How to Check the Quality of Cement on Site

Cement is widely used construction material that is generally used as binding agent in mortar and concrete, just like lime. Cement is rarely used on its own, but majorly used in combination with fine and coarse aggregates to form mortar and concrete. Constituents of cement are basically inorganic in nature mainly lime and calcium silicate based compounds, having hydraulic nature.

1. Use of Cement in Mortar

Mortar is the combination of Binding Agents like cement or lime with Filler Agents (the fine aggregate) like sand, surkhi (dust of over burnt broken bricks or clay balls), cinder (generic term for residue of burnt coal or similar fuels). Mortar is widely used for cement plastering, damp proof course (DPC), etc.

Cement may be described as a binding material that shows adhesive and cohesive properties in the presence of water, through which it is capable to bind different aggregates together following the process of setting, hardening, and adhering with the other filler materials.

2. Use of Cement in Concrete

While concrete is formed when Filler Agents i.e. fine aggregates and coarse aggregates are mixed with Binding Agents in the presence of water, the liquid medium. Concrete is widely used in Plain Cement Concrete (P.C.C.) members like footings, and also used in Reinforced Cement Concrete (R.C.C.) like beams, slabs, columns, piers, piles, etc. Prestressed Concrete Members and Precast Concrete Members are also prepared with the help of cement.

3. Importance of Testing the Cement

As we learnt the utilization of cement in mortar and concrete. It is utmost important learning for the Site Engineer and the Material Testing Engineer belonging to the Construction Firm or belonging to any Consultant Firm to thoroughly investigate the properties and adequacy of cement for the said use. Without testing, one need not to proceed further, as inadequacy of binding material may compromise the strength of the casted member.

4. Suitability of Cement

Proper Mix Design of concrete members needs to be is carried out first thus specifying the requirements for the Grade of the Cement and the Quantity of the Cement. However, the Grade of Cement is related to strength of cement, while Quantity of Cement is related to number of bags of cement, that can be calculated through Quantity Surveying techniques. Both of these specifications are not suggesting the suitability / quality of the cement.

5. Types of Cement Tests

All kind of tests that are carried out on a sample of cement can be categorized into the following types;

1. Physical Testing
2. Chemical Testing
3. Mechanical Testing

5.1 Physical Testing of Cement

Physical testing of the cement may be involving all the senses of the human. Human have 5 senses (smell, sight, hearing, taste, touch) through which one can deducted quite a lot of logical reasoning and can identify and differentiate between a lot of physical properties of cement.

5.2 Chemical Testing of Cement

Chemical testing of the cement may involve chemical analysis for the identification of chemical composition of cement that are in the form of oxides and elements available with the cement sample, that may involve XRD and XRF analysis.

5.3 Mechanical Testing of Cement

Mechanical testing or experimentation may involve cement being directly tested for strength testing like compression testing, tensile testing, or the flexural / bending testing of the cement sample. Different combinations of fine aggregate and cement, like in mortar, may be tested. Or concrete sample maybe tested against mechanical properties for verifying the strength enhancement with the addition of cement.

6. Testing the Quality of Cement in the Field

Material Engineer or Site Engineer needs to test the quality of cement for which various preliminary observational tests related to physical testing of the cements needs to be carried out first. These initial tests may not give the full description of the properties of cement, but still, they are enough for checking the preliminary usability of cement.

Now let us dive into the details of the physical tests that can be performed at the site without the need of instruments;

6.1 Check – The Packaging Date of Cement Bags

The first step the Site Engineer should carry out is to inspect the date of manufacturing or packaging of cement bags. Manufacturing date is printed directly on the side or on the front of the cement bag.

Read and note the manufacturing dates of random cement bags. Usually many bags are manufactured and ordered in series. If cement bags are bought from different vendors then do check out the random cement bags manufacturing dates.

And if the dates on cement bags are within first 90 days of manufacturing, then it is suitable to use. Otherwise, strength of the cement might have been compromised.

6.1.1 Why Old Cement Bags Cannot be Used?

It is globally accepted standard that cement bag should be consumed within first 3 months or 90 days of manufacturing. As with each passing day, strength of the cement starts reducing, due to the presence of moisture in the environment. As cement is hydroscopic (readily taking or absorbing moisture) compound i.e. it starts reacting with the moisture present in the atmosphere.

