1. CC 203
CONCRETE TECHNOLOGY
TOPIC 2
CONCRETE WORKS AT THE
CONSTRUCTION SITE
Lecturer name:
MOHD HAZMAN BIN ABDUL AZIZ
2. SUB TOPIC 2
– Factor that cause of occurrence material
segregation and bleeding.
– Fresh concrete.
– Concept of hard concrete.
– Preparation of concrete at site.
– Concept of transporting concrete.
– Concept of casting and placing concrete.
– Method of compaction concrete.
– Method of curing concrete.
– Standard laboratory testing on concrete mixture.
3. SUB TOPIC 2.1
Factor that cause of occurrence material
segregation and bleeding.
- Describe the segregation and bleeding of
concrete.
- Show the segregation and bleeding of
concrete mix.
- Effect of segregation and bleeding on
quality of concrete.
4. Segregation
Separation of the constituent materials of
concrete.
Source - low limit of compacting
Can divide by 3 types cause :
a) Coarse aggregate separating out or
settling down from the concrete mix.
b) Paste separating away from coarse
aggregate.
c) Water separating out from the material
being of lowest specific gravity.
7. Bleeding
Bleeding in concrete is sometimes referred as
water gain
It is a particular form of segregation, in
which some of the water from the concrete
comes out to the surface of the concrete,
being of the lowest specific gravity among all
the ingredients of concrete.
Source – over limit of compacting
9. Effect of segregation and bleeding on
quality of concrete
e) Strength of concrete
f) Surface cracking.
g) Bonding of material in concrete mix
10. SUB TOPIC 2.2
Fresh concrete
- Relate the workability of wet concrete with
water cement ratio.
- Testing on workability of concrete
a) Slump test.
b) Vebe test.
11. Relate the workability of wet concrete with
water cement ratio.
One of material in concrete mixture.
If volume of water are over limit the
strength and density of concrete is reduced.
Ifvolume of water are low limit the
concrete will be difficult to do and the
hydration process is not perfect.
12. •
Slump Test
Purpose :
To determine the workability of concrete at
site. ( BS 1881: Part 102:1983 )
Apparatus :
Cone dan base plate.
Circular tamping rod 12mm.
Ruler steel and concrete mixing equipment.
Concrete.
13. Procedure:
Prepare materials for the concrete mix according
to the mix ratio as directed.
Clean the surface of the cone, then lay on a flat
base plate.
Include the concrete mix into the cone of 3
layers and each layer compacted by 25 times
using a tamping rod stuffing until full.
Flatten the top and clean the concrete surface.
Slowly and carefully remove the cone by lifting it
vertically and place the cone next the concrete
mix.
14. Place the rod horizontal at cone and
concrete slump.
Measure and record the distance slumps the
concrete.
Repeat the testing with add water cement
ratio.
15. Data result:
No. of testing 1 2
Mix Ratio 1:2:4 1:2:4
Mass of materials ( kg ) 28 kg 28 kg
Volume of water ( liter ) 2.3 L 2.8 L
Height of cone ( mm ) 300 mm 300 mm
Height of slumps ( mm ) 275 mm 245 mm
Distance of slumps ( mm ) 25 mm 55 mm
* Range BS( Limit slump 0 – 150 mm )
16.
17. b) Vebe test
Objective : to determine the workability of
fresh concrete
Apparatus
Concrete
Vebe consistometer mechine
18. PROCEDURE
i) A conventional slump test is performed, placing
the slump cone inside the cylindrical part of the
consistometer.
ii) The glass disc attached to the swivel arm is
turned and placed on the top of the concrete in the
pot.
iii) The electrical vibrator is switched on and a stop-
watch is started, simultaneously.
iv) Vibration is continued till the conical shape of the
concrete disappears and the concrete assumes a
cylindrical shape.
v) When the concrete fully assumes a cylindrical
shape, the stop-watch is switched off immediately.
The time is noted.
19. SUB TOPIC 2.3
Concept of hard concrete.
- Criteria of hard concrete
a) Compression strength
b) Tensile / bending strength
c) Durability ( Ketahanlasakan )
d) Permeability ( Resapan )
e) Resistant to chemical reaction
f) Changing of shape
g) Shrinkage
h) Creeping ( rayapan )
i) Fire resistant
20. a) Compression strength
Most important property of hard concrete.
Generally considerad for the design.
For ordinary construction compressive
strength in a range of 20-40 MPa.
Low range (cast in-situ), High range (precast)
Testing concrete prepared in standard cube
100 or 150mm for 7,14,21 and 28 days.
21. b) Tensile / bending strength.
Should be high to resist cracking from
shrinkage and temperature changes.
Measured using one or more for
i) Direct tension test
ii) Split cylinder test
iii) Flexural test.
