CEMENT Flashcards
_______ and ______ were perhaps the first to use _____ as cementing material.
Assyrians and Babylonians, Clay.
In ancient monuments, e.g. forts, places of worship and defence structures, stones have been invariably used as a construction material with _____ as the _____.
Records show that Egyptians have used _____ and ______ as cementing materials in the famous pyramids.
Lime as the Binder, Lime and Gypsum.
_________, a Roman scientist, is believed to be the first to have the know how about the chemistry of the ______.
Vitruvius, Cementitious lime.
One of the most notable examples of Roman work is the _______. It consists of a concrete dome 43.43m in span.
The calcareous cements used by the Romans were either composed of suitable limestones burned in _____ or were mixtures of _____ combining into a hard concrete.
Pantheon.
Kilns, Lime and pozzolanic materials (volcanic ash, tuff).
He was the first to introduce ______ in 1824 formed by heating a mixture of limestone and finely divided clay in a furnace to a temperature high enough to drive off the carbonic acid gas.
Joseph Aspedin of Yorkshire, Portland cement.
In 1845, _____ invented the cement by increasing the temperature at which the mixture of limestone and clay were burned to form _____.
This cement was the prototype of the modern Portland cement.
Issac C. Johnson, Clinker.
The binding compound of concrete, is a fine, pulverized material consisting of compounds of lime, iron, silica, and alumina.
The manufacture of these produces a combination of these elements in proper proportion under carefully controlled conditions.
Portland cement.
The three constituents of hydraulic cements are ______.
In addition, most cements contain small proportions of iron oxide, magnesia, sulphur trioxide and alkalis.
Lime, silica and alumina.
The chemical reaction between cement and water is known as _____. The reaction takes place between the active components of cement (C4AF, C3A, C3S and C2S) and water.
The factors responsible for the physical properties of concrete are the extent of hydration of cement and the resultant microstructure of the hydrated cement.
Hydration of cement
When the cement comes in contact with water, the hydration products start depositing on the outer periphery of the nucleus of hydrated cement. This reaction proceeds slowly for 2-5 hours and is called ______.
As the hydration proceeds, the deposit of hydration products on the original cement grain makes the diffusion of water to unhydrated nucleus more and more difficult, consequently reducing the rate of hydration with time.
Induction or dormant period.
About an average 23% (24% C3S, 21% C2S) of water by weight of cement is required for complete hydration of Portland cement.
This water combines chemically with the cement compounds and is known as _____.
Bound water.
Some quantity of water, about 15% by weight of cement, is required to fill the cement gel pores and is known as ______.
Gel water.
If excess water is present, it will lead to _____.
Capillary cavities.
The degree of ____ of cement is the measure of the mean size of the grains in it.
Finer the cement, more is the strength since surface area for hydration will be large.
Fineness.
Fineness test.
This is a test to estimate the quantity of mixing water to form a paste of normal consistency defined as that percentage water requirement of the cement paste, the viscosity of which will be such that the Vicat’s plunger penetrates up to a point 5 to 7 mm from the bottom of the Vicat’s mould.
Consistency Test.
