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Questions and Answers
What are the physical properties of cement?
Bulk density, density and relative density, fineness, soundness, time of setting, consistency, heat of hydration, strength characterization, loss on ignition.
What is the main use of Portland cement?
To make Portland cement concrete.
What is the typical specific gravity range of cement?
The fineness of cement does not affect its hydration behavior.
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What methods are used to measure the fineness of cement?
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What is the bulk density of cement typically?
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What does soundness of cement refer to?
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The bulk density of cement should be measured by _____ instead of volume for batching concrete.
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Study Notes
Portland Cements Definition and Uses
- Portland cement is a fine powder that binds aggregate together in concrete when mixed with water
- Its primary use is in the production of portland cement concrete
- Can also be used for soil stabilization and highway construction aggregate bases
Physical Requirements of Portland Cement
- The quality of Portland cement is assessed based on physical properties tested per ASTM C183:
- Bulk density
- Density and relative density (specific gravity)
- Fineness
- Soundness
- Setting time
- Consistency of cement mortar or paste
- Heat of hydration
- Strength characterization
- Loss on Ignition
1. Bulk Density (Unit weight)
- The mass of cement particles, including the voids (air) between them per unit volume
- Bulk density is not consistent due to variations in handling and storage
- As a result, cement quantities for concrete should be measured by mass (weight) instead of volume
- Bulk density can vary between 830 to 1650 kg/m3
- Compaction can impact bulk density: 20% difference
2. Density and Relative Density (Specific Gravity)
- The mass of a unit volume of cement solids or particles excluding air in between
- Relative density or specific gravity is the density of cement divided by the density of water
- Specific gravity ranges from 3.10 to 3.25, averaging 3.15
- Crucial for mixture-proportioning calculations
- Can be determined using a Le Chatelier flask with kerosene or a helium pycnometer (ASTM C188)
- Particle size: Finer than a #200 sieve (75 μm)
- A commercial bag of cement in Saudi Arabia weighs around 50kg
3. Fineness of Cement
- The extent to which cement is ground
- Influences hydration behavior:
- Increases the rate of hydration with increasing fineness
- Higher rate of strength development and heat evolution in the first seven days
- Requires more water for workability at high fineness, causing increased drying shrinkage
- High fineness reduces the durability of concrete subjected to freeze-thaw cycles
- Fineness is expressed as specific surface area (m2/kg)
- Measured by:
- Wagner Turbidimeter test (ASTM C115)
- Blaine Air Permeability test (ASTM C204) (most used)
- Percent passing the 0.045 mm sieve (No. 325) (ASTM C430) (old method)
4. Soundness of Cement
- The ability of a hardened paste to retain its volume after setting without excessive expansion
- Unsound cement: exhibits excessive expansion, leading to cracking and disintegration
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Description
This quiz covers the definition, physical requirements, and primary uses of Portland cement. Learn about its role in concrete production, soil stabilization, and the various properties that affect its quality. Test your knowledge on the bulk density and other important metrics of this essential construction material.
