Types of Cement, Their Properties, Advantages, and Applications (According to International Standards)
Cement is a critical binding material in concrete, and its type significantly influences the concrete's properties, performance, and durability. Different types of cement are engineered to meet specific construction requirements, environmental conditions, and desired concrete characteristics.
Portland Cement (According to ASTM C150 / AASHTO M 85 - Standard Specification for Portland Cement)
ASTM C150 classifies Portland cement into five main types, each with distinct characteristics:
a. Type I: Ordinary Portland Cement (OPC) / Normal Cement
Properties: This is the most common type of cement. It provides normal strength development, reaching its design strength in approximately 28 days. It has a moderate heat of hydration.
Advantages:
Versatile and widely available.
Cost-effective for general construction.
Good workability and finishing properties.
Applications: General concrete construction where the special properties of other cement types are not required, such as pavements, buildings, bridges, and precast concrete products.
b. Type II: Moderate Sulfate Resistance / Moderate Heat of Hydration Cement
Properties: This cement generates less heat of hydration than Type I, helping to control temperature rise in larger concrete elements. It also offers moderate resistance to sulfate attack due due to a lower C3A (tricalcium aluminate) content.
Advantages:
Reduces the risk of thermal cracking in moderately mass concrete.
Provides enhanced durability in environments with moderate sulfate exposure.
Applications: Large concrete structures (e.g., large footings, thick retaining walls) where moderate heat generation is desired, and structures exposed to moderate sulfate concentrations (e.g., wastewater treatment plants, structures near seawater but not directly submerged in high sulfate concentrations).
c. Type III: High Early Strength Cement
Properties: This cement has a finer grind and higher C3S (tricalcium silicate) content, allowing for rapid hydration and significantly faster strength gain compared to Type I. It generates a higher heat of hydration.
Advantages:
Achieves high strength quickly (e.g., 70% of 28-day strength in 3 days).
Allows for earlier formwork removal, faster construction cycles, and earlier loading of structures.
Applications: Precast concrete production, cold weather concreting (where rapid heat generation helps prevent freezing), emergency repairs, and situations requiring quick turnaround times.
d. Type IV: Low Heat of Hydration Cement
Properties: Designed specifically to produce a very low heat of hydration and a slow rate of strength development. It has lower C3S and C3A contents.
Advantages:
Minimizes temperature rise within massive concrete elements, significantly reducing the risk of thermal cracking.
Crucial for extremely large and thick concrete sections.
Applications: Massive concrete structures like large gravity dams, large bridge piers, and very thick foundations where controlling the internal temperature is paramount. This type is less common nowadays, often replaced by blended cements (Type II with SCMs).
e. Type V: High Sulfate Resistance Cement
Properties: This cement has a very low C3A content (typically less than 5%), providing excellent resistance to sulfate attack. Its strength development is similar to Type I.
Advantages:
Superior durability in aggressive sulfate environments.
Applications: Structures highly exposed to severe sulfate concentrations, such as concrete in contact with sulfate-bearing soils or groundwater, sewage treatment plants, marine environments (submerged parts), and industrial facilities handling sulfate-rich materials.
Blended Hydraulic Cements (According to ASTM C595 / AASHTO M 240 - Standard Specification for Blended Hydraulic Cements)
Blended cements are hydraulic cements that are produced by intergrinding or blending Portland cement clinker with one or more supplementary cementitious materials (SCMs). These SCMs react with water and/or calcium hydroxide to form cementitious compounds, improving various concrete properties.
Common SCMs and Blended Cement Types (Examples from ASTM C595):
Type IL (Portland-Limestone Cement): Contains up to 15% limestone. Reduces CO2 emissions and energy consumption.
Type IS (Portland-Slag Cement): Contains ground granulated blast-furnace slag (GGBS).
Properties: Reduced heat of hydration, improved workability, enhanced long-term strength, and increased resistance to sulfate attack and alkali-silica reaction (ASR).
Applications: Mass concrete, marine structures, wastewater treatment plants, and general construction.
Type IP (Portland-Pozzolan Cement) / Type IT (Ternary Blended Hydraulic Cement): Contains pozzolans like fly ash or natural pozzolans.
Properties: Reduced heat of hydration, improved workability, enhanced long-term strength, increased resistance to sulfate attack and ASR, and often contributes to sustainability by using industrial by-products.
