What is the difference between hydraulic cement and non-hydraulic cement?
The products of hydraulic cements are water-resistant and do not disintegrate in water
What are the two most common non-hydraulic and hydraulic cements? (4 total)
non-hydraulic: gypsum and lime cements
hydraulic cements: lime cement and reactive silica, portland cement
Write the reaction that happens when gypsum cement is heated. What happens when these products react with water?
CaSO42H2O (binder) -> CaSO41/2H2O (hemihydrate) + CaSO4 (anhydrite).
After water, turns back to gypsum binder
Write the reaction that happens when limestone is heated. What happens when these products react with water?
CaCO3->CaO+CO2.
Then, CaO+H2O->Ca(OH)2
Write the reaction that occurs when quick lime reacts with amorphous silica.
CaCO3->CaO+H2O+SiO2->CaO-SiO2-H2O (calcium silicate hydrate gel)
What is the difference between reactions that create hydraulic and non-hydraulic Lime cement?
For lime cement to be hydraulic, amorphous silica must be present during the reaction. the reaction results in calcium silicate hydrate gel instead of hydrated lime, calcium hydroxide
What is the typical size of clinker?
5-60 mm nodules
What is portland cement and what are its primary compounds?
hydraulic cement made of griding portland clinker with calcium sulfate. it is primarily made of calcium silicate compounds with some calcium aluminate and calcium aluminoferrites
Which calcium sulfates are used in portland cement?
anhydrite, hemihydrate, gypsum
Where does the manufacturing process of clinker take place?
rotary kiln
What are the essential components of kiln raw feed?
calcium oxide and a source of silica
What are the raw materials used in making portland clinker and what do they contain?
Limestone (calcium carbonate, calcium oxide).
Iron-bearing aluminosilicates (silica, alumina, iron oxide clays)
What are the effects of the compounds derived from iron and alumina content of the siliceous raw materials in cement and why do we use them?
Little contribution to strength and negative effect on durability, abnormal setting behavior.
Used as fluxing agents to reduce the temp needed in the kiln for the formation of compounds. They are economical.
In kiln operation in manufacturing of portland cement, what are the zones (in the order they occur?)
Dehydration zone
calcination zone
clinkering zone
cooling zone
What happens in the dehydration zone in the kiln?
raw feed goes in, free water goes out, clay decomposes
What happens in the calcination zone in the kiln?
Limestone decomposes, formation of initial compounds, initial formation of C2S
What happens in the clinkering zone in the kiln?
Formation of melt, formation of C3S
Describe the process of manufacturing of Portland cement clinker in the kiln from the calcination zone to the clinkering zone.
first tri-calcium aluminate forms the matrix of the clinker particle. alumina and iron aluminates form. tetracalcium alunimoferrite forms.
Then, dicalcium silicate forms. melt forms then tricalcium silicate forms.
Which compounds are called alite and belite?
Alite is tricalcium silicate, belite is dicalcium silicate
What are the most abundant compounds in general-purpose clinker by order of abundance?
Majority alite, then belite, smaller amounts of tricalcium aluminate, tetracalcium alunimoferrite, and gypsum
What are the two ways to express compounds in Portland Cement and which is preferred?
Elemental oxides or compounds. Compounds are preferred for strength/heat generation/hydration kinetics
