Making Cement
Cement is produced by roasting powdered limestone with powdered clay in a rotary kiln.
In the kiln on the right the fuel (methane) reacts with oxygen from the air to produce CO2 in the waste gases. This reaction produces the heat to decompose the limestone. CO2 also is given off by the decomposing limestone
The Argon and Nitrogen in the waste gases come from unreacted air.
Quicklime (calcium oxide) reacts with water to produce slaked lime (calcium hydroxide) (This reaction gives out lots of heat).
Limestone and its products have many uses, including slaked lime, mortar, cement, concrete and glass.
When cement is mixed with water, sand and crushed rock, a slow chemical reaction produces a hard, stone-like building material called concrete.
Mortar consists of cement mixed with calcium hydroxide. This makes a smooth slow setting mixture suitable for bricklaying
Glass is made by heating a mixture of limestone, sand and soda (sodium carbonate).This reaction requires a lot of energy. Recycling glass reduces the amount of energy needed to produce new glass products and also uses less raw materials
slaked lime (calcium hydroxide) is used to reduce the acidity of soil.
evaluate the developments in using limestone, cement, concrete and glass as building materials, and their advantages and disadvantages over other materials.
Limestone: Some possible points
Limestone is beautiful
Limestone suffers badly with acid rain
easy to cut but there is a fair amount of waste in cutting to shape
no processing needed so low energy costs required to use as stone
Widely available/abundant
Cement and Concrete: Some possible points
Concrete is long lasting and does not corrode or rot or react with acid rain
Easily moulded to shape needed and so no waste
Quick and cheap to use to make buildings
raw materials abundant
can be reinforced with steel rods to make stronger
On its own it is ugly
Glass
Transparent and allows in light
Breaks easily
Can be toughened and turned into safety glass
Limestone, glass and concrete do not rot when wet or attacked by bugs like wood does, and are also fireproof
consider and evaluate the environmental, social and economic effects of exploiting limestone and producing building materials from it
Quarrying of limestone:
Some positive points
Limestone a useful building material
Limestone very important raw material for cement, concrete, glass
Job benefits in quarries
Negative points
Often done in areas of beauty e.g. peak district
Visual pollution of quarrying
Produces noise and dust
Air pollution of lorries carrying rock
Damage to wildlife/plants
Reduced tourism
Production of cement: Some points
Making cement is extremely energy intensive
Making cement produces huge amounts of CO2 greenhouse gas
Reactions of carbonates with acid
Carbonates react with acids to produce carbon dioxide, a salt and water.
Hydrochloric acid will make a chloride salt
CaCO3 + 2HCl CaCl2 + H2O + CO2
Here the salt made is calcium chloride
Sulphuric acid will make a sulphate salt
CuCO3 + H2SO4CuSO4 + H2O + CO2
Here the salt made is copper sulphate
Limestone is damaged by acid rain.
Learn this equation:
Calcium carbonate Calcium oxide + carbon dioxide
CaCO3 CaO + CO2
Learn this equation:
Calcium oxide + water calcium hydroxide
CaO + H2O Ca(OH)2
Understand this reaction (don’t need to remember)
Calcium hydroxide can react with carbon dioxide to produce solid calcium carbonate.
Ca(OH)2 + CO2 CaCO3 + H2O
This is the reaction that makes limewater go cloudy when CO2 is bubbled through it
