Concrete Technology-I Chapter 2: Cement
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Questions and Answers

What is the primary property of cement?

  • Chemical reaction with air
  • Adhesive and cohesive properties (correct)
  • Water absorbency
  • Electrical conductivity

    • What is Portland cement primarily made of?

  • Sand and gravel
  • Granite and marble
  • Gypsum and shale
  • Calcareous material, alumina, and silica (correct)

    • What type of cements are used in making concrete?

  • Hydraulic cements (correct)
  • Slow-setting cements
  • Fast-setting cements
  • Non-hydraulic cements

    • Who is attributed with the invention of Portland cement?

    <p>Joseph Aspdin</p> Signup and view all the answers

    When did Joseph Aspdin take the patent for Portland cement?

    <p>21st October 1824</p> Signup and view all the answers

    Why was Portland cement named as such?

    <p>Due to its resemblance to natural stone</p> Signup and view all the answers

    What was the process used by Joseph Aspdin to create Portland cement?

    <p>Mixing limestone and clay, then calcining it in a furnace</p> Signup and view all the answers

    What was the result of Joseph Aspdin's process of creating Portland cement?

    <p>A fine powder</p> Signup and view all the answers

    How have ancient civilizations used cementing materials?

    <p>In their ancient constructions</p> Signup and view all the answers

    What percentage of the material becomes liquid in the hottest part of the kiln?

    <p>20 to 30</p> Signup and view all the answers

    What is the size range of the balls formed in the kiln?

    <p>3 to 25 mm</p> Signup and view all the answers

    Why is gypsum added to the cooled clinker?

    <p>To prevent flash-setting of the cement</p> Signup and view all the answers

    What is the main difference in water content between the wet and dry processes?

    <p>Wet process has 35-50% water, dry process has 12% water</p> Signup and view all the answers

    What is a comparison between the wet and dry processes in terms of fuel consumption?

    <p>Dry process requires less fuel</p> Signup and view all the answers

    What is an advantage of the dry process compared to the wet process?

    <p>It is more economic</p> Signup and view all the answers

    What is a disadvantage of the dry process compared to the wet process?

    <p>It is less accurate to control mixing of raw materials</p> Signup and view all the answers

    What are the main raw materials used in the manufacture of cement?

    <p>Lime, silica, alumina, and iron oxide</p> Signup and view all the answers

    What is the final product of the kiln formed into balls?

    <p>Clinker</p> Signup and view all the answers

    What is the primary factor that influences the properties of cement?

    <p>Proportions of oxide compositions</p> Signup and view all the answers

    Who is credited with identifying the major compounds in Portland cement?

    <p>R.H. Bogue</p> Signup and view all the answers

    What is the process called when the oxides combine at high temperature in the kiln?

    <p>Clinkering</p> Signup and view all the answers

    What are the four major compounds in Portland cement?

    <p>C3S, C2S, C3A, C4AF</p> Signup and view all the answers

    What is the name given to the calculation of the potential composition of Portland cement?

    <p>Bogue Composition</p> Signup and view all the answers

    What are the two minor compounds of particular interest in Portland cement?

    <p>Na2O and K2O</p> Signup and view all the answers

    What is the primary function of the kiln in cement production?

    <p>Combining the oxides at high temperature</p> Signup and view all the answers

    What is the name given to the complex compounds formed in the kiln?

    <p>Bogue's Compounds</p> Signup and view all the answers

    What are the oxides of sodium and potassium known as in Portland cement?

    <p>Alkalis</p> Signup and view all the answers

    What is the primary characteristic of rapid-hardening Portland cement?

    <p>Higher early strength</p> Signup and view all the answers

    What is the main difference between rapid-hardening and ordinary Portland cement?

    <p>Rate of hardening</p> Signup and view all the answers

    Why should rapid-hardening Portland cement not be used in mass concrete construction?

    <p>It has a higher rate of heat development</p> Signup and view all the answers

    What is the benefit of using rapid-hardening Portland cement in cold weather concrete?

