LIME - Building Materials short notes and previous year questions

LIME

• BC 4000 Egypt Rome 

• Lime is an oxide of calcium, CaO 

CALCINATION : process of converting limestone into redness nature 

HYDRAULICITY : process of hardening in the presence of moisture 

QUICK LIME / LUMP LIME / CAUSTIC LIME ( CAO ) 

• Formed by the calcination of limestone 

SLAKING 

• Converting quick lime to hydrated / slaked / lime water 

• 2 - 3 hrs for completion 

• In theory water content of 32 % of cao is taken 

• In practical condition 2 - 3 times WC taken 

• MILK OF LIME : pourable suspension of slaked lime (4-6 times water content of cao ) 

CONSTITUENTS OF LIME

1. CLAY 

• 8 - 30 % 

• Improves hydraulicity 

2. SOLUBLE SILICA 

• Silicates of mg, ca, al 

• Improve hydraulicity at high temp 

3. MAGNESIUM CARBONATE 

• Slows down slaking process 

• Increase setting time 

• It can replace clay content in limestone by 30% 

4. ALKALIES / METALLIC OXIDES 

• Accelerated hydraulicity 

5. SULPHATE : speedup slaking , reduce setting time 

6. PYRITES : should not contain pyrites 

CLASSIFICATION OF LIME

1. FAT LIME / QUICK LIME / WHITE LIME / PURE LIME / HIGH CALCIUM LIME 

• only 5 % impurity , 95 % cao 

• Min quantity max area ( white washing , plastering) 

• 2 - 2.5 % volume increase 

• White color 

• Low strength 

• Has no hydraulic property Not used in underwater , masonry works 

• Shurki or pozzolona added to improve strength

2. HYDRAULIC LIME 

• High strength 

• Used in underwater , masonry , rcc works 

• High setting time 

Feebly  

• Clay content 5 - 10 % 

• Slakes in few minutes 

• Setts in 3 weeks 

• Low hydraulic property 

Moderate / medium 

• Clay content 11 - 20 % 

• Slakes in 1 - 2 hrs 

• Setts in 1 week 

Eminent

• Clay content 21 - 30 % 

• Slaking difficult 

• Setts in 1 day

3. POOR LIME 

• Clay content > 30 % 

• Cannot be used for construction 

• Slakes and sets very slowly 

PREVIOUS YEAR REPEATED QUESTIONS BASED ON LIME