Unit 10 Module: Determination of the Time Setting of Portland Cement Flashcards

Objectives: 1. Describe the importance of classifying Portland cement. 2. Identify the properties of Portland cement. 3. Explain the importance of testing the setting time of Portland cement.

1
Q

is the most common type of cement in general use around the world, used as a
basic ingredient of concrete, mortar, stucco, and most non-specialty grout.

A

Portland cement

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2
Q

What are the most common products that includes portland cement as its basic ingredient

A

concrete, mortar, stucco, and most non-specialty grout.

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3
Q

It was developed from other
types of hydraulic lime in England in the mid-19th century and usually originates from limestone

A

Portland cement

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4
Q

In what material does portland cement originate

A

Limestone

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5
Q

What chemical is this?|
(C3S)

A

Tricalcium silicate

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6
Q

What chemical is this?
(C2S)

A

Dicalcium silicate

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7
Q

What chemical is this?
(C3A)

A

Tricalcium aluminate

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8
Q

What chemical is this?

(C2AF)

A

Tetracalcium aluminoferrite

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9
Q

When Portland cement is mixed with water its chemical compound constituents undergo a series
of chemical reactions that cause it to harden. This chemical reaction with water is called ____

A

Hydration

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10
Q

starts as soon as the cement and water are mixed.

A

Hydration

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11
Q

Hydrates and hardens rapidly and is largely responsible for initial set and early
strength. Portland cements with higher percentages of (35 will exhibit higher early strength.

A

Tricalcium Silicate (C3S)

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12
Q

Hydrates and hardens the quickest. Liberates a large amount of heat almost
immediately and contributes somewhat to early strength. Gypsum is added to Portland cement to retard
C~ hydration. Without gypsum, C?A hydration would cause Portland cement to set almost immediately
after adding water.

A

Tricalcium Aluminate(C3A)

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13
Q

Hydrates and hardens slowly and is largely responsible for strength increases
beyond one week.

A

Dlcalcium Silicate(C2S)

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14
Q

admirably suited to all construction
work which is free from sulphate attack, has a medium rate of strength development and heat generation
and has an adequate resistance to dry shrinkage and cracking, but has less resistance to chemical attack.

A

Ordinary Portland Cement (Type I)

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15
Q

Used as a precaution against moderate sulfate attack and usually generate less heat at a slower
rate than Type I cement.

A

Moderate Sulfate Resistance(Type II)

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16
Q

Strength developed in standard mortar cube after 3 days is of the same order as the 7 days
strength ordinary Portland cement, used where high early strength is necessary and should not be used
in mass concrete works owing to high rate of heat development since the difference in temperature
between interior and exterior of the concrete may lead to cracks.

A

Rapid Hardening Portland Cement (Type Ill)

17
Q

Percentage of C3S are lower in this cement than ordinary Portland cement and rapid
hardening cement while that of C2S is higher, results in a slower rate of reaction, lower evolution of heat
and lower early strength but the ultimate strength remains more or less unaffected and used in mass
concrete and places where moderate sulphate attack is likely to occur.

A

Low Heat Cement (Type IV)

18
Q

This type of cement is specially made to resist sulphate attack and it is suitable for structures to
be built in places where sulphate attack is likely to occur.

A

Sulphate Resisting Cement (Type V)

19
Q

a waste product in the manufacture of steel.

A

Slag

20
Q

It is a mixture of lime, silica and alumina, the
same oxides as required for manufacture of Portland cement,

A

Slag

21
Q

This type of cement provides protection against both sulphate attack and
chloride attack In concrete.

A

Portland Blast Furnace Slag Cement

22
Q

is manufactured by grinding together a mixture of 80-85 percent
granulated slag, 10-15 percent gypsum, and about 5 percent Portland cement cl inker. The product is
ground finer than that of Portland cement.

A

Super sulphated Cement

23
Q

It is a special cement compound that develops strength that develops very quickly. It is produced
much in the same way as other forms of cement, but its unique makeup result in characteristics that are
unique to it.

A

High Alumina Cement high alumina cement, also known as HAC

24
Q

are designed to be resistant to sulfate attack

A

Types II and V OPC

25
Q

is an important
phenomenon that can cause severe damage to concrete structures.

A

Sulfate attack

26
Q

It is a chemical reaction between the
hydration products of (3A and sulfate ions that enter the concrete from the outside environment.

A

Sulfate attack

27
Q

t is designed to develop early strength more quickly than a Type I cement. This is
useful for maintaining a rapid pace of construction, since it allows cast-in-place concrete to bear loads
sooner and it reduces the time that precast concrete elements must remain in their forms.

A

Type Ill cement

28
Q

s designed to release heat more slowly than a Type I cement, meaning of course
that it also gains strength more slowly. A slower rate of heat release limits the increase in the core
temperature of a concrete element.

A

Type IV cement

29
Q

is made with raw ingredients that are low in iron and magnesium.

A

White Portland cement (WPC)

30
Q

constitute about 70 to 80% of all Portland cements.

A

C3S and C2S

31
Q

the first to react with water and causes the initial set

A

C3A

32
Q

____ reacts with C3A and turns into calcium sulpho aluminite
which causes expansion during setting.

A

Gypsum

33
Q

develops strength in concrete for the first 28 days.

A

C3S

34
Q

comparatively inactive and contributes little to the strength of concrete and the heat of
hydration.

A

C4AF

35
Q

ASTM Code for Test for Setting Time of Portland Cement

A

ASTM Designation C 191- 08

36
Q

Specimen Preparation:

A

Prepare a cement paste by mixing with the required amount of water to achieve standard
consistency.
* Start the time immediately when water is added to cement, fill the Vicat mold with cement paste
resting on plane non-absorptive plate.
* Completely fill the mold with cement paste and smooth off the surface and level of the top of the
mold as the test block.
* After molding, immediately p

37
Q

For Initial Setting Time:

A
  • Place the test block resting on plane non-absorptive plate under the rod bearing needle.
  • Slowly lower the needle until it comes in contact on the surface of the test block and quickly
    release to allow the needle to penetrate in to the test block.
  • Repeat the previous step as described, the time elapsed when water is added to cement and the
    time the needle fails to penetrate the test block to a point 5.0 ± 0.5 mm measured from the
    bottom of the mold is the initial setting time.
38
Q

c. For Final Setting Time

A
  • For final setting time test, replace the needle of the Vicat apparatus by a needle angular
    attachment
  • Slowly apply the needle to the surface of the test block until it makes an impression.
  • The time elapsed between the time when water is added to cement and the needle makes an
    impression; and the attachment fails is the final setting time.
  • In case there is unpleasant form on the surface of the test block use the under surface of t he test
    block.