- When water is added in cement , hydration process starts.
- The active ingredients in cement start reacting with each other and chemical reaction in cement takes place.
- This chemical reaction, is responsible for forming new CHS gels in cement which forms bonding between cement and water.
- This complex gel is formed due to some compound which knows as ‘bogues compound’
The bogues compound, which is responsible for hydration and forming bonds are listed below,
- Tri-calcium Aluminate
- Tri-calcium silicates
- Di-calcium silicates
- Tetra-calcium alumina ferrite
Percentage of Bogues Compound
- The Bogues compound is nothing but these above-mentioned compounds which is mainly responsible for strength and hydration process in cement.
- Every compound has some specific feature and posses some properties of cement.
- The features of compound is depend upon their percentage in cement and can be modified or changed by varying the percentage of compound in cement.
- Many types of cement is available in market depending upon the use and quality of cement. This can be changed by changing percentage of Bogues Compound.
- Some of the characteristics and percentage of compound is listed below in table format,
|Responsible for lateral strength (After 7 days)|
Mostly used in hydraulic structures and bridges
|C3A||3CaO.Al2O3||8-12%||Responsible for early strength|
Make cement sulphate resistant in sulphate prone environment
Produce Rapid hardening cement
|Tricalcium silicate||C3S||3CaO.SiO2||50-60%||Initiate Strength up to 50-60%|
Responsible for initial strength (7 days strength)
Can be produce rapid hardening cement
|Dicalcium silicate||C2S||2CaO.SiO2||20-45%||Responsible for lateral strength (After 7 days)|
Mostly used in hydraulic structures and bridges
|Tetra-calcium Alumino Ferrite||C4AF||4CaO.Al2O3.Fe2O3||6-10%||Greyish colour to cement|
Enhances filler property
Provides lower clinkering temperature in production of cement
The heat of hydration of bogues compound is about 8651/Cal. C4AF hydrates in enormous fractions premature a the time of setting while the final one to be hydrated are C2S. So, we can note the compounds in the declining ranking of hydration as C4AF, C3A, C3S, and C2S.
Types of Bogues Compound:
- Make cement sulphate resistant and responsible for strength of cement.
- It can be also written as C3A and chemical formula for same is 3CaO.Al2O3. Approximate percentage of Tri-calcium aluminate is 8-12% and can be vary according to composition of cement.
- Tri-calcium aluminate induces early strength to cement, which is produced after 24 hours after mixing with water.
- The percentage of Tri-calcium aluminate is raised where quick set is required. For example, grouting drain holes or to avoid water leakage.
- High percentage of Tri-calcium aluminate also produces the high heat of hydration, due to this it should be avoided in structures like water retaining wall and roller compacted concrete hydraulic.
- High percentage of Tri-calcium aluminate produces high heat of hydration. If this high heat of hydration is not deal properly, it causes the cracking in structures, erosion of structure.
- One of the advantages of Tri-calcium aluminate is, it minimises the corrosion of steel due to its chemical nature. –
- Tri-calcium aluminate reacts with chlorides ions present in water and cement, and thus reduction of chlorides also reduces the corrosion of steel in structures.
- The major disadvantages of Tri-calcium aluminate is it make cement prone to sulphate attack where the environment is rich in sulphate.
- Also, Tri-calcium aluminate reacts very quick with water and solidifies faster, this causes Flash set or False set of cement.
- To avoid the flash set, gypsum or plaster of Paris can be added to cement in 4-8% ratio during manufacturing. Here gypsum is used as retarding admixture.
- It can be also written as C3S and chemical formula for same is 3CaO.SiO2. Approximate percentage of Tri-calcium sulphate is 30-50% and can be vary according to composition of cement.
- Tri-calcium sulphate produced 50-60% of strength in cement.
- Tri-calcium sulphate also produces early strength of cement, and that can be developed up to 7 days after mixing with water.
- When water is added in cement, Tri-calcium sulphate reacts with water in an exothermic hydration reaction and forms calcium and hydroxide irons at the end.
- Once the irons forms completely it will start to form crystalline calcium hydroxide ions.
- These crystals get thicker and thicker by decreasing the rate of reaction.
- During the crystallization process, all solid mass start forming and cement gets harden completely.
- The percentage of Tri-calcium sulphate can be increased to achieve rapid hardening cement, generally used for pre cast construction or pre fab construction. Rapid hardening cement can be used in cold weather construction.
- It can be also written as C2S and chemical formula for same is 2CaO.SiO2. Approximate percentage of Di-calcium sulphate is 20-45% and can be vary according to composition of cement.
- As compared to Tri-calcium sulphate, Di-calcium sulphate is less reactive in nature.
- It is second large most compound in Bogues compound,
- Di-calcium sulphate reacts with water gradually but in exact in same way as Tri-calcium sulphate. This is also generated exothermic reaction but heat production is very less as compared to C3S
- It induces the lateral strength in cement, which can be start producing after 7 days up to 1 year.
- Similarly, for constructions where smaller heat of hydration is required, like in low heat cement, the ratio of di-calcium silicate is modified consequently.
Tetra Calcium Alumino Ferrite
- It can be also written as C4AF and chemical formula for same is 4CaO.Al2O3.Fe2O3. Approximate percentage of Tetra Calcium Alumino Ferrite is present as 6-10% and can be vary according to composition of cement.
- Tetra Calcium Alumino Ferrite not at all responsible for strength of cement.
- At the time of hydration reaction of cement, it results in a hydrated iron oxide gel in a quick reaction producing sufficient heat but the reaction delays down once calcium alumino ferrite crystals are composed.
- Tetra Calcium Alumino Ferrite helps to lower the clinker temperature at time of manufacturing of cement.
- It provides greyish colour to cement, this grey colour is due to ferrite.
Other than Bogues Compound, some com-pounds are present in cement in smaller quantity, which are listed below,
- Magnesia (MgO)
- Sulphur trioxide
- Iron oxide/ Ferric oxide
- Free lime
- Silica fumes
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Uses of Bogues Compound:
- Gives strength (early and lateral strength) to the cement.
- Provides and induces heat of hydration to cement, which gradually hardens the cement after mixing with the water.
- Makes cement more significant and resistance to chemical attack.
- It delivers heat of hydration which is liable for setting of cement.
- Provides colour to cement.
- Make cement rapid hardening cement, if needed.