Arduino_CSE ece ppt for working and principal of arduino.ppt
Under water concreting
1. BANGALORE INSTITUTE OF TECHNOLOGY
DEPARTMENTOFCIVIL
ENGINEERING
UNDER THE GUIDEANCE
OF
B S KARTHIK
Asst.professor
PRESENTED BY
AGNESH B S
1BI11CV008
3. IntroductionIntroduction
There are often situations such as basements ,
sewerage ,ducts , harbours , bridges and marine works ,in
which concrete is to be placed underwater.
Special precaution need to be taken whenever the
concrete is to be placed underwater.
The concrete should be plastic and cohesive but should
have good flowability.
4. Performance requirements for UWC
Workability & self compaction
Cohesion against washout & segregation
Low heat of hydration
Controlled set time
Compressive strength
Adequate bond
Problems faced
Segregation of fine aggregates from coarse aggregates
Water pollution
Increased w/c ratio
washout
5. Types of Materials usedTypes of Materials used ::
Cement
Coarse Aggregates
Fine Aggregates
Admixtures
7. AGGREGATESAGGREGATES :
Coarse Aggregates :
The coarse aggregate for intruded in concrete
shall conform to the following gradation:
Maximum Size - 1.5-2 inch (100% shall pass a 75
mm sieve )
Minimum Size - material passing a 19 mm sieve
shall not exceed 5% by mass of the coarse
aggregate.
8. Fine Aggregates :
The sand for the intruded grout shall be well
graded, preferably of round grains and shall
conform to the following gradation:
Passing 1.18 mm sieve 95 - 100%
Passing 600 um sieve 60 - 85%
Passing 300 um sieve 20 - 45%
Passing 150 um sieve 15 - 30%
Passing 75 um sieve 0 - 10%
9. Use of Different AdmixturesUse of Different Admixtures
Anti-washout admixtures
Hydrocem
Mellose
Viscosity modified admixtures
Naphthalene Formaldehyde
Sulfonated Melamine Formaldehyde
10. Concrete Particles with adding MELLOSE
Concrete Particles without MELLOSE
* Black Dots
Indicates Water
12. TREMIE METHOD
A Tremie is a watertight pipe
Generally 250mm in dia.
Funnel shaped hopper at its upper end
and a loose plug at the bottom.
It is supported on a working platform
above water level.
13. Specifications of concrete to
be used in Tremie method:
Coarse Aggregate: Gravel of 3/4” (20mm) max. size. Use
50-55 % of the total aggregate by weight.
Sand, 45-50% of the total aggregate by weight
Water/Cement Ratio: 0.42 (0.45 Maximum).
Water-Reducing Admixture (preferably it is also
plasticizer): Do not use super plasticizers.
Air-Entrainment Admixtures: To give 6% total air.
Retarding Admixture: To increase setting time to 4-24
hours, as required.
Slump: 6 1/2" ± 1"
This mix will develop compressive strength in the range
of 5,600 – 7,000 psi at 28 days.
14. Laying of concrete by using Tremie
14
Basic principle behind Method
of underwater concreting -
Tremie method
Method of underwater
concreting— Tremie
method (inside view)
17. PUMP METHOD:
Pumping concrete directly
into its final position,
involving both horizontal
and vertical delivery of
concrete.
Pumping concrete has the
advantage of operational
efficiency with potential
savings of time and labour.
17
PUMP METHOD OF
LAYING CONCRETE
18. Repair worksRepair works
Defining the Area
Cleaning the Affected Area
Equipment Haulage
Personnel requirements
Inspection methods
Environment considerations
19. At present, the Tremie placement method is
the standard way of placing high-quality
concrete underwater. The other placement
method are not able to reliably place high-
quality underwater concrete for major
structures, although they may find
application in special cases.