3/31/2020
Concrete – used for more than 2000
years
CONCRETE – B.F. de Belidor (1697-1761)
« Architecture hydraulique »
CONCRETE WITH
INORGANIC
BINDERS
•
•
hydraulic mortar with coarse aggregates, used by the
Romans
statistically, 9 billion tons of concrete are
manufactured every year. This requires:
– 1.3 billion tons of cement;
– 800 billion liters of water (23 – fold the daily flow of the
Seine river);
– 4.7 billion tons of gravel (670 pyramids of Cheops);
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– 2.2 billion tons of sand (22 million waggons – 264,000 km).
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CONCRETE WITH INORGANIC
BINDERS
1. Definition, advantages, disadvantages
2. Classification of concrete
1. Definition, advantages,
disadvantages
3. Ordinary heavy concrete
4. Special concrete
5. Concrete products
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4
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1. Definition, advantages,
disadvantages
1. Definition, advantages,
disadvantages
Concrete = material in the form of
conglomerate obtained by the hardening of a
well homogenized mixture of:
binder + aggregate + water
Advantages of the use of concrete:
•
•
•
•
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low cost price;
elements of any shape;
high mechanical strengths
compressive strength);
use of local materials.
(especially
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1. Definition, advantages,
disadvantages
2. Classification of
concrete
Disadvantages of the use of concrete:
•
heavy weight compared to metal or wood
elements;
•
long waiting period before it can be used.
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2. Classification of concrete
2. Classification of concrete
b) Depending on workability
a) Depending on density
Type of concrete
Very heavy
Heavy
Medium heavy
Light
Very light
• the property of concrete of not decomposing
into component materials during transportation
and handling;
“”
[kg/m3]
2500
2200 – 2500
2000 – 2200
1000 – 2000
1000
• the readiness with which it fills the shape of the
molds into which it is cast.
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• it is assessed depending on compression,
degree of compaction, spreading, remodelling.
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2. Classification of concrete
2. Classification of concrete
Depending on compression (tasare)
Depending on spreading (răspândire)
• compression: reduction of the height of the concrete
pile (in the shape of a cone trunk) under its own mass.
NO.
1
2
3
4
5
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TYPE OF ELEMENTS
PLAIN OR POORLY REINFORCED CONCRETE
FOUNDATIONS, MASSIVE ELEMENTS
REINFORCED
CONCRETE
FOUNDATIONS,
PILLARS, BEAMS, STRUCTURAL WALLS
IDEM, BUILT WITH PUMPED CONCRETE,
MONOLITHIC STRUCTURES
MONOLITHIC
ELEMENTS
WITH
DENSE
REINFORCEMENTS
OR
COMPACTION
DIFFICULTIES, ELEMENTS WITH REDUCED
SECTIONS
ELEMENTS
FOR
WHICH
THE
BUILDING
TECHNOLOGY
REQUIRES
HIGHLY
FLUID
CONCRETE
• spreading: degree of spreading of a concrete pile in
the shape of a cone trunk.
CONSISTENCY
CLASS
COMPRESSION
[MM]
S1
10 – 40
S2
50 – 90
1
S3
100 – 150
2
S4
160 – 210
NO.
PLAIN
OR
POORLY REINFORCED
CONCRETE
FOUNDATIONS, MASSIVE ELEMENTS
REINFORCED CONCRETE FOUNDATIONS, PILLARS,
BEAMS, STRUCTURAL WALLS
IDEM, BUILT WITH PUMPED CONCRETE, MONOLITHIC
STRUCTURES
CONSISTENCY
CLASS
SPREADING
DIAMETER
[MM]
F1
≤ 340
F2
350 – 410
F3
420 – 480
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MONOLITHIC
ELEMENTS
WITH
DENSE
REINFORCEMENTS OR COMPACTION DIFFICULTIES,
ELEMENTS WITH REDUCED SECTIONS
F4
490 – 550
5
ELEMENTS FOR WHICH THE BUILDING TECHNOLOGY
REQUIRES HIGHLY FLUID CONCRETE
F 5*
F 6**
* 550 –12620
** ≥ 630
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S5
TYPE OF ELEMENTS
≥ 22011
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2. Classification of concrete
2. Classification of concrete
c) Depending on permeability Pab
d) Depending on gelivity
P410,P810,P1210,P420,P820 and P1220
a – pressure at which concrete does not allow water to
pass through its mass, in atm.
b – depth of penetration of water into concrete, in mm.