22. c) Durability ( Ketahanlasakan )
Concrete should be design to serve its
purpose
Factors that influence durability can be
divided into:
– the environment and usage factors (outside
control)
– the composition and production factors
23. d) Permeability ( Resapan )
The low permeability of concrete is essential
to increase the resistance properties of cooled
action, chemical action and protects the place
of steel corrosion occurs.
To obtain a low permeability, the concrete
should be fully compressed and the
preservation of good done.
Permeability can also be reduced by using
water content and increase the cement
content.
24. e) Resistant to chemical reaction
Portland cement concrete is often attacked by
acids such as organic acids and other food
processing, especially when the work
performed.
Chemical elements are commonly attacked
concrete sulphate salt present in the soil and
in sea water.
Resistance properties of concrete sulphate
attack depends on the type of cement used,
the cement content and water cement ratio.
25. f) Changing of shape
Elastic deformation that occurs at that time
and depending on the value of applied stress.
Drying shrinkage that occurs in a long time
and does not depend on the stresses in the
concrete.
Creep occurred in the long run, but
depending on the value of the stresses on the
concrete.
As other materials, the concrete will also
experience expansion and contraction due to
temperature changes.
26. g) Shrinkage
Shrinkage of concrete depends on the amount of drying that
occurs.
Thus it is affected by humidity and ambient air temperature,
air flow rate on the surface and the rate of surface area and
volume of concrete.
In normal conditions, contraction was influenced by the
amount of available water in the concrete during the mixing
and the cement content.
For a small concrete, usually assumed that half of the drying
occurs in one of the first month and the balance within six
months thereafter.
27. h) Creeping ( rayapan )
Creep of concrete depends on the value of the stresses in it.
For stresses up to 1 / 3 of the cube strength is considered to
be directly proportional to the creep stress.
Creep is affected by temperature and moisture environment,
the cement content in concrete, water cement ratio, cement
type and nature of aggregates.
The mass of concrete also has some influence on the creep,
but much less than its effect on contraction.
The parameters used to evaluate the creep is the ratio of
applied stress on concrete cubes at one point of time.
28. i) Fire resistant
The combustion temperature is below 400[degrees] F (200[degrees] C).
At this temperature, only the free water in the concrete will be lost, and
the strength loss is minimal. Mineralogical changes in hydrated cement
occur at higher temperatures. The most important factor is consider is
the selection of aggregate. The differential thermal movement between
the cement paste and the aggregate is what can cause damage.
Quartzite aggregate is the most prone to fire damage by cracking through
the quartzite aggregate and bond failure between the cement paste and
the aggregate. Limestone aggregate exhibits better fire resistance when
exposed to low temperature fire. Lightweight aggregate also performs
well. For this situation, a 6 1/2-sack lightweight concrete should provide
all the heat resistance needed.
At higher temperatures (above about 800[degrees]F), high-heat-resistant
concrete is generally needed. Light-weight aggregates have proven to be
more heat resistant and so that is the first step--use lightweight. When
temperatures get extremely high, above 1000[degrees]F, calcium
aluminates cement produces a fire-resistant concrete.
29. SUB TOPIC 2.4
Preparation of concrete at site.
- The batching method of concrete.
a) Volume method.
b) Weigh method.
- The mixing method of concrete.
a) Manually.
b) Machinery.
30. The batching method of concrete.
a) Volume method.
using the measuring box and the conventional method,
which has long been used to work at construction site.
This method can not be used for work that requires
accuracy because of the volume of concrete depends on its
density.
The ratio of each substance is calculated based on the
volume of concrete.
volume of cement is calculated based on the volume of one
bag / weight of cement and sand as well as for coarse
aggregate measured by volume of the same bag
31. Density of cement ( BS = 1442kg/m2 ) to
determine the measure of box :
1bag cement = 50kg/ 1442kg/m3
= 0.035 m3
The measuring of box is
( 0.33m x 0.33m x 0.33m = 0.035m3 )
32. b) Weigh method.
using the principles of the scales.
suitable for control purposes in the laboratory
for testing purposes.
Example:
Mix ratio (1:1.9:3.8 ) and W/C = 0.5
1 bag cement x 50kg = 50kg
1.9 x 50kg fine agg. = 95kg
3.8 x 50kg coarse agg. = 190kg
Volume of water = 25L
33. The mixing method of concrete.
a) Manually.
Mixing by hand.
Can’t to used or efection for the high
workability.
Mixing for are small quantity mixture.
35. b) Machinery.
i )Types T – drum are lean
This machine are used drum for mixing the
materials of concrete.
When mixing are finish the concrete will be
throut.
The shape of machine is cone and spin in one
direction.
The angle of casting is 400 to 600 .
