Composite materials such as concrete and steel are commonly used in house construction worldwide as steel bars adds tensile strength to your concrete which has compressive strength, making your structure stronger and durable.
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| concrete and steel |
Common Sizes for Small Scale Projects such as Residential
- 10mm diameter x commercial length
- 12mm diameter x commercial length
- 16mm diameter x commercial length
Grade
Common in provinces are grade 33, the higher the grade will also means additional cost.
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| image from pagasasteel.com/ |
Color Coding
For easy identification of steel grade here is a sample color code for steel bars including weldable rebars. Colors can be found at one end or both ends.
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| PNS49:2020 Color coding of steel bars |
Commercial Length
Common length for small scale projects used is a 6 meters length of steel bar which is readily available almost throughout the market.
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| image from pagasasteel.com |
Common available in the market is 6m length, other lengths needs pre-orders if in provinces.
STEEL WEIGHT DERIVATION:
steel density = 7850kg/cu.m or 0.00785/kg/cu.mm cross section area of steel = (Ï€ D²/4)
Weight of Steel = 0.007850kg/cu.mm x (Ï€ D²/4) x L
where L = 1000mm
D = diameter of bar in mm
cu.m = 1000mm x 1000mm x 1000mm
Weight of Steel = 0.00785 x 0.785 x D²
Weight of Steel = 0.006162 x D²
therefore:
Table for steel weights per length:
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| Table 01_steel weight_in_kilograms |
DEFORMED BARS
usually used as reinforcement to your concrete with uniformly spaced ribs and lugs (deformations) as you can see around its surface to bond properly with your concrete mixture.
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| image from steelasia.com/rebar |
WHICH SIZE TO USE?
It is highly recommended to let your Structural/Civil Engineer handle the proper design of size of rebars needed for your structure.
A careful study and consideration of the different factors of pressure, loads and unseen forces to come up with a solution on how to withstand these forces is where your professionals will step in.
Not only considering the size of bars but also how they are distributed with required distances, the right location of lap splice, length of lap, the required development lengths and so on.
HOW TO KNOW IF STEEL IS STANDARD OR SUBSTANDARD?
The only accurate way to find out is to have samples be tested in testing facilities to check if it has the correct yield strength, tensile strength and properties.
To mention some facilities in the country are:
- Metals Industry Research and Development Center
- Matest Laboratory Services, Inc.
Second option is to directly purchase from trusted manufacturing companies who have certificates and adheres to PNS49 (Philippine National Standards)*
Alternative options is to check if diameter of bar is not undersized using caliper.*
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| image from chronos.ltd.uk |
Cut a 1 meter length of any steel diameter and check its weight then compare from table 01 under weight/m if approximately near computed value in kilograms +/-6% tolerance.*
In reference to "color code" of steel located on its end is not reliable, as hardware stores can easily paint with corresponding color, but rather request for a MIL certificate from supplier.*
*not guaranteed as materials still needs to be tested in laboratories accredited by DPWH
If you happen to have access to manufacturing plants with cut and bend services to save space, time and labor in fabricating your steel rebars, then try to consider this if this would be more economical plus you get the precise cuts and bends without worries vs manual fabrication on site.
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| image from steelasia.com |
Be reminded that because it passed from your manual inspection of the right color, the right markings and even weight, if there are recycled raw materials or impurities mixed during the process that may weaken its yield strength, then through testing on laboratories is the safest way to find out.
Disclaimer: This is not a paid promotion of any brands mentioned in this post but for sample reference only to get some idea.