Ex.: P410 – the concrete submitted to:
• a pressure of 4 atm does not allow water to penetrate
it to
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• a depth of more than 10 mm.
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G50, G100, G150
• number of freeze – thaw cycles in which
strength or mass loss is lower than
standardized values.
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S.R. CLASS
Notation Strength
Rcyl/cube
2. Classification of concrete
C 2.8/3.5
C 4/5
C 6/7.5
e) Depending on brand and class
C 8/10
C 12/15
• Brand “B” = mean compressive strength at 28 days
determined on cubes with a 200 mm side, daN/cm2;
C 16/20
C 18/22.5
C 20/25
• Class (STAS) “Bc” = minimal compressive strength
at 28 days in cubes with a 141 mm side, N/mm2;
C 25/30
C 28/35
C 30/37
• Class (SR) “CRcyl./Rcube” = standard compressive
strength, determined in cylinders with a 150 mm
diameter and 300 mm height (Rcyl) or cubes with a 150
mm side (Rcube), at 28 days.
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C 32/40
C 35/45
C 40/50
C 45/55
C 50/60
BRAND
S.T.A.S. CLASS
Notation
Strength
Rc [N/mm2]
B 50*
Bc 3.5
3.5
B 75
Bc 5
5.0
B 100
Bc 7.5
7.5
B 150
Bc 10
10.0
B 200
Bc 15
15.0
B 250
Bc 20
20.0
B 300*
Bc 22.5
22.5
B 330
Bc 25
25.0
B 400
Bc 30
30.0
B 450*
Bc 35
35.0
-----
-----
-----
B 500*
Bc 40
40.0
-----
-----
-----
B 600
Bc 50
50.0
-----
-----
-----
B 700
Bc 60
60.0
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2. Classification of concrete
2. Classification of concrete
g) Depending on the mode of casting
f) Depending on the mode of preparation
- normal
- by pumping
- by injection
- by casting under water
• manual (works of lesser importance)
• mechanical (in situ, in concrete stations or
in concrete factories)
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2.8
3.5
4.0
5.0
6.0
7.5
8.0
10.0
12.0
15.0
16
20
18
22.5
20
25
25
30
28
35
30
37
32
40
35
45
40
50
45
55
50
60
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2. Classification of concrete
2. Classification of concrete
h) Depending on the mode of treatment or
hardening
• normal (untreated);
• steamed (aburit);
• Autoclaved
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i) Depending on the mode of compaction
•
•
•
•
•
•
•
•
•
•
non-compacted;
vacuumed;
manually compacted;
pressed;
compacted with a mechanical ram (mai);
gunited (torcretat);
vibrated;
vibropressed;
revibrated;
vibrovacuumed.
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2. Classification of concrete
j) Depending on the mode of reinforcement
3. Ordinary heavy
concrete
• plain concrete;
• concrete reinforced with:
–flexible reinforcement (steel-concrete);
–rigid reinforcement (profiles);
• prestressed concrete.
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
3.1 Binder
a = 2200 – 2500 kg/m3
• Portland cement
• with additions of:
–slag;
–trass (tras);
–flying ash (cenuşă de termocentrală).
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
The choice of the binder will take into account
the following:
• conditions of use of the concrete structure:
– aggressive environment;
– freeze-thaw frequency;
– action of chemical agents.
• the class of concrete;
• the rate of development of the strength of concrete
from casting to demolding (decofrare);
• conditions of preparation, transportation and casting
(punere în operă) – (normal, in cold weather,
massive, with sliding molds (cofraje glisante));
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
* In the case of concrete cast (turnate) in massive
elements, it is recommended to use low hydration heat
cements, set retarding additives, in order to avoid the
excessive thermal dilation of the elements.
Obs:
* For obtaining higher class concretes, it is
recommended to use higher class cements and
water reducing additives.