6.1.1.1 Moisture in Environment Matters for Cement

Greater is the moisture content present is the atmosphere, the greater will be moisture absorbed by the bag of cement which is very fine reactive powder. Moisture levels in various states and various seasons might differ. So due consideration needs to be given to such environment dependent situations. Moisture absorption may also be affected by the Fineness Index of the cement i.e. the surface area of the cement particles. The finer the particle size the more reactive it will be.

6.1.1.1 What happens when Cement absorbs Moisture?

When bag of cement absorbs moisture it starts is hydration process i.e. the reaction starts when cement powder particles react with moisture and setting of the cement starts. Leading towards the hardening stages, thus a time comes when cement do not remain reactive at all. As it has already been hardened. It should be noted that cement reacts in single stage i.e. multiple hydration cycles do not occur, ever.

6.1.2 Percentage Reduction in Strength of Cement with Age

If bag of cement is 3 months old, the reduction in compressive strength will be 20% as compared to the fresh cement bag. This 20% reduction in strength is acceptable. However greater then 20% reduction in cement strength will not be acceptable.

Similarly in 6, 12 and 24 months old bag of cement the reduction in strength will be 30%, 40% and 50% respectively. However, as stated earlier, cement bag older then 3 months or 90 days is not recommended for construction purposes.

The following table summaries the reduction of strength in percentage with the passage of time in months.

6.1.3 How to Check the Manufacturing Date on Bag of Cement

In Pakistan, the bag of cement usually do not contain the manufacturing dates. While in India, manufacturing dates are labeled at the longitudinal side of the cement bags.

Manufacturing date might be written in abbreviation like MGF on the bag of cement.

Here in above figure manufacturing date of this cement bag is June W22, that means it is the Week 22 of the year, that can be check in Online Week Calendar that starts from 30th May to 5th June.

Some cement bags might contain more descriptive manufacturing dates like the above. Here, one can read W48 DEC Y13. That shows that the cement was manufactured on the 48th week of the Year 2013 which come to be in the month of December. By observing the Online Weeks Calendar, the 48th week is from 25th of Nov to 1st of Dec of the year 2013.

6.2 Check – The Color of Cement Particles

The second physical site investigation on quality of cement that can be carried out is to check the color of cement particles inside the bag of cement.

• If the color of the cement particles is uniform then that indicates uniform mixing and ingredients.
• The color of the cement observed through naked eyes should be light grey in color.
• If the color of cement particles in dark greenish then that indicates excessive amount of clay or lime or coloring pigments like Chromium Oxide.

6.2.1 How is Colored Cement produced?

Coloring in cement can be achieved by mixing uniformly the coloring pigments with the Ordinary Portland Cement ranging from 5% to 10%.

If the coloring pigments increase 10%, the reduction in cement strength might be observed. Thorough physical, chemical, and mechanical test needs to be carried for further investigation of the effect of coloring pigments on strength of cement.

6.2.2 What is the White Cement?

1. White Cement is similar to the Ordinary Portland Cement (OPC) but free from coloring pigment like iron, manganese, chromium, cobalt, etc.
2. In production of white cement, burning oil is used instead of coal.
3. As the name indicates, this cement is white in color and used for ornamental and decorative works like colored flooring, colored plastering work, etc.
4. The Setting Time of white cement is similar to Ordinary Portland Cement.

6.3 Check – The Lumps Test for Cement Particles

Cement on site should be checked thoroughly for lumps. Lumps are hardened coalesced cement particles combined in the presence of moisture though the process of hydration. As stated previously, cement particles are hygroscopic and absorb moisture from the atmosphere and its hydration process initiate at the time its particles are in contact with moisture.

Thus, if there are lumps found in the cement bag, that means either the cement bag is too old or the bag of cement had been in placed in the moist environments. Such cements should be avoided and returned to the supplier or manufacturer.

6.4 Check – The Rubbing Test or Cement Adulteration Test

As cement is a fine aggregate, hence it should feel soft when rubbed in between your fingers. Take a small quantity of cement in your hand, and with the help of finger try to rub the cement particles.

1. If you feel smooth touch then cement is fine.
2. If your finger feels hard particles then that means either sand particles are present or lumps have been formed.

This test is also known as Cement Adulteration Test. By Adulteration it means lower quality substance have been mixed in the substance. If gritty or rough text particles are observed during rubbing then that may mean cement has adulterated.

6.5 Check – The Cement Float Test

If the cement is placed in a bucket full of water, then fresh cement will sink after floating for a while. However, if the cement is aged then it might sustain on the surface of water.

1. The greater the freshness, the quicker cement will in sink.
2. The little the freshness, the longer cement will take to sink.

