Adulteration of Cement: Test, Chemical & Instrumental Analysis

adulteration of cement

In the forensic analysis of cement, adulteration of cement test is done to determine whether the cement sample have adulterants or not. And to identify the type of adulterant, the various preliminary and forensic defined tests are performed which helps in the determination of adulterant.

Adulteration of cement can be defined as the addition of other components to the cement that changes their standard chemical compositions in contrast to various observable and unobservable changes.

Observable changes like color, texture, etc. and unobservable changes like the addition of certain macro elements and metals.

The following is the table of content that states what you get to learn from this blog post on the adulterated cement. And you can also check our dedicated post on Mortar and Concrete Analysis: Forensic Aspects & Chemical Tests.


What do you mean by the Adulteration of Cement?

It is defined as the addition of visible or invisible contaminants to the cement that alters the standard composition set by the manufacturing company of cement.

And the cement that is being altered is called adulterated cement. The materials that are used to make cement adulterated is called adulterants. And this process is called adulteration.

Definition:

Cement’s Adulteration: It is defined as the addition of non-cemented substances which diminishes cement quality.

Adulterant: It is the substance that is used to adulterate the cement. Some adulterants used in adulteration of cement are Rag-stone, furnace ashes, sand, etc.

Common Adulterants of Cement

Common AdulterantObservations
Rag-stonebluish-grey color
Blast Furnacesilver grey
Slaglight grey
Furnace ashescoarse and gritty, with a medium to dark gray color.
Dessert Sandvery light reddish-yellow color, with 2-3 mm of particle size with brittle edges
River Bed sandrounded particles, and may contain clay or other impurities. And a saturated yellow color.

Why their is need to check Adulteration of Cement?

Because adulteration of the quality cement is one of the major cause of structural failure and these are added to cement:

  • To reduce the margins of cost.
  • To decrease the quality of cement.
  • By decreasing quality results in weaker bonding between their particles.

So in major structural failure cases, whether it is a multistoried building or a transport bridge, analysis of the cement is one of the major elements for understanding the standard quality and strength.

Before going any further we have to understand the various type of cement are in the industry and major components of a cement.

More About Cement

What is Cement?

Cement is a mixture of chemicals such as mostly calcium carbonate, silica, alumina, and iron oxide-bearing materials, etc. They are generally prepared from the action of heat and grinding of all the components together. 

Major Components of Cement

The Main Constituents of Cement are:

NameFormula% Composition
Di calcium Silicate 2CaO.SiO230%
Tri calcium Silicate 3CaO.SiO240%
Tri calcium Aluminate Ca3Al2O6, or 3CaO·Al2O311%
Tetracalcium Alumino Ferrite 4CaO. Al2O3 Fe2O311%

Types of Cement

  1. Ordinary Portland Cement (OPC)
  2. Portland Pozzolana Cement (PPC)
  3. High Alumina Cement
  4. White Cement
  5. Colored cement
  6. Rapid Hardening Cement
  7. Quick Setting Cement
  8. Low-Heat Cement
  9. Blast Furnace Slag Cement
  10. Air Entraining Cement
  11. Hydrographic cement

1. Ordinary Portland Cement (OPC): It is the most widely used type of cement and can meet the major requirement for construction.

2. Portland Pozzolana Cement (PPC): It is as same as OPC but the addition of one of the major constituent gives its name i.e. pozzolanic materials. And its percentage ranges between 10% to 30%.

3. High Alumina Cement:  It is manufactured by crushing, melting and mixing clinkers of alumina and calcareous material ( mainly calcium carbonate) such as lime. It is mainly employed in an industry where the concrete has to face acidic, heat and frost conditions. 

4. White Cement: In this type of cement, the proposition of iron-oxide is very negligible or zero. This is why it is also called as free from iron cement. It is a costly cement mainly used as a decorative cement in internal parts of the building.

5. Colored cement: These cements are pigment-based. And consist of 5% to 10% of pigment in ordinary cement or for more contrast pigment is added to iron-free cement. 

6. Rapid Hardening Cement: As per the name, it suggested they attain high strength in earlier days. They contain high lime content wrong with more finer grinding particles. They are generally used in prefabricated concrete construction, like blocks of the bridge, roads, etc. 

7. Quick Setting Cement: Quick-setting cement has less settling time i.e. designed to sets earlier but the rate of gain strength is similar to Ordinary Portland Cement.

8. Low-Heat Cement: This cement has a low heat of hydration that is generally used in mass concrete construction like dams. They are manufactured by constriction the amount of tricalcium aluminates below 6% and increasing the composition of dicalcium Silicate.

