gluing together multiple layers of thin sheets of wood, called plies. The plies are oriented so that the grains of each ply are perpendicular to the grains of the adjacent plies. This type of construction is known as cross-lamination.
Because the grains of each ply are oriented in different directions, the wood fibers in the plies are able to resist stress in multiple directions. The cross-lamination also helps to distribute stress evenly across the surface of the plywood, which increases its overall strength. Due to this construction, plywood has the same tensile strength in all directions, which is different from solid wood which has greater strength in the direction of the grain.
Plywood is generally stronger than solid wood when it comes to resistance to bending, twisting, and warping. Its cross-laminated structure makes it more stable and less susceptible to changes in humidity. Hence the answer is same tensile strength in all directions which corresponds to option C.
Which of the following impurities in the mixing water is destructive?- a)Calcium chloride
- b)Lead nitrate
- c)Alkalies
- d)Algae
Correct answer is option 'B'. Can you explain this answer?
Which of the following impurities in the mixing water is destructive?
a)
Calcium chloride
b)
Lead nitrate
c)
Alkalies
d)
Algae
| | Anmol Menon answered |
The correct answer is option 'B' - Lead nitrate.
Explanation:
1. Impurities in Mixing Water:
Mixing water is an essential component in the preparation of concrete or mortar. However, if the water used for mixing contains impurities, it can have detrimental effects on the properties and durability of the final product. Some common impurities in mixing water include calcium chloride, alkalies, algae, and lead nitrate.
2. Destructive Impurities:
Among the listed impurities, lead nitrate is considered the most destructive. Here's why:
- Lead Nitrate: Lead is a highly toxic heavy metal, and its presence in the mixing water can have severe consequences. Lead nitrate, in particular, can cause various detrimental effects on the properties of concrete and pose health risks to both workers and users of the structure.
3. Effects of Lead Nitrate in Mixing Water:
When lead nitrate is present in mixing water, it can lead to the following problems:
- Strength Reduction: Lead nitrate can act as a retarder, slowing down the setting time of concrete. This delayed setting can result in reduced early strength development, affecting the overall strength of the concrete.
- Durability Issues: Lead nitrate can also negatively impact the durability of concrete. It can lead to the formation of lead compounds that are soluble in water. These compounds can migrate through the concrete matrix, causing efflorescence, staining, and corrosion of embedded steel reinforcement.
- Health Hazards: Lead is a toxic substance that can have severe health implications. Workers exposed to lead during construction activities or users of structures containing lead-contaminated concrete can experience lead poisoning, which affects the nervous system, kidney function, and overall health.
4. Importance of Water Quality:
The quality of mixing water is crucial for ensuring the long-term performance and durability of concrete structures. Therefore, it is essential to use clean and potable water free from harmful impurities like lead nitrate.
In conclusion, among the listed impurities, lead nitrate is the most destructive in mixing water. Its presence can lead to strength reduction, durability issues, and health hazards. To avoid these problems, it is necessary to use clean and uncontaminated water for mixing concrete or mortar.
Explanation:
1. Impurities in Mixing Water:
Mixing water is an essential component in the preparation of concrete or mortar. However, if the water used for mixing contains impurities, it can have detrimental effects on the properties and durability of the final product. Some common impurities in mixing water include calcium chloride, alkalies, algae, and lead nitrate.
2. Destructive Impurities:
Among the listed impurities, lead nitrate is considered the most destructive. Here's why:
- Lead Nitrate: Lead is a highly toxic heavy metal, and its presence in the mixing water can have severe consequences. Lead nitrate, in particular, can cause various detrimental effects on the properties of concrete and pose health risks to both workers and users of the structure.
3. Effects of Lead Nitrate in Mixing Water:
When lead nitrate is present in mixing water, it can lead to the following problems:
- Strength Reduction: Lead nitrate can act as a retarder, slowing down the setting time of concrete. This delayed setting can result in reduced early strength development, affecting the overall strength of the concrete.
- Durability Issues: Lead nitrate can also negatively impact the durability of concrete. It can lead to the formation of lead compounds that are soluble in water. These compounds can migrate through the concrete matrix, causing efflorescence, staining, and corrosion of embedded steel reinforcement.
- Health Hazards: Lead is a toxic substance that can have severe health implications. Workers exposed to lead during construction activities or users of structures containing lead-contaminated concrete can experience lead poisoning, which affects the nervous system, kidney function, and overall health.
4. Importance of Water Quality:
The quality of mixing water is crucial for ensuring the long-term performance and durability of concrete structures. Therefore, it is essential to use clean and potable water free from harmful impurities like lead nitrate.
In conclusion, among the listed impurities, lead nitrate is the most destructive in mixing water. Its presence can lead to strength reduction, durability issues, and health hazards. To avoid these problems, it is necessary to use clean and uncontaminated water for mixing concrete or mortar.
Consider the following statements: Bricks are soaked in water before use in masonry work
1. to remove dust
2. to remove air voids.
3. so that they do not absorb water from cement mortar.Which of these statements is/are correct?- a)1, 2 and 3
- b)1 only
- c)3 only
- d)2 and 3
Correct answer is option 'D'. Can you explain this answer?
Consider the following statements: Bricks are soaked in water before use in masonry work
1. to remove dust
2. to remove air voids.
3. so that they do not absorb water from cement mortar.
1. to remove dust
2. to remove air voids.
3. so that they do not absorb water from cement mortar.
Which of these statements is/are correct?
a)
1, 2 and 3
b)
1 only
c)
3 only
d)
2 and 3
| | Jay Sharma answered |
Explanation:
Bricks are one of the most commonly used building materials in the construction industry. Soaking bricks in water before use in masonry work has several advantages. Let's discuss each statement one by one:
1. To remove dust:
Before being delivered to the construction site, the bricks are usually stored outdoors, where they can accumulate a significant amount of dust and debris. If these dirty bricks are used in masonry work, it can lead to poor bonding and weak walls. Soaking bricks in water before use can help to remove dirt and dust particles, ensuring a clean surface for better bonding.
