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Hydration Of Cement...PRC-I

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Hydration of cement
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Prepared by madam rafia firdous. She is a lecturer and instructor in subject of Plain and Reinforcement concrete at University of South Asia LAHORE,PAKISTAN.

Prepared by madam rafia firdous. She is a lecturer and instructor in subject of Plain and Reinforcement concrete at University of South Asia LAHORE,PAKISTAN.

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Hydration Of Cement...PRC-I

  1. 1. CEMENT HYDRATION AND ADMIXTURES Engr. RAFIA FIRDOUS PRC-I
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  4. 4. HYDRATION  Series of irreversible exothermic chemical reactions between cement and water  Cement-water paste sets and hardens, “gluing” the aggregate together in a solid mass Formation of hydration products over time leads to:  Stiffening (loss of workability)  Setting (Solidification)  Hardening (Strength gain) 4
  5. 5. WHY IS IT IMPORTANT? Understanding the basics of hydration is important to • Ensure the strength and durability of concrete • Recognize and mitigate the thermal stresses to prevent cracking • Appreciate the importance of good curing and construction practices 5
  6. 6. 6 CEMENT-Hydration
  7. 7. 7 CEMENT-Hydration
  8. 8. COMPOSITION OF CEMENT CLINKER 8
  9. 9. 9 CEMENT-Hydration
  10. 10. 10 CEMENT-Hydration
  11. 11. 11 CEMENT-Hydration
  12. 12. 12 CEMENT-Hydration
  13. 13. 13 CEMENT-Hydration
  14. 14. 14
  15. 15. 15 Pozzolanic Materials  Pozzolanic cements are those cements in which we add artificially some pozzolans (ASTM C-618)  Pozzolans are natural or artificial material containing silica in a reactive form.  Pozzolans are usually added to improve certain characteristics of concrete resulting in improved durability.  Commonly used pozzolan in the world are:  Fly Ash  Metakaoalin  Silica Fume  Rice husk Ash  Blast furnace slag etc
  16. 16. 16 ADMIXTURES  Admixtures are chemicals added to concrete, mortar or grout at he time of mixing to modify the properties either in the wet state immediately after mixing or after the mix has hardened.  The dosage may be expressed as liters or “kg” per 100 kg of cement  Important types of Admixtures are:  Normal Plasticizing/ water reducing (WRA)  Super plasticizing/ high range water reducing (HRWRA)  Retarders  Accelerators  Air entraining  Water retaining  etc
  17. 17. 17 ADMIXTURES  Admixtures act in the following ways  Chemical interaction with the cement hydration process  Adsorption onto cement surfaces, typically causing better particle dispersion  Affecting the surface tension of the water, typically resulting in increased air entrainment.  Affecting the rheology of the water usually resulting in an increased plastic viscosity or mix cohesion.  The benefits obtained from the using the admixture are often in the hardened properties. The properties affected by affecting the following:  Affect water demand  Change the stiffening rate  Change the air content and plastic viscosity.

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