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Questions and Answers
What is the primary purpose of conducting laboratory tests on Portland cement?
What is the primary purpose of conducting laboratory tests on Portland cement?
- To evaluate the cost of production
- To analyze its chemical composition
- To assess its physical properties and quality (correct)
- To determine its color and size
Which of the following is NOT a physical property of aggregates?
Which of the following is NOT a physical property of aggregates?
- Specific gravity
- Bulk density
- Thermal conductivity (correct)
- Moisture content
What does the bulking of sand refer to in the context of aggregate properties?
What does the bulking of sand refer to in the context of aggregate properties?
- The increase in volume of sand due to moisture (correct)
- The grading of sand particles based on size
- The reduction in weight of sand when wet
- The presence of impurities within the sand
Which type of cement is specifically designed for underwater construction?
Which type of cement is specifically designed for underwater construction?
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Which of the following factors does NOT affect the specific gravity of aggregates?
Which of the following factors does NOT affect the specific gravity of aggregates?
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Study Notes
Cement: Physical Properties
- Portland cement is a hydraulic cement, meaning it sets and hardens by chemical reaction with water.
- Key physical properties that affect performance:
- Fineness: Determines the rate of hydration and strength development.
- Specific surface area: Measured using the Blaine air permeability method.
- Chemical composition: Influences the strength, setting time, and resistance to chemical attack.
- Soundness: Resistance to expansion due to internal chemical reactions.
- Setting Time: Time required for the cement paste to lose its plasticity.
Laboratory Tests on Cement
- Tests assess quality and conformity to standards.
- Setting Time: Vicat apparatus measures the initial and final setting times.
- Compressive Strength: Measured using standard test cubes after curing.
- Fineness: Blaine air permeability test or sieve analysis.
- Soundness: Le Chatelier test measures expansion due to reaction with water.
- Chemical Composition: Chemical analysis determines the proportions of various oxides.
Types of Cements
- Ordinary Portland Cement (OPC): Most common type, used in general construction.
- Rapid Hardening Cement: Sets and gains strength faster than OPC.
- Low Heat Cement: Generates less heat during hydration, suitable for large structures.
- High Alumina Cement: High strength and resistance to high temperatures.
- Sulphate Resisting Cement: Resistant to attack by sulphates, used in marine environments.
Aggregate: Classification
- Fine Aggregate: Sand, maximum size less than 4.75 mm.
- Coarse Aggregate: Gravel, crushed stone, maximum size varies based on application.
- Classification: Based on origin (natural or crushed) and gradation (size distribution).
Aggregate: Physical Properties
- Specific Gravity: Ratio of the weight of a material to the weight of an equal volume of water.
- Bulk Density: Weight of a unit volume of aggregate, including voids.
- Absorption: Ability of aggregate to absorb water.
- Moisture Content: Percentage of water in aggregate, affects its weight and volume.
- Bulking: Expansion of aggregate when wet, due to water filling voids.
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