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Cement Standards & Specifications

Chemical composition, types, and quality requirements

Chemical Composition

Main oxides and their role in cement properties

Main Raw Materials

The raw materials used for the manufacture of cement consist mainly of:

Lime (CaO)
C
Calcium Oxide - Primary binding component
Silica (SiO₂)
S
Silicon Dioxide - Strength development
Alumina (Al₂O₃)
A
Aluminum Oxide - Early strength
Iron Oxide (Fe₂O₃)
F
Flux material - Reduces clinkering temperature
Water (H₂O)
H
Hydration component

Bogue Equations

Calculating percentages of major compounds:

C₃S (Tricalcium Silicate)
C₃S = 4.07(CaO) – 7.60(SiO₂) – 6.72(Al₂O₃) – 1.43(Fe₂O₃) – 2.85(SO₃)
C₂S (Dicalcium Silicate)
C₂S = 2.87(SiO₂) – 0.754(3CaO.SiO₂)
C₃A (Tricalcium Aluminate)
C₃A = 2.65(Al₂O₃) – 1.69(Fe₂O₃)
C₄AF (Tetracalcium Aluminoferrite)
C₄AF = 3.04(Fe₂O₃)
Values in brackets represent the percentage of oxides in raw materials
Lime Saturation Factor (LSF)

Ratio of percentage of lime to percentage of silica, alumina and iron oxide

Acceptable Range: Not greater than 1.02 and not less than 0.66

Types of Portland Cement

ASTM and Iraqi Classification Standards

Type I
Ordinary Portland Cement (OPC)

For use in general concrete construction where special properties are not required

Applications:
  • General construction
  • Residential buildings
  • Commercial structures
  • Standard concrete works
Type II
Moderate Sulfate Resistant

For use in construction exposed to moderate sulfate action or where moderate heat of hydration is required

Applications:
  • Drainage structures
  • Moderate sulfate exposure
  • Foundations in sulfate soils
  • Moderate heat requirement
Type III
Rapid Hardening Portland Cement

For use when high early strength is required

Applications:
  • Emergency repairs
  • Cold weather concreting
  • Quick formwork removal
  • Fast-track construction
Type IV
Low Heat Portland Cement

For use when low heat of hydration is required

Applications:
  • Mass concrete structures
  • Concrete dams
  • Large foundations
  • Thick walls
Type V
Sulfate Resisting Portland Cement

For use when high sulfate resistance is required

Applications:
  • Marine construction
  • High sulfate soils
  • Sewage treatment plants
  • Aggressive environments

Chemical Requirements Specifications

Specifications Types of Cement
I & IA II & IIA III & IIIA IV V
Magnesium Oxide (MgO), max, %
ASTM 6 6 6 6 6
IQS 5 5 5 5 5
Sulfur Trioxide (SO₃), max, %
ASTM - C₃A ≤ 8% 3 3 3.5 2.3 2.3
ASTM - C₃A > 8% 3.5 - 4.5 - -
IQS - C₃A ≤ 5% 2.5 2.5 3 2.5 2.5
IQS - C₃A > 5% 2.8 2.8 3.5 3 2.5
Loss on Ignition, max, %
ASTM 3 3 3 2.5 3
IQS 4 4 4 4 4
Insoluble Residue, max, %
ASTM 0.75 0.75 0.75 0.75 0.75
IQS 1.5 1.5 1.5 1.5 1.5
Tricalcium Aluminate (C₃A), max, %
ASTM - 8 15 7 5
IQS - 8 15 7 3.5
Lime Saturation Factor
IQS 0.66-1.02 0.66-1.02 0.66-1.02 0.66-0.88 0.66-1.02

Special Types of Cement

Portland Blast Furnace Cement

Mixture of Portland cement and ground granulated blast furnace slag (25-65%)

Properties:
  • Lower early strength, equal at 2 months
  • Higher workability than OPC
  • Lower heat of hydration
  • High sulfate resistance
Slag Content: 25-65% by weight (ASTM)

Pozzolanic Cement

Mixture of Portland cement and Pozzolana (15-40%)

Types of Pozzolana:
  • Natural: Volcanic ash
  • Industrial: Fired clay, fly ash
Properties:
  • Similar to blast furnace cement
  • Reacts with calcium hydroxide
  • Forms CSH gel compounds
Pozzolana Content: 15-40% by weight (ASTM)

White Portland Cement

Made from raw materials with very little iron oxide (<0.3%) and magnesium oxide

Characteristics:
  • Uses China clay (white Kaoline)
  • Requires higher firing temperature
  • Low C₄AF content
  • Slightly lower strength than OPC
Iron oxide content: < 0.3% by mass of clinker

Colored Portland Cement

Prepared by adding special pigments (2-10% by weight)

Preparation:
  • Light colors: Add to white Portland cement
  • Dark colors: Add to ordinary Portland cement
Pigment Requirements:
  • Insoluble and lightfast
  • Chemically inert
  • 28-day strength ≥ 90% of control
  • Water demand ≤ 110% of control

Important Cement Properties

Setting Time

Transition from fluid to rigid stage

Initial Setting:
≥ 45 minutes (IQS No. 5)
Final Setting:
≥ 45 minutes (IQS No. 5)
Factors Affecting:
  • Water/cement ratio
  • Temperature & humidity
  • Cement fineness
  • Chemical composition
Soundness

Volume stability - cement should not undergo excessive expansion

Causes of Expansion:
1. Free Lime (CaO)
CaO + H₂O → Ca(OH)₂
2. Free MgO
MgO + H₂O → Mg(OH)₂
ASTM: ≤6%, IQS: ≤5%
3. Excess Gypsum
Slow expansion if excess of C₃A reaction
Test Methods: Autoclave test, Le Chatelier
Fineness

Particle size affects hydration rate and strength development

Advantages:
  • Rapid strength development
  • Better aggregate coverage
  • Improved workability
Disadvantages:
  • Higher grinding cost
  • Faster deterioration
  • Higher shrinkage
  • More gypsum required
Test Methods: Sieve analysis, Blaine, Wagner, Sedimentation

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