Adulterants In Cement : Forensic Analysis

Cement

Cement is made from a chemical mixture of calcium, silicon, aluminium, iron ore, and other materials such as fly ash, minor amounts of gypsum, limestone, and clay that is carefully managed.

The Main Constituents of Cement are:

NameFormula%
Di calcium Silicate2CaO.SiO230%
Tri calcium Silicate3CaO.SiO240%
Tri calcium AluminateCa3Al2O6, or 3CaO·Al2O311%
Tetracalcium Alumino Ferrite4CaO. Al2O3 Fe2O311%

Types Of Cement

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

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.

Adulteration in Cement

Adulteration of cement refers to the addition of non-cement elements to the cement’s raw sources. It may result in:

1.) Loss in cement strength.

2.) Formation of lumps

3.) The mixing percentage will be incorrect.

4.) Bonding will be porous owing to contaminated cement.

Forensic Analysis of Cement

  • Sampling
  • Preliminary analysis
  • Laboratory Chemical analysis
  • Instrumental analysis

Sampling

Sample of cement should be collected maintaining chain of custody. It should be stored in an airtight plastic jar/Steel Jar with the collecting officer’s signature and the necessary details. The batch number or specifics of a cement bag, as well as the written data on the cement bag: firm name, kind of cement, should be documented for future reference of the collected sample.

Field and Laboratory Test

Colour Test and luminescence

Take 1 gm of the sample and evenly put it on a petridish or plate under normal conditions. Adulterants in cement may include ashes or burned bone. When the cremated bone was illuminated with a wavelength of 450 nm and examined through a yellow long-pass filter, it turned a dark purple colour.

Fine-Test

The finer the particle, the better the quality guarantees against adulterants such as sands. Take a little sample between your fingers and feel it, if it’s a case of unaltered cement, squeezing it should feel smooth. If it doesn’t feel smooth and uninform in nature it may possible that it’s been contaminated with sand.

Smell Test

Adulterants such as ashes, pounded clay, and silt have an earthy odour, and if the cement smells earthy, it indicates that a significant amount of sand or silt have been added as an adulterant.

Lump Test

Lumps are described as the hardening of cement as a result of moisture application. The amount of water that reacts with cement is determined by the size of the lumps. Take a 100 gm sample and inspect it for visible lumps. It’s also noticeable while compressing the cement sample, where little lumps feel like sands. When using a spatula to smash these lumps, they are readily crushed.

Temperature Test

Take roughly 500g of sample and dip your hand into it while wearing rubber gloves to sense the temperature. If it feels chilly to the touch, it might be pure cement. In comparison to cement, it seems warmer if it is mixed with sand and ashes.

Heat Test

Take 1 gm of the sample and heat it on a steel plate for around 20 minutes. The colour of the sample changes when it is composed of adulterated cement.

Float Test

Spread a few gm of cement over 100 ml of the clear beaker filled with water. Unadulterated cement should float on the surface for a while before shrinking and then settling on the beaker’s bottom.

Particle-like ashes in adulterated cement begin to shrink immediately.

Shape/Performance Test

Make a paste using 10gm of cement sample and water. Make a firm and sharp-edged cake. Place the prepared paste in another 250ml beaker containing water and let aside for 24 hours.

If the cement sets without cracking, it might be an indicator of pure cement and an excellent result.

Strength Test

A cement block measuring 25mm x 25mm x 200mm is constructed and then submerged in water for seven days. Then one side of the cement block is secured with a hook, while the other is fastened to 34 kg of weight stings.

If the cement does not shatter, it is likely that it is pure of adulterants.