3 Soundness – The soundness of cement refers to the stability of the volume change in the process of setting and hardening. If the volume change is unstable after setting and hardening, the concrete structures will crack, which can affect the quality of buildings or even cause serious accidents, known as poor dimensional stability.
- The cement product whose dimensional stability is poor will be disposed as spoiled product, not used in projects.
- The reasons for poor dimensional stability are: the free calcium oxide ( f -CaO) in the clinker is too much, or the free magnesium oxide in the clinker ( f -MgO) is quite a little, or the gypsum mixed in the clinker is excessive.
f -CaO and f -MgO in the clinker are all sintered, so their ageing speed is very slow. They start ageing slowly after the setting and hardening. CaO + H 2 O = Ca OH 2 MgO + H 2 O = Mg OH 2 In the ageing process, there is volume expansion which causes the cracking of cement.
- The excessive amount of gypsum will react with the solid calcium aluminate hydrate to generate crystals of calcium sulfoaluminate hydrate.
- Thus, the volume will expand 1.5 times, which leads to the cracking of cement paste matrix.
- The national standards require: boiling method can be used to inspect the poor dimensional stability of the cement caused by the free CaO.
The so-called boiling method includes Pat test and Le Chatelier test. Pat test is to make the cement paste of normal consistency into cement cake, boil it for 3 h, and then observe it by naked eyes. If there is no crack and no bending by ruler inspection, it is called qualified soundness.
- Le Chatelier test is to measure the expansion value after the cement paste is boiled and get hardened on Le Chatelier needles.
- If the expansion value is within the required value, its stability is qualified.
- If there is contradictory between the results measured by Pat test and Le Chatelier test, Le Chaterlier test should prevail.
The hydration of free magnesium oxide is slower than that of free calcium oxide. Therefore, its harm can be inspected only by autoclave test. The harm of gypsum will be found by immersing in room-temperature water for a long time. Then the poor dimensional stability caused by magnesium dioxide and gypsum is inconvenient to be tested rapidly.
- Thus, they should be controlled strictly in the production of cement.
- The national standards require: the content of free magnesium oxide in cement should not be more than 5.0%, and the content of sulfur trioxide in slag cement should not be more than 4.0% and that in other kinds of cement should not exceed 3.5%.
Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781845699550500049
- 0.1 What is soundness of Portland cement?
- 0.2 What is the soundness test?
- 1 What is the strength of cement?
- 2 What is tensile strength of cement?
- 3 What is specific gravity of cement?
- 4 What is soundness and validity?
What is soundness of cement Mcq?
Free Gujarat Engineering Service 2019 Official Paper (Civil Part 1) 150 Questions 150 Marks 90 Mins Soundness Test: Expansion of cement is measured/computed by soundness test. Soundness means the ability to resist volume expansion and it is indication durability.
- The unsoundness in cement is due to the presence of an excess of free lime than that could be combined with acidic oxide at the kiln.
- The soundness of cement may be determined by two methods, namely Le-Chatelier method and autoclave method.
- The Le-Chatelier test detects unsoundness due to free Lime only.
This method of testing does not indicate the presence and after effect of the excess of magnesia. As per Indian Standard specification, if the content of magnesia is greater than 3% in cement then Autoclave Test is performed which is sensitive to both Lime and Magnesia.
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What is soundness of Portland cement?
Portland Cement Soundness When referring to portland cement, “soundness” refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion (PCA, 1988). This destructive expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO).
- Most portland cement specifications limit magnesia content and expansion.
- The typical expansion test places a small sample of cement paste into an autoclave (a high pressure steam vessel).
- The autoclave is slowly brought to 2.03 MPa (295 psi ) then kept at that pressure for 3 hours.
- The change in specimen length due to its time in the autoclave is measured and reported as a percentage.
ASTM C 150, Standard Specification for Portland Cement specifies a maximum autoclave expansion of 0.80 percent for all portland cement types.
What is the soundness test?
Durability and Soundness The soundness test determines an aggregate ‘s resistance to disintegration by weathering and, in particular, freeze-thaw cycles. Aggregates that are durable (resistant to weathering) are less likely to degrade in the field and cause premature HMA pavement distress and potentially, failure.
- The soundness test repeatedly submerges an aggregate sample in a sodium sulfate or magnesium sulfate solution.
- This process causes salt crystals to form in the aggregate’s water permeable pores.
