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Questions and Answers
The first ASTM specification was issued in ______.
The first ASTM specification was issued in ______.
1904
The raw materials required for the manufacture of Portland cement include calcareous materials such as limestone and ______.
The raw materials required for the manufacture of Portland cement include calcareous materials such as limestone and ______.
chalk
The process of manufacture of cement includes grinding, mixing, and burning the materials in a ______ at high temperatures.
The process of manufacture of cement includes grinding, mixing, and burning the materials in a ______ at high temperatures.
kiln
The temperature range for burning the raw materials in the kiln is about ______ to 1500°C.
The temperature range for burning the raw materials in the kiln is about ______ to 1500°C.
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Cement factories are established where raw materials are available in ______.
Cement factories are established where raw materials are available in ______.
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After the clinker is formed, it is cooled and ground to fine powder with the addition of about ______ to 5% of gypsum.
After the clinker is formed, it is cooled and ground to fine powder with the addition of about ______ to 5% of gypsum.
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The mixture is fed into a rotary kiln, which is slightly ______.
The mixture is fed into a rotary kiln, which is slightly ______.
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In the hottest part of the kiln, some 20 to 30 percent of the material becomes ______.
In the hottest part of the kiln, some 20 to 30 percent of the material becomes ______.
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False set refers to the abnormal stiffening of cement within a few minutes of mixing with ______.
False set refers to the abnormal stiffening of cement within a few minutes of mixing with ______.
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The total surface area of cement particles represents the material available for ______.
The total surface area of cement particles represents the material available for ______.
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Finer cement offers a greater surface area for hydration, leading to a ______ development of strength.
Finer cement offers a greater surface area for hydration, leading to a ______ development of strength.
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Unsoundness in cement is often due to an excess of lime (CaO) or an excess of ______.
Unsoundness in cement is often due to an excess of lime (CaO) or an excess of ______.
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Strength tests for cement are typically performed on cement–______ mortars.
Strength tests for cement are typically performed on cement–______ mortars.
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It is recommended that there should be about 25-30 percent of cement particles of less than ______ micron in size.
It is recommended that there should be about 25-30 percent of cement particles of less than ______ micron in size.
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Field testing of cement is often sufficient for use in ______ works.
Field testing of cement is often sufficient for use in ______ works.
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The reaction of cement with water is ______.
The reaction of cement with water is ______.
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The liberation of heat during the hydration process is called ______ of hydration.
The liberation of heat during the hydration process is called ______ of hydration.
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Calcium silicate hydrate is abbreviated as ______.
Calcium silicate hydrate is abbreviated as ______.
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Complete hydration cannot be obtained under a period of one year or ______.
Complete hydration cannot be obtained under a period of one year or ______.
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C3S produces a comparatively lesser quantity of calcium silicate hydrates and more quantity of ______.
C3S produces a comparatively lesser quantity of calcium silicate hydrates and more quantity of ______.
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Calcium hydroxide constitutes ______ to 25 percent of the volume of solids in the hydrated paste.
Calcium hydroxide constitutes ______ to 25 percent of the volume of solids in the hydrated paste.
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C3S readily reacts with water and produces more ______ of hydration.
C3S readily reacts with water and produces more ______ of hydration.
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C2S hydrates rather slowly and is responsible for the ______ strength of concrete.
C2S hydrates rather slowly and is responsible for the ______ strength of concrete.
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After 28 days of curing, cement grains have been found to have hydrated to a depth of only ______.
After 28 days of curing, cement grains have been found to have hydrated to a depth of only ______.
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In hydraulic structures, the presence of Ca(OH)2 can make the concrete ______.
In hydraulic structures, the presence of Ca(OH)2 can make the concrete ______.
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The main compounds of Portland cement include C3S, C2S, C3A, and ______.
The main compounds of Portland cement include C3S, C2S, C3A, and ______.
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C3S and C2S are the most important compounds responsible for the ______ of hydrated cement paste.
C3S and C2S are the most important compounds responsible for the ______ of hydrated cement paste.
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The calculation of the potential composition of Portland cement is often referred to as ______ composition.
The calculation of the potential composition of Portland cement is often referred to as ______ composition.
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The reaction between cement and water is known as the ______ of cement.
The reaction between cement and water is known as the ______ of cement.
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The presence of C3A in cement is considered ______ as it contributes little to strength.
The presence of C3A in cement is considered ______ as it contributes little to strength.
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Minor compounds such as Na2O and K2O are known as ______.
Minor compounds such as Na2O and K2O are known as ______.
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C4AF reacts with gypsum and accelerates the ______ of silicates.