36. ii )Types NT – drum are not lean ( Cylinder )
This machine shape like cylinder and same
are machine Types T.
The drum spin in vertical part.
The concrete mixing well throut at bottom
part of machine.
37.
38. SUB TOPIC 2.5
Transporting method of concrete.
- Defination of ready mix concrete.
- Transporting method of concrete on site.
a) Wheelbarrow.
b) Chute.
c) Pump.
d) Crane.
39. Ready mix concrete
Ready-mix concrete is a type of concrete that
is manufactured in a factory or batching
plant, according to a set recipe, and then
delivered to a work site, by truck mixers.
40. Transporting method of concrete on site.
a) Wheelbarrow
Used for concrete transporting in small
quantity.
Used to transport the concrete materials such
as cement and aggragate.
41. b) Chute.
Tools to transporting concrete from heigth to
the lower place.
Made from PVC pipe , wood and other
materials.
Chute limited for 3m and diameter is 300mm.
42. c) Pump.
fast method and economical if careful
planning.
using pipe ɸ 6” to pumped from the mixing
place.
used for large quantities concrete.
can carry as long 30m – 50m vertically and
300m – 500m horizontal direction.
have two type is plunger pump and press
pump.
used in difficult to utilise lorry and trasport
machine.
43.
44. d) Crane.
Have two types:
i) mobile crane.
ii) tower crane.
i) Mobile crane
Used for project large and in the construction
of high structures less than 30m.
The concrete include in large container have a
trap door at bottom.
45. ii) Tower crane
Used for building higher than 30m
Use skrip depend on load of size
Size of skrip is 1394kg @12.57m3
If the concrete placing is high, a large of
skrip should be used to make it more
economical.
46.
47.
48. SUB TOPIC 2.6
Casting and placing of concrete.
- Method of casting and placing for
concrete.
- Procedures of casting and placing on site.
49. Method of casting and placing
Casting
Space to casting the concrete in formwork at
each structure member much be less than
1.2m for avoid the segregation cause.
Must be casting the concrete layer by layer.
Placing
Must be placing early after mixing with
water.
Maksimum times is 11/2 hour.
50. Procedures of casting and placing on site.
Concrete mix must be near at site.
Must be placing in a uniform layer by layer
for avoid separation materials.
For structure concrete wall and column must
be placing in layer thickness 450mm.
Concrete must be quickly as possible to
prevent from hardening.
Make sure every layer must be compact
before the next layer.
Avoid for cold joint.
Avoid bar reinforcement move during the
51. SUB TOPIC 2.7
Compacting method of concrete.
- Method of compacting for concrete.
a) Steel rod.
b) Vibrator machine. ( internal , external
and platform )
- The advantages and disadvantages of
compacting concrete using vibrator and
steel rod.
52. Method of compacting for concrete.
a) Steel rod
Using for laboratory testing.
Diameter steel rod 12mm.
53. b) Vibrator machine. (internal , external
and platform)
Internal vibrator
Widely used by electric or diesel power.
Compaction of this type has different sizes of
vibrating pins 10mm to 25mm.
Must be done carefully so that the
reinforcement in the mold is not move or
damaged.
55. External vibrator
is done outside the mold side of the
concrete until the mixture became
compressed.
Usually it is used in workshops and
performed by the power to make beam,
piling, box culvert.
57. Platform vibrator
is a table supported by a number of springs
that run by electricity which allows the face
of the vibrating table.
usually used in workshops to make the
precast concrete.
Concrete parts shall be made in formwork
and placed on the table to vibrator for
compact.
59. The advantages and disadvantages of
compacting concrete using vibrator and
steel rod.
60. SUB TOPIC 2.8
Method of curing concrete.
- Purpose of curing.
- Method of curing concrete.
a) Covered with wet materials( sacks,
plastic, wood dust ) .
b) Flooding or spraying with water.
c ) Sweeping with chemicals.
d ) Using a vapor steam.
61. Purpose of curing.
Prevents the loss of water from the concrete
during the hardening process.
Avoid loss of water from the concrete.
Can control the temperature of concrete.
Can guarantee a hard surface, compact to
avoid the risk of cracking.
Can prevent the bleeding.
62. Method of curing concrete.
a) Covered with wet materials( sacks,
plastic, wood dust ).
Covered with sacks wet, plastic,wood dust,
sand, and other wet materials.
Materials that may damage the color of
concrete can not be used.
63. b) Flooding or spraying with water.
Flooding or spray on the concrete surface
with water.
This method is suitable for concrete work
on the floor.
c ) Sweeping with chemicals.
Sweeping chemicals such as silica
compounds in the concrete surface to
prevent water loss from evaporation.
64. d ) Using a vapor steam.
This method is used in the factory to
accelerate the curing process, especially for
pre – stressed concrete.
