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MS 146: Hot Rolled Steel Bars for the Reinforcement of Concrete

posted May 8, 2022, 5:50 PM by jeffery jim
Many civil & structural engineers in the industry have yet to fully comprehend the need to inspect reinforcement bars before construction use. It is commonly known that most QAQC engineer will only cross check the Purchase Order to the Mill Certificate provided during offloading. But what is the essential checking before a delivery is deemed acceptable for use and compliance to the standard specification?

2. After close to 8 years since MS 146:2014 being introduced, not many fully understood the actual requirements for reinforcement periodical checking and in-situ checking. The typical requirement would be the sampling of specimens for every 30 tons of each size and each manufacturer as required by Inspection and Test Plan, JKR Standard Specification for Building Works as well as JKR Standard Specification for Road Works.

3. It is essential for site engineers attached to the contractor's QAQC team to check the reinforcement bars prior to joint inspection with consulting engineers or inspector-of-works. What are the essential checks an engineer has to conduct before signing off invoices and Material Receiving Report upon delivery?

4. There are a few things an engineer need to do before steel bundles are offloaded but first of all is primary check visually based on the Mill Certificate. First of all, for greenhorns, it is recommended that they take measurement of the steel diameter using Vernier caliper to verify the size as per Invoice. After inspecting the reinforcement size, engineers should compare the steel marking to the serial embossed on the steel reinforcement. Every steel produced shall be stamped with markings specifying the country origin and the manufacturer (or work number). Then the inspection can be continued to verify the steel grade based on the rib pattern. Many cases, purchases made were CQ (commercial quality) steel which are not recognized by MS146 due to its lack (can be substantial) in area size and mass.

5. Apart from dimension check for physical that is obvious and measurable, the Mill Certificate should be inspected for its carbon and elements content to ensure forged reinforcement bars are suitable. Another thing that one has to remember is the change that involving weldability. In superseded version(s), reinforcement bars are considered weldable but in MS 146:2014, these cannot be welded (with exception for spot weld) together with others.

6. Recently, a contractor did write in to us for this kind of approval, we rejected it unless it is proven with calculation(s). In addition to that, one has to justify how physical properties changed and workable after welding. I advised them to just tie reinforcement bars using slightly smaller reinforcement bars with proper lapping length.

7. Five specimens or samples should be made available for quality control procedures and testing. This exercise will allow engineers to conduct other physical tests. The mass per meter length and the area size should be verified and comply with the specification. For smaller reinforcement bars (below 8mm), the variation allowed is ±6% while 8mm and above will be ±4.5%. In previous revision, smaller low yield (plain hot rolled) reinforcement bars are allowed to deviate up to ±9%. The reinforcement bars are graded into G250, G460 and G500 for MS146:2006 while the latest version only recognize B500A, B500B and B500C. In most cases, structural drawings which are not updated still make reference to MS146:1997 with G460A and G460B and G250. Always double check the general notes in your drawing and highlight this to the consultant or designer. Sampled specimens should undergo tensile test in SAMM accredited laboratory to see the actual yield and tensile properties with reading on its 0.2% proof.

8. One the most common mistakes many QAQC engineer did was to only read the tensile strength of the reinforcement bar, assuming it has no limit. The stronger the reinforcement bar, the better. One has to understand that there are ceiling limits that these reinforcements have to achieve in order to performed in desired ductility. In this case, the yield strength during the tensile test should not exceed 650N/mm2. The grading is based on yield strength and therefore, all reinforcement bars should at least reach 500N/mm2. The essential ceiling limitation for G500C’s tensile over yield strength ratio should not exceed 1.35 and at least achieved 1.15. For typical G500B which are commonly used in the industry, this ratio should exceed 1.08 with total elongation at maximum force exceeding 5%.

9. After tensile test is conducted, other tests to be performed are the deformed bar bending test and deformed bar re-bend test. This to see the outcome if these reinforcement bars are still workable condition after performing these tests. We witnessed some failed tests for MS146 accredited reinforcement bars where the ductility of specimens is questionable after it cracked (torn).

I hope this write-up can guide young engineers specifically QAQC engineers to understand the importance of steel bar approval prior to use for construction purposes

May be an image of text that says "3/26/22 AM STEEL INDUSTRIES (SABAH) Sabah Steel Mile BHD 263484-U) Jalan Tuaran, Locked Bag 7,88992 Kota Kinabalu, Sabah Steel Industries (Sabah) Sdn. Bhd.: Tel: 088-427111 Fax: 088-420111 Buyer: Certificate Date. MS No.0 Description Batch Manufacturin Precess Delivery Destination MS146:2014 MS146:2014 4449:2005+A MILL CERTIFICATE fos TotalN Item certificate, ignature required. 2U22035784 0.197 0.184 0.645 0.041 0.041 0.310 0.062 0.108 0.012 0.001 0.000 30,000 0.354 111.39 tated, PHYSICALTEST R(MPa) R/R 0.874 577 Bend 678 Rebend 10.2 PASSED PASSED ESTHER JOSEPH ÛUTHRTRE"