Pre-stressed Concrete Steel Bar (PC bar) is one main component used in manufacturing of concrete spun piles other the concrete itself. Made of low carbon steel, PC bar is manufactured by using high frequency quenching and induction heat treatment process to gain the utmost mechanical property of high tensile steel bar.
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Basically, PC Bar can be classified into six (6) grades that is differentiated by the yield and tensile strength capacity. In spun pile, PC bar type SBPDL / is used since the tensile strength is the highest compared to the other types of PC bar available. With standard density of kg/m³, the relaxation value for SBPDL / PC Bar is expected not to exceed 2.5%.
PC bar is manufactured in accordance with Japan Standard (JIS G-) which have been adopted by many manufacturers around the world. In Malaysia, MS: is used as a manufacturing reference besides the JIS G.
PC Bar is usually the preferred material in the pre-stressed concrete industry due to its low relaxation property that provides high tensile capacity and enables concrete to withstand substantial tension force. Produced in spiral groove shape, PC bar comes in various diameters; with common ones are 7.1 mm, 9.0 mm, 10.7 mm, 11.2 mm and 12.6 mm.
The PC Bar Verification Test
The ability of PC bar to withstand tensile stresses can be checked by putting the samples of Pre-stressed Concrete Steel Bar through tensile strength testing. It is a fundamental mechanical test to determine and verify the ultimate tensile strength of PC bar that is newly procured prior to using to make spun piles (or even any other concrete products).
In spun pile industry, tensile test is conducted by first forming the button heads; these are formed at both ends of the PC bar as to simulate the actual application scenario. In actual application, the button heads are formed and locked into countersunk holes at end plate (at both end of the spun piles) in order to anchor the PC bar before applying the pre-stressing force.
Similarly, in tensile testing machine, PC bar sample with button head is first anchored to button grips at both ends, then the PC Bar is pulled by stressing until it breaks. This would give us the ultimate tensile capacity and the failure point of the sampled PC Bar.
During the testing stage while load is being applied, the PC bar will actually go through two (2) different phase, namely the elastic deformation and plastic deformation. Elastic (also known as reversible deformation) occurs when a PC bar is still able to return to its original dimension once the load is released.
While the plastic (also known as irreversible deformation) occurs when PC bar passed beyond the elastic limit state and will not be able to return to its original dimension when load is relaxed. At this point the PC Bar hasn&#;t reached the failure point yet; prior to failure there would be permanent elongation point at PC bar where you can notice the particular failure point will be thinning.
While the plastic (also known as irreversible deformation) occurs when PC bar passed beyond the elastic limit state and will not be able to return to its original dimension when load is relaxed. At this point the PC Bar hasn&#;t reached the failure point yet; prior to failure there would be permanent elongation point at PC bar where you can notice the particular failure point will be thinning.
Stress-Strain Graph of PC Bar Testing
The stress-strain curve defines the property of PC bar when subjected to tensile load. Generally, there are three categories of tensile property as per stress-strain graph above. At point A, PC Bar reached Yield Strength which it can withstand the tensile load without permanent deformation.
The highest or maximum tensile load that PC Bar able to withstand is called Ultimate Tensile Strength (point B). Under continuing loading, PC bar continues to plastically deform. Small elongation of PC Bar sample begins to appear thus will result in necking. The PC Bar will break at point C; called Breaking Strength where it snapped at necking section. According to JIS G: , the minimum yield strength of PC bar used in spun shall be N/mm² and the minimum tensile strength shall be N/mm².
How to Determine Good Quality PC Bar
The quality of the PC Bars can also be determined by observing the failure pattern of the PC Bar at the ultimate load. Due its extremely high tensile property, fundamentally the PC Bar would be brittle. Usually, when the PC Bar fails at ultimate load; two kind of failure pattern can be expected.
The first type of failure (which is desirable) would the &#;necking cup and cone shape&#; pattern. When the PC Bar is being continuously loaded to its maximum capacity, as mentioned earlier it will go through an elongation stage prior to failure. At this stage, the internal molecular of steel is being altered and eventually it will snap at the elongated section creating &#;cup and cone&#; shaped failure section. This is highly desirables kind of failure.
In second type of failure, the PC Bar will have a sudden brittle failure, without allowing the steel to go through the plastic and elongation stage. The failure pattern at this stage would look like the steel has been chopped into two section with flat surface at both end of failure point.
The second type of failure is not desirable, because it will also cause the structure that using it also to have a sudden brittle failure without any warnings.
