This presentation contains very interesting informations about Pumping,under water concreting,Shotcrete and High Volume Fly Ash Concrete (HVFAC)

1. Methods of
Concreting
1

2. Different methods
• Pumping
• Under Water Concreting
• Shotcrete
• High Volume Fly Ash Concrete
2

3. Pumping
• The placing of concrete at certain place with the help of a
pump is termed as pumping.
• It is used at inaccessible places.
• Mostly used along with RMC.
3

4. Types of Pumping
1) Direct acting concrete pumps
2) Squeeze type concrete pumps
4

5. Direct acting concrete pumps
• Direct-acting, horizontal piston type with semi-rotary valves
set to permit always the passage of the largest aggregate
particles.
• It can cover a horizontal distance of 1000m and vertical
distance of 120m.
• The concrete is fed in by gravity and is also partially sucked in
during the suction stroke.
• The valves open and close with definite pauses so that
concrete moves in a series of impulses, but the pipe always
remains full.
• These pumps are capable of pumping 130 m3 of concrete per
hour with 8 inch pipes.
5

6. Direct acting concrete pump
6

7. Working of Direct acting concrete
pump
• During the ‘suction stroke’ the inlet valve opens and concrete
is admitted into the pumping cylinder, the outlet valve
remaining closed.
• In the ‘delivery stroke’ the outlet valve gets opened and the
inlet valve being closed, the concrete gets pushed into the
delivery pipeline.
7

8. Squeeze type concrete pumps
• Squeeze pumps or peristaltic pumps are the ones that use
vacuum pumping.
• This type of pump can cover a distance of 90m horizontal and
30m vertical.
• It has capacity to pump 20m3 of concrete using 75mm pipe.
8

9. Squeeze type concrete pump
9

10. Working of Squeeze type concrete
pump
• The concrete from the collecting hopper is fed by rotating
blades into a flexible pipe connected to the pumping chamber.
• The vacuum pressure is maintained at 0.08N/mm2.
• The two rotating rollers mounted on planetary drives
progressively squeeze the flexible pipe and thus push the
concrete into the delivery pipe.
10

11. Condition required for unhindered
flow
• Diameter of the suction pipe should be equal to the diameter
of the pumping cylinder.
• Diameter of the suction pipe should be at least 3 times that of
largest aggregate.
• The bends in the pipes conveying concrete from the pump
should be minimal in order to avoid losses.
• Aluminium pipes should be avoided, as the Al reacts with
alkalis in the cement, and leads to the evolution of hydrogen
gas. These gases tend to introduce voids in the concrete,
which reduce the efficiency of pumping.
11

12. Requirements for pumped
concrete
• Concrete mixture should neither be too harsh nor too sticky;
also, neither too dry nor too wet.
• A slump between 50 and 150 mm is recommended.
• There should be sufficient amount of water in the concrete.
• High cement content in concrete is generally beneficial for
pumping.
• Other mixture factors that could affect pumping are the
cement content, shape of aggregate, presence of admixtures
such as pumping aids or air entrainment. Air entrainment is
helpful in moderate amounts, but too much air can make
pumping very inefficient.
12

13. Under Water Concreting
• Whenever there is a requirement of underwater, to avoid
cement washout under water concreting is adopted.
13

14. Methods of under water concreting
1) Tremie method
2) Pumping technique
3) Hydro valve method
4) Pneumatic valve method
5) Skip method
6) Tilting pallet barge method
7) Preplaced aggregate concrete
8) Toggle bags method
9) Bagged concrete method
14

15. Tremie method
• Underwater concreting using tremie method is convenient for
pouring large amount of high flowable concrete.
• Tremie pipe, which upper end connected to a hopper and
lower end continuously submerged in fresh concrete, is used
to place concrete at the exact location from a hopper at the
surface.
• The reason to immerse the tremie pipe lower end is to
prevent intermixing of both concrete and water.
15

16. Typical Arrangement of Tremie
Method of Underwater Concreting
16

17. Process of Underwater Concreting
using Tremie Method
• Tremie Equipment
• Tremie seal
• Placing the concrete
• Flow pattern
17

18. Shotcrete
• ‘Shotcrete’ is a concrete conveyed through a hose and
pneumatically projected at high velocity at the projected
surface, as a construction technique.
• It is a sprayed concrete which is batched in a predetermined
ratio of cement and aggregates and mixed with (or without)
water.
• The shotcrete process was first used in Pennsylvania, USA in
1907 by Dr. Akeley.
• Shotcrete undergoes placement and compaction at the same
time due to the force with which it is projected with nozzle.
• Shotcrete is an excellent tool for stabilization and support of
structure in a very short time and for concrete applications
without using any moulds.
18

19. Types of Shortcrete
• Dry mix Shortcrete
• Wet mix Shortcrete
19

20. Dry mix Shortcrete
• The cement and sand mixture are stored in the
pressurized chamber and projected towards the nozzle
where water is added just before the release of the
mixture.
20

21. Wet mix Shortcrete
• The sand, cement and water are to be mixed before
being sprayed from the machine.
21

22. Comparison between Dry mix &
Wet mix Shotcrete
22

23. Applications
• Sealing of Ground Mass Interface
• Component of Excavation Support System
• Canal Lining
• Repair Work
23

24. High Volume Fly Ash Concrete
(HVFAC)
• High volume fly ash concrete is a concrete where a
replacement of 50 to 60 percentage of cement and w/c<0.4 is
made with the usage of fly ash.
• IS: 456 – 2000(Code of Practice for Plain and Reinforced
Concrete) allows replacement of OPC by Fly ash up to 35% as
binding material.
24

25. Characteristics Affecting
Performance of Fly Ash Concrete
• Fineness - Finer the fly ash, the more the surface area
available to react with lime and thus more will be the
pozzolanic activity of fly ash.
• Calcium (CaO) content – Higher the CaO content, the greater
will be the pozzolanic activity and greater the contribution to
the strength in concrete.
25

26. Usage & Benefits of fly ash
• Mixing fly ash with cement clinker at the factory to produce
Portland Pozzolana Cement (PPC).
• Using fly ash as an admixture at the time of making concrete
at work site.
• Low heat of hydration and thermal shrinkage.
• Improved resistance to attack by sulfate soils and sea water.
26

27. Chemical composition of fly ash
27

28. Fresh properties of HVFAC
• Workability
• Air Entraining of HVFAC
• Bleeding
• Setting Time
28

29. Hardened properties of HVFAC
• Autogenous Temperature rise
• Drying Shrinkage and Creep
• Strength Properties
• Durability
29

30. Thank You
30