Forensic analysis of cement is majorly performed when there is a possibility of adulteration in cement samples. In analysis, one of the key steps is to identify which type of adulterant is used with cement. So, in general terms, it is defined as:
Adulteration of cement is characterized as the addition of extra components to the cement that results in observable changes such as color, texture, strength, and other properties, as well as unobservable modifications with macro elements and metals.
The following is the table of content that states what you get to learn from this blog post on 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 diminish cement quality.
Adulterant: It is the substance that is used to adulterate cement. Some adulterants used in the adulteration of cement are ragstone, furnace ashes, sand, etc.
Common Adulterants of Cement
| Common Adulterant | Observations |
|---|---|
| Rag-stone | bluish-grey color |
| Blast Furnace | silver grey |
| Slag | light grey |
| Furnace ashes | coarse and gritty, with a medium to dark gray color. |
| Dessert Sand | very light reddish-yellow color, with 2-3 mm of particle size with brittle edges |
| River Bed sand | rounded particles, and may contain clay or other impurities. And a saturated yellow color. |
Why is need to check Adulteration of Cement?
Because adulteration of quality cement is one of the major causes 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 types of cement in the industry and the major components of cement.
More About Cement
What is Cement?
Cement is a mixture of chemicals such as mostly calcium carbonate, silica, alumina, 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:
| Name | Formula | % Composition |
| Di calcium Silicate | 2CaO.SiO2 | 30% |
| Tri calcium Silicate | 3CaO.SiO2 | 40% |
| Tri calcium Aluminate | Ca3Al2O6, or 3CaO·Al2O3 | 11% |
| Tetracalcium Alumino Ferrite | 4CaO. Al2O3 Fe2O3 | 11% |
Types of Cement
- Ordinary Portland Cement (OPC)
- Portland Pozzolana Cement (PPC)
- High Alumina Cement
- White Cement
- Colored cement
- Rapid Hardening Cement
- Quick Setting Cement
- Low-Heat Cement
- Blast Furnace Slag Cement
- Air Entraining Cement
- Hydrographic cement
1. Ordinary Portland Cement (OPC): It is the most widely used type of cement and can meet the major requirements for construction. To make these types of cement, they are heated in a rotating kiln at a high temperature of around 1500°C.
2. Portland Pozzolana Cement (PPC): It is as same as OPC but the addition of one of the major constituents 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 negligible or zero. This is why it is also called free from iron cement. It is a costly cement mainly used as decorative cement in internal parts of the building.
5. Colored cement: These cement are pigment-based. And consists of 5% to 10% 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 attained high strength in earlier days. They contain high lime content wrong with 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 be set 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 and is generally used in mass concrete construction like dams. They are manufactured by constriction the number 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 is 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 are many used for dams, spillways, water tanks, etc.
Read More:
- 7 Importance of Casting In Forensic Crime Investigation [Explained]
- Forensic Casting Materials: How to Choose One For Different Surfaces?
How to identify an Adulterated Cement?
Forensic analyses and tests of adulterants in cement (Basic workflow):
- Sampling
- Preliminary analysis
- Laboratory Chemical analysis
- Instrumental analysis
Part 1: Sampling
1 kg sample of cement should be collected in an airtight plastic jar along with recommended details and the signature of the 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, and type of cement, are to be noted for future references of the collected sample.
Sampling in case of fewer 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 companies or types of cement bags, then all the cement bags have the same details and appear similar, a minimum of three random samples are collected, and 1kg of questioned adulterant cement for analysis.
Part 2: Preliminary Adulteration Test of Cement
The preliminary test for cement analysis for adulteration is listed as:
- Color test
- Fine Test
- Smell test
- Presence of lumps
- Temperature test
- Heat test
- Float Test
- Shape/ Performance Test
- Strength Test
1. Color Test and luminescence
Take 1 gm of the sample and even spread it on the china dish or plate and observe the color under normal conditions.
In this, the color of all the samples is noted in normal conditions as well as various 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 is the quality assurance from adulterants like sands.
For this test take a small sample between your fingers and if it is a case of unaltered 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 earthy then it clearly shows 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 with the application of moisture. The size of lumps defines the amount of water that 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 feel like sand. These lumps 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 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 feels 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, and heat it for about 20 minutes on a steel plate. And note the observation.