- The formation of these crystals creates internal forces that apply pressure on aggregate pores and tend to break the aggregate (Figure 1).
After a specified number of submerging and drying repetitions, the aggregate is sieved to determine the percent loss of material. Figure 1: Aggregate before (top) & after (bottom) the soundness test. The formation of salt crystals is supposed to mimic the formation of ice crystals in the field and could therefore be used as a surrogate to predict an aggregate’s freeze-thaw performance.
AASHTO T 104 and ASTM C 88: Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate
What is the strength of cement?
Types Of Concrete Strength – In this section, let us quickly take a look at the different types of concrete strengths that impact its quality, durability, and cost:
Compressive Strength Of Concrete
Compressive strength is a widely accepted measure to access the performance of a given concrete mixture. Considering this aspect of concrete is important because it is the primary measure determining how well concrete can withstand loads that affect its size.
- It accurately tells you whether or not a particular mix is suitable to meet the requirements of a specific project.
- Concrete can excellently resist compressive loading.
- This is why it is suitable for constructing arches, columns, dams, foundations, and tunnel linings.
- Concrete’s compressive strength is ascertained with cylindrical specimens made of fresh concrete.
It is then tested in compression at various ages. The size and shape may also affect the indicated strength. Additional tests are further conducted to obtain detailed information on the competence of strength development. Usually, the compressive strength of concrete varies from 2500 psi (17 MPa) to 4000 psi (28 MPa) and higher in residential and commercial structures.
Tensile Strength Of Concrete
The tensile strength of concrete is its capacity to resist cracking or breaking under tension. Although concrete is rarely loaded under pure pressure in a structure, determining the tensile strength is necessary to understand the extent of the possible damage.
Breaking and cracking arise when tensile forces surpass the tensile strength. Compared to the ultra-high performance concrete, traditional concrete has relatively high compressive strength compared to tensile strength, which is significantly lower. This indicates that any concrete structure that may undergo tensile stress must first be reinforced with high tensile strength materials like steel.
The knowledge about the tensile strength of concrete is increasingly getting vast due to its significance in managing potential cracking. However, testing the tensile strength of concrete is somewhat tricky – in fact, there is no field test for direct judgment.
Flexural Strength Of Concrete
Flexural strength establishes the ability of concrete to withstand bending. It is an indirect measure of tensile strength. Let us understand flexure strength with this classic example – several structures, including pavements, slabs, and beams, and its components are subject to bending or flexure.
Talking of a beam, it may be loaded at the center and be supported at the ends. Its bottom fibers are in tension, whereas upper ones are in compression. If this beam is constructed with concrete, it will experience a tensile failure in the lower fibers because concrete has a weaker tension. However, including a few steel bars in the lower region will sustain a more significant load as the reinforcing steel has high tensile strength.
In fact, if the reinforcing steel is pre-stressed in concrete, the beam will still be strong. The flexural strength of concrete is usually determined by testing a simple beam where the concentrated load is applied at each of the third points. The numbers are then expressed in a Modulus of Rupture (MR) in psi.
How do you test concrete for sound?
Non-Destructive Field Testing of Concrete – The most common method of non-destructive field testing is through a process called sounding, Sounding involves striking the concrete surface and interpreting the sound produced. Solid concrete will produce a ringing sound, while concrete that is spalled, delaminated, or contains voids will produce a flat or hollow sound. Sounding of concrete by chain dragging Sounding test of concrete by striking with a hammer Sounding test of concrete is accomplished using a variety of tools. Sounding of small areas and vertical or overhead structural elements is best achieved by using a hammer or steel rod. A steel chain can also be dragged over the surface under evaluation.
- This method is best suited for slab surfaces where large areas can be tested in a reasonable amount of time.
- Non-destructive evaluations is also conducted using ultrasonic pulse velocity methods,
- Two common approach include a pulse velocity meter and an impact echo system,
- The pulse velocity meter can detect defects such as the depth of cracks and loss of bond.
The impact echo system can detect the thickness of a thin concrete section, locate a crack within the concrete, and locate voids or defects such as honeycombing. Should the approximate size and location of the embedded reinforcing steel be desired, nondestructive testing methods include ground-penetrating radar and magnetic testing using a pachometer.
What is strength test of cement?
The tests that measure the rate at which a cement develops strength are usually made on a mortar commonly composed of one part cement to three parts sand, by weight, mixed with a defined quantity of water, Tensile tests on briquettes, shaped like a figure eight thickened at the centre, were formerly used but have been replaced or supplemented by compressive tests on cubical specimens or transverse tests on prisms.
