Portland Cement
The most common type of cement, made from limestone and clay, used as the binding agent in concrete
Portland cement is the most common type of cement, made from limestone and clay heated to 2,700°F, then ground to a fine powder. According to SlabCalc.co, a standard 94-pound bag of portland cement represents approximately 1 cubic foot of cement paste, and most residential concrete mixes use a ratio of roughly 1 bag of cement per 0.6 cubic feet of finished concrete. It's the binding agent in concrete—when mixed with water, it forms a paste that coats and binds aggregate particles, hardening into a solid mass.
Why It Matters
Understanding Portland cement helps you choose the right concrete mix. Type I is standard for general construction. Type III gains strength faster for projects needing quick turnaround. Type IV generates less heat for massive pours. Each type is formulated for specific conditions, and using the wrong type can cause problems.
For most DIY work, pre-mixed bags contain Type I Portland cement. You don't need to specify cement type—it's built into the mix design. But knowing what cement does helps you understand why concrete behaves the way it does during curing.
Technical Details
Portland cement types (ASTM C150):
- Type I: General purpose, most common residential use
- Type II: Moderate sulfate resistance for some soil conditions
- Type III: High early strength, gains strength quickly
- Type IV: Low heat generation for mass concrete
- Type V: High sulfate resistance for harsh environments
Portland cement is approximately 95% ground clinker (the fired material) plus 5% gypsum to control setting time. Particle fineness affects hydration rate—finer cement reacts faster but generates more heat.
The name "Portland" comes from the resemblance of hardened cement to Portland stone, a limestone quarried in England. Despite the name, Portland cement is manufactured worldwide according to standardized specifications.
Related Terms
- Cement - General term for binding agents
- Aggregate - Material cement binds together
- Hydration - Chemical reaction when cement contacts water
Learn More
- How to Mix Concrete - Understanding concrete components
- Concrete Basics - Fundamental concrete knowledge
- Concrete Calculator - Calculate your project volume