    <p>It reduces the vulnerability of concrete to frost damage</p> Signup and view all the answers

    What is the primary reason for using low heat Portland cement in mass concrete construction?

    <p>It has a lower rate of heat evolution</p> Signup and view all the answers

    What is the main difference between rapid-hardening and low heat Portland cement?

    <p>Rate of heat development</p> Signup and view all the answers

    What is the result of the higher fineness of rapid-hardening Portland cement?

    <p>It increases the strength at 10 to 20 hours</p> Signup and view all the answers

    What is the recommended use of rapid-hardening Portland cement?

    <p>In all of the above</p> Signup and view all the answers

    What is the main characteristic of ASTM Type III cements?

    <p>Higher fineness</p> Signup and view all the answers

    What is the result of calcium hydroxide reacting with sulphates in soils or water?

    <p>Formation of calcium sulphate</p> Signup and view all the answers

    What is the primary advantage of calcium hydroxide in concrete?

    <p>It resists the corrosion of reinforcements</p> Signup and view all the answers

    What is the structure of hydrated cement at the macro level?

    <p>A two phase material</p> Signup and view all the answers

    What is the transition zone in concrete?

    <p>The interfacial region between the particles of coarse aggregate and hardened cement paste</p> Signup and view all the answers

    What is the effect of drying shrinkage or temperature variation on the transition zone?

    <p>It forms microcracks</p> Signup and view all the answers

    What happens to the microcracks in the transition zone when the structure is loaded at high stress levels?

    <p>They propagate and form bigger cracks</p> Signup and view all the answers

    Why does concrete fail at a lower stress level than the strength of bulk paste or aggregate?

    <p>Due to the presence of transition zone</p> Signup and view all the answers

    What is the composition of fresh cement paste?

    <p>A plastic mass consisting of water and cement</p> Signup and view all the answers

    What happens to the quantity of unhydrated cement in the paste with the lapse of time?

    <p>It decreases</p> Signup and view all the answers

    Study Notes

    Cement

    • Cement is a material with adhesive and cohesive properties that bonds mineral fragments into a compact whole.
    • Portland cement is made primarily from calcareous material, such as limestone or chalk, and from alumina and silica found as clay or shale.

    Historical Background

    • The history of cementing material is as old as the history of engineering construction.
    • Egyptians, Romans, and Indians used cementing materials in their ancient constructions.
    • Joseph Aspdin, a Leeds builder and bricklayer, patented Portland cement in 1824.

    Manufacturing Process

    • The manufacturing process involves mixing and grinding hard limestones and finely divided clay into a slurry, which is then calcined in a furnace.
    • The mixture undergoes a series of chemical reactions, and the resulting clinker is interground with gypsum to prevent flash-setting.
    • There are two main processes: wet process and dry process, which differ in the amount of water used and the heat required.

    Chemical Composition of Portland Cement

    • The raw materials used for the manufacture of cement consist mainly of lime, silica, alumina, and iron oxide.
    • These oxides interact with each other in the kiln at high temperature to form more complex compounds.
    • The relative proportions of these oxide compositions influence the properties of cement.

    Bogue's Compounds

    • The major compounds formed in the kiln are: C3S, C2S, C3A, and C4AF.
    • The calculation of the potential composition of Portland cement is based on the work of R.H. Bogue.

    Structure of Hydrated Cement

    • Concrete is considered as a two-phase material: paste phase and aggregates phase.
    • The transition zone, which is the interfacial region between the particles of coarse aggregate and hardened cement paste, is a plane of weakness.
    • The transition zone develops microcracks due to drying shrinkage or temperature variation, which can lead to failure of bond.

    Types of Portland Cement

    • Rapid-hardening Portland cement (Type III) develops strength more rapidly and has a higher C3S content and a finer grinding of the cement clinker.
    • Low heat Portland cement (Type IV) has a lower rate of heat evolution, making it suitable for mass concrete construction.

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    Description

    This quiz covers the basics of cement in concrete technology, including its characteristics and uses. It is designed for 2nd-year civil engineering students.

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