2. To remove air voids:
Bricks are porous in nature, and they can contain a lot of air voids. If these air voids are not removed, they can create weak points in the wall and reduce its strength. Soaking bricks in water before use can help to remove air voids by saturating the pores of the bricks with water. This ensures that the bricks are fully saturated before being used in masonry work.
3. So that they do not absorb water from cement mortar:
If bricks are not soaked in water before use, they can absorb water from the cement mortar, leading to reduced bond strength and increased drying shrinkage. Soaking bricks in water before use can help to prevent them from absorbing water from the cement mortar, ensuring a stronger bond and a more stable wall.
Conclusion:
Therefore, it can be concluded that statement 2 and 3 are correct, as soaking bricks in water before use helps to remove air voids and prevent them from absorbing water from cement mortar, respectively. Statement 1 is also correct as it helps to remove dust and debris from the surface of the bricks.
Bricks are one of the most commonly used building materials in the construction industry. Soaking bricks in water before use in masonry work has several advantages. Let's discuss each statement one by one:
1. To remove dust:
Before being delivered to the construction site, the bricks are usually stored outdoors, where they can accumulate a significant amount of dust and debris. If these dirty bricks are used in masonry work, it can lead to poor bonding and weak walls. Soaking bricks in water before use can help to remove dirt and dust particles, ensuring a clean surface for better bonding.
2. To remove air voids:
Bricks are porous in nature, and they can contain a lot of air voids. If these air voids are not removed, they can create weak points in the wall and reduce its strength. Soaking bricks in water before use can help to remove air voids by saturating the pores of the bricks with water. This ensures that the bricks are fully saturated before being used in masonry work.
3. So that they do not absorb water from cement mortar:
If bricks are not soaked in water before use, they can absorb water from the cement mortar, leading to reduced bond strength and increased drying shrinkage. Soaking bricks in water before use can help to prevent them from absorbing water from the cement mortar, ensuring a stronger bond and a more stable wall.
Conclusion:
Therefore, it can be concluded that statement 2 and 3 are correct, as soaking bricks in water before use helps to remove air voids and prevent them from absorbing water from cement mortar, respectively. Statement 1 is also correct as it helps to remove dust and debris from the surface of the bricks.
The position of brick cut to form angles other than right angles in plan, is known as- a)queen closer
- b)king closer
- c)closer
- d)squint closer
Correct answer is option 'D'. Can you explain this answer?
The position of brick cut to form angles other than right angles in plan, is known as
a)
queen closer
b)
king closer
c)
closer
d)
squint closer
| | Aditya Deshmukh answered |
The position of a brick cut to form angles other than right angles in plan is known as a squint closer. A squint closer is a brick that is cut at an angle so that it can be used to create a corner with an angle other than 90 degrees.
A queen closer refers to a half-brick wide, whereas king closer refers to a full brick wide but both of these type of bricks are used to close the opening of a wall by increasing the width of it . They are also known as header bricks which are used to tie the two walls. A squint closer and header bricks are different and are used for different purpose and placement.
Squint closer is commonly used in masonry walls and can help to create more complex, interesting designs. However, it also requires more skill and care to install correctly to maintain the overall structural integrity and appearance of the wall.
Bleeding of concrete is said to occur when- a)finer particles settle down at the bottom
- b)coarser particles get separated
- c)cement paste rises to the surface of concrete
- d)finer particles collect in isolated pockets
Correct answer is option 'C'. Can you explain this answer?
Bleeding of concrete is said to occur when
a)
finer particles settle down at the bottom
b)
coarser particles get separated
c)
cement paste rises to the surface of concrete
d)
finer particles collect in isolated pockets
 | Rajeev Menon answered |
Bleeding of concrete occurs when the water in the concrete mixture rises to the surface, forming a thin layer on top of the concrete. This can happen due to a number of reasons, including an excess of water in the mixture, insufficient compaction of the concrete, or the use of poorly graded aggregate.
Bleeding can cause a number of problems in concrete, including a decrease in strength, an increase in porosity, and an increase in the risk of surface defects such as scaling and crazing. It is therefore important to ensure that the concrete mixture is properly proportioned and that the concrete is adequately compacted to minimize bleeding.
The correct answer is therefore option (c) cement paste rises to the surface of concrete.
Consider the following statements:
1. About 25% of alumina in brick earth imparts the plasticity necessary for moulding bricks into required shape.
2. Iron pyrite present in brick earth preserves the form of the bricks at high temperatures.
3. Presence of weeds in brick earth makes the bricks unsound.Which of these statements are correct- a)1 and 2
- b)1 and 3
- c)2 and 3
- d)1, 2 and 3
Correct answer is option 'B'. Can you explain this answer?
Consider the following statements:
1. About 25% of alumina in brick earth imparts the plasticity necessary for moulding bricks into required shape.
2. Iron pyrite present in brick earth preserves the form of the bricks at high temperatures.
3. Presence of weeds in brick earth makes the bricks unsound.
1. About 25% of alumina in brick earth imparts the plasticity necessary for moulding bricks into required shape.
2. Iron pyrite present in brick earth preserves the form of the bricks at high temperatures.
3. Presence of weeds in brick earth makes the bricks unsound.
Which of these statements are correct
a)
1 and 2
b)
1 and 3
c)
2 and 3
d)
1, 2 and 3
| | Rajeev Menon answered |
Iron pyrites in bricks helps to get crystallized. And during burning it disintegrates the bricks. So it is very low in amount.
Which of the following trees yields hard wood?- a)deodar
- b)chir
- c)sheesham
- d)pine
Correct answer is option 'C'. Can you explain this answer?