- The American Society for Testing and Materials (ASTM) specification requires tensile tests on a 1:3 cement-sand mortar and compressive tests on a 1:2.75 mortar.
- The British Standards Institution (BSI) gives as alternatives a compressive test on a 1:3 mortar or on a concrete specimen.
- An international method issued by the International Organization for Standardization (ISO) requires a transverse test on a 1:3 cement-sand mortar prism, followed by a compressive test on the two halves of the prism that remain after it has been broken in bending.
Many European countries have adopted this method. In all these tests the size grading of the sand, and usually its source, is specified. In the testing of most cements, a minimum strength at 3 and 7 days and sometimes 28 days is specified, but for rapid-hardening portland cement a test at 1 day also is sometimes required.
For high-alumina cement, tests are required at 1 and 3 days. Strength requirements laid down in different countries are not directly comparable because of the differences in test methods. In actual construction, to check the strength of a concrete, compressive tests are made on cylinders or cubes made from the concrete being placed.
Frederick M. Lea The Editors of Encyclopaedia Britannica
What is tensile strength of cement?
Properties of normal strength Portland cement concrete. Compressive strength : 20 – 40 MPa (3000 – 6000 psi) Flexural strength : 3 – 5 MPa (400 – 700 psi) Tensile strength – σ : 2 – 5 MPa (300 – 700 psi)
What is specific gravity of cement?
Why We Calculate Specific Gravity of Any Substance – We calculate specific gravity of any substance to know the behavior of the material in water. And we can know the material will sink or floats in the water. All of the materials in our environment have a fixed specific gravity.
- The usual range is 1-100.
- If the specific gravity is greater than 1, then it sinks in water.
- If the specific gravity Is less than 1 it floats in water.
- So if the specific gravity of any substance is known to us we can use the materials in suitable place of any work.
- Basically, specific gravity defines that the substance is how much heavier than water or reference substance of the same volume.
The specific gravity of cement ranging from 3.1 to 3.16 g/cc. By this statement, we can ensure that cement 3.1-3.16 times heavier than water of the same volume. And it sinks in water. Because the specific gravity is greater than 1. Every material consists off so many little pores, which may contain voids in it.
- And a material becomes useless when any void present in the material.
- If the cement covered by extreme moisture content due to bad weather conditions, then the specific gravity of cement may go up to 3.19.
- If the specific gravity value reaches 3.19, then the pores in cement are filled with the moisture.
Cement undergoes a chemical reaction when it is reacted with the atmospheric moisture this process is termed as hydration. Moisture is very harmful to cement. Cement becomes useless once it is hydrated with water. The presence of excessive moisture is the reason for finding a lot of lumps in old cement is due to content in it.
Which cement is strongest?
World’s Hardest Concrete With Improved Impact Resistance for Disaster Prevention Outline of degassing and water absorption treatment. The PFC specimens are then placed in a closed vessel that was depressurized using a vacuum pump, and water introduced from the outer surface to the inside.
- Credit: Kanazawa University A research team including Kanazawa University tests the impact response of the world’s hardest concrete.
- Concrete is the most widely used building material in the world and consequently is being continuously developed to fulfill modern-day requirements.
- Efforts to improve concrete strength have led to reports of porosity-free concrete (PFC), the hardest concrete tested to date.
Some of the basic properties of PFC have already been explored, and now a team including Kanazawa University has probed the impact response of this innovative material. Their findings are published in International Journal of Civil Engineering, Ultra-high-strength concrete offers significant advantages including reducing the weight of large structures and protecting them against natural disasters and accidental impacts.
- PFC is an ultra-high-strength concrete whose properties can be further enhanced by incorporating steel fibers.
- Curing process.
- After the water absorption treatment, the specimen was subjected to steam curing (heating rate: 15 ºC/h, maximum temperature: 90 ºC, maximum temperature holding time: 48 h, cooling rate: 15 ºC/h).
Next, heat curing (heating rate: 60 ºC/h, maximum temperature: 180 ºC, maximum temperature holding time: 48 h, cooling rate: 60 ºC/h, 1 atm) was applied. Credit: Kanazawa University The way in which PFC is prepared leads to very few voids in the final material, which gives it its high strength — 400 MPa can be applied to PFC before it fails, compared with 20-30 MPa for standard concrete.