The Basic Chemical Composition of PC Bar
The chemical composition of the raw steel/iron bar will affect the ductility and tensile property of PC bar produced. Thus, the main chemical composition that needs to be checked are the maximum content of Phosphorus; P (0.030% max.), Sulfur; S (0.035% max.), and Copper; Cu (0.30% max.).
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For the commercial reason purpose (due to high testing cost), the chemical composition test will be carried out by the PC bar manufacturers at independent laboratories, and a copy test certificate will be issued to the end users upon delivery of the products (the PC Bar).
How the PC Bar Used in Making Spun Pile
The PC bar will be welded together with spiral wire to form a reinforcement cage for spun pile. It is very important to ensure the incoming PC bar is in good quality as to avoid any wastages in manufacturing of spun pile.
The PC Bars shall be free from rust, as this would weaken the strength of welding points, and eventually the PC Bar will disintegrate from the spiral wires. The PC Bars delivered also must be checked for any visible cracks as these will affect the tensile characteristic of the PC bar.
The stock of the PC Bar delivered to the plant shall be subjected to physical checking as well as mechanical testing to ensure its quality. And this process shall be repeated prior to actually using it in making the steel cages for the spun piles. This is to ensure that all the PC bar used in the production of spun piles are in good condition, so that it can be safely pre-stressed.
Summary
In Spun Pile manufacturing process, Pre-Stressed Concrete Steel Bar plays extremely important role in making sure the piles meet the intended design criteria. Therefore, the PC Bars selected and used shall be off optimum quality as well.
Huayongxin is the PC strand manufacturer in the China. We offer a full range of seven- and three-wires, low-relaxation Prestressed concrete strand, post-tensioning and mining applications. Our experienced domestic and international sales team is ready to provide you with the services and support you need to meet your specific reinforcement requirements. Contact us for a quote!
Prestressed concrete steel bars, referred to as PC steel bars, are widely used because of their high strength and toughness, low relaxation, strong bonding force with concrete, good weldability, upsetting, and material saving (for example, φ11mm PC steel bars can replace φ20mm hot-rolled steel bars). Used for high-strength pre-stressed concrete centrifugal pipe piles, electric poles, viaduct piers
Product Description
PC steel bars are mainly used in the construction industry. It is the main steel for pipe pile foundations. It has high strength, small amount of metal materials, convenient use, and easy quality assurance. It has a wide range of uses in the construction industry.
Features of PC steel bars
PC steel bars (also referred to as Prestressed Concrete Steel Wire) is high tensile, low relaxation steel wire made from high-carbon steel and widely used for prestressed and post-tensioning technology in various shapes of PC structures. It has the following characteristics and advantages:
&#; High tensile strength and low relaxation
&#; More bonding stress between wire and concrete
&#; Stable modulus of elasticity
If you have any questions, please feel free to contact us! We will provide you with the most professional answer in the shortest possible time.
PC steel bars Properties
Product Name
PC steel bar
Type of Surface
Spiral Ribbed, Indented, Plain
Materials
SWRH82B
Diameter
4.0mm, 4.8mm, 5.0mm, 6.0mm, 7.0mm, 8.0mm, 9.0mm
Tensile Strength
Mpa-Mpa
Relaxation (%)
&#;2.5
Elongation (%)
&#;3.5
Standard
ASTM A 421, GB/T, BS, JISG, and required standard.
Packing
Packed in coils (around 700-kg/coil). Each coil is strapped by steel bands at 8 places, fully wrapped with anti-rust plastic & PP woven sheet.
Application
PC Wire is characterized with high tensile strength and low relaxation. It's widely used in production of prestressed spun concrete poles, PHC Piles, in construction of large scale railroad, high-way bridges, building trusses, overhead crane beams, industrial and civil prefabricated concrete slabs, wall board, power station, etc.
Our Advantages
&#; Extensive experience in exporting.
&#; Professional team to manage production and control product quality.
&#; Equipped with advanced testing facilities and abide by the principle of testing each coil produced.
Application of PC steel bars
Centrifuge tube pile
Viaduct pier
Railway sleepers
Electric pole
Why choose Huayongxin&#;
1. Rich experience: We have 20 years of experience in the production of PC Steel Wire and PC Steel Strand. We are the most professional manufacturer in China.
2. Strong supply capacity: Covering an area of 120,000 square meters, it has 4 workshops, 2 laboratories, 8 PC wire production lines and 4 PC wire production lines, and the production capacity of each line is tons/month.
3. Product quality is guaranteed: obtain ISO: certificate
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