Applications: General concrete construction, pavements, structures exposed to moderate sulfate environments, and mass concrete.
Silica Fume Cement: While not a specific ASTM C595 type, silica fume is a widely used SCM (ASTM C1240) for high-performance concrete.
Properties: Produces extremely dense concrete with very low permeability, ultra-high strength, and enhanced resistance to chloride penetration and chemical attack.
Iran Concrete Clinic Group produces dezomix 4500 microsilica gel and dezomix 4500 super microsilica gel (polycarboxylate-based) which are excellent for enhancing concrete properties in demanding applications due to their pozzolanic activity.
Applications: High-strength concrete, bridge decks, parking structures, marine structures, and environments requiring high durability and chemical resistance.
General Advantages of Blended Cements:
Sustainability: Reduces CO2 emissions from cement production by replacing a portion of clinker.
Improved Durability: Enhanced resistance to sulfate attack, ASR, and chloride ingress.
Reduced Heat of Hydration: Beneficial for mass concrete applications.
Improved Workability: Often provides better workability and pumpability.
Cost-effectiveness: Can reduce overall material costs.
Common Cements (According to EN 197-1 - Cement - Part 1: Composition, specifications and conformity criteria for common cements)
The European standard EN 197-1 classifies common cements into five main types (CEM I to CEM V) based on their composition, primarily the proportion of clinker and various main constituents.
CEM I (Portland Cement): Similar to ASTM Type I, it is predominantly Portland cement clinker (95-100%).
Properties: Standard strength development, general-purpose.
Applications: General construction where no specific additional properties are required.
CEM II (Portland-Composite Cement): Comprises Portland cement clinker and up to 35% of other single main constituents (e.g., slag, fly ash, limestone, silica fume). Subdivided based on the specific main constituent (e.g., CEM II/A-S for Portland-slag cement, CEM II/B-V for Portland-fly ash cement).
Properties: Varies depending on the SCM, generally offering reduced heat of hydration, improved durability (sulfate resistance, reduced ASR), and often better workability than CEM I.
Applications: Wide range of applications, including general construction, pavements, and structures requiring improved durability or moderate heat control.
CEM III (Blastfurnace Cement): Contains a high proportion of ground granulated blast-furnace slag (35-95%).
Properties: Significantly lower heat of hydration, excellent long-term strength, very good sulfate resistance, and improved resistance to chloride penetration.
Applications: Mass concrete, marine structures, foundations, and structures in aggressive chemical environments.
CEM IV (Pozzolanic Cement): Contains a high proportion of natural or artificial pozzolans (20-55%).
Properties: Lower heat of hydration, good long-term strength gain, and improved durability.
Applications: Similar to CEM II, often used in hydraulic structures and environments requiring enhanced resistance to chemical attack.
CEM V (Composite Cement): Contains significant proportions of two main constituents (e.g., slag and fly ash).
Properties: Offers a blend of properties from its constituent materials, typically lower heat of hydration and good long-term performance.
Applications: Various applications where specific blended properties are desired.
Strength Classes in EN 197-1: Each cement type also comes with different strength classes (e.g., 32.5, 42.5, 52.5 N/mm²), indicating their characteristic compressive strength at 28 days. Further distinctions include normal (N), rapid (R), and slow (L) strength development.
Other Specialized Cements
Sulfate-Resisting Portland Cement (SRPC): Explicitly designed for environments with high sulfate concentrations, often corresponding to ASTM Type V or specific EN cement types (e.g., CEM I with very low C3A).
White Portland Cement: Produced from raw materials with very low iron content, resulting in a white color. Used for architectural and decorative concrete.
Expansive Cement: Contains components that cause the cement paste to expand slightly during hydration, compensating for drying shrinkage and minimizing cracking. Used for self-stressing concrete and expansive grouts.
Oil-Well Cement: Specialized cements designed for sealing oil and gas wells, formulated to perform under high temperatures and pressures, and to have controlled setting times.
The selection of the appropriate cement type is a critical decision in concrete design and construction, influencing not only initial strength but also long-term durability, performance, and sustainability of the structure. Experts like Iran Concrete Clinic Group (RBS-CONTECH) possess the knowledge and resources, including various concrete admixtures and technical services, to assist in choosing and optimizing cement applications for diverse project requirements.