9. Blast Furnace Slag Cement: The cement contains clinkers along with slag  60% (approx).

10. Air Entraining Cement: It serves the frost resistance nature, and manufactured by adding air-entraining agents such as resins, glues, sodium salts of sulfates, etc.

11. Hydrographic Cement: Hydrographic cement is prepared by mixing water-repelling chemicals. And they serve the property of water resistance and many used for dams, spillways, water tanks, etc.

How to identify an Adulterated Cement?

How to identify Adulterants and test for Adulterated Cement?

Forensic determination of adulterants in cement (Basic workflow):

  1. Sampling
  2. Preliminary analysis
  3. Laboratory Chemical analysis
  4. Instrumental analysis

Part 1: Sampling 

1 kg sample of cement should be collected in an airtight plastic jar along with recommended details and signature of collecting officer.

Points such as the batch number or details of a cement bag along with the printed details on the cement bag: company name, type of cement, to be noted for future references of the collected sample.

Sampling in case of less than 12 bags: The sample is drawn from each bag irrespective of the number of bags (up to 12 samples only).

Sampling in case of more than 12 bags: If they have different company’s or types of cement bags, then from all the cement bags have the same details and appearing similar,  a minimum of three random samples are collected and sealed 1kg of questioned adulterant cement for analysis.

Part 2: Preliminary Test for Adulterated Cement

Preliminary test for cement analysis for adulteration is listed as:

  1. Color test
  2. Fine Test
  3. Smell test
  4. Presence of lumps
  5. Temperature test
  6. Heat test
  7. Float Test
  8. Shape/ Performance Test
  9. Strength Test

1. Color Test and luminescence

Take 1 gm of sample and even spread on the china dish or plate and observe the color under normal condition.

In this, the color of all the samples is noted in normal conditions as well as various in alternative light sources.

Example: Adulterants like ashes or cremated bone in cement.
Dark purple color when the cremated bone was illuminated with a wavelength of 450 nm and viewed through a yellow long-pass filter. {Source}

2. Fine Test

Finner the particle more is the quality assurance from adulterant like sands. 

For this test take a small sample between your fingers and if it is a case of un-altered cement then it should feel smooth while squeezing. And if it feels un-uniform in nature then it may be adulterated with sand.

3. Smell Test

Adulterant like ashes, pounded clay, and silt have an earthy smell, and if the cement smell like earthy then it clearly show that a large proportion of sand or silt is used as adulterants.

4. Presence of Lumps

Lumps are defined as the hardening of the cement on the application of moisture. The size of lumps defined the amount of water gets reacted with cement. 

Take a 100 gm of sample and check for the observable lumps.

It can also be felt during squeezing the cement sample as small lumps are getting feel like sands. These lumps are easily get crushed when you use a spatula for crushing. 

For example: if a cement sample has small lumps then it can be due to exposure of cement to the tiny droplets of water or moisture. 

5. Temperature Test

Take about 500gm of sample and put your hand with rubber gloves into the sample to feel its temperature. 

If it feels cool then it may be an indication of unadulterated cement. If it is adulterated with sand and ashes feel warmer in contrast to cement. 

It should be noted that this test must be done if the examiner has ambient samples. 

6. Heat Test

Take 1 gm of the sample, heat it for about 20 minutes on a steel plate. And note done the observation.

In the case of adulterated cement, the sample changes its color. But in a case of un-adulterated cement, it retains its color. 

7. Float Test

Take a few grams of cement sample and spread over 100 ml of the water-filled transparent beaker.

Unadulterated cement should first float on the surface for some time, and then starts shrinking and finally settle on the base of the beaker.

While in the case of adulterated cement, particle-like ashes start shrinking right away when sprinkles on the water surface.

8. Shape/Performance Test

Take 10gm of cement sample and make a paste using water.  Make a cake with stiff and sharp edges. Now in another 250ml beaker containing water put the prepared paste and kept for 24 hours. 

If the cement set without a crack, this may be the indication of unadulterated cement and said to be a good performance.

This phenomenon also related to the term called “the hydraulic cement”.

9. Strength Test

A 25mm x 25mm x 200mm cement block is made and then immersed in water for 7 days. Then one side of the cement block is held firm with a hook and the other side has attached to the stings of 34 kg of weight.

If the cement doesn’t broke it is an indication of cement is free from the adulterants.


Part 3: Chemical Analysis of Adulteration of Cement

  1. ThymolphthaleinTest
  2. Acid insoluble
    • Silica
    • Combined Ferric Oxide and Alumina
  3. Determination of Calcium by EDTA Titration
  4. Direct Cement Percentage by acid titration

1. Thymolphthalein Test

This test is based on the use of the thymolphthalein acid-base indicator. The indicator color ranges from 9.3 (colorless) to 10.5 (blue). 