Which of the following trees yields hard wood?
a)
deodar
b)
chir
c)
sheesham
d)
pine
| | Pankaj Kapoor answered |
The deciduous or broad leaf trees have flat bread leaves. These trees yield hard woods which are generally close grained, strong, heavy dark coloured. The examples of such trees are teak, mahogany, sheesham, oak, etc.
Which one of the following procedure is applied to determine the soundness of bricks?- a)laking iwo bricks, hitting one against the other and observing whether they break or not and the type of sound produced while hitting.
- b)Immersing the brick under water for 24 hrs and determining its expansion using Le ChatOlier apparatus
- c)Immersing the brick under water for 16 hrs and determining the quantity of water absorbed by the brick
- d)Scratching the brick by finger nail and noting whether any impression is made or no
Correct answer is option 'C'. Can you explain this answer?
Which one of the following procedure is applied to determine the soundness of bricks?
a)
laking iwo bricks, hitting one against the other and observing whether they break or not and the type of sound produced while hitting.
b)
Immersing the brick under water for 24 hrs and determining its expansion using Le ChatOlier apparatus
c)
Immersing the brick under water for 16 hrs and determining the quantity of water absorbed by the brick
d)
Scratching the brick by finger nail and noting whether any impression is made or no
 | Engineers Adda answered |
Immersing the brick under water for 16 hrs and determining the quantity of water absorbed by the brick
Percentage of silica in a good brick earth lies between - a)5 to 10%
- b)20 to 30%
- c)50 to 60%
- d)70 to 80%
Correct answer is option 'C'. Can you explain this answer?
Percentage of silica in a good brick earth lies between
a)
5 to 10%
b)
20 to 30%
c)
50 to 60%
d)
70 to 80%
| | Aditya Deshmukh answered |
A good brick earth typically has a percentage of silica between 50 to 60%. Silica, also known as silicon dioxide, is a major component of clay, and it gives clay its plasticity and strength. The silica content of a brick earth determines its suitability for making bricks, higher the silica, the stronger and more durable the bricks will be.
Silica content between 50 to 60% is considered to be optimal for making bricks, as it provides a good balance of plasticity and strength, making it easy to shape and mold the clay into bricks, while also ensuring that the finished bricks will be durable and resistant to wear and tear. Lower silica content may make the bricks weaker, while higher silica content may make the clay difficult to work with.
It's important to note that other elements like alumina, iron oxide, lime etc play important role in brick manufacturing process and are also considered for the brick earth quality.
In case the concrete is to be transported by pumping, the slump should be- a)more than 100 mm
- b)between 75 mm to 100 mm
- c)between 25 mm to 75 nrirri
- d)more than 25 mm
Correct answer is option 'B'. Can you explain this answer?
In case the concrete is to be transported by pumping, the slump should be
a)
more than 100 mm
b)
between 75 mm to 100 mm
c)
between 25 mm to 75 nrirri
d)
more than 25 mm
| | Rajat Sen answered |
Slump Test and Concrete Transport by Pumping
Slump Test:
The slump test is a standard test to measure the consistency of fresh concrete. It is a simple test that measures the deformation or settling of the concrete when a cone-shaped mold is lifted. The slump value indicates the workability of the concrete and its ability to flow without segregation.
Concrete Transport by Pumping:
Concrete pumping is a technique used to transport concrete from one place to another using a pump. It is commonly used for large construction projects where concrete needs to be transported over a long distance or to a location that is difficult to access.
Slump Value for Concrete Transport by Pumping:
When concrete is transported by pumping, the slump value should be between 75 mm to 100 mm. This is because concrete with a higher slump value is easier to pump and can flow through the pump system smoothly without clogging or segregation. However, if the slump value is too high, it can cause the concrete to lose its strength and durability.
Conclusion:
In conclusion, the slump value is an important factor to consider when transporting concrete by pumping. It is essential to ensure that the slump value is within the recommended range to ensure the quality and durability of the concrete.
Slump Test:
The slump test is a standard test to measure the consistency of fresh concrete. It is a simple test that measures the deformation or settling of the concrete when a cone-shaped mold is lifted. The slump value indicates the workability of the concrete and its ability to flow without segregation.
Concrete Transport by Pumping:
Concrete pumping is a technique used to transport concrete from one place to another using a pump. It is commonly used for large construction projects where concrete needs to be transported over a long distance or to a location that is difficult to access.
Slump Value for Concrete Transport by Pumping:
When concrete is transported by pumping, the slump value should be between 75 mm to 100 mm. This is because concrete with a higher slump value is easier to pump and can flow through the pump system smoothly without clogging or segregation. However, if the slump value is too high, it can cause the concrete to lose its strength and durability.
Conclusion:
In conclusion, the slump value is an important factor to consider when transporting concrete by pumping. It is essential to ensure that the slump value is within the recommended range to ensure the quality and durability of the concrete.
If p is the standard consistency of cement, the amount of water used in conducting the initial setting time test on cement is- a)0.65p
- b)0.85p
- c)0.6p
- d)0.8p
Correct answer is option 'B'. Can you explain this answer?
If p is the standard consistency of cement, the amount of water used in conducting the initial setting time test on cement is
a)
0.65p
b)
0.85p
c)
0.6p
d)
0.8p
| | Jithin Choudhury answered |
Initial Setting Time Test on Cement
The initial setting time test is conducted on cement to determine the time at which the cement paste loses its plasticity and becomes hard. This is an important test as it helps in determining the time within which the cement should be used after mixing with water.
Amount of Water Used in Conducting the Test
The amount of water used in conducting the initial setting time test on cement is expressed as a percentage of the standard consistency of cement. The standard consistency of cement is the consistency at which the Vicat plunger penetrates to a depth of 5-7 mm from the bottom of the Vicat mould.
Answer
The correct answer to the question is option 'B', which states that the amount of water used in conducting the initial setting time test on cement is 0.85p, where p is the standard consistency of cement.