Some of the basic material properties of steel fiber-reinforced PFC have already been reported; now the researchers have evaluated the impact response of a range of PFC preparations with different steel fiber contents and section heights. Failure condition after impact loading. The damage degree of the beams can be reduced by changing the steel fiber mixing rate in the PFC beam from 1 to 2 vol.%.
Credit: Kanazawa University “The continued development of building materials is particularly important in areas where frequent natural disasters threaten the integrity of structures,” study lead author Yusuke Kurihashi explains. “We carried out impact tests on a variety of steel fiber-reinforced PFC samples to determine their reactions, and in so doing, accelerate the widespread application of PFC in building projects.
Our testing is designed to simulate responses to events such as rock falls, blasts and flying objects.” The researchers made two key findings. Firstly, they observed that increasing the steel fiber content from 1% to 2% reduced the damage due to the impact by 30%-50%. This significant improvement in performance is expected to inform future material design decisions.
In addition, they showed that it was possible to predict the behavior of the samples with approximately 80% accuracy by comparing calculated values with those that were measured, which will help to streamline development processes. “We hope that PFC will contribute to enhanced building safety in the future,” says Dr.
- Although additional experimental work and statistical processing is required to fully translate PFC into widespread practical applications, our findings make a significant contribution to understanding PFC’s role in improving the safety of many large structures including high-rise buildings, bridges, and roads.” Reference: “Response Characteristics of a Steel Fiber-Reinforced Porosity-Free Concrete Beam Under an Impact Load” by Yusuke Kurihashi, Katsuya Kono and Masato Komuro, 4 February 2020, International Journal of Civil Engineering,
: World’s Hardest Concrete With Improved Impact Resistance for Disaster Prevention
What is soundness and validity?
A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. Otherwise, a deductive argument is said to be invalid, A deductive argument is sound if and only if it is both valid, and all of its premises are actually true,
Otherwise, a deductive argument is unsound. According to the definition of a deductive argument (see the Deduction and Induction ), the author of a deductive argument always intends that the premises provide the sort of justification for the conclusion whereby if the premises are true, the conclusion is guaranteed to be true as well.
Loosely speaking, if the author’s process of reasoning is a good one, if the premises actually do provide this sort of justification for the conclusion, then the argument is valid, In effect, an argument is valid if the truth of the premises logically guarantees the truth of the conclusion.
- The following argument is valid, because it is impossible for the premises to be true and the conclusion nevertheless to be false: Elizabeth owns either a Honda or a Saturn.
- Elizabeth does not own a Honda.
- Therefore, Elizabeth owns a Saturn.
- It is important to stress that the premises of an argument do not have actually to be true in order for the argument to be valid.
An argument is valid if the premises and conclusion are related to each other in the right way so that if the premises were true, then the conclusion would have to be true as well. We can recognize in the above case that even if one of the premises is actually false, that if they had been true the conclusion would have been true as well.
Consider, then an argument such as the following: All toasters are items made of gold. All items made of gold are time-travel devices. Therefore, all toasters are time-travel devices. Obviously, the premises in this argument are not true. It may be hard to imagine these premises being true, but it is not hard to see that if they were true, their truth would logically guarantee the conclusion’s truth.
It is easy to see that the previous example is not an example of a completely good argument. A valid argument may still have a false conclusion. When we construct our arguments, we must aim to construct one that is not only valid, but sound, A sound argument is one that is not only valid, but begins with premises that are actually true,
- The example given about toasters is valid, but not sound.
- However, the following argument is both valid and sound: In some states, no felons are eligible voters, that is, eligible to vote.
- In those states, some professional athletes are felons.
- Therefore, in some states, some professional athletes are not eligible voters.
Here, not only do the premises provide the right sort of support for the conclusion, but the premises are actually true. Therefore, so is the conclusion. Although it is not part of the definition of a sound argument, because sound arguments both start out with true premises and have a form that guarantees that the conclusion must be true if the premises are, sound arguments always end with true conclusions.
- It should be noted that both invalid, as well as valid but unsound, arguments can nevertheless have true conclusions.
- One cannot reject the conclusion of an argument simply by discovering a given argument for that conclusion to be flawed.
- Whether or not the premises of an argument are true depends on their specific content,
However, according to the dominant understanding among logicians, the validity or invalidity of an argument is determined entirely by its logical form, The logical form of an argument is that which remains of it when one abstracts away from the specific content of the premises and the conclusion, that is, words naming things, their properties and relations, leaving only those elements that are common to discourse and reasoning about any subject matter, that is, words such as “all,” “and,” “not,” “some,” and so forth.
