What is a rebar?
A rebar or reinforcing bar or reinforcement steel is a steel bar etched with protrusions called lugs or deformation used as a tension device in reinforced concrete to strengthen and hold the concrete together.
What is PNS 49?
Steel bars are covered by a mandatory standard called the Philippine National Standard 49 or PNS 49, as formulated by the Bureau of Product Standards (BPS) of the Department of Trade and Industry (DTI) with the help of the Steel Industry, the Association of Structural Engineers of the Philippines, and the Philippine Construction Association.
How do I know if the steel bars I buy conform to PNS 49?
Check if the manufacturer is accredited by the Bureau of Product Standards (BPS). All manufacturers accredited by the BPS are required to place their distinguishing logo on every meter of their steel bars. The logo is registered with the BPS. However, a manufacturer can still attempt to circumvent PNS 49 despite its accreditation. Always have two or three specimen steel bars tested in a reputable laboratory. The laboratories will measure, weigh and test the yield point, tensile strength, elongation, and bending of the steel bars. One cannot ascertain the quality of a steel bar simply through visual inspection.
Where can I have my steel bars tested?
Your sample can be tested either at the Metals Industry Research and Development Center (MIRDC) in Bicutan or the Philippine Geoanalytics in Quezon City to see if it conforms to PNS specifications.
Why is it important to have standard steel bars?
In an earthquake prone country like the Philippines, the use of substandard steel bars can be life-threatening. The yield point and tensile strength ratio ensures that there is enough “reserve energy” for the steel you use to withstand the sustained swaying motions and the subsequent aftershocks of an earthquake.
What are some practices that should concern a buyer?
One common practice is to maximize the 6% weight tolerance allowed by PNS 49 for each steel bar. Since weight deviations of 2% – 3% occur during the rolling process, undersized steel bars are included in the production batch. Another practice is the use of unsuitable raw materials to produce steel bars that are too brittle and cannot pass bending tests under laboratory conditions. Still another practice is passing a lower grade off as a higher grade by switching the color coding of the steel bar. A rule of thumb is never to buy from a manufacturer whose selling price is more than 2% lower than other competitors. The savings involved are not commensurate to the risk.
How do you measure the diameter of a ribbed bar?
Does it refer to the core or the ribs?
The nominal diameter of a bar, say 16 mm, refers to the mean nominal diameter of the total cross sectional area of the bar. That is, it is a theoretical diameter which cannot be accurately measured using a rule, caliper or micrometer. It can only be measured by accurately weighing and measuring a length of bar and calculating the mean diameter from these measurements.
Does rusting affect the performance of reinforcement?
Surface rusting of reinforcing bars or mesh does not effect the performance of the steel. In fact, surface rusting can increase the bond of the steel to the concrete. However, prolonged surface rusting can eventually lead to pitting of the steel and this may lead to a weakening of the steel section. Suspect steel can be checked by weighing a cleaned sample to check that the section is not below the lower unit mass tolerance and tensile testing undertaken to ensure that the physical properties are still above the minimum requirements.
What is the smallest bend radius that we can bend a bar?
The PNS 49 Standard sets out the minimum pin diameter for the bend radii of the various sizes and grade of rebars. See PIN DIAMETER in our Technical Specifications.