Ch02 concrete ingredients

Conrete, Concrete Technology, Constructional Material, Cemet

1. University of Salahaddin/ College of Engineering 2015-2016
Dept. Of Dams & Water resources Engineering By: Goran Adil

Ch2: Concrete ingredients Construction Material 5


Lecture No. 02
Subject: Concrete Ingredients



Objectives of Lecture:
 To explain the basic Concrete ingredients
 relationship between components of concrete



Concrete Ingredients
The general definition for Concrete is that material or mass which is
composed by the effect of adhering media. Generally, the adhering media
is the product of the reaction between the hydraulic cement and the water.

Now a days this definition can include large amount of products such as:
concrete produced by various kinds of cement and also concrete containing
pozzolana or fly ash or blast furnace slag or admixtures regulating setting time
or sulfur or concrete admixtures
or polymers or fibers . . . etc. This concrete can be heated or cured by steam or
putting it in water bath or compressing it or shake it by vibrators
. . . . Etc.

Generally, the concrete is composed of the following materials:
a. Cement: The cement is the bonding material of the concrete components.
The cement paste is the product of the reaction between the cement and the
water. This paste interacts with the fine and coarse aggregate particles and
fills most of the spaces between the aggregate particles. Little number of
spaces is filled partially or totally by air.

2. University of Salahaddin/ College of Engineering 2015-2016
Dept. Of Dams & Water resources Engineering By: Goran Adil

Ch2: Concrete ingredients Construction Material 6


Hydraulic cements
Cements that harden by reaction with water and form a water-resistant
product.




Non hydraulic Cement:



b. Aggregate: It is the granular filling material presents about 80% of the total
volume of the concrete. The cement paste after hardening, bonds the
aggregate particles to gather giving the specified strength of the concrete as
a construction material.
The aggregate can be classified
1) According to its density, to normal weight, light weight and heavy
weight aggregate.
2) According to its source, to natural and artificial aggregate.
3) According to its particle size, to coarse and fine aggregate. The
aggregate greater than 4.75mm is accepted as coarse aggregate.
c. Water: The water reacts chemically
with cement leading to hydration of
cement and forming hydrates of
calcium silicates to which the strength
of concrete is referred after hardening.
The water which is used in concrete
should not be deleterious. It should be
free of salts, alkalis, acids, clay, and
other organic materials. So the
drinking water is preferred to be used
in concrete production. The water
presents 40-65% by weight of the
cement in the mix.

3. University of Salahaddin/ College of Engineering 2015-2016
Dept. Of Dams & Water resources Engineering By: Goran Adil

Ch2: Concrete ingredients Construction Material 7


d. Concrete Admixtures:
All the materials used in the production of concrete except cement, aggregate
and water are accepted as concrete admixtures. Some chemicals are added to
moderate some properties of the fresh or hardened concrete such as retarders,
accelerators, water reducers, air entrained admixtures, coloring admixtures . . .
etc.





What is the relationship between components of concrete?
The solution of this question can be discussed by three explanations:
1. First explanation: Considering the adhering media produced by the process
of hydration is the basic material while the aggregate is a cheap diluting
material only.
2. Second explanation: simulating the concrete as rock building but in small
scale where the coarse particles of aggregate are bonded to gather by the
mortar of hydrated cement and sand.
3. Third explanation: considering the concrete is composed of two
components. Those are the hydrated cement and the aggregate. And so, the
properties of concrete can be controlled by the properties of these two
materials and the interactions between them.
By the second and the third explanations, some properties of concrete can
be understood. While the first explanation can be discussed by that: Can we use
a composition of cement and water only as a building material? The certain sure
answer is NO, because the volumetric changes for the hydrated cement paste is
very large. The shrinkage of the cement paste is ten times the shrinkage of the
concrete containing 250 kg/m3. So as for creep. In addition, the amount of heat
evaluated by the large quantity of cement especially in hot whether leads to
dangerous cracks in concrete. It can also be noted that most kinds of aggregate
are less active to the external chemical reactions than the cement paste.
That means the aggregate is more stable and durable.

From the above discussion, it is clear that the aggregate is very important
component despite its price.