2. STORAGE AND SAFETY PRECAUTIONS [IS: 7969-1975]
In any construction project the material cost constitute about 60 % of the
total project cost. Therefore, materials should be used effectively by reducing
wastage of materials to minimise the project cost. The wastage of material is
mainly due to pilferage, fire, deterioration etc. The store keeper is responsible
for the safety of materials in the store.
The following precautions should be taken for the safety of materials.
1. Timber and plywood should be stacked separately
2. There should be sufficient gap between two stacks of material to avoid
damage during fire.
3. Smoking and open fire should be prohibited.
4. Petroleum products (i.e. petrol, diesel, oil) should be stored separately.
5. Only limited stock of petroleum products should be stored at the site.
6. Fire extinguishing equipments should be made available at the site.
7. Explosives should be stored and handled separately and very carefully.
8. Wastage of cement, sand, aggregate should be prevented.
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3. STACKING AND STORAGE OF CONSTRUCTION MATERIALS
Usually large quantities of construction materials have to be stored at
the sites of construction. Thus to prepare a proper job layout at site, it
is neccerry to know the correct method of storing materials at site
Points to be Considered while storing materials at site :
Following points should be kept in mind while storing materials at site.
1. Materials should be stored in such a way that they are not affected
wind or by impurities or by atmospheric agencies such as sun,
moisture etc
2. Cement should be stored in covered sheds.
3.The plinth level of the shed should be at least one metre higher than
the adjoining ground.
4.The cement bags should be stacked on a raised platform of bricks or
on plants about 15 to 20 cms above the shed floor.
5. The space between the walls and cement bags all-round should be
at least 30 cms.
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4. 6. The inflammable materials must be stored separately from
other combustible materials. This area should be specially
protected from fire hazards. In such area smoking should be
prohibited.
7. Explosives should be stored in a safe place, away from
combustible and inflammable materials under lock and key.
8. Materials of common use must be stored near the place of
their use to minimize the handling.
9. As far as possible materials used for similar purpose must be
stored close together.
10.Heavy items must be kept near the crane or hoist for ease in
handling.
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8. Material Purchase procedure
Recognition of the need
Selection of source of supply
Inviting tenders
Analysis of tenders
Placing the order and follow up
Receipt and inspection
Approval of payment
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9. Recognition of the need
When on the site, the stock of certain materials is
exhausted, the site engineer or supervisor or inventory
control clerk send a purchase requisition to the purchase
department.
The purchase requisition contains the following details :
•material to be purchased
•quantity of material required
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11. 2. Selection of source of supply
The purchase department, prepares a list of suppliers of
different materials.
For the purchase of new items, the information regarding
suppliers are obtained from:
directories
catalogues
advertisements
exhibitions and fairs
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12. 3. Inviting quotations / tenders
Quotations/tenders are invited from the selected
suppliers. The following information is included in the tender:
quality of material, specifications, drawings
quantity of material
time limit for delivery of material
EMD
Conditions of purchase
Date, time and place of opening of tenders
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15. 4. Analysis of Quotations
The tenders received within stipulated time limit are opened in the
office of the purchase officer on date and time mentioned in the
tender notice.
A comparative statement is prepared. The analysis of comparative
statement is done keeping in mind the following points.
Material cost
Specifications
Delivery place
Delivery period
Taxes
Payment terms and conditions
Guarantee period etc
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18. Placing the order and follow-up
After studying the comparative statement precisely, the best supplier is selected.
When all other conditions are same, the lowest tender is selected.
The lowest tenderer may not be always the best. Therefore, while selecting the
supplier the rates quoted by him, specifications, quality of materials, sales tax,
transportation fares, image of the supplier etc. should also be considered.
As per the purchase policy the total supply order may be split up
among two-three suppliers or local supplier may be given preference.
Number of copies of the purchase order are prepared.
Two copies are given to the supplier and one copy to account section, store and
costing department each. After sending the purchase order, regular follow up is
required to get specified quantity of material on specified date.
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21. Receipt and inspection
After receiving the materials at site its inspection and testing is
done. The receiving clerk prepares the material receive report
indicating the actual types and quantities of material received.
The receiving report is verified with the purchase order and any
change in the quantity of material is recorded.
The quality of material is checked. Any change in the specification
or quality of material is brought to the notice of the supplier.
The rates in the bill and tendered rates are also verified.
The material may be sent back if needed.
The receiving clerk prepare three copies of the receiving report.
One copy is given to the concerned department, one copy to the
supplier and one copy is retained by him.