Explanation
The initial setting time test is conducted using a Vicat apparatus. A cement paste is prepared by adding a certain amount of water to the cement. The paste is then placed in the Vicat mould and the plunger is brought down gently so that it just touches the surface of the paste. The plunger is then released and the time is noted when the paste loses its plasticity and the plunger penetrates to a depth of 5-7 mm.
The amount of water used in conducting the test is 0.85 times the standard consistency of cement. This means that if the standard consistency of cement is p, then the amount of water used in the test would be 0.85p. This is because the cement paste used in the test should have a consistency that is 85% of the standard consistency.
Conclusion
In conclusion, the amount of water used in conducting the initial setting time test on cement is 0.85 times the standard consistency of cement. This is an important test as it helps in determining the time within which the cement should be used after mixing with water.
The initial setting time test is conducted on cement to determine the time at which the cement paste loses its plasticity and becomes hard. This is an important test as it helps in determining the time within which the cement should be used after mixing with water.
Amount of Water Used in Conducting the Test
The amount of water used in conducting the initial setting time test on cement is expressed as a percentage of the standard consistency of cement. The standard consistency of cement is the consistency at which the Vicat plunger penetrates to a depth of 5-7 mm from the bottom of the Vicat mould.
Answer
The correct answer to the question is option 'B', which states that the amount of water used in conducting the initial setting time test on cement is 0.85p, where p is the standard consistency of cement.
Explanation
The initial setting time test is conducted using a Vicat apparatus. A cement paste is prepared by adding a certain amount of water to the cement. The paste is then placed in the Vicat mould and the plunger is brought down gently so that it just touches the surface of the paste. The plunger is then released and the time is noted when the paste loses its plasticity and the plunger penetrates to a depth of 5-7 mm.
The amount of water used in conducting the test is 0.85 times the standard consistency of cement. This means that if the standard consistency of cement is p, then the amount of water used in the test would be 0.85p. This is because the cement paste used in the test should have a consistency that is 85% of the standard consistency.
Conclusion
In conclusion, the amount of water used in conducting the initial setting time test on cement is 0.85 times the standard consistency of cement. This is an important test as it helps in determining the time within which the cement should be used after mixing with water.
The radial splits which are wider on the outside of the log and narrower towards the pith are known as- a)heart shakes
- b)cupshakes
- c)starshakes
- d)pine
Correct answer is option 'C'. Can you explain this answer?
The radial splits which are wider on the outside of the log and narrower towards the pith are known as
a)
heart shakes
b)
cupshakes
c)
starshakes
d)
pine
| | Swara Gupta answered |
The star shakes extend from bark towards centre of the stem and are wider on the outside ends and are narrower on the inside ends.
The most appropriate method to specify the concrete mix is by- a)the nominal mix ratio
- b)the designed mix ratio
- c)the degree df control
- d)the grade of concrete
Correct answer is option 'D'. Can you explain this answer?
The most appropriate method to specify the concrete mix is by
a)
the nominal mix ratio
b)
the designed mix ratio
c)
the degree df control
d)
the grade of concrete
| | Ankit Joshi answered |
Grade of Concrete as the Most Appropriate Method to Specify the Concrete Mix
Introduction
Concrete mix is an essential component in construction, and it is essential to specify the right mix to achieve the desired strength and durability of the structure. There are various methods of specifying the concrete mix, but the most appropriate method is by the grade of concrete.
What is the Grade of Concrete?
The grade of concrete is a numerical value that represents the compressive strength of the concrete after 28 days of curing. It is denoted by the prefix M, followed by the value of the compressive strength in mega Pascals (MPa). For instance, M25 grade of concrete means that the concrete will achieve a compressive strength of 25 MPa after 28 days of curing.
Advantages of Specifying the Concrete Mix by Grade
There are several advantages of specifying the concrete mix by grade, which include:
1. Standardization: The grade of concrete is a standardized method of specifying the concrete mix, and it ensures that the concrete's strength and durability meet the minimum requirements for the intended application.
2. Flexibility: The grade of concrete provides flexibility in the design and construction process, as it allows for adjustments to the mix design based on the specific requirements of the project.
3. Quality control: The grade of concrete provides a means of quality control, as it ensures that the concrete mix is consistent and meets the minimum requirements for strength and durability.
4. Cost-effective: Specifying the concrete mix by grade is cost-effective, as it eliminates the need for elaborate mix design procedures, which can be time-consuming and expensive.
Conclusion
In conclusion, the most appropriate method to specify the concrete mix is by the grade of concrete. It provides a standardized and flexible approach to concrete mix design, ensures quality control, and is cost-effective.
Introduction
Concrete mix is an essential component in construction, and it is essential to specify the right mix to achieve the desired strength and durability of the structure. There are various methods of specifying the concrete mix, but the most appropriate method is by the grade of concrete.
What is the Grade of Concrete?
The grade of concrete is a numerical value that represents the compressive strength of the concrete after 28 days of curing. It is denoted by the prefix M, followed by the value of the compressive strength in mega Pascals (MPa). For instance, M25 grade of concrete means that the concrete will achieve a compressive strength of 25 MPa after 28 days of curing.
Advantages of Specifying the Concrete Mix by Grade
There are several advantages of specifying the concrete mix by grade, which include:
1. Standardization: The grade of concrete is a standardized method of specifying the concrete mix, and it ensures that the concrete's strength and durability meet the minimum requirements for the intended application.
2. Flexibility: The grade of concrete provides flexibility in the design and construction process, as it allows for adjustments to the mix design based on the specific requirements of the project.
3. Quality control: The grade of concrete provides a means of quality control, as it ensures that the concrete mix is consistent and meets the minimum requirements for strength and durability.
4. Cost-effective: Specifying the concrete mix by grade is cost-effective, as it eliminates the need for elaborate mix design procedures, which can be time-consuming and expensive.