* In cold weather, cements with high initial strengths and
set accelerating additives are recommended.
* For obtaining concretes that should be demolded
before 28 days, it is recommended to use cements
with a high initial resistance (R), which harden much
more rapidly than normal cements.
* In hot weather, it is recommended to use slow setting
cements and set retarding additives.
* In aggressive sulfate environments,
recommended to use sulfate resistant cements.
it
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
3.2 Water
Binder amount
•
•
•
•
•
water + binder → cement stone
4 < pH < 9
drinking water
water of rivers, lakes (odorless fresh water, without
waste resulting from the manufacture of different
materials in industry)
• sea water
• mineral water
•
•
•
•
depending on the concrete class;
degree of environmental aggressiveness;
type of concrete (plain or reinforced);
size of the aggregate grain;
type of additive used.
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
MAXIMUM VALUE OF THE WATER CEMENT (A/C) RATIO
CONCRETE
CLASS
C 8/10
C12/15
C 16/20
C 18/22.5*
C 20/25
C 25/30
C 28/35*
C30/37
C 32/40*
C 35/45
C 40/50
C 45/55
C 50/60
32.5
0.75
0.65
0.55
0.53
0.50
0.45
0.40
CEMENT CLASS
42.5
0.65
0.62
0.60
0.55
0.50
0.47
0.45
0.40
Estimate amount of mixing water
52.5
CONCRETE CLASS
< C 8/10
C 8/10→C 20/25
> C 25/30
0.60
0.55
0.53
0.50
0.47
0.45
0.42
0.40
* Concrete classes that are not found in European norms.
WATER QUANTITY (A0) – L/M3
CONSISTENCY CLASS DEPENDING ON THE COMPRESSION
(TASARE)
S1, S2, F1, F2
160
170
185
S3, F3
170
185
200
S4, F4
200
215
S5, F5, F6
220
230
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
Corrections:
Corrections:
• reduction of up to 10 in the case of aggregates with 0 – 71
mm grains
• 10 increase in the case of broken stone
• reduction of up to 5 in the case of aggregates with 0 – 40
mm grains
• 10 increase in the case of aggregates with 0 – 16 mm
grains
• reduction of up to 10 – 20 in the case of the use of
additives
• 5 increase in the case of aggregates with 0 – 20 mm grains
• 20 increase in the case of aggregates with 0 – 8 mm grains
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3. Ordinary heavy concrete
3. Ordinary heavy concrete
3.3 Aggregates
• b/a  0.66, c/a  0.33
- river or crushing aggregates.
- impurity content:
- mica < 3
- coal < 0.5
- levigable parts:
- sand 3
- gravel 1
• volume coefficient  0.2
• granulometric curve – between the lower and
upper limit of the favorable zone of the
granularity areas
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3.4 Additives
3.4 Additives
• chemical products
• are added in concrete in amounts of less than
5 of the binder mass
• in order to improve properties in both fresh and
hardened state.
• the Romans – pig fat and blood in lime
concrete with pozzolan in order to increase its
durability.
• the first waterproof additives – 1910 for the
construction of water reservoirs,
• the first air-entraining additives in 1939, in USA
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3.4 Additives
3.4 Additives
The main groups of additives are:
Effects
•
•
•
•
water reducers,
strong water reducers,
plasticizers, superplasticizers,
set accelerators, set retarders, hardening
accelerators,
• air entrainers,
• anti-freezers, waterproofing additives,
• corrosion inhibitors.
• they improve the workability of concrete;
• concrete with high impermeability and good freezethaw resistance;
• increase in mechanical strengths, wear resistance,
resistance to chemical aggressiveness;
• regulation of binder setting and concrete hardening.
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Additives that change setting and
hardening
3.4 Additives
Effect
Water reduction
Increase in
workability
Increase /
decrease in the
setting time
Air entrainment
Increase in
resistance
Increase in
durability
Water
reducers
and strong
water
reducers
xx
x
Superplasticizers
x
x
x
xx
x
x
x
Note: xx – main effect;
x – secondary effect
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Type of additive
Set
Set
accelerators
retarders
3.4.1 Set accelerators
Hardening
accelerators
x
xx
Air
entrainers
x
x
xx
xx
x
xx
x
xx
xx
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•
•
•
•
•
accelerate the setting time (2 – 5) minutes;
fill cracks, holes;
stop water infiltrations;
protection against water flooding,
disadvantage – the high heat released during
the first minutes after mixing.
 concrete with immediate hardening, but
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without spectacular strength.
