Cement

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Cement Specification and PerformanceHugh
WangEduardo CaballeroCEMEX USAhugh.wang_at_cemex.
com
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Use of cement

• Cement is ONLY one of the ingredients in any
  applications well cementing or construction
  concreting.
• The specified quality parameters of cement are
  tested without considering other ingredients.
• Lessons learned from concrete mixtures -
  interaction of cement with other ingredients can
  be critical to performance.

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Production of quality well cement involves
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Desired clinker characteristics for well cement
Mineral C3S, C2S, C3A, C4AF

• Well crystallized alite
• Optimize burning condition in order to minimize
  f-CaO content
• Generally very low in C3A content a challenge
  for kiln operation.

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Physical properties requirements

• Fineness
• Thickening time (TT)
• Free fluid (FF).

Physical fineness, strength, TT, free fluid,
etc

• Potential conflicting response
• Fineness vs TT
• Fineness vs FF.

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Specifications - ASTM vs API

• Fineness ASTM lowered the limit from 280 to 260
  m2/kg
• SO3 ASTM adopted performance based
  specification
• D It is permissible to exceed the values in the
  table for SO3 content, provided it has been
  demonstrated by Test Method C1038 that the cement
  with the increased SO3 will not develop expansion
  exceeding 0.020 at 14 days.
• C3S No requirement for MSR and HSR cements.
• C4AF2C3A 24 API vs 25 ASTM.

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Mineral calculation ASTM
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Mineral calculation ASTM
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Mineral calculation API 10A
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Mineral calculation API vs ASTM
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Discussions ASTM vs API

• Minimum blaine 400 m2/kg for API Class-C if high
  blaine is intended for early strength, its
  benefit may be potentially reduced due to the
  higher water demand.
• Minimum blaine for other types of cements should
  be harmonized with ASTM requirements from 280 to
  260 m2/kg. This will improve thickening time
  performance.
• Why ASTM revised cement SO3 content?
• Critical in the mixtures containing supplementary
  cementitious materials (SCM) and chemical
  admixtures. Construction industry has gone
  through the learning process.
• Potential incompatibility problems in the
  mixtures shall be considered when complex
  components are used in slurry.

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Cement hydration rate profile
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Cement hydration heat release strength
indication
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Incompatibility uncontrolled early hydration
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Incompatibility slow strength development
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Well cement examples
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Hydration rate at 23C (73F)
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Hydration heat at 23C (73F)
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Hydration rate at 38C (100F)
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Hydration heat at 38C (100F)
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Example cement and fly ash combination
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Well cement with 50 Class-C fly ash (C-FA)

• Viscosity increase

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Well cement with 50 C-FA and 1.5 gypsum
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Viscosity profile comparison

• Gypsum addition eliminates high viscosity during
  early stages

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SO3 Supply - Demand Rule
false normal flash
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If SO3 supply is greater than demand
false normal flash
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If SO3 supply is greater than demand
false normal flash
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If SO3 supply is less than demand
false normal flash
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If SO3 supply is less than demand
false normal flash
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Recommendations

• In order to make well cement more robust for
  slurry mixtures containing SCM and chemical
  admixtures, the cement SO3 needs to be optimized.
  
• The 280 m2/kg blaine requirement needs to be
  revised to 260 m2/kg, this will help to improve
  thickening time.
• The minimum blaine 400 m2/kg for Class-C cement
  may be eliminated by specifying the strength
  requirement.
• Harmonize cement mineral phase calculation to
  reflect lasted advance in understanding cement
  chemistry.

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