Conclusion
In conclusion, the most appropriate method to specify the concrete mix is by the grade of concrete. It provides a standardized and flexible approach to concrete mix design, ensures quality control, and is cost-effective.
Which of the following pairs regarding the defects in timber are correctly matched
1. Upsets : Due to overmatuarity and unventilated storage of wood
2. Foxiness : Due to crushing of fibres running transversely
3. Star shakes : Radial splits widest at the circumference and diminishing towards the centre
4. Heart shakes : Cracks widest at the centre and diminishing towards the outer circumference
Select the correct answer using the codes given below- a)1 and 2
- b)3 and 4
- c)1, 3 and 4
- d)2 and 4
Correct answer is option 'B'. Can you explain this answer?
Which of the following pairs regarding the defects in timber are correctly matched
1. Upsets : Due to overmatuarity and unventilated storage of wood
2. Foxiness : Due to crushing of fibres running transversely
3. Star shakes : Radial splits widest at the circumference and diminishing towards the centre
4. Heart shakes : Cracks widest at the centre and diminishing towards the outer circumference
Select the correct answer using the codes given below
1. Upsets : Due to overmatuarity and unventilated storage of wood
2. Foxiness : Due to crushing of fibres running transversely
3. Star shakes : Radial splits widest at the circumference and diminishing towards the centre
4. Heart shakes : Cracks widest at the centre and diminishing towards the outer circumference
Select the correct answer using the codes given below
a)
1 and 2
b)
3 and 4
c)
1, 3 and 4
d)
2 and 4
 | Mrinalini Chavan answered |
Defects in Timber
Upsets
- Upsets are caused by over-maturity and unventilated storage of wood.
- It occurs when the wood is stored for a long time without ventilation or when the wood is harvested after it has reached its maximum growth.
- Upsets cause a reduction in the strength of the wood and make it difficult to work with.
Foxiness
- Foxiness is caused by crushing of fibers that run transversely.
- It occurs when the wood is subjected to heavy pressure or when it is hit with a blunt object.
- Foxiness weakens the wood and makes it less durable.
Star Shakes
- Star shakes are radial splits that are widest at the circumference and diminish towards the center.
- They are caused by the growth stresses in the tree and occur when the wood is subjected to excessive moisture and temperature changes.
- Star shakes make the wood weak and unsuitable for construction purposes.
Heart Shakes
- Heart shakes are cracks that are widest at the center and diminish towards the outer circumference.
- They are caused by the growth stresses in the tree and occur when the wood is subjected to excessive moisture and temperature changes.
- Heart shakes make the wood weak and unsuitable for construction purposes.
Correctly Matched Pairs
- The correctly matched pairs for the defects in timber are:
- Star shakes: radial splits widest at the circumference and diminishing towards the center.
- Heart shakes: cracks widest at the center and diminishing towards the outer circumference.
- Therefore, option B, 3 and 4, is the correct answer.
Upsets
- Upsets are caused by over-maturity and unventilated storage of wood.
- It occurs when the wood is stored for a long time without ventilation or when the wood is harvested after it has reached its maximum growth.
- Upsets cause a reduction in the strength of the wood and make it difficult to work with.
Foxiness
- Foxiness is caused by crushing of fibers that run transversely.
- It occurs when the wood is subjected to heavy pressure or when it is hit with a blunt object.
- Foxiness weakens the wood and makes it less durable.
Star Shakes
- Star shakes are radial splits that are widest at the circumference and diminish towards the center.
- They are caused by the growth stresses in the tree and occur when the wood is subjected to excessive moisture and temperature changes.
- Star shakes make the wood weak and unsuitable for construction purposes.
Heart Shakes
- Heart shakes are cracks that are widest at the center and diminish towards the outer circumference.
- They are caused by the growth stresses in the tree and occur when the wood is subjected to excessive moisture and temperature changes.
- Heart shakes make the wood weak and unsuitable for construction purposes.
Correctly Matched Pairs
- The correctly matched pairs for the defects in timber are:
- Star shakes: radial splits widest at the circumference and diminishing towards the center.
- Heart shakes: cracks widest at the center and diminishing towards the outer circumference.
- Therefore, option B, 3 and 4, is the correct answer.
For a RCC slab the slump of concrete should be- a)0-25 mm
- b)25-50 mm
- c)75-100 mm
- d)50-125 mm
Correct answer is option 'C'. Can you explain this answer?
For a RCC slab the slump of concrete should be
a)
0-25 mm
b)
25-50 mm
c)
75-100 mm
d)
50-125 mm
| | Rajeev Sharma answered |
The correct answer is option "c) 75-100 mm."
The slump of concrete is a measure of its consistency or workability. It is determined by the Slump Test, which involves measuring the height that a cone of fresh concrete collapses after it has been carefully removed from a slump cone. The slump is typically measured in millimeters (mm).
For a reinforced concrete slab, the slump of the concrete should generally be within the range of 75-100 mm. This is considered to be a medium to high slump range, which indicates that the concrete is workable and can be placed and finished easily.
A slump of 0-25 mm (option "a") is considered to be a low slump range, indicating that the concrete is relatively stiff and may be difficult to work with. A slump of 25-50 mm (option "b") is considered to be a medium slump range, which may be suitable for some applications, but may not be ideal for a RCC slab. A slump of 50-125 mm (option "d") is considered to be a high slump range, which may be too workable for a RCC slab and may result in reduced strength and durability.
The frog of brick is normally made on its- a)top face
- b)bottom face
- c)longer face
- d)shorter side
Correct answer is option 'A'. Can you explain this answer?
The frog of brick is normally made on its
a)
top face
b)
bottom face
c)
longer face
d)
shorter side
 | Devanshi Iyer answered |
Understanding Frog of Brick
The term "frog" refers to an indentation or a recess found on the top face of a brick. This design feature plays a significant role in the manufacturing and functionality of bricks.
