Methods for Testing Soundness of Cement: Le-Chatelier and Autoclave Methods

What is Soundness of Cement Test?

The soundness of cement test Changes of volume after completion of mold cast. After casting change of volume of molded cement test, this changing call soundness of cement test.

Relevant IS Code: IS 4031 Part 3

Two methods may determine the soundness of cement. as per below

1. Le-Chatelier method
2. Autoclave method

 1. Le-Chatelier Method

Aim of Le-Chatelier Method

To determine the Cement Soundness test use Le-Chatelier method

Apparatus of Le-Chatelier Method

1. Weighing Balance

2. Le-Chataleier molds/ Le chatelier apparatus

The test shall conform to IS: 5514-1969*.

3. Miscellaneous ( trowels, tray, stopwatch, etc.)

Procedure of Le-Chatelier Method

1. Take 400gm of Cement and find its standard consistency for Cement soundness test
2. Place the lightly oiled Le- Chatelier mold on a lightly oiled glass sheet
3. Prepare a cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency.
4. Fill the Le-Chatelier mold with this cement paste made in step (iii) of the procedure.
5. Cover the mold on the top with another piece of a lightly oiled glass sheet.
6. Place a small weight on this covering glass sheet and immediately submerge the whole assembly in the water at a temperature of 27° to 32° degree Celsius and keep it there for 24 hours.
7. Measure the distance between the indicator points. Submerge the mold again in water. Bring to boiling point in about 25-30 minutes and kept it boiling for 3 hours.
8. Removal, the mold from water, allows it to cool and measure the distance between the indicator points. The difference between these two measurements represents the expansion of cement.

Water Bath of Le-Chatelier Method

Water bath capable of containing immersed Le-Chatelier molds with specimens and of raising their temperature from 27 ± 2°C to boiling in 27 ± 3 minutes. From IS Code 4031 Part 3 Cl 5.1.4

Calculation of Le-Chatelier Method

Calculate the mean of two values to the nearest 0.5 mm to represent the expansion of cement. From IS Code 4031 Part 3 Cl 5.3

Acceptance Criteria of Le-Chatelier Method

This must not exceed 10mm for ordinary, rigid hardening & low heat Portland cement. If in case the expansion is more than 10mm as tested above, the cement is said to be unsound.

2. Autoclave Method

Aim of Autoclave Method

To determine the Cement Soundness test use Autoclave method

Apparatus of Autoclave Method

1. Weighing Balance

2. Autoclave

3. Graduated Glass Cylinders

Graduated glass cylinders of 150 ml capacity shall be used, The permissible variation on these cylinders shall be plus or minus one milliliter. The main graduation lines of the cylinders shall be in circles and shall be numbered.

The east graduations shall extend at least one-seventh of the way around, and intermediate graduations shall extend at least one-fifth of the way around the cylinder. The graduation lines may be omitted for the lowest 5 mI. From IS Code 4031 Part 3 Cl 6.1.3

4. Molds

Molds of 25 X 25 mm size and 282 mm internal length and other accessories conforming to IS: 10086-1982

Procedure of Autoclave Method

1. At 24 ± t h after molding, the specimens shall be removed from the moist atmosphere, measured for length, and placed in the autoclave at room temperature in a rack so that the four sides of each specimen shall be exposed to saturated steam. For soundness of cement test  From IS Code 4031 Part 3 Cl 6.3
2. The autoclave shall contain enough water to maintain an atmosphere of saturated steam vapor during the entire period oftest. From IS Code 4031 Part 3 Cl 6.3
3. Ordinarily; 7 to 10 percent of the volume of the autoclave shall be occupied by water.
4. To permit air to escape from the autoclave during the early portion of the heating period, the vent valve shall be left open until steam begins to vanish.From IS Code 4031 Part 3 Cl 6.3
5. The valve shall then be closed, and the temperature of the autoclave shall be raised at such a rate as will bring the gauge pressure of the steam to 2.1 MPa in I to Ii h from the time the heat is turned on.. From IS Code 4031 Part 3 Cl 6.3
6. The 2.1 ± O’lMPa pressure shall be maintained for 3 h. At the end of 3 hours period, the heat supply shall be shut off, and the autoclave cooled at a rate such that the pressure will be less than 0.1 MPa at the end of the hour, and any pressure remaining shall be slow-released by partially opening the vent valve until atmospheric pressure is attained. From IS Code 4031 Part 3 Cl 6.3
7. The autoclave shall then be opened, and the test specimens immediately placed in water,
8. The temperature of which is above 90°C.
9. The water surrounding the bars shall·then be cooled at a uniform rate by adding cold water so that the temperature of the water shall be lowered to 27 ± 2°C in 15 min.
10. The water surrounding the specimens shall then be maintained at 27 ± 2°C in 15 min when the samples shall be surface-dried, and their lengths measured again. From IS Code 4031 Part 3 Cl 6.3

Calculations of Autoclave Method

The difference in lengths of the test specimen before and after autoclaving shall be calculated to the nearest 0’01 percent of the effective gauge length which is the length between the innermost points of the metal inserts used as reference points and shall be reported as the autoclave expansion of the cement.

A contraction ( negative expansion) shall be indicated by prefixing a minus sign to the percentage expansion reported. From IS Code 4031 Part 3 Cl 6.3

Frequently Asked Questions (FAQ) about Cement Soundness Testing

What is the significance of the soundness test for cement?

The soundness test assesses the stability of cement against volume changes after setting. It is crucial to ensure the durability and performance of cement in various construction applications.

How is the soundness of cement tested?

Two primary methods are used: the Le-Chatelier method and the Autoclave method. Both methods involve subjecting cement specimens to specific conditions to measure volume changes.

What apparatus are required for the Le-Chatelier method?

The Le-Chatelier method requires a weighing balance, Le-Chatelier molds or apparatus, and miscellaneous items such as trowels, trays, and stopwatches.

What is the procedure for the Le-Chatelier method?

The procedure involves preparing a cement paste of standard consistency, filling the Le-Chatelier mold, submerging it in water, and measuring the expansion after specified time intervals.

What are the acceptance criteria for the Le-Chatelier method?

According to IS Code 4031 Part 3, the expansion of cement should not exceed 10mm for certain types of cement. If the expansion exceeds this limit, the cement is considered unsound.

What apparatus are required for the Autoclave method?

The Autoclave method necessitates a weighing balance, an autoclave, graduated glass cylinders, molds, and other accessories conforming to relevant standards.

What is the procedure for the Autoclave method?

The procedure involves subjecting cement specimens to saturated steam in an autoclave at specified pressure and temperature conditions, followed by measuring the length changes.

How are the results calculated for the Autoclave method?

The difference in lengths before and after autoclaving is calculated as a percentage of the effective gauge length. A contraction is indicated by prefixing a minus sign to the reported percentage expansion.

What are the implications of unsound cement?

Unsound cement can lead to structural defects and compromise the integrity of concrete structures. It is crucial to identify and reject unsound cement to ensure the quality and longevity of construction projects.

Why is it essential to follow standard procedures and guidelines for soundness testing?

Standardized testing procedures ensure consistency, reliability, and comparability of results across different testing laboratories and construction projects. Adhering to standards helps maintain quality control and regulatory compliance in the construction industry.