trainning

1. PREPARATION FOR CONCRETING

Equipment
Site
1) Chemical protective gloves
2) Anti-vibration protective gloves
3) Rubber boots
4) Concrete protective suit
5) Impulse vibrator
Horizontal and
vertical surfaces of
construction joints
shall be cleaned
off mud and
garbage, dust, and
cement film
before concreting.
Cleaned surfaces shall be
dampened with water and
blown with compressed air
immediately prior to placement
of concrete mix. At the moment
of concrete placement, the
surface of the construction joint
shall be wet.

2.

Concrete pouring
Concrete mixture is placed
in the wall with concreting
intensity of not less than
30.0 m³/h, in consecutive
direction of the concrete
placement to one way. The
overlap time of concreting
layers averages up to 2.0
hours.
The free dropping height of
concrete mixture shall not
exceed 1.0 m (according to
the standard Process
Schedule for Concreting
Operations).
Concrete mix in shall be poured in the formwork in
horizontal layers without any technological gaps
with the same direction of the pouring in all layers.
With substantial cross areas of the structures to be
concreted, it is allowed to compact the concrete mix
in inclined layers by forming an advanced horizontal
area 1.5.-2 m long in each layer. Before compacting,
the inclination angle to the horizon of the surface of
the concrete mix laid shall not exceed 30°. After
concrete mix is laid and spread over the entire area
of the layer being poured, start compacting from its
advanced part.
The process of concreting
must be continuous and
without interruption,
allowing to maintain
fluidity and reduce defects.
Supply intensity shall
correspond to pouring
speed.
Concrete mix is distributed
uniformly in the concreting
bay via flexible hood
starting from the
outermost point. Each
concrete placement point
should be re-treated not
later than 2 hours upon
completion of the previous
concreting stage. Concrete
mix compacting of each
layer shall be done
When concreting each next layer of the concrete
mixture shall be placed prior to starting of
setting of the concrete in the previously laid
layer. A construction joint is required if a break
during the concreting exceeds the time during
which the concrete in the placed layer starts to
harden (the concrete looses its thixotropic
properties (flowability) with available vibration
means). In this case the concrete in the laid layer
shall be cured until it reaches the strength of at
least 1.5 MPa.
When laying concrete mix it is necessary to take measures to prevent its
stratification: avoid moving of the concrete mixture by vibrators, concrete mix
shall be compacted thoroughly. It is strictly forbidden! To increase consistency of
the concrete mixture (delivered to the placement zone) - dilution with water and
plasticizers as wells as their mixtures.

3. CONCRETE MIX COMPACTING

Concrete mix compaction is carried out by high-frequency deep vibrators IV-116А
(length of the working part is 430 mm) in each layer being placed with observance of
the following requirements: - before the beginning of compaction of each layer, the
concrete mix shall be evenly distributed over the entire cross-sectional area of the
structure being concreted. The height of the individual bumps above the total level of
the surface of the concrete mix before compaction shall not exceed 10 cm. It is
forbidden to use vibrators for redistribution and leveling in the layer of the concrete
mix fed into the formwork. The concrete mix in the laid layer shall be compacted only
after the end of the distribution and leveling on the area being concreted; continuation of vibration shall be specified by the construction laboratory immediately
at the workplace as per visual features characterized by termination of sedimentation
of the mixture and release of air bubbles on the surface.
-
The concrete mixture in each poured layer or at each position of the vibrator head
shall be compacted until settling stops and the cement paste shine appears on the
surface and at the formwork contact areas;
-
Spacing of a vibrator relocation to receive homogeneous grade of compaction shall
be restricted to 1.5 R of the vibrator action; - the depth of immersion of the
vibrator shall provide its partial 5-10-cm deepening into the previously laid layer
which is not set yet for better bonding between the layers;
-
It is not allowed to rest the vibrators against rebars and embedded parts, tie rods
and other formwork fastening elements.
-
When compacting the concrete mixture unproven places, laminations and cracks
are unacceptable.

4. CONCRETE MATURATION AND CURING

Start curing the concrete
within maximum 15
minutes in areas where the
level of freshly laid
concrete in the layer has
reached the required
elevation.
Immediately after concreting
(including the time during breaks in
concreting), open surfaces of freshly
placed concrete must be reliably
protected against water evaporation.
Freshly placed concrete mix shall be
protected against dewatering by
means of film-forming coatings of АЗ
Teknonicol Lotus type or with any
other similar coating
Further, periodically
monitor the condition of
the moisture-retaining
material, preventing it from
damage and regularly
moisten it as necessary.
The decision to stop
concrete curing and to
remove the formwork shall
be made by a person
responsible for work
performance and quality.