And the cement is incredibly alkaline, with a pH of 12 to 13. This means a blue indication is an indication of the cement. 

Procedure:

  • Take 10 mg of cement sample in a test tube.
  • Add 1-2 ml water followed by  1-2 drops of indicator.

Indication:

The development of the blue color indicates the presence of cement. And colorless solution indicates that the sample is stone powder.

*Preparation of Thymolphthalein Indicator:

Materials Required:

  • 0.04 g thymolphthalein
  • 50 ml of 95% ethanol
  • 100 ml  of distilled water

Procedure 

  • Take a beaker of 250 ml and dissolve 0.04 g thymolphthalein in 50 ml of ethanol.
  • Now dilute the solution to 100 ml with distilled water.

2. Acid Insoluble Test

Principle: The Acid Insoluble Residue test is based on the proportion of a sample that is not hydrolyzed by sulphuric acid with the original sample.

Material and Equipment Required

  • Drying oven
  • Beaker 200 ml
  • Stirring rods
  • Filter paper number 2 or ashless filter paper
  • Drying dish

Procedure:

  • Make a paste with 1.0 gm cement in a 100 ml beaker and 20 ml water.
  • Slowly add conc. hydrochloric acid, stirring constantly so that no lumps should be formed. 
  • Again digest the sample with 10 ml of conc. HCl, so to assures that the reaction is completed.
  • Allow the solution to stand under a ventilated hood until it settles. 
  • Use ashless filter paper or Filter paper number 2.
  • Wash the residue with distilled water until all HCl gets removed.
  • Transfer the residue to a drying dish and oven-dry the residue at 104°C for 2 hr or 800°C -900°C  for 1 hr.
  • Weigh the residue, till constant weight (nearest to 1 gm)

Now, calculate the percentage of weight acid-insoluble residue using the above-mentioned formula.

Part A:  Percentage of Silica

The residue contains precipitated silica which has different compositions on the basis of cement types. But generally, silica is about 20% of the cement composition. 

So, if the Silica residue percentage is close to 20%, then it can be an un-adulterated cement.

Part B: Combined Ferric Oxide and Alumina
  1. Concentrate the above-obtained filtrate (silica precipitated) by adding 250 ml and boil up to the solution to become 200 ml.
  2. Now, to oxidize any ferrous iron to ferric condition,  add 2-3 drops of nitric acid.
  3. Add 1-2 grams of ammonium chloride with constant stirring. 
  4. Now add the filtrate with conc. ammonia solution till the smell of ammonia persist. 
  5. Boil the solution containing the precipitate of Fe and Al hydroxides for 5 minutes. 
  6. Filter, wash with hot water, and dry the precipitate.
  7. Weigh as alumina and ferric oxide.

3. Determination of Calcium by EDTA Titration

This is one the widely used to define the adulteration in cement adulteration. It is based on a complexometric titration, which can also be used to determine the calcium content of milk, or water, and also the amount of calcium carbonate in various solid materials.

This titration is based on the reaction of 

  Ca2+ + [EDTA]4− → [Ca-EDTA]2-
Pink/Red Blue

Procedure:

Part A: Sample preparation

  1. Weigh about 0.5  g of the cement into a small beaker or conical flask followed by the addition of  20 ml of dilute HCl, and allow stir the solution for about 5 minutes.
  2. The next step is to neutralize the unreacted acid with dilute sodium hydroxide solution until the pH of the cement solution is almost  7.
  3. Now transfer the solution to a 100 ml volumetric flask and add distilled water till solutions will become of 100 ml.

Burette Solution: 0.1 M EDTA  Solution

Indicator: Patton Reeder`s Indicator; Grind 10 mg of the indicator with 10 gm of sodium sulphate. 

Part B: Titration

  1. Pipette  10 ml of the sample solution into a conical flask.
  2. Now add 40 ml of distilled water along with  4 ml of 8 mol/l sodium hydroxide solution.
  3. Allow the solution to stand for about 5 minutes.  
  4. Wait for a small precipitation of magnesium hydroxide. 
  5. Add  Patton and Reeder indicator and swirl the conical flask.
  6. Now, titrate the sample with the prepared  0.01 M EDTA solution. The endpoint should be identified by a color change from pink/red to blue. 
  7. Repeat the titration minimum three times and use the average of reading for more absolute results.

Alternative method

  1. Take filtrate from ferric oxide and alumina and make a solution up to 250 ml in a volumetric flask.
  2. Take out 25 ml solution in a separate flask and, add 50 ml water, 5 ml (1:1) glycerol, 5 ml diethylamine with constant stirring.
  3. Add 5-6 pellets of NaOH followed by 50 mg of Patton and Reeder’s indicator with constant stirring.
  4. Titrate the obtained solution against 0.01 M EDTA solution, color change from pink/red to blue indicates the endpoint. 