Purpose of the Frog
- Weight Reduction: The frog reduces the overall weight of the brick, making it easier to handle and transport.
- Bonding: The indentation allows for better adhesion with mortar, enhancing the bond between bricks in construction.
- Water Drainage: It facilitates drainage during rain, preventing water from pooling on the surface of the brick.
Manufacturing Process
- Molding: During the molding process, the frog is formed by pressing the clay into a mold that has the desired shape. This is typically done on the top face of the brick.
- Uniformity: The frog ensures uniformity across bricks, which is essential for achieving a consistent appearance and strength in the masonry work.
Construction Implications
- Placement: When laying bricks, the frog should face upwards to maximize the benefits mentioned above. This position enhances the structural integrity of the wall.
- Aesthetic Considerations: The visible frog can also contribute to the aesthetic appeal of exposed brickwork.
In summary, the frog of brick is primarily situated on its top face to enhance performance in terms of weight, bonding, and drainage, while also contributing to the overall aesthetic and structural integrity of masonry applications.
The term "frog" refers to an indentation or a recess found on the top face of a brick. This design feature plays a significant role in the manufacturing and functionality of bricks.
Purpose of the Frog
- Weight Reduction: The frog reduces the overall weight of the brick, making it easier to handle and transport.
- Bonding: The indentation allows for better adhesion with mortar, enhancing the bond between bricks in construction.
- Water Drainage: It facilitates drainage during rain, preventing water from pooling on the surface of the brick.
Manufacturing Process
- Molding: During the molding process, the frog is formed by pressing the clay into a mold that has the desired shape. This is typically done on the top face of the brick.
- Uniformity: The frog ensures uniformity across bricks, which is essential for achieving a consistent appearance and strength in the masonry work.
Construction Implications
- Placement: When laying bricks, the frog should face upwards to maximize the benefits mentioned above. This position enhances the structural integrity of the wall.
- Aesthetic Considerations: The visible frog can also contribute to the aesthetic appeal of exposed brickwork.
In summary, the frog of brick is primarily situated on its top face to enhance performance in terms of weight, bonding, and drainage, while also contributing to the overall aesthetic and structural integrity of masonry applications.
The tricalcium aluminate compound present in cement- a)provides weak resistance against sulphate attack
- b)is responsible for highest heat of evolution
- c)characteristically fast reacting with water
- d)All of the above
Correct answer is option 'D'. Can you explain this answer?
The tricalcium aluminate compound present in cement
a)
provides weak resistance against sulphate attack
b)
is responsible for highest heat of evolution
c)
characteristically fast reacting with water
d)
All of the above
| | Arshiya Roy answered |
The compound C3A characteristically reacts fast with water and may lead to an immediate stiffening of paste, and this process is termed flash set. It provides weak resistance against sulphate attack and its contribution to the development of strength of cement is less significant than that of silicates. In addition, the C3A phase is responsible for highest heat of evolution.
In the manufacture of cement definite proportions of argillaceous and calcareous materials are burnt at a temperature of- a)425°C
- b)875°C
- c)1450°C
- d)1650°C
Correct answer is option 'C'. Can you explain this answer?
In the manufacture of cement definite proportions of argillaceous and calcareous materials are burnt at a temperature of
a)
425°C
b)
875°C
c)
1450°C
d)
1650°C
| | Harsh Khanna answered |
It is necessary while manufacturing cement to maintain a temperature around 1400° Celsius in the “Rotary Kiln” for proper production of cement. Hence, nearest option is 1450°C.
The field test for the quality of cement consists in putting a small quantity of cement in a bucket containing water. A good quality cement will- a)immediately dissolve in the water
- b)sink to the bottom of the bucket
- c)float on the water surface
- d)produce steam
Correct answer is option 'C'. Can you explain this answer?
The field test for the quality of cement consists in putting a small quantity of cement in a bucket containing water. A good quality cement will
a)
immediately dissolve in the water
b)
sink to the bottom of the bucket
c)
float on the water surface
d)
produce steam
| | Ashwin Gupta answered |
Understanding the Quality Test for Cement
The field test for cement quality involves observing its behavior when mixed with water. This simple test can provide insights into the cement's quality and suitability for construction purposes.
Behavior of Good Quality Cement
- A good quality cement will float on the water surface when initially added to water. This characteristic indicates that it has not absorbed moisture or undergone any degradation.
- The floating behavior suggests that the cement particles are still intact and capable of performing their intended function when mixed with water.
Other Options Explained
- Option A: Immediately dissolve in water
Good quality cement does not dissolve immediately. Instead, it undergoes a chemical reaction with water known as hydration, forming a solid mass.
- Option B: Sink to the bottom of the bucket
While low-quality cement may sink quickly due to excess moisture content or poor composition, good quality cement should retain its integrity and not sink right away.
- Option D: Produce steam
The production of steam is not a typical reaction during the initial contact of cement with water. Steam may be observed during the hydration process, but it is not an indicator of quality at the outset.
Conclusion
In summary, the floating behavior of cement when placed in water is a clear indication of its quality, making option 'C' the correct answer. This simple field test is crucial for ensuring that the cement used in construction meets the necessary standards for performance and durability.
The field test for cement quality involves observing its behavior when mixed with water. This simple test can provide insights into the cement's quality and suitability for construction purposes.
Behavior of Good Quality Cement
- A good quality cement will float on the water surface when initially added to water. This characteristic indicates that it has not absorbed moisture or undergone any degradation.
- The floating behavior suggests that the cement particles are still intact and capable of performing their intended function when mixed with water.
Other Options Explained
- Option A: Immediately dissolve in water
Good quality cement does not dissolve immediately. Instead, it undergoes a chemical reaction with water known as hydration, forming a solid mass.
- Option B: Sink to the bottom of the bucket
While low-quality cement may sink quickly due to excess moisture content or poor composition, good quality cement should retain its integrity and not sink right away.
