Questions and Answers
What is the required room temperature range for cement testing?
Which sieve numbers are used for physical and chemical tests?
What is the cube size used in the 3-gang mold?
2 in by 2 in
How much water is needed for 2 molds using Type 1p and 1t?
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The required temperature for the moist cabinet is ______ °C.
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Which type of cement is used for general use construction?
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What is the allowable expansion of cement in the autoclave specimen?
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What is the strength requirement for Type I cement after 28 days?
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Type IP cement is used for plastering.
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What is the ideal weight of the cylindrical measure for testing fineness?
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The sample must achieve a strength of ______% at least on the 7th day for Type I cement.
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Study Notes
Compressive Mortar Strength Testing
- Testing temperature for cement should be between 20°C to 27°C with 50% humidity in a moist cabinet.
- Sieve no. 20 must pass while being retained on sieve no. 30 for physical tests.
- For chemical tests, material must pass through sieve no. 100.
Molds and Measurements
- A 3-gang mold is used with cube dimensions of 2 inches by 2 inches for cement mix molding.
- For two molds, use 500 g of cement, 1375 g of Ottawa sand, and 242 ml of water.
- For three molds, use 740 g of cement, 2035 g of Ottawa sand, and 359 ml of water.
Equipment Used
- Key equipment includes a graduated cylinder, wash bottle, rubber tamper (1/2 in x 1/2 in x 150 mm), timer, conical mold (4 in), and flow table.
Mixing and Flow Table Testing
- Cement mixture on flow table requires 110 ± 5% consistency.
- Layer the sample in conical mold, tampering each layer with 20 blows.
- Standby time is 1 minute before removing the conical mold.
- Conduct 25 blows on flow table in 15 seconds; repeat if the sample fails.
Mixing Procedure
- For the cement mixer, the slow speed is set at 140 ± 5 rpm and medium speed at 285 ± 10 rpm.
- Mix with Ottawa sand for a total of 1 minute, allowing for 90 seconds scraping.
- After mixing, load the sample into the conical mold and perform flow tests.
Curing Process
- Place molded samples in a moist cabinet for 24 hours before submerging in water baths at increments of 3, 7, and 28 days.
- Required strengths for Type I cement:
- 12 MPa at 3 days
- 19 MPa at 7 days
- 28 MPa at 28 days.
Tolerances for Strength
- Strength measurement tolerances are:
- 3 days — 1 hour
- 7 days — 3 hours
- 28 days — 12 hours.
Types of Cement
- Type IP: Blended Cement (Portland Pozzolan) for plastering.
- Type IL: Blended Cement (Portland Limestone).
- Type IT: Blended Cement (Portland Volcanic Tuff).
- Type I: General-use Portland Cement.
Specific Gravity Testing
- Specific gravity of cement assessed using a Le Chatelier flask, kerosene, and a cement sample, measuring displacement and submerging techniques.
Fineness Module Testing
- For Type I cement, must pass through sieve no. 200; for Type IP and IT, must pass sieve no. 325.
- Procedures include sieving for 4 and 9 minutes, with a wet sieving method for blended cement.
Normal Consistency Testing
- Normal consistency indicates water requirement with a penetration target of 10 ± 1 mm within 30 seconds using Vicat apparatus.
Autoclave Testing
- Autoclave testing allows 0.8% cement expansion and 0.2% allowable shrinkage.
- Process involves mixing 650 g of cement, adjusting water content, and measuring time settings for consistency and penetration.
Time Setting Procedure
- Time setting occurs 45 minutes after normal consistency checking, aiming for 25 mm penetration within a specified interval. Specimens must maintain conditions in the autoclave for final measurements.
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Description
This quiz covers the essential aspects and requirements for testing the compressive strength of mortar. Topics include temperature and humidity conditions, sieve analysis, and the equipment used in the testing process. Ensure you understand the procedures and standards necessary for accurate cement testing.