Calculation and Result: 

60% of CaO = 100% of Cement, and CaO% = 3 times the Silica %. If this condition various too much from standard notation then it may be the case of adulteration in cement.

4. Direct Cement Percentage by Acid Titration

This is based on the two-phase analysis;

Phase 1: The cement is mixed with a known amount of HCl causing the dissolution of the carbonate (‎CaCO3) by creating Calcium chloride (CaCl2), water and carbon dioxide.

Reaction Involved: 

CaCO3 2HCl ⇒ CaCl2 + H2O + CO2

Phase 2: The amount of acid leftover is measured by titrating against sodium hydroxide (NaOH) to produce sodium chloride (NaCl) and water. Adding a phenolphthalein indicator to the solution causes it to turn pink.

Reaction Involved:

HCl + NaOH ⇒ NaCl + H2O

Procedure:

Part A: Sample Preparation

  1. Take 0.5 g of cement sample into a conical flask and add  20 ml of 2M HCl.
  2. Now, wait until the reaction stop. It is indicated by effervescence stops. 
  3. Boil the solution on the hotplate for 10 minutes.
  4. After cooling the solution at room temperature, filter the solution into 100 ml volumetric flasks and make up the solution of 100 ml mark using distilled water.

Burette Solution: 0.1M NaOH

Indicator: Phenolphthalein Indicator

Part B: Titration

  1. Pipette out 10 ml of the sample solution into a clean conical flask.
  2. Add 50 ml of distilled water and a few drops of phenolphthalein indicator.
  3. Now, titrate the sample with  0.1 M NaOH solution. The endpoint should be identified by a permanent pink color.
  4. Repeat steps minimum 3 times and then average the results.

Calculation and Result:

Cement percentage (%)  = 28 x N x Diff. in Reading         (N= Normality of NaOH)

Part 4: Instrumental Analysis of Adulteration of Cement

There are generally two instruments used in adulteration of cement. These are

  1. ICP-AES
  2. XRD

1. ICP- AES

Inductively Coupled Plasma Atomic Emission Spectroscopy is an analytical technique for the detection of chemical elements. 

ICP-AES is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit EM radiation. This EM radiation is a characteristic measure that corresponds to a particular element.

In forensic, apart from cement analysis, ICP-AES is often used for the analysis of trace elements in the soil to ascertain the origin of soil samples found at crime scenes or on victims, etc.

2. X-Ray Diffraction (XRD)

It is a rapid analytical technique that is primarily employed for phase identification of crystalline material. The analyzed material is first finely ground and homogenized.

X-ray diffractometers consist of three basic elements: an X-ray tube, a sample holder, and an X-ray detector.

X-rays are first generated by a cathode ray tube by heating a filament to produce electrons. Then these electrons are bombarded to the target by applying a voltage. When electrons get sufficient energy, they eject inner shell electrons of the target material by which a characteristic X-ray spectrum is produced.

But it serves a major limitation, i.e. for mixed materials, the detection limit is ~ 2% of the sample. And in case of adulteration of cement, the adulterated material exceeds 2%, which makes it difficult for analysis.

Frequently Asked Questions on Cement Adulterants

What is meant by the adulteration of cement?

The addition of components to the cement that changes their standard chemical compositions in contrast to various observable and unobservable changes.

What are the common adulterants of cement?

Rag-stone, blast furnace, slag, furnace ashes, dessert sand, river bed sand, etc are the common adulterants of cement. 

What are the tests of cement?

There are basically three broad categories which are: quality test or field test, laboratory chemical test, and instrumental analysis.

What is the common laboratory test for adulterated cement?

ThymolphthaleinTest, Acid insoluble ashes test, Silica, Combined Ferric Oxide, and Alumina, determination of calcium by EDTA Titration, direct cement percentage by acid titration are some of the chemical tests to check the cement quality of adulterated cement.  

What is the quality test for cement?

Some quality tests for cement are the color test, fine test, smell test, presence of lumps, temperature test, heat test, float test, shape/ performance test, and strength test.

What are the forensic significance of cement analysis?

Cement analysis is a common test that is performed along with mortar ad concrete analysis. With the analysis of cement as forensic evidence, the examiner can extract very useful leads or information related to the case. The cement analysis can help in finding the source of their origin, know the reason for structural failure, or the company of cement by interpreting their composition elements and ratio proportion.

What are the instrumental analysis techniques for adulterated cement?

Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and X-Ray Diffraction (XRD)


Check Our MCQ Series from here. Also check our other post on cement, mortar, and concrete forensic analysis