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3.4.2. Hardening accelerators – accelerated
hardening in the initial period (without
affecting setting)
3.4.1 Set accelerators
• for the consolidation of vaults (boltilor), walls
of underground galleries in mining;
• for the construction and maintenance of
concrete roads;
• concreting of slopes (taluzurilor), concreting
in cold weather.
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• the most widely used additive was calcium
chloride (reaching at 28 hours at least 85% of
concrete strength for 2% CaCl2) → corrosion of
reinforcement;
• in prefabricated parts;
• for the rapid demolding (decofrare) of all
elements of monolithic concrete;
• for concreting in sliding molds (cofraje glisante),
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concreting in cold weather;
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3.4.3. Set retarders
3.4.4. Waterproofing additives
• reduction of the water amount;
• fluidizing effect, reaching a (15 – 25)% increase
in mechanical strengths at 28 days;
• in order to avoid working joints (rosturi);
• for massive foundations;
• for large surface elements;
• for the maintenance of concrete workability
during transportation;
• in hot weather for pumped concrete and
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injections.
• they increase the impermeability of hardened
concrete:
– by the reduction of permeability to fluids
under pressure and of capillary ascension;
– by changing the concrete structure;
– by the covering of the concrete surface.
• in hydrotechnical concrete for dams, tunnels,
basins, channels, pools, reservoirs, silos, pillars
(stâlpi) and foundation walls
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Fluidizing additives
3.4.5. Tensioactive additives
• they reduce the superficial tension;
• they cause important changes in
concrete;
• depending on the action mechanism:
–fluidizing additives (plasticizers and
superplasticizers);
–air entrainers;
–mixed additives.
• they increase the workability of concrete for a
constant W/C ratio;
• or they reduce the W/C ratio for a constant
workability;
• they cause a dispersion of cement, so that the
cement surface exposed to hydration is larger
and initial strengths increase more rapidly.
• increase in strengths.
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Fluidizing additives
•
•
•
•
•
Superplasticizers
in high performance concrete,
concrete with dense reinforcement,
road cement concrete,
maritime works, dams,
for special works: injections, concrete
cast by pressure.
• act on the concrete structure, reducing the
W/C ratio,
• entraining air, forming a closed pore
system,
• interrupting the capillaries  increase in
impermeability and gelivity.
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Air entraining additives
Anti-freezing additives
• tensioactive substances that entrain and stabilize an
extremely high number of fine separate air bubbles,
uniformly distributed in the matrix, which interrupt
capillary porosity, forming a closed pore system.
• they improve workability and increase freeze-thaw
resistance.
• they influence water absorption, capillary ascension,
freeze-thaw resistance and permeability, the amount
of water is reduced (for workability equal to that of
fresh concrete), segregation decreases and the
appearance of concrete after hardening is improved.
• they significantly decrease the water freezing
temperature;
• they favor the hydration of the binder at low
temperatures.
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3.5 Additions
Inert additions
• solid substances;
• water insoluble;
• (5 – 85) of the binder mass is added to
concrete
• aim – to improve the properties of
concrete in fresh and hardened state
They are substitutes of the fine
aggregate part,
• the amount of 0-4 mm sand decreases by
approximately 10.
• they improve the workability and
compactness of concrete.
• clay, finely ground limestone.
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Active-hydraulic additions
3.6 Structure of concrete
• in the presence of the binder, they acquire
hydraulic properties.
• in the calculation of the W/C ratio, their mass is
added to the cement mass.
• volcanic tuffs, flying ash.
