Construction of house needs different materials and hence needs study. The general guide points have been discussed by us in Material Buying Guide In General. Here we discuss buying guide for steel.
One need to do adequate research when you plan to buy steel bars. The steel bars are important for the life of the structural system. They are known as rebars in short form. They are also known as reinforcing bar or reinforcement steel.
Steel bars and cement are the most important materials used in the building. The strength of building is directly related to the strength of steel bars. We already discussed the cement buying guide in our recent content.
There are two types of steel bars in the market.
a) Mild Steel Bars:
Mild steel bars are plain in surface and are round sections of diameter from 6 to 50 mm. They can be manufactured in long length and can be cut quickly and bend easily without damage.
Mild steel bars are available in Fe410-S (Grade 60) or Fe410-O (Grade 40).
Medium tensile steel bars are available in Fe540 (Grade 75)
b) High Strength Deformed Steel Bars:
High strength deformed steel bars are provided with lugs, ribs or deformation on the surface of the bar to improve the bond with the concrete. They are also twisted to improve the bond with the concrete.
Cold twisted deformed bars (Ribbed or Tor Steel Bars) are recommended as best quality steel bars for construction work.
They are available in Grade Fe415, Fe415D, Fe500, Fe500D, Fe550, Fe550D, and Fe600.
Fe indicates the specified 0.2 percent proof stress or yield stress in Newton per square millimeter.
You will have to spend a lot of time towards reviewing types, brands and its grade while buying.
Tips to Buy Steel Bars for Construction
01. Why do You Want to Buy Steel Bars?
Steel bars are needed as reinforcement in RCC structure. Concrete is the materials that is very weak in tension but strong in compression. To compensate for this imbalance of concrete, we provide steel bars in concrete to increase its tensile strength.
You therefore have to select the right type and grade of steel bars depending on your requirement or as considered in structural design/structural drawing by the structural engineer.
First you have to decide why and where do you need steel? i.e. for foundation, slab, and beam, column or for water tank and where is your area located? I.e. near the sea shore is It in corrosion prone area? You may than need CRS steel.
02. Quality and Specification of Steel Bars:
You can check the quality of steel bars by following steps
- Buy only that grade of steel, as prescribed in drawing.
- Check the identification mark on the bars from the manufacturing company. Identification mark will be marked at every running meter of the bar length.
- There should not be any rust film on bars. Always buy steel bars, which are rust free.
- Check the diameter of the bar by vernier calliper and it should be the same as specified in drawing.
a) Steel Rolling Margin:
Check the percentage of deviation (Rolling Margin) in weight of reinforcement steel.
Rolling margin is very important when you buy in tonnes, and you get paid in lengths.
Avoid using steel from those rolling mills which use “rerolled or scrap steel” as a row material. These are likely to have higher carbon content, which are prone to high corrosion.
b) Always ask for “chemical composition” test from the supplier. Apart from other material, the content of carbon is very important. It should not be more that 0.25 percent as it would accelerate corrosion and which will not only reduce the life of building but also will increase periodical repairing work.
c) Readymade Cut Bars:
Normally in advanced countries, people don’t buy steel, but they buy “Readymade cut bars” as per designed length and shape i.e. as per bar bending schedule.
They have to be simply placed in position. But here also you need to exercise many of the above points.
When you buy “Readymade Cut bars”, check the following
(i) Check the shape and length of each type of bar as per bar bending schedule.
(ii) Check nos and stack each bar separately.
(iii) Always check the hooks, its shape and length.
(iv) Check the quantity.
d) Certification:
Check whether the steel bars you buy bears a national certification like ASTM A706, JIS G3112, BS4449, ASTM A615, JIS G3109 and IS 432 (Mild Steel Bar), IS 1786 (High Strength Deformed Steel Bar) etc. The certification assures you about its quality as well as the reputation of the manufacturer.
03. Study of Product Literature:
When you buy steel bars, you should read all the technical specifications which are either described in the product literature or on the manufacturer’s website. We have to check whether the product specification represented by sales persons and the literature confirms or not. Try to understand and follow all the cautions of use and advice for use, etc. as per the written specifications in the literature. It is also necessary to read the terms and condition of warranty, guarantee, etc.
04. Finance:
- Budget:
You may economise and save on each and every individual item, but you should not save on steel bars. They are the definite requirement of your house and directly related to safety and stability of your house.
