Ready
Mixed Concrete
Ready Mixed Concrete is a principal building material obtained by mixing of
cement, aggregate (i.e. sand, gravel, crushed stone), water and some additives
when necessary, according to a particular production technology. Concrete which
initially is plastic or fluid in consistency after the mixing process can easily
be formed, and hardens with time and attains strength.
 |
Cement
% 10
Water % 15
Aggregate % 75 |
Concrete, by absolute volume consists of aggregate by 75
%, cement by 10 % and water 15 %. If necessary, additives
might be added into concrete, provided that these are limited
with 2 % of the cement content, by weight.
Concrete is categorized in 3 classes in
TS EN 206-1:
Normal concrete: Concrete with oven-dry unit weight greater
than 2000 kg/m3 and smaller than 2600 kg/m3.
Heavy concrete: Concrete with oven-dry unit weight greater
than 2600 kg/m3.
Lightweight concrete: Concrete with oven-dry unit weight
greater than 800 kg/m3 and less than 2000 kg/m3. A part
or whole of the aggregate to be used in lightweight concrete
is produced as lightweight aggregate.
CEMENT
Cement is the name of the powder like binder,
produced by mixing and then grinding of clinker together
with gypsum
and some other additives. Clinker in turn is obtained by
mixing of ground limestone and other raw materials in line
with particular mixing ratios and baking of this mixture
in rotating ovens.
Cement is a ground inorganic substance,
which forms a paste when mixed with water. This paste sets
through hydration
reactions and processes and eventually hardens and once
hardened, maintains its strength and stability even under
water.
The role of cement in concrete is to act as binder
by covering the surface of the aggregate particles and filling
in the cavities amongst the particles.
AGGREGATE
Materials such as crushed stone, gravel, sand that constitute
60-80 % of concrete are named aggregates.
Basically
there are two types of aggregates, namely natural (sand-gravel,
crushed stone) and artificial (blast
furnace slag, expanded clay, perlite). Yet every mineral
based material or industrial waste cannot be utilized
as aggregate.
In our day, most concrete producers still
stick to a wrong belief that aggregate quality depends
only on its
color. However, there are many physical and chemical
features that affect aggregate quality, which have been
laid down in TS 706 EN 12620 standard.
At Betonsa, conformity
of all the aggregates used to TS 706 EN 12620 standard,
are verified by tests and thus
quality is maintained.
Aggregates play a major role in
concrete. Grain size, form, hardness of aggregates directly
affects concrete
characteristics. It is essential to determine aggregate
features by tests, before using it in concrete production.
| Aggregate
Type |
Unit
weight (kg/m3) |
| Normal Aggregate |
2000-3000 |
| Lightweight Aggregate |
≤ 2000 |
| Heavy Aggregate |
≥ 3000 |
Nominal maximum aggregate size (Dmax), has to be determined
by taking into consideration the thickness of the concrete
level covering the reinforcing bars and the minimum dimension
of the concrete member’s cross section. Aggregate recovered
from washing water or fresh concrete can well be used as
concrete aggregate.
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