6.5.1 Reasoning behind the Cement Float Test

As cement particles are highly reactive. If it comes into direct contact with water it will absorb moisture thus sinking down due to increase in density of the particles. While if cement particles are already hydrated and have created lumps then they might take longer to sink as they will not be as reactive as fresh cement particles because their hydration cycle have already been completed.

6.6 Check – The Temperature Test or Hand Insertion Test

One of the easiest test that can be carried out to check the quality of cement is by Hand Insertion Method in which dry clean hand is directly inserted within the opened cement bag.

1. If the cement particles on contact with hand gives feels cool, that means it is fresh.
2. If the cement particles on contact with hand gives warm feeling, that means hydration has already start.

6.6.1 Limitation of Hand Insertion Test for Cement

One cannot differentiate between coolness due to not hydrated particles or hydrated particles as both may give cooling effect unless The Lump Test is being carried out.

6.7 Check – The Cement Odor Test

Simply stating, cement do not smell. If their is significant smell then ingredients are mixed in different proportion then standard set for Ordinary Portland Cement.

1. If cement is smelled and it smells nearly odorless, then that means it is having standard chemical composition.
2. If upon smelling the cement particles, it smells earthly then that means large amount of calcareous or clay particles are present.

6.8 Check – The Cement Strength Test or Cement Soundness Test

For carrying out strength test on cement a block of cement having dimension of 2.5 cm x 2.5 cm and 20 cm long should be cast. After 24 hours, dismantle the formwork and submerge the cement block in water for a period of 7 days. The submerged cement block when loaded with a weight of 34 kg or 340 N.

1. If the cement block under load showed no signs of failure then the block is prepared of good cement.
2. If the cement block under load showed signs of failure then that is not a good cement.

Load carrying capacity is the significant indicator of quality of cement.

6.9 Check – The Shape Test on Cement or Consistency Test

Quality of cement can also be checked by the Consistency Test of Cement, unlike the Setting Time Test of Cement, which is a Laboratory Test.

In this test cement specimen of 100gm is taken on a glass, and mixed properly and uniformly with little amount of water. Quantity of water should be enough to hydrate all the cement particles and make the sample stiff.

With the help of trowel, formulate a cement cake with the help of straight edges of trowel. Later on submerge the glass plate having the stiff cement sample into the water tub.

Keep the sample submerged under water for 24 hours, after which it should be taken out to check the edges of the casted sample.

1. If on the cement sample one can spot cracks and the edges of sample have been eroded away, that indicates the cement was not of good quality.
2. Otherwise, if the sample is having uncracked surface, and edges are sharp and straight, that indicates cement sample was fresh and of good quality.

6.9.1 Precaution – The Cement Shape Test

As this test involves manual mixing, the quantity of added water may change due to randomness, thus such test should be done by Experts who are good at hands on practice.

6.10 Check – The Specific Gravity Test on Cement

The last test that can be conducted on site or field is the Test for Specific Gravity of Cement Sample. This test is based on Le Chatelier’s Principle, in which specific gravity of cement is determined by Le Chatelier’s Flask Method.

The method for conducting this test requires an additional article. However, the following deductions for the measurement to standard of cement needs to be known;

1. A good quality cement should have specific gravity of cement in between 3.1 g/cm3 to 3.6 g/cm3. The optimum specific gravity should be 3.16 g/cm3.
2. Specific gravity or density of 3.16 g/cm3 means the material is 3.16 times denser or heavier then water.
3. Specific gravity is unitless or dimensionless quantity, that can be converted to density by multiplying specific gravity of sample with the specific gravity of water which is 0.99756.
4. Every material has its own specific gravity ranging from 0.1 to 100.
5. If the specific gravity of the material is less then 1, that will float on the surface of water. Means the density sample is lower then the density of water, thus, it will float.
6. If the specific gravity of the material is more then 1, than the material will sink in the water.

6.10.1 Precaution – The Specific Gravity Test on Cement

As this test is technical, thus recommended to be performed by expert and should be carried out in the laboratory.

7. Conclusion

The prolonged testing list ends here. You have seen several methods through which Civil Engineers specially the Site Engineers or the Quality Control Engineers can verify the standard of cement by performing various physical, chemical and mechanical tests on the sample specimen. Here we only went through the physical tests that did not involve heavy instruments for testing the quality of cement.

Hopefully, you would have learnt a lot. Feel free to share your comments below. If you have any query then please do let me know. Sharing is Caring!

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