C4AF reacts with gypsum and accelerates the ______ of silicates.
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The actual proportions of compounds in cement can vary considerably from ______ to cement.
The actual proportions of compounds in cement can vary considerably from ______ to cement.
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Anhydrous cement does not bind aggregates until it is mixed with ______.
Anhydrous cement does not bind aggregates until it is mixed with ______.
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Bogue's equations are used to determine the percentages of the main ______ in cement.
Bogue's equations are used to determine the percentages of the main ______ in cement.
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Capillary pores may be fully filled with water or ______ with water.
Capillary pores may be fully filled with water or ______ with water.
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The nominal diameter of gel pores is about ______ nm.
The nominal diameter of gel pores is about ______ nm.
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For C3S and C2S compounds, an average of ______ % of water by weight of cement is required for chemical reaction.
For C3S and C2S compounds, an average of ______ % of water by weight of cement is required for chemical reaction.
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A total of ______ % of water by weight of cement is required for complete hydration.
A total of ______ % of water by weight of cement is required for complete hydration.
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Excess water over 38 % will cause undesirable ______ cavities.
Excess water over 38 % will cause undesirable ______ cavities.
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Setting refers to a change from a fluid to a ______ stage.
Setting refers to a change from a fluid to a ______ stage.
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Initial setting time is the time elapsed from when water is added to cement until the paste starts losing its ______.
Initial setting time is the time elapsed from when water is added to cement until the paste starts losing its ______.
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Flash set occurs in cement with insufficient ______ to control the rapid reaction of C3A with water.
Flash set occurs in cement with insufficient ______ to control the rapid reaction of C3A with water.
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The final setting time is when the paste has completely lost its ______ and has attained firmness.
The final setting time is when the paste has completely lost its ______ and has attained firmness.
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If less than 38 % of water is used, complete hydration is not ______.
If less than 38 % of water is used, complete hydration is not ______.
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Study Notes
What is Cement?
- Cement is a material with adhesive and cohesive properties, bonding mineral fragments into a whole.
- Portland cement is primarily made from calcareous materials (e.g., limestone, chalk) and alumina and silica (e.g., clay, shale).
- Hydraulic cements harden and set under water due to chemical reactions.
Historical Background
- Cementing materials have been used in construction by ancient civilizations (e.g., Egyptians, Romans, Indians).
- Joseph Aspdin, a Leeds builder, patented Portland cement in 1824.
- The name "Portland" comes from a resemblance to a natural stone found in England.
- Initially, cement was used to make mortar, later for concrete.
Manufacture of Portland Cement
- Raw materials include calcareous and argillaceous materials (e.g., limestone, chalk, shale, clay).
- The process involves grinding raw materials, mixing in specific proportions, burning in a kiln (1300-1500°C), cooling, and grinding to a fine powder, and adding gypsum (3-5%).
- Two processes exist: wet and dry. Wet involves mixing and grinding raw materials in wet conditions, while dry does so in dry conditions.
- The resulting powder is Portland cement.
Chemical Composition of Portland Cement
- Cement's makeup involves lime, silica, alumina, and iron oxides.
- Different oxides form various compounds: C3S, C2S, C3A, C4AF (Bogue compounds).
- The relative proportions of these compounds affect cement properties.
Hydration of Cement
- Cement's reaction with water is called hydration, a crucial process for strength development.
- Hydrated products, like calcium silicate hydrates (C-S-H) and calcium hydroxide (Ca(OH)2) are vital.
- The hydration process occurs at a decreasing rate, taking longer than a year to fully hydrate.
- Heat is released during hydration.
- Complete hydration requires water and fine particles of cement.
Setting and Hardening of Cement
- Setting: The transition from fluid to solid stage.
- Setting time involves the loss of plasticity. Initial setting is when the paste loses its plasticity momentarily, and final setting defines the time where the paste has attained sufficient firmness.
- Hardening: Further strength development.
- The rate of setting/hardening varies with cement type and external conditions.
Fineness of Cement
- Finer cement has more surface area for hydration and faster strength development.
- Cement particle size influences initial strength.
Types of Portland Cement
- Different types cater to specific needs, like rapid hardening, low heat, or sulfate resistance.
- Types include OPC, rapid, low heat, and sulfate resistant cement types.
- Standard classifications exist based on strength and other properties.
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Description
Explore the fascinating world of cement, highlighting its adhesive properties, historical significance, and manufacturing process. Learn how ancient civilizations contributed to cement's evolution and understand the steps involved in producing Portland cement. This quiz delves into essential aspects of one of the key materials in construction.
