6 different cement tests

No cement is used without first being tested. This is an integral part of the cement manufacturing and construction process.

Cement is one of the most used materials in the world. It is very rare to see a structure without the use of this material. To produce cement, limestone, shells and chalk or marl are used in combination with shale, clay, slate, blast furnace slag, quartz sand and iron ore.

The physical and chemical properties of cement are tested as per standards to ensure they are within limits. The frequency of testing and the number of cement tests depend on the relevant guideline (code) or technical specification. The physical properties of cement are generally tested during construction. Seven cement tests can be identified that are most frequently tested as a measure to control cement quality.

1. fineness
2. Compressive strength
3. Heat of hydration
4. Initial and final setup time
5. solidity
6. Normal consistency

The background and basic technical information for each cement test is explained here.

CEMENT FINISHING TEST

The size of the cement particles directly affects the strength of the concrete. Finer particles react very quickly than comparatively large particles. Additionally, thin cement has a greater surface area and therefore develops strength more quickly. There are two methods to test the fineness of cement

1. Through seven
2. When determining specific surface area

The following standards and methods are commonly used to test cement fineness.

1. AASHTO T 98 and ASTM C 115: Fineness of Portland cement using turbidity meter.
2. AASHTO T 128 and ASTM C 184: Fineness of hydraulic cement with 150 mm sieves (#100) and 75 mm sieves (#200)
3. AASHTO T 153 and ASTM C 204: Fineness of hydraulic cement using air permeability device o AASHTO T 192 and
4. ASTM C 430: Fineness of hydraulic cement using 45 mm sieve (no. 325).

The sieve test involves taking a 100 mg sample and continuously passing it through a standard BIS #9 sieve for 15 minutes. The weight of the remaining cement is measured. It should not exceed 10% of the original weight.

The specific surface area of ​​cement particles is calculated using a permeability test. This test provides a better result compared to the sieve analysis test. Additionally, it provides information about fineness uniformity. The specific surface area of ​​the cement should not be less than 2,250 cm. ² /gm.

CEMENT NORMAL CONSISTENCY TEST

Normal consistency or standard consistency is the ideal water content required for a cement paste. Normal consistency is the proportion of water to weight of cement required to produce cement paste that permits penetration of a 10 mm diameter piston to a value of 10 mm ± 1 mm below the original surface within 30 seconds after the Letting go shows.
Normal consistency testing can be done based on BS 12 or ASTM C-187-04 using a Vicat device. The cement sample weighs 500g (as per BS12) and pure water is used for the test.

Vicat device

Consistency checking is performed as follows:

1. Mix 500g of cement with a known quantity of water and make a cement paste using the standard procedure
2. Place the cement paste on the Vicat device ring and remove excess cement paste with the spatula.
3. Finish the piston with the past surface and tighten the fixing screw
4. Place the movable pointer at the upper zero marks on the scale or take the first reading. Then release the stick immediately. Wand release should occur within 30 seconds of completion of blending.
5. The device must not be moved and must be free from vibration.
6. The paste will be of normal consistency if the stick sinks to a depth of 10mm±1mm below the original surface within 30 seconds of release.
7. Experiment until normal consistency is achieved.
8. Based on the tests carried out, the proportion of water to be added to reach normal consistency is around 22-30 percent of the amount of cement.

TESTING THE INITIAL AND FINAL CURING TIME OF CEMENT -Cement tests More related to construction

When cement is mixed with water, a hard, sticky paste is formed. Cement paste remains plastic for a short time and its plasticity gradually decreases. Eventually it becomes a solid mass. This phenomenon in which the cement paste passes from a plastic state to a solid mass is called cement setting.

The cement setting time is divided into two parts. They are the initial setting time and the final setting time. The point at which the cement begins to harden and completely loses its plasticity is called the initial setting time. The point at which the cement completely loses its plasticity and becomes hard is the final setting time of the cement.

The water-cement ratio, temperature and relative humidity, cement fineness and chemical composition of the cement are factors that affect the cement setting time. Cement setting time testing can be performed using the Vicat device. Setting time can be determined using ASTM C 191 or BS EN 196-3:2005.

The following procedure can be used to determine the initial adjustment time specified in BS EN 196-3:2005.

1. Place the filled mold and base plate in a room or humidity closet with the recommended humidity.
2. Position the Vicat device needle in contact with the paste
3. Release the needle slowly to avoid starting speed or forced acceleration of moving parts.
4. Then quickly release the moving parts and let the needle penetrate the paste vertically
5. Read the scale when penetration is complete or 30 seconds after releasing the needle, whichever comes first.
6. Record the scale value indicating the distance between the tip of the needle and the base plate, along with the time from zero.
7. Repeat the penetration test on the same sample at suitably spaced locations, at least 10 mm from the mold edge or each other at suitably spaced intervals, e.g. B. in 10-minute intervals.
8. The Vicat needle must be cleaned immediately after each puncture.
9. Record the time measured from the zero point where the distance between the needle and the base plate is (4±1) mm as the initial setting time of the cement to the nearest 5 mm.