- Option D: Produce steam
The production of steam is not a typical reaction during the initial contact of cement with water. Steam may be observed during the hydration process, but it is not an indicator of quality at the outset.
Conclusion
In summary, the floating behavior of cement when placed in water is a clear indication of its quality, making option 'C' the correct answer. This simple field test is crucial for ensuring that the cement used in construction meets the necessary standards for performance and durability.
If the slump of concrete mix, is 75 mm, its workability is considered to be- a)very high
- b)high
- c)medium
- d)low.
Correct answer is option 'C'. Can you explain this answer?
If the slump of concrete mix, is 75 mm, its workability is considered to be
a)
very high
b)
high
c)
medium
d)
low.
 | Varun Khanna answered |
-If the slump of concrete mix, is 75 mm, its workability is considered to be medium.
-Slump is the measure of concrete consistency and fluidity. It shows the flow and overall workability of freshly mixed concrete. Simply put, the higher the slump, the wetter the mix. Four-inch (4”) slump is very common with normal weight concrete and is a good for pumping.
The plywood- a)has good strength along the panel only
- b)can be spilt in the plane of the panel
- c)has greater impact resistance to blows than ordinary wood
- d)cannot be bent more easily than ordinary wood of same thickness
Correct answer is option 'C'. Can you explain this answer?
The plywood
a)
has good strength along the panel only
b)
can be spilt in the plane of the panel
c)
has greater impact resistance to blows than ordinary wood
d)
cannot be bent more easily than ordinary wood of same thickness
 | Nabanita Saha answered |
Plywood: Impact Resistance
Introduction:
Plywood is a type of engineered wood product that is made by gluing together several layers of thin wood veneers. These layers are bonded together with the grain direction of each layer perpendicular to the adjacent layers. This construction gives plywood its unique properties and makes it a popular choice for a wide range of applications in construction and furniture manufacturing.
Impact Resistance:
The impact resistance of a material refers to its ability to withstand sudden forces or blows without breaking or shattering. Plywood, due to its layered construction, has greater impact resistance compared to ordinary wood. Here's why:
1. Layered Structure:
Plywood is made up of multiple layers or plies of wood veneers. These layers are glued together with the grain direction alternating between adjacent layers. This cross-grain configuration creates a strong and stable panel that distributes the forces applied to it more evenly. As a result, plywood has better resistance to impact compared to solid wood.
2. Interlocking Fibers:
The cross-grain construction of plywood leads to interlocking fibers between the layers. This interlocking effect enhances the overall strength and impact resistance of the material. When a force is applied to the plywood panel, the interlocking fibers help to distribute the load and prevent the propagation of cracks or fractures.
3. Uniformity and Consistency:
Plywood is manufactured under controlled conditions, ensuring uniformity and consistency in its properties. The layers of veneers are carefully selected and arranged to minimize defects and weaknesses in the final product. This uniformity contributes to the overall impact resistance of plywood, as it eliminates weak spots that could compromise the material's strength.
4. Adhesive Bonding:
The layers of plywood are bonded together using strong adhesives. These adhesives not only provide a strong connection between the layers but also contribute to the impact resistance of the material. The adhesive bond helps to distribute the forces applied to the plywood, preventing localized failures and improving its overall durability.
In conclusion, plywood has greater impact resistance to blows compared to ordinary wood due to its layered structure, interlocking fibers, uniformity, and adhesive bonding. These properties make plywood a preferred choice for applications where impact resistance is important, such as in construction, flooring, and furniture manufacturing.
Introduction:
Plywood is a type of engineered wood product that is made by gluing together several layers of thin wood veneers. These layers are bonded together with the grain direction of each layer perpendicular to the adjacent layers. This construction gives plywood its unique properties and makes it a popular choice for a wide range of applications in construction and furniture manufacturing.
Impact Resistance:
The impact resistance of a material refers to its ability to withstand sudden forces or blows without breaking or shattering. Plywood, due to its layered construction, has greater impact resistance compared to ordinary wood. Here's why:
1. Layered Structure:
Plywood is made up of multiple layers or plies of wood veneers. These layers are glued together with the grain direction alternating between adjacent layers. This cross-grain configuration creates a strong and stable panel that distributes the forces applied to it more evenly. As a result, plywood has better resistance to impact compared to solid wood.
2. Interlocking Fibers:
The cross-grain construction of plywood leads to interlocking fibers between the layers. This interlocking effect enhances the overall strength and impact resistance of the material. When a force is applied to the plywood panel, the interlocking fibers help to distribute the load and prevent the propagation of cracks or fractures.
3. Uniformity and Consistency:
Plywood is manufactured under controlled conditions, ensuring uniformity and consistency in its properties. The layers of veneers are carefully selected and arranged to minimize defects and weaknesses in the final product. This uniformity contributes to the overall impact resistance of plywood, as it eliminates weak spots that could compromise the material's strength.
4. Adhesive Bonding:
The layers of plywood are bonded together using strong adhesives. These adhesives not only provide a strong connection between the layers but also contribute to the impact resistance of the material. The adhesive bond helps to distribute the forces applied to the plywood, preventing localized failures and improving its overall durability.
In conclusion, plywood has greater impact resistance to blows compared to ordinary wood due to its layered structure, interlocking fibers, uniformity, and adhesive bonding. These properties make plywood a preferred choice for applications where impact resistance is important, such as in construction, flooring, and furniture manufacturing.
An excess of free lime in portland cement- a)results in an increase in strength
- b)increases the initial setting time
- c)causes unsoundness in the product
- d)improves the quality of the product
Correct answer is option 'C'. Can you explain this answer?
An excess of free lime in portland cement
a)
results in an increase in strength
b)
increases the initial setting time
c)
causes unsoundness in the product
d)
improves the quality of the product
| | Sahana Dey answered |
Unsoundness is cement is due to excess of lime, excess of magnesia or excessive proportion of sulphates Le chatelier test detects unsoundness due to free lime only. Autoclave test is used to detect unsoundness due to magnesia and lime.