One can represent the logical form of an argument by replacing the specific content words with letters used as place-holders or variables. For example, consider these two arguments: All tigers are mammals. No mammals are creatures with scales. Therefore, no tigers are creatures with scales. All spider monkeys are elephants.
No elephants are animals. Therefore, no spider monkeys are animals. These arguments share the same form: All A are B; No B are C; Therefore, No A are C. All arguments with this form are valid. Because they have this form, the examples above are valid. However, the first example is sound while the second is unsound, because its premises are false.
- Now consider: All basketballs are round.
- The Earth is round.
- Therefore, the Earth is a basketball.
- All popes reside at the Vatican.
- John Paul II resides at the Vatican.
- Therefore, John Paul II is a pope.
- These arguments also have the same form: All A’s are F; X is F; Therefore, X is an A.
- Arguments with this form are invalid.
This is easy to see with the first example. The second example may seem like a good argument because the premises and the conclusion are all true, but note that the conclusion’s truth isn’t guaranteed by the premises’ truth. It could have been possible for the premises to be true and the conclusion false.
- This argument is invalid, and all invalid arguments are unsound.
- While it is accepted by most contemporary logicians that logical validity and invalidity is determined entirely by form, there is some dissent.
- Consider, for example, the following arguments: My table is circular.
- Therefore, it is not square shaped.
Juan is a bachelor. Therefore, he is not married. These arguments, at least on the surface, have the form: x is F; Therefore, x is not G. Arguments of this form are not valid as a rule. However, it seems clear in these particular cases that it is, in some strong sense, impossible for the premises to be true while the conclusion is false.
However, many logicians would respond to these complications in various ways. Some might insist–although this is controverisal–that these arguments actually contain implicit premises such as “Nothing is both circular and square shaped” or “All bachelors are unmarried,” which, while themselves necessary truths, nevertheless play a role in the form of these arguments.
It might also be suggested, especially with the first argument, that while (even without the additional premise) there is a necessary connection between the premise and the conclusion, the sort of necessity involved is something other than “logical” necessity, and hence that this argument (in the simple form) should not be regarded as logically valid.
Lastly, especially with regard to the second example, it might be suggested that because “bachelor” is defined as “adult unmarried male”, that the true logical form of the argument is the following universally valid form: x is F and not G and H; Therefore, x is not G. The logical form of a statement is not always as easy to discern as one might expect.
For example, statements that seem to have the same surface grammar can nevertheless differ in logical form. Take for example the two statements: (1) Tony is a ferocious tiger. (2) Clinton is a lame duck. Despite their apparent similarity, only (1) has the form “x is a A that is F.” From it one can validly infer that Tony is a tiger.
- One cannot validly infer from (2) that Clinton is a duck.
- Indeed, one and the same sentence can be used in different ways in different contexts.
- Consider the statement: (3) The King and Queen are visiting dignitaries.
- It is not clear what the logical form of this statement is.
- Either there are dignitaries that the King and Queen are visiting, in which case the sentence (3) has the same logical form as “The King and Queen are playing violins,” or the King and Queen are themselves the dignitaries who are visiting from somewhere else, in which case the sentence has the same logical form as “The King and Queen are sniveling cowards.” Depending on which logical form the statement has, inferences may be valid or invalid.
Consider: The King and Queen are visiting dignitaries. Visiting dignitaries is always boring. Therefore, the King and Queen are doing something boring. Only if the statement is given the first reading can this argument be considered to be valid. Because of the difficulty in identifying the logical form of an argument, and the potential deviation of logical form from grammatical form in ordinary language, contemporary logicians typically make use of artificial logical languages in which logical form and grammatical form coincide.
- In these artificial languages, certain symbols, similar to those used in mathematics, are used to represent those elements of form analogous to ordinary English words such as “all”, “not”, “or”, “and”, and so forth.
- The use of an artificially constructed language makes it easier to specify a set of rules that determine whether or not a given argument is valid or invalid.
Hence, the study of which deductive argument forms are valid and which are invalid is often called “formal logic” or “symbolic logic.” In short, a deductive argument must be evaluated in two ways. First, one must ask if the premises provide support for the conclusion by examing the form of the argument.
- If they do, then the argument is valid.
- Then, one must ask whether the premises are true or false in actuality.