To determine the final setting time of the cement paste, the following procedure can be used

1. The filled mold that was used to determine the initial solidification time is inverted. Final solidification tests are performed on the sample surface that was originally in contact with the base plate.
2. Insert the needle with a ring to facilitate close observation of small holes. The same procedure described for testing the initial setup time can also be used for this test.
3. Time intervals between penetration tests can be increased to, for example, 30 minutes.
4. The test must be carried out at the specified humidity
5. The needle must be cleaned immediately after each test.
6. Record the time (measured from zero) after which the needle first penetrates just 0.5 mm into the sample, to the nearest 15 minutes, as the final setting time of the cement.

CEMENT COMPRESSION STRENGTH TESTING – Cement testing in connection with production

The compressive strength of cement is a very important factor because we basically use concrete to withstand compressive loads. The compressive strength of cement is directly related to the strength of concrete.

Cement compressive strength tests may be carried out in accordance with the procedures specified in ASTM C 109 or BS EN 196-1-2005. This section explains cement testing in accordance with BS EN 196 Part 01. When testing cement, the following procedure can be followed.

1. Prismatic specimens measuring 40x40x160mm are used.
2. Samples are molded from a batch of plastic mortar containing a cement:sand (standard sand) mixture ratio of 1:3. The water-cement ratio is maintained at 0.5.
3. Each batch of test sample must consist of 450 ± 2 g of cement, 1350 ± 5 g of sand and 225 ± 1 g of water.
4. The mortar is produced by mechanical mixing and compacted in the mold using a commercially available vibrator.
5. The samples are kept in a humid environment for 24 hours and then the demolded samples are stored under water until testing.
6. At the time of testing, the samples are broken in half by bending stress and each half is tested for compressive strength. The following figure shows the test setup

The strength of the cement shall be as specified in BS EN 196-Part 01. The table below indicates the strength requirements based on the type of cement.

TESTING THE HEAT OF HYDRATION OF CEMENT

The heat generated during hydration is called heat of hydration. The heat of hydration is mainly influenced by the proportions C. ₃ S and C ₃ A in cement. In addition, water-cement ratio, cement fineness and curing, installation temperature, etc. also affect the heat of hydration of the cement.

The heat of hydration test can be carried out using the solution method in accordance with BS EN 196-8:2010 or the semi-adiabatic method in accordance with BS EN 196-9:2010. Additionally, the procedure specified in ASTM 186 can also be followed.

CEMENT STRENGTH TEST

The ability of a hardened paste to maintain its volume after setting is called cement strength. A cement is considered to have no strength if it is subjected to delayed destructive expansion. The expansion may be due to hydration of unbound calcium oxide and/or magnesium oxide. Cement strength tests are carried out using a Le Chatelier device. The following procedure is followed for resistance testing in accordance with BS EN 196 – Part 3.

1. The test must be carried out simultaneously on two specimens from the same batch of cement paste.
2. Prepare a standard consistency cement paste
3. Place a lightly oiled Le Chatelier mold onto the lightly oiled base plate and fill immediately without over-compacting or vibrating. To do this, use only your hands and, if desired, a straight tool to smooth the top surface.
4. When filling, prevent the mold opening from opening inadvertently, e.g. B. applying light pressure with your fingers or tying it or using a suitable elastic band.
5. Cover the mold with the lightly oiled cover plate, add additional mixture if necessary, and immediately place the entire apparatus in the humidity cabinet.
6. Keep at (20±1) for (24±0.5) hours ⁰ C and not less than 98% relative humidity.
7. After (24 ± 0.5) hours, measure the distance between the display points to the nearest 0.5 mm.
8. Then heat the mold slowly (30 ± 5) minutes until boiling and keep the water bath at boiling temperature for 3 hours ± 5 minutes.
9. The distance between the indicator points can be measured with an accuracy of 0.5 mm at the end of the cooking time.
10. Allow the mold to cool to (20±2) ⁰ C. Measure the distance between the display points to the nearest 0.5 mm.
11. For each sample, calculate the difference measured in Step 10 and Step 7.
12. Calculate the average of the two values ​​(two samples) to the nearest 0.5 mm

CHEMICAL ANALYSIS OF CEMENT

Chemical analysis may be carried out in accordance with BS EN 196-2:2013 or another applicable standard. Depending on the availability of different chemicals, the content of the chemicals is evaluated. To determine the content, for example, pure silica, soluble silica, total silica, etc. can be determined.

The same applies to other materials such as aluminum, iron, magnesium oxide, calcium oxide, etc. All determinations can be carried out in accordance with BS EN 192-2.

Summary of Limitations of Cement Testing