1.0
OBJECTIVE
To carry
out the site mix concrete work as per approved design mix for each particular
grade.
2.0
SCOPE
This method
covers for site mix concrete and trial mix for grade 20N, grade 25N and grade
30N by using mixer truck (dry mix).
3.0
REFERENCES
Construction
Drawings
Project
Specifications
Inspection
Request Form
Approved
design mix
4.0
RESPONSIBILITIES
Site Manager
QA/QC
Engineer
Site
Supervisor
Lab
Technician
5.0
WORKERS
Machine
Operator
General
Worker
6.0
MATERIALS
Cement,
Fine Aggregate & coarse Aggregate, Water
7.0
HANDLING
AND STORAGE OF MATERIALS
Handling: Transport of concrete using
mixer truck and 20 tonne of mobile crane to location of concrete work.
Storage: Fine aggregate and course aggregate shall be
place nearest at batching area.
Cement shall be place in the
store in dry condition and protected from weather
8.0
PLANT,
MACHINERY AND EQUIPMENT
Concrete
Mixer Truck.
Batch
boxes (800mm x 800mm x 500mm)
Water
tank (5786 litre)
Nominated
lab (Hermes Lab, for compression test)
Cube
mould
Weighing
scale
Slump
equipment
Wheel
barrow
9.0
PREPARATORY
WORKS
9.1
Before the site mixes commence, check will be
carried out to ensure all the various control devices of the concrete mixer is
functioning properly.
10.0 WORK
METHODOLOGY
10.1 Prior to commencement of the site mix,
batch boxes should be fabricated, measuring 800mm x 800mm x 500mm to measure
the proportion of coarse and fine aggregate, based on of 1 bag cement (50kg
with loose weight 1436kg/m3), 0.035m3. Meanwhile, water shall be fill in full
water tank 5786 litre complete with measuring gauge. Therefore, quantity water
shall be control as per approved design mix proportion.
10.2 The coarse and fine aggregate shall be
passed all the testing such as sieve analysis, aggregate crushing value,
flakiness and other as per specification before placed into the concrete mixer.
10.3 Before carry out the site mix, a trial site
mix approximately 1m3of mix concrete shall be batched based on
approved design mix to required grade of concrete to check workability of mix
and compressive strength. A set six (6) 150mm concrete test cubes, 3 for
testing at 7 days and 3 for testing at 28 days will be made and tested to
achieve as per required target mean strength. Summary of mix proportion for
trial mix as per table 1 below:
Table 1
Materials required per 0.05 cubic metre of trial
mix
|
||||||||
Concrete Grade
(N/mm2)
|
Mix Proportion
(Cement: Sand: Course Aggregate)
|
Weight
|
Volume (m3)
|
Volume (L)
|
Cement per m3 “all in” No. bags of 50kg
each
|
|||
Cement
|
Sand
|
Coarse
|
Cement
|
Sand
|
Coarse
|
Water
|
||
20
|
1
|
2.63
|
3.95
|
14.25
|
0.014
|
0.021
|
9.25
|
0.29
|
25
|
1
|
2.20
|
3.68
|
18.5
|
0.016
|
0.019
|
9.25
|
0.37
|
30
|
1
|
2.14
|
2.43
|
19.5
|
0.016
|
0.018
|
9.25
|
0.39
|
10.4 When trial mix are approved, site mix
shall be agitated for approximately 6-8 minutes to produce a certain quantity
of mixed concrete to required grade within the mix to proportion as per table 3.
Table 2
Materials required per cubic metre of mix
concrete
|
||||||||
Grade
|
Mix Proportion
|
Weight (kg)
|
Volume (L)
|
Cement per m3 “all in” No. bags of 50kg
each
|
||||
Cement
|
Sand
|
Coarse
|
Cement
|
Sand
|
Coarse
|
Water
|
||
20
|
1
|
2.63
|
3.95
|
285
|
748
|
1125
|
185
|
5.70
|
25
|
1
|
2.20
|
2.68
|
370
|
814
|
991
|
185
|
7.40
|
30
|
1
|
2.14
|
2.43
|
390
|
836
|
949
|
185
|
7.80
|
10.4 Preparatory
Work
10.4.1
Obtain relevant approved construction
drawings from Consultant.