It is advisable to provide steel bars as specified in drawing or as instructed by the structural consultant. Some people avoid consulting the structural consultant and providing the steel as per thumb rule to save the fees of the structural consultant. They forgot that every structure has carried different behaviour and one cannot use the same thumb rule for different structures. Do not get away by idiotic thumb rule of using this 2 to 3 kg of steel per Sq.ft. One thing we can tell you that thumb rules will raise your budget in future as they ultimately increase the cost of repairing work. They either excess your budget by over design or reduce the lifespan of the structure by under design.
- The Quantity You Want to Buy:
You should also estimate the exact quantity of steel diameter wise. The wastage of steel bars will cost you high. You need to work out quantity in advance so you can bargain with the supplier or distributor.
- Where is it Available, From Where to Buy Steel Bars?
You must search for the right supplier or distributor and their location. You should also find out whether it is directly available from the manufacturers or distributors or retailers etc. The price will definitely depend on from whom you buy the steel bars.
- The Cost of Transport/Taxes:
The cost of transportation, taxes and duties including the cost of loading and unloading at the site are the necessary point to remember as they also affect your budget while buying steel bars. Steel being heavy material, they form substantial weight and hence higher cost of the transportation.
05. Brand:
Always use the popular brand of steel bars as they may have a certain quality. It is advisable to use the brand suggested by your structural consultant or use the government-approved brand or ISI brand.
The Price of steel bars vary between Rs 30 to Rs 60 per kg. Kamdhenu, Thermax, Tata Tiscon, Jindal, Essar, Vizag and Electro are the popular brands of steel bars in India who make different types of steel with different grade.
06. Buy Steel Bars after Testing:
Always try to learn how to test the materials on site as well as in laboratory in case of bulk buying.
a) Hardness Test:
- Take 1 m length from each diameter of bars belonging to different lots. Bend the bar by applying pressure at both ends with your hands.
- Observe the bend portion. It should be smooth.
- If the steel is not of good quality, it may break or develop cracks on the surface. Such steel should be rejected.
b) Weight Checking:
- Take the exactly 1-meter length of each diameter of the bars on the random basis.
- Weigh each sample on a weighting scale.
- Compare the weight with the theoretical weights given in codes and assume rolling margin.
- The difference in weight which is called rolling margin should not be more than 5%.
07. Selection of Material and Supplier to Buy Steel Bar:
Study the above factors of steel bars and then select the right material and the supplier.
- Placing Order:
It is advisable to place written order if you are buying the large quantity. It should include specifications of steel bars, rates including taxes, transportation, and loading-unloading charges, etc. It should also include quantity, time of delivery, warranty, guarantee, terms of payment including advance.
- Receiving Material:
When you receive steel bars at the site, please check the make, quantity and quality. Also check ISI marks, brand and whether there are any damages to the steel bars.
Also check the weight of steel bar received on site by at approved weighbridge.
Use this formula for the actual weight of steel (site) = Total weight of truck with steel bars – The empty weight of truck (Weight without steel).
Do not stack directly on the ground as the ground moisture will rust it. Store the steel bars in godown and place wooden batten below them so they should not directly rest on ground.
- Payment:
If you are satisfied with the quality and quantity of the steel bars, then make payment as per the contract and obtain the receipt of payment. Preserve all the bills, product literature and the warrant/guarantee certificate, etc.
08. Life of Material:
The steel bars are generally one-time purchase, and it has a long lasting service life when embedded in concrete. If we leave them in open environment, they get corroded fast. Hence try to use them as early as possible or store steel bars in warehouse.
You can buy steel bars in 8 mm (18 nos per bundle), 10 mm (12 nos per bundle), 12 mm (8 nos per bundle), and 16 mm (5 nos per bundle) sizes. They are commonly used for house construction. You can also buy steel bars with the bigger diameter of 20 mm (3 nos per bundle), 25 mm, 28 mm, and 32 mm, which are used for high-rise buildings only. They are generally packed in the bundle, and above 20 mm diameter, they are available in the single piece.
The standard length of steel bars is 12 meter, but you can select the length as per your requirement.
Nowadays Thermo Mechanically Treated (TMT) steel and Corrosion Resistance Steel (CRS) are also used in Reinforced Concrete Framed Structure construction. They have good elongation, bending strength, ductility and high tensile strength and high corrosion resistance.
Conclusion:
- Buy the popular brand of right type and grade of steel bars from the right supplier as per your need.
- Place the written order. Written order should include specification, the quantity, type, grade, time of delivery and terms of payment, etc.
- Once you are satisfied with quality and quantity as per your requirement, make the payment and obtain the receipt of payment. Preserve the entire purchasing document as you may need them in future.