In the case of adulterated cement, the sample changes its color. But in the case of un-adulterated cement, it retains its color.
7. Float Test
Take a few grams of cement sample and spread it over 100 mL of the water-filled transparent beaker.
Unadulterated cement should first float on the surface for some time, and then start shrinking and finally settle on the base of the beaker.
In the case of adulterated cement, particle-like ashes start shrinking right away when sprinkled on the water’s 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 keep it for 24 hours.
If the cement is set without a crack, this may be the indication of unadulterated cement and is said to be a good performance.
This phenomenon is also related to the term called “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 is attached to the stings of 34 kg of weight.
If the cement doesn’t break it is an indication that the cement is free from adulterants.
Part 3: Chemical Analysis of Adulteration of Cement
These are some chemical forensic analysis of cement tests that helps in the determination of adulteration:
- ThymolphthaleinTest
- Acid insoluble
- Silica
- Combined Ferric Oxide and Alumina
- Determination of Calcium by EDTA Titration
- 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 as to assure 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
- Concentrate the above-obtained filtrate (silica precipitated) by adding 250 mL and boil up to the solution to become 200 mL.
- Now, to oxidize any ferrous iron to ferric conditions, add 2-3 drops of nitric acid.
- Add 1-2 grams of ammonium chloride with constant stirring.
- Now add the filtrate with conc. ammonia solution till the smell of ammonia persists.
- Boil the solution containing the precipitate of Fe and Al hydroxides for 5 minutes.
- Filter, wash with hot water, and dry the precipitate.
- Weigh as alumina and ferric oxide.
3. Determination of Calcium by EDTA Titration
This is one of the widely used to define 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
- 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 to stir the solution for about 5 minutes.
- The next step is to neutralize the unreacted acid with dilute sodium hydroxide solution until the pH of the cement solution is almost 7.
- Now transfer the solution to a 100 mL volumetric flask and add distilled water till the solution becomes 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 sulfate.
Part B: Titration
- Pipette 10 mL of the sample solution into a conical flask.
- Now add 40 mL of distilled water along with 4 mL of 8 mol/l sodium hydroxide solution.
- Allow the solution to stand for about 5 minutes.
- Wait for a small precipitation of magnesium hydroxide.
- Add Patton and Reeder indicator and swirl the conical flask.
- 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.
- Repeat the titration a minimum of three times and use the average reading for more absolute results.
Alternative method
- Take filtrate from ferric oxide and alumina and make a solution of up to 250 mL in a volumetric flask.
- Take out 25 mL solution in a separate flask and, add 50 mL water, 5 mL (1:1) glycerol, and 5 mL diethylamine with constant stirring.
- Add 5-6 pellets of NaOH followed by 50 mg of Patton and Reeder’s indicator with constant stirring.
- Titrate the obtained solution against 0.01 M EDTA solution, the 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 varies 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 left over 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
- Take 0.5 g of cement sample into a conical flask and add 20 mL of 2M HCl.
- Now, wait until the reaction stop. It is indicated by effervescence stops.
- Boil the solution on the hotplate for 10 minutes.
- 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
- Pipette out 10 mL of the sample solution into a clean conical flask.
- Add 50 mL of distilled water and a few drops of phenolphthalein indicator.
- Now, titrate the sample with 0.1 M NaOH solution. The endpoint should be identified by a permanent pink color.
- Repeat steps a minimum of 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 that are used for forensic analysis of cement for adulteration. These are
- ICP-AES
- 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 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 forensics, 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 the 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 the 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 changes their standard chemical compositions in contrast to various observable and unobservable changes.
What are the common adulterants of cement?
Rag-stone, blast furnaces, 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, and 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 and 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, knowing 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 other post on cement, mortar, and concrete forensic analysis
FR Author Group at ForensicReader is a team of Forensic experts and scholars having B.Sc, M.Sc, or Doctorate( Ph.D.) degrees in Forensic Science. We published on topics on fingerprints, questioned documents, forensic medicine, toxicology, physical evidence, and related case studies. Know More.