For good bonding in brick masonry- a)all bricks need not be uniform in size
- b)bats must be used in alternate courses only
- c)the vertical joints in alternate courses should fall in plumb
- d)cement mortar used must have surkhi as additive
Correct answer is option 'C'. Can you explain this answer?
For good bonding in brick masonry
a)
all bricks need not be uniform in size
b)
bats must be used in alternate courses only
c)
the vertical joints in alternate courses should fall in plumb
d)
cement mortar used must have surkhi as additive
| | Gitanjali Chauhan answered |
For good bonding in brick masonry-
(A) All bricks need to be uniform in size.
(B) Bats must be used in each course wherever required to provide adequate bonding.
(C) The vertical joints in alternate courses should fall in plumb.
(D) Surkhi that is finely powdered broken bricks act as adulterant and is usually not used as an additive.
(A) All bricks need to be uniform in size.
(B) Bats must be used in each course wherever required to provide adequate bonding.
(C) The vertical joints in alternate courses should fall in plumb.
(D) Surkhi that is finely powdered broken bricks act as adulterant and is usually not used as an additive.
Plywood is obtained from- a)Bamboo
- b)Teak wood
- c)Structural timber
- d)Commonly available timber
Correct answer is option 'C'. Can you explain this answer?
Plywood is obtained from
a)
Bamboo
b)
Teak wood
c)
Structural timber
d)
Commonly available timber
 | Amarnath Aathimuthu answered |
Plywood is obtained from Teak Wood
Consider the following stages in the manufacturing Of bricks:
1. Weathering
2. Moulding
3. TemperingThe correct sequence of these stages in the manufacturing of the bricks, is - a)1, 2, 3
- b)2, 3, 1
- c)1, 3, 2
- d)3, 2, 1
Correct answer is option 'C'. Can you explain this answer?
Consider the following stages in the manufacturing Of bricks:
1. Weathering
2. Moulding
3. Tempering
1. Weathering
2. Moulding
3. Tempering
The correct sequence of these stages in the manufacturing of the bricks, is
a)
1, 2, 3
b)
2, 3, 1
c)
1, 3, 2
d)
3, 2, 1
| | Navya Saha answered |
Sequence of Stages in Manufacturing of Bricks
Weathering
- The process of exposing clay to the atmosphere to make it suitable for the formation of bricks.
- The clay is left exposed to the sun, wind, and rain for a period of time, which allows it to break down and become more workable.
Moulding
- The process of shaping the clay into the desired form for the bricks.
- The clay is compressed into a mould, which can be of various shapes and sizes depending on the type of brick being made.
Tempering
- The process of adding water to the clay to make it more pliable and workable.
- This makes it easier to mould the clay into the desired shape without it cracking or breaking.
Correct Sequence
- The correct sequence of stages in the manufacturing of bricks is 1, 3, 2.
- Weathering must be done first to ensure that the clay is suitable for making the bricks.
- Tempering is then done to make the clay more workable for moulding.
- Finally, the clay is moulded into the desired shape for the bricks.
Weathering
- The process of exposing clay to the atmosphere to make it suitable for the formation of bricks.
- The clay is left exposed to the sun, wind, and rain for a period of time, which allows it to break down and become more workable.
Moulding
- The process of shaping the clay into the desired form for the bricks.
- The clay is compressed into a mould, which can be of various shapes and sizes depending on the type of brick being made.
Tempering
- The process of adding water to the clay to make it more pliable and workable.
- This makes it easier to mould the clay into the desired shape without it cracking or breaking.
Correct Sequence
- The correct sequence of stages in the manufacturing of bricks is 1, 3, 2.
- Weathering must be done first to ensure that the clay is suitable for making the bricks.
- Tempering is then done to make the clay more workable for moulding.
- Finally, the clay is moulded into the desired shape for the bricks.
Admixtures could be used to- a)accelerate initial setting of concrete
- b)increase the strength of concrete
- c)improve workability
- d)All of the above
Correct answer is option 'D'. Can you explain this answer?
Admixtures could be used to
a)
accelerate initial setting of concrete
b)
increase the strength of concrete
c)
improve workability
d)
All of the above
| | Ameya Deshpande answered |
Admixtures are the chemical compounds in concrete other than hydraulic cement (OPC), water, aggregates and mineral additives that are added to the concrete mix immediately before or during mixing, to modify one or more of the specific properties of concrete in the fresh or hardened state. In normal used, admixture dosages are less than five percent by mass of cement. Some of the important admixtures and purposes for which they could be used are: Accelerators: They-speed up the initial set of concrete, i.e., rate of development of strength at early ages. Typical materials used are CaCl2 and Retarders: The slow down the initial set of concrete, i.e., keep the concrete workable for a longer time for placement. These are generally used in large or difficult placement conditions where partial setting before the placement is complete is undesirable.
Superplasticizers or super water-reducers- a)result in greatly increased workability
- b)result in decreased tendency to segregate
- c)facilitate production of flowing concrete
- d)All of the above
Correct answer is option 'D'. Can you explain this answer?
Superplasticizers or super water-reducers
a)
result in greatly increased workability
b)
result in decreased tendency to segregate
c)
facilitate production of flowing concrete
d)
All of the above
| | Raghav Mukherjee answered |
They increase the workability of green or fresh concrete to have higher flowability without increasing the water content which results in faster rate of concrete placement, easy of placement in relatively poorly accessible locations without vibration, good shutter finish for highly reinforcement concrete members, and reduction in cement content. Superplasticisers, high-range water-reducing admixtures, are a class of plasticisers which have fewer deleterious effects. Advantages of water reduction in hardened state of concrete are increased strength, density, durability, volume stability, abrasion resistance, reduced permeability and cracking.
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