- Only if an argument passes both these tests is it sound,
- However, if an argument does not pass these tests, its conclusion may still be true, despite that no support for its truth is given by the argument.
Note: there are other, related, uses of these words that are found within more advanced mathematical logic. In that context, a formula (on its own) written in a logical language is said to be valid if it comes out as true (or “satisfied”) under all admissible or standard assignments of meaning to that formula within the intended semantics for the logical language.
Moreover, an axiomatic logical calculus (in its entirety) is said to be sound if and only if all theorems derivable from the axioms of the logical calculus are semantically valid in the sense just described. For a more sophisticated look at the nature of logical validity, see the articles on ” Logical Consequence ” in this encyclopedia.
The articles on ” Argument ” and ” Deductive and Inductive Arguments ” in this encyclopedia may also be helpful.
What is fineness of cement Mcq?
Explanation: The fineness of cement is represented as cm 2 / gram i.e Area/mass. The fineness of cement is measured by sieving it on the standard sieve. The proportion of cement of which the grain sizes are larger than the specified mesh size is thus determined.
What is workability of concrete Mcq?
Concrete Technology Questions and Answers – Workability of Fresh Concrete This set of Concrete Technology Questions and Answers for Aptitude test focuses on “Workability of Fresh Concrete”.1. What do you mean by workability? a) ASTM C 125 defines workability as the property determining the effort required to manipulate a freshly mixed quantity of concrete with a maximum loss of homogeneity b) ASTM C 125 defines workability as the property determining the effort required to manipulate a freshly mixed quantity of concrete with minimum loss of heterogeneity c) The strict definition of workability is the amount of useful external work, against the external friction between the individual particles in the concrete, necessary to produce full compaction d) The workability is also defined as the ease with which a freshly mixed concrete can be properly compacted and also that it can be transported, placed, and finished View Answer Answer: d Explanation: The workability is defined as the ease with which a freshly mixed concrete can be properly compacted and also that it can be transported, placed, and finished.
2. Workability of concrete can be improved by the addition of _ a) Iron b) Sodium c) Zinc d) Sulphur View Answer
Answer: c Explanation: Inorganic retardants include oxides of lead, zinc, phosphate and magnesium salts. Most retarders also act as water reducers.3. Workability of concrete can be improved by _ a) More sand b) More cement c) More fine aggregates d) Fineness of coarse aggregate View Answer Answer: b Explanation: Workability of concrete can be improved by more cement and water with proper water cement ratio.
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- Workability of concrete can be improved by _ a) Increasing size of aggregates b) Decreasing size of aggregates c) Increasing fine aggregates d) Increasing flaky aggregates View Answer Answer: a Explanation: Workability should be obtained by the use of a well-graded aggregate which has the largest maximum particle size possible.5.
Workability of concrete is directly proportional to _ a) Grading of the aggregates b) Time of transit c) Aggregates cement ratio d) Water cement ratio View Answer Answer: a Explanation: Grading of aggregate: Poor grading reduces consistency. That’s why it is directly proportional to grading of the aggregates.6.
Workability of concrete is inversely proportional to _ a) Grading of the aggregates b) Time of transit c) Aggregates cement ratio d) Water cement ratio View Answer Answer: d Explanation: Workability of concrete is inversely proportional to the Water cement ratio because if the amount of w/c ratio increases, workability decreases.7.
If compaction factor of concrete is,90, then workability is _ a) Low b) Very low c) Medium d) High View Answer Answer: c Explanation: At the less workable end of this group, manually compacted flat slabs using crushed aggregates. Normal reinforced concrete manually compacted and heavily reinforced sections with vibration.8.
- A compaction factor of,85 for a cement concrete sample indicates _ a) Low workability b) Medium workability c) Good workability d) Very good workability View Answer Answer: a Explanation: Roads vibrated by hand-operated machines.
- At the more workable end of this group, concrete may be manually compacted in roads using aggregate of rounded or irregular shape.9.
Adding water increases _ a) Workability b) Strength c) Fame d) Quality View Answer Answer: a Explanation: Adding water increases workability because it is inversely proportional to the workability.10. Why Shape and texture of aggregates is a must? a) Smooth surfaces give better workability b) Smooth surfaces give poor workability c) Rough surfaces give better workability d) Rough surfaces give poor workability View Answer Answer: a Explanation: The use of smooth and rounded, rather than irregularly shaped aggregate also increases workability.
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