• in fresh state – plastic material–viscous
• solid phase – aggregate + cement
• liquid phase – free and hydration water
• gas phase – air bubbles
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3.6 Structure of concrete
3.6 Structure of concrete
• free water evaporates  the hardening of
cement stone begins
- pores under the aggregate grains 0.01 – 0.1 mm,  evaporation of water
under the aggregate grains;
• capillary pores 1 – 50 – open pores 
evaporation of excessive mixing water;
- occupying 1 of the concrete volume;
• occupying 10 – 15 of the concrete volume;
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3.6 Structure of concrete
3.6 Structure of concrete
- natural air pores 0.1 – 5 mm,  either by
air included during mixing, or by the
generation of pores with additives;
- 3 – 5% of the concrete volume.
• cracks resulting during concrete hardening.
• caverns – major defects generally due to the
non-observance
(nerespectării)
of
the
technology for the preparation and casting of
concrete.
• total pore volume 15 – 25, influencing all the
properties of concrete.
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3.7. The composition of concrete:
- to calculate the amounts of each component material required for the
preparation of 1m3
The calculation of the composition of concrete involves the following stages:
1. Choice of the type of binder;
2. Choice of the degree of homogeneity of concrete;
3. Choice of the class of consistency of concrete;
4. Choice of the W/C ratio;
5. Choice of the mixing water amount Ao;
6. Calculation of the cement amount;
7. Choice of the aggregate type;
8. Calculation of the aggregate amount;
9. Calculation of the water correction;
10. The optimum mixture of aggregates is calculated using one of the following
methods:
a) Method of successive approximations;
b) Graphic method;
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c) Experimental method;
d) Method of sorts.
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3.8 Preparation of concrete
Manually – in small amounts – works of
lesser importance.
• on concreted platforms or on board
flooring.
• aggregate + cement → homogenization +
water
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3.9 Transportation and casting of
concrete
3.8 Preparation of concrete
Mechanically – concrete mixers (100 – 2000)l.
• concrete stations;
• prefabricated part factories;
• dosage of materials:
– volumetric for works of lesser importance;
– gravimetric – for important works.
Manual (wheel barrows – roabe)
• works of lesser importance;
• viscous concrete
• distances  40 m
Mechanical – with the concrete agitator
• every 5 minutes the concrete is agitated for 3
minutes.
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Casting
3.10 Concrete compaction
• direct;
Manual – striking with a wooden ram
(hard concrete – betoane vârtoase)
• troughs (jgheaburi);
• thrusting (împungere) a metal rod over
the entire height (plastic concrete)
• by pumping at a 200 m distance, h 40m;
• by injection.
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3.10 Concrete compaction
a) Vibration
Mechanical:
a) Vibration
• application of shocks to concrete particles;
• the friction between particles disappears
 they are stuck to one another;
• reduction of W/C;
 very good concrete compactness
• 20 – 30 increase in mechanical strength,
• vibration duration:
–30s for b = 2400 kg/m3
–240s for b = 2460kg/m3
• vibrating tables,
• mold vibrators (vibratoare de cofraj),
• surface vibrators,
• pervibrators.
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b. Revibration
c. Centrifugation
• at a certain time interval from the
completion of vibration, a new vibration
is applied 
–decrease of inner tension due to
contraction;
–an increase in mechanical
strength of up to 20%.
• circular electric tubes and pillars;
• concrete centrifugation;
• centrifugation force  1 daN/cm2.
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e. Lamination
f. Compression
• casting of elements with a particular geometrical
shape T, , I, U;
• is performed in small elements
pressing the concrete into shapes
by
• small sizes.
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3.11 Influence of the exterior
environment on concrete
g. Guniting (Torcretare)
• application of (2 – 4) cm concrete layers
under pressure from a distance of 60 –
120 cm
 very good compaction,
 high mechanical strengths,
 significantly increased impermeability.
a) Moisture
• protection of normal concrete for min. 7 days,
and of concrete with additions for 14 days, by
its covering with mats or a sand layer (rogojini);
• sprinkling with direct jet of water
contraindicated → concrete exfoliation.