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22. Approval of Payment
Before approving the payment to the supplier the
bill is verified with the purchase order. The purpose
of such verification is to check any calculation error,
quality change or quantity change.
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23. ECONOMIC ORDER QUANTITY - EOQ OR OPTIMUM LOT
SIZE
Economic order quantity’ is the order quantity of materials which
reduces the inventory cost.
For examples, let a construction company needs 12000 bags of
cement. The following options are there:-
1. All cement bags (12000) may be purchased at once.
2. Total quantity of cement bags may be purchased in two lots
6000 nos. each.
3. Every month 1000 bags are purchased for one year.
Out of the three options, the one which gives minimum material
cost is chosen.
Therefore, the size of order or a size of lot which reduces the
inventory cost is called “Economic order quantity”.
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26. The graph shows relation between unit cost (cost period)
and order quantity (Q). Total cost = Inventory cost +
order cost
OM shows the Economic order quantity (EOQ).
At point ‘M* the total cost per period is minimum.
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27. INSPECTION AND TESTING THE QUALITY OF MATERIAL
Inspection :
Inspection means the comparison of the actual sepcificatioris of any
material with its standard specifications. Inspection is an important
tool for measuring the quality of material and quality control.
Inspection is an art in which tests are conducted on material using
measuring equipments and it is decided whether the specifications of
the materials are within prescribed limit or not.
The following steps are involved in the inspection of any
construction :
1. collection of samples
2. taking dimensions and standards of material
3. inspection of layout, foundation etc..
4. inspection of various construction activities
5. laboratory testing
6. inspection of plants and equipments
7. checking records and reports 27
28. Objectives of Inspection :
1. To find defects in the production of material. The defects found during
inspection are brought to the notice of the concerned officer so that future
quality of product can be improved.
2.To see that the clients does not receive inferior quality materials.
3.To verify the quality of material.
4.To ensure that construction quality is not spoiled due to poor quality
materials.
Types of Inspection :
1. Dimensional inspection
2. Inspection for physical and
mechanical properties
3. Superficial inspection
4. Performance testing
5. Statistical methods 28
29. a) Inspection and testing of bricks
•Standard size of brick = 19 cm x 9 cm x 9 m
•For 20 bricks, the dimensions shall be as under :
Sr.
No.
Class
Lenth
cm
Width
cm
Height
cm
1. A 368 to 392 174 to 186 174 to 186
2.. B 350 to 410 165 to 195 165 to 195
Weight of one brick is about 2.5 kg.
For first class bricks water absorption should not be more than 20 %.
Compressive strength of bricks should not be less than 7.5 N/mm2.
Sub-Class A bricks :
tolerance limit ± 3%
rectangular faces,shrap edges, shall give clear ringing sound when
strike each other,
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30. (b) Inspection and testing of cement
Field testing of cement is done as under :
•The colour of cement should be greenish - grey.
•When hand is inserted in a cement bag, it should give cool feeling.
•When rubbed between fingers, it should give smooth feeling.
•If handful of cement is thrown on the surface of water it should float for
sometime.
•Thick cement paste kept in water should set.
Criteria for Physical Properties of O.P.C. :
Fineness of Cement :
For O.P.C. - Not more than 10%
(Residue on 90 micron IS - Sieve)
For R. H. C. - not more than 5%
Setting time : (For OPC)
initial setting time - not less than 30 min.
final setting time - not more than 600 min.
Soundness :
not more than 10 mm Compressive strength :
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31. Time
days
Minimum
Compressive
Strength N/mm2
3 16
7 22
28 33
(c) Inspection and testing of Fine and Coarse
Aggregate
IS : 383 - 1963, IS : 515 - 1959.
If size > 4.75 mm Coarse aggregate
If size < 4.75 mm fine aggregate
Water absorption test :
For C.A. - 0.5 to 1 %
For F.A. - 1 to 10 %
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32. Fineness modulus of sand (FM) :
Type of Sand Value of F.M.
Fine Sand 2.2 - 2.6
Medium Sand 2.6 - 2.9
Coarse Sand 2.9 - 3.2
density of aggregates 2000 to 3000 kg/m.
Impact test :
For road aggregate ------ Impact value should be less than
30 %
For building aggregate------ Impact value should be less
than 45 %
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33. (d) Reinforcement (IS : 1139, IS : 1786)
Normally in the construction mild steel (Fe 250) is used as distribute steel
and Tor steel Fe-415 is used as main steel in slab, beam, column etc
The steel reinforcement should be free from rust.
It should be free from oil, grease, paints etc.
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