10.4.2
Obtain material characteristics test result
from supplier as references.
10.4.3
Prepare required material, machinery and
tools for site mix.
10.4.4
Prepare proper material storage location and
facilities.
10.4.5
Prepare fresh concrete test tools and mould
for preparation of compression test specimens according to specifications.
10.5
Work Execution
10.5.1
All tools and materials shall be cleaned from
debris and other materials, which will affect the quality of concrete produced.
10.5.2
Volume of all materials shall be measured by
using backhoe bucket whereby 1 bucket of fine aggregate is equal to 0.153cu.m
and coarse aggregate 0.157cu.m.
10.5.3
Transportation and handling tools and
equipment shall not affect the quality of concrete during the process of
delivery.
10.6
Quality Control
10.6.1
The slump test shall be conducted using a
cone test at random or instructed by SE.
10.6.2
Slump shall be visually checked to ensure
conformance to the specification. The result shall be documented in the
inspection sheet.
Testing
method
·
Concrete shall be poured into the slump mould
in three layers. Each layer shall be tamped with the tamping rod as per
specification.
·
Once the cone is filled to the top, the
concrete shall be removed from the mould by raising the mould slowly and
carefully in vertical direction.
·
The concrete slump is the measured using
measuring tape immediately by determining the difference between the height of
the mould and that of the highest point of the specimen being tested.
·
The slump measured shall be recorded to the
nearest 5mm.
10.6.3
For the Compression Test, specimen shall be
prepared according to the specification. The test specimen shall be cured as
tested as below :
A standard
practice, 6 nos of cubes would normally be prepared for per day production. 3
nos shall be tested at 7 days and the balance 3 nos shall be tested at 28 days.
Testing
procedure
·
Clean internal surface of the mould
thoroughly.
·
Place the mould on a smooth, horizontal and
rigid metal plate and hold the mould firmly in place.
·
The mould shall be filled in 4 approximately
equal layers.
·
Each layer shall be tamped with 25 strokes
and distributed in a uniform manner over the cross-section of the layer. The 2nd
and subsequent layers shall penetrate into the underlying layer.
·
Later, concrete shall be filled to finished
level with a trowel.
10.6.4
Test result shall be documented in the
Concrete Cube Result and shall be submitted to Consultant and client.
10.6.5
The Compressive Strength of the Concrete Cube
shall achieve as per stated in the table below :
Concrete Grade
(N/mm2)
|
Minimum Compressive Strength of Concrete
Cube
|
|
at 7 days
|
at 28 days
|
|
≤ 15
|
-
|
-
|
20
|
14
|
20
|
25
|
17
|
25
|
30
|
20
|
30
|
11
SAFETY AND
ENVIRONMENTAL ISSUE
11.1Safety
11.1.1
All workers shall provide with PPE (Personal
Protective Equipment) and shall be worn every time they are entering the site.
Safety Supervisor shall ensure all the workers wear all the safety equipment
provided.
11.1.2
Portland cement can cause burns on
unprotected skin. Do not breathe the dust from the Portland cement or aloe it
in your eyes. A respirator and safety glasses are recommended.
11.1.3
Safety Supervisor shall ensure that the
activity shall ensure that activity shall carried out in a safe manner.
11.1.4
All workers shall fully support and actively
participate in all safety related activities and comply with all practicable
safety measures.
11.1.5
All workers shall be advised to report any
accident or injury to supervisor and proper treatment to be obtained.
11.1.6
The safety supervisor shall ensure that
workers understand the safety regulations and explain in detail in particular
hazards, where the workers are working and the precaution to be taken to ensure
their safety.
11.2Environmental
11.2.1
All workers shall ensure that all tools and
equipment machinery are in good condition to avoid any oil leakage that could
harm to environment.
11.2.2
Water from particular construction area shall
be diverted into proper drain which is eventually empties into silt trap.
11.2.3
Domestic and construction waste from
construction area must be collected into centralized garbage bin and disposed
at the designated area.
Thank You
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