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b)Temperature
a) Moisture
• determinations are performed at 20°C
• covering with a polyethylene sheet
• dispersion on the concrete surface of
waterproof substances that prevent the
evaporation of water from concrete
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•
•
•
•
•
Measures in cold weather:
aggregates are heated at 50°C;
the mixing water is heated at 60°C;
up to 5 set accelerator is added
molds are heated if possible;
if possible, concrete is protected with thermal
insulating elements, for minimum 3 days;
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b)Temperature
STEAMING
• 150 – 400°C - water loss  decrease in tensile
strength
• t  400°C - loss of chemically bound water
• t  800°C the dehydration of the mineralogical
components of cement starts  concrete breaks
• normal pressure,
• moisture 90 – 95 
• temperature 80 – 90°C, - at 2 hours from
casting.
 more rapid hardening,
 about 10% lower final strengths.
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STEAMING
AUTOCLAVING
• oversaturated steam at a 2 – 12 atm.
pressure,
• 120 – 190°C temperature,
• at 2 hours from casting.
• heating and cooling last 3-4 hours.
• unchanged final strengths.
A steam cycle consists of:
• a heating period of about 2 hours;
• a steaming period of min. 4 hours;
• a cooling period of about 2 hours.
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Other thermal treatments
3.12 Properties of concrete
Treatment with:
- infrared radiation;
- thermal agents.
3.12.1 Properties of fresh concrete
• Determination of apparent density.
• Determination of workability
1. Compression (tasare) method.
2. Spreading (răspândire) method.
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Workability
• the property of concrete not to decompose into
component materials during transportation and
handling;
• the readiness (uşurinţa) with which it fills the
molds into which it is cast.
• it is assessed depending on:
– compression: decrease in the height of the
concrete pile (in the shape of a cone trunk), under
its own mass;
– spreading: degree of dispersion of a concrete pile
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in the shape of a cone trunk;
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3.12.2 Properties of hardened concrete
• Compressive strength
• Bending strength
• Apparent density
• Compactness and porosity
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Behavior of concrete in use
Type I corrosion
a) Corrosion = destruction of cement
stone under the action of aggressive
chemical agents
• decalcification of the mineralogical
components of cement,
• their conversion to gels,
• they are easily washed by water or other
aggressive agents.
• fresh water with a high CO2 content,
• ammonium salts except for sulfates.
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Type II corrosion
Type III corrosion
• decalcification of mineralogical components
• their conversion to gels
• formation of gels from the aggressive chemical
substance itself
• they overlap the cement paste gels, removing
cement from the cement stone structure
• induced by fats, sugar and magnesium salt
solutions, except for magnesium sulfate.
• expansion in the cement stone mass of new
compounds which in contact with water
crystallize and are easily removed from cement
stone.
• soluble sulfate solutions and calcium chloride.
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Behavior of concrete in use
Behavior of concrete in use
b) Destruction of concrete by physical
actions
• t  repeated freezing – thawing
• action of substances that prevent or destroy the
bond between cement stone and aggregates
(oils or soluble salts that crystallize in pores,
fissures or cracks, increasing them).
c) Deterioration of concrete due to the
incompatibility between aggregates and
cement.
• in alkali-rich cements with aggregates that
contain active silicon dioxide.
• in contact with water, alkalis react with silicon
dioxide, forming gels that increase volume,
finally destroying the concrete structure.
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Protection of concrete
Protection of concrete
• choice of the type of cement adequate for
the class of exposure of the building,
• choice of the adequate aggregate from the
point of view of the chemical composition
of the rock of origin and granularity,
• avoidance of horizontal sides exposed to
rain;
• protection of horizontal sides with metal
sheet or other insulating materials;
• treatment of the exposed concrete surface with
chemical additions that react with the cement
stone, resulting in a protection layer;
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• covering with anticorrosive substances such as:
bitumen, plastic masses, dyes (vopsele),
varnishes (lacuri);
• vibration and revibration of concrete.
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4. SPECIAL CONCRETE
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4.1 Light concrete
4.1 Light concrete
4.2 Hydrotechnical concrete
4.3 Road concrete
4.4 Radiation protection concrete
4.5 Polymer concrete
4.6 High resistance concrete
4.7 High temperature resistant concrete
4.8 Antacid concrete
4.9 Apparent concrete – decorative
4.10 Asbestos cement
• a < 2000 kg/m3
• high thermal and sound insulation capacity
• increased fire resistance compared to heavy
concrete.
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4.1 Light concrete
Class
Concrete type
S
Load bearing light
concrete
Load bearing and
thermal insulation
light concrete
Thermal insulation
light concrete
S.I.
I
Apparent
density
“a”
Kg/ m3
1600 – 2000
Compressive
strength
”Rc”
N/mm2
30 – 70
Thermal
conductivity
“”
W/(m K)
0,6 – 1,0
1300 – 1600
15 – 20
0,5 – 0,8
< 1450
< 15
< 0,5
The light aggregates used can be:
a) mineral aggregates: diatomite, volcanic tuffs,
furnace slag, expanded clay, burned waste;
b) plant aggregates: saw dust (rumeguş), rice
husk, flax and hemp chaff (puzderie de in şi
cânepă), tree bark (coji de copac), dried leaves.
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Light aggregate
Light macroporous concrete
The most widely used light aggregate is
expanded granulated clay which is called
granulite.
Rc smaller with 10 – 15 
Rt smaller with 10 – 30 
E = (0,33 – 0,66) Eb
• aggregates with discontinuous granularity;
• the fine part of the aggregate is completely
eliminated;
• the cement paste coats (îmbracã) the
aggregate grains with a fine film that joins them
only in the points of contact .
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Celular concretes
Light macroporous concrete
• about 50 porosity
• substances that generate – gases (gas
concrete) – Al; Zn; Mg powders.
• foam (foam concrete) – foam agent – glues
and colophony (colofoniu) soaps in amounts
of maximum 0.5 kg/m3.
• autoclaved aerated concrete AAC – in the
form of blocks or bands.
• type A; monogranular aggregate, Vg= 25 – 35;
• type B; aggregate - 2 or 3 sorts, Vg = 20 – 25;
• type C; Vg < 20  a low  a 0–3 mm sort.
• in large and small blocks for masonry;
• thermal insulating coverings (şape).
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Autoclaved Aerated Concrete – AAC
(Beton Celular Autoclavizat – BCA)
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YTONG technology
HEBELL technology
DANSK GASBETON technology
SIPOREX technology
SILCATEX technology
Cellular concrete without thermal treatment
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YTONG technology
• 1924 – dr. Axel Erikdson (Swedish) – light concrete with
properties similar to present day concrete.
• based on the activation of thermal power station ash – flying
ash using slaked lime.
• raw material–flying ash + 15 furnace slag and aluminium
powder
• homogeneous mixture (with metal powder addition) → porous
structure → it solidifies (steam treatment).
• ash and lime lumps are ground in dry state in a ball mill;
• they are mixed for 20 – 40 minutes at a 60°C temperature with
the expansion reagent (reactiv de expandare) which is the
aluminium powder;
• they are cast in molds and expanded at 70°C;
• they are shaped (fasoneaza) and cut (debiteaza);
• steam autoclaving (autoclavizare la abur) treatment at 250°C
and 12 atm pressure
• cooling for 6 hours (moisture drops from 40 to 15),
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• package, storage, delivery
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4.2 Hydrotechnical concrete
• they are cast in massive building elements – in
hydrotechnical dams
• they are permanently or periodically in contact with
water.
• concrete in periodic contact with water (zone A) 
concrete resistant to freezing – thawing and to the
corrosive action of water
Max. level
Max. level
Zone C
Zone A
Max. level
Max. level
Zone C
Zone C
Zone A
Min. level
• concrete permanently under water (zone B) 
waterproof concrete, resistant to the corrosive action
of water
• the concrete is not in contact with the water from the
accumulation lake (zone C)  ordinary concrete
• mass concrete – inside the dams (zone D)  it is
forbidden to use high hydration heat concrete or
concrete presenting swelling phenomena.
Min. level
Zone B
Zone A
Zone D
Downstream
level
Zone A
Min. level
Min. level
Zone B
Zone C
Zone D
Downstream
level
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4.3 Road concrete
4.4 Radiation protection concrete
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concrete for the load bearing layer – C 18/22,5
concrete for the wear (uzurã) layer – C 22/30
G100 or G150 degree of gelivity.
unprocessed natural aggregates (sand and gravel);
quarry products processed as broken stone and chippings
(cribluri);
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cements of ordinary or special types and brands;
additives (plasticizers, air entrainers, etc);
water;
reinforcement: steel bars, steel fibers;
materials for joints (boards, bituminous mastic);
• obtained with an extremely high cement
dosage 800 – 1000 kg/m3;
• crushing aggregates derived from very heavy
rocks – barite, magnetite or limonite.
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4.5 Polymer concrete
4.6 High resistance concrete
• for preparation, polymer emulsions are added in
selected dosages in order to fill the capillary
pores of concrete
• concrete with significantly increased tensile
strength, wear resistance, impermeability and
resistance to chemical attack
• for the manufacture of flooring, road coating
(îmbracaminţi rutiere) or finishing works
• Rc > 40 N/mm2
• with an increased Portland cement dosage,
without additions
• reduced W/C ratio
• crushed aggregates with a good granulometric
curve
• for building elements with large openings.
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4.7 High temperature resistant
concrete
• exposed for a long time to temperatures higher than
1000°C, they do not diminish their physicalmechanical characteristics.
• used for the lining (căptuşirea) of all thermal devices
in metallurgy, cement industry, chemical industry,
and nuclear technique.
• binder – aluminous cement
• aggregates – chamotte (şamota), chromium ore
(minereu de crom), refractory white bauxite (bauxita
albã refractarã)
• chemically neutral water.
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• W/C ratio = (0.4 – 0.5).
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4.7 High temperature resistant
concrete
• thermal resistant concrete – refractoriness
lower than 1500°C, t = (200 – 1100)°C;
• refractory concrete – with refractoriness
values ranging between 1500 – 1790°C, t
=(1100 – 1300)°C;
• highly
refractory
concrete
–
with
refractoriness values higher than 1790°C, t >
1300°C.
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4.9 Apparent concrete – decorative
4.8 Antacid concrete
• high resistance to the action of acids and
bases;
• binders – based on soluble glass – their
mass also contains polymer resins
• aggregates – rocks resistant to these
chemical agents
• in acid environments or in highly aggressive
carbonate or sulfate environments.
• large concrete elements that will not be finished,
• high resistances C 18/22.5, C 20/25,
• good compactness and high freeze-thaw
resistance (G100 – G150).
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4.10 Asbestos cement (azbociment)
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• cement + water + asbestos fibers
• products in the shape of flat or undulated plates contain
(11-12) asbestos and (88-89) cement
• for roof covers (învelitori), thermal insulating walls
• ADVANTAGES:
– low mass of the element;
– high prefabrication degree – reduced manual
labor;
– high durability;
– good fire resistance;
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– special esthetic appearance – it can be colored.
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5.1 Concrete products for alleys and
sidewalks (trotuare)
5.2 Concrete products for water supply
and sewerage (canalizãri) – tubes
• pavement
slabs
(pavele
de
pavaj)
manufactured in one or two layers (wear and
load bearing layer), can be square or
hexagonal;
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• plain or mosaic concrete kerbs (borduri) can be
field kerbs, corner kerbs or kerbs for access to
sidewalks.
plain concrete tubes for sewerage;
reinforced concrete tubes for water supply
different sections, different diameters,
rubber ring joint, tongue and groove joint
(lambã şi uluc) etc.
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5.3 Concrete blocks for masonry
• of light macroporous or cellular concrete
• with horizontal or vertical pores when macroporous concrete is
used
• compact when AAC is used
• silico-calcareous bricks – by the autoclaving of a lime (6 – 10)
and siliceous sand (94 – 90) mixture  vertical pore blocks.
• Advantages:
– short manufacturing duration (24 hours),
– energy saving,
– significantly higher precision,
– manpower saving,
– easy handling compared to concrete blocks.
5.4 Prefabricated concrete products
• concrete elements for fences – pillars (stâlpi)
and slabs (plãci);
• concrete elements for floors (T and );
• prefabricated pillars and beams (grinzi) for
frame structures (structuri în cadre).
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