Sedikit latar belakang bagaimana besi beton dibuat

Besi beton diproduksi secara umum terdiri dari 3 jenis: besi beton permukaan polos (round bar), besi beton ulir (deformed bar) dan besi beton kanal u (shape). Bahan baku besi beton adalah billet, yang juga merupakan balok baja berukuran 100 x 100 mm, 110 x 110 mm, 120 x 120mm dengan panjang masing-masing sekitar 170 mm. Bahan baku dari billet sendiri adalah besi-besi tua, skrap, serta bahan penolong seperti kokas, grafit, lime, ferro alloys yang dilebur dengan berbagai metode. Bahan penolong tadi digunakan untuk mendapatkan unsur carbon (C), Si (silicon), Mn (Mangan) yang akan sangat berpengaruh pada qualitas besi beton.
Mutu besi beton yang baik adalah yang telah memiliki kekuatan tarik (standard yield strength / Ys) minimal 24 kg / mm2. Kadar carbon berpengaruh besar kepada sifat mekanik dari besi beton. Kadar carbon yang terlalu besar akan membuat besi beton menjadi lebih getas dan akan meningkatkan kekerasan dan kekuatan tarik tetapi keuletannya cenderung menurun. Kadar unsur silikon berpengaruh terhadap struktur mikro besi beton. Kadar silikon yang rendah mengakibatkan besi menjadi kropos. Kadar unsur mangan berpengaruh besar pada keuletan besi beton. Unsur mangan yang terlalu banyak dapat meningkatkan keuletan tetapi mengurangi kekerasan.

Cara menghitung berat besi beton SNI (Standard Nasional Indonesia)
Polos dengan grade U24 (Standard Yield Strength: 24 kg / mm2)

Ulir dengan grade U40 (Standard Yield Strength: 40 kg / mm2)

Berat (dalam kg) = diameter (mm) * diameter (mm) * panjang (m) * 0.006165

0.006165 merupakan coefisien dalam mencari berat besi beton.

Sebagai contoh besi dengan diameter 10mm dan panjang 12m mempunyai berat

10*10*12*0.006165 = 7.398 kg

Untuk daerah bali dan sekitarnya, besi yang banyak dipasarkan adalah besi dari PT Hanil Jaya Steel - Surabaya. Hal ini dikarenakan biaya transportasi yang lebih murah dan kualitas besi beton yang baik. Besi beton SNI dari pabrik Hanil mempunyai toleransi 0.2mm dengan panjang 12m. Besi beton jenis ini mempunyai marking seperti "HIJ SNI 16mm" untuk ukuran 16mm.

Besi Beton Ulir/Sirip SNI 13mm

Besi Beton Polos SNI 10mm

Contoh diatas adalah besi beton ulir SNI 13mm (S13 = Sirip 13) dan besi beton polos SNI 10mm (P10 = Polos 10)

Selain besi beton jenis SNI, terdapat juga besi beton NON-SNI atau sering kali disebut BANCI. Kekuatan tarikan atau yield strength dari besi beton jenis ini tidak dapat dipastikan. Untuk besi beton dengan marking HJ menurut informasi dari pabrik mempunyai kekuatan U19-20 untuk yang jenis polos dan untuk jenis ulir mempunya kekuatan U25-30. Toleransi untuk besi beton jenis ini biasanya lebih besar sampai 0.3mm dengan panjang 12m dan terdapat marking dengan berbagai tanda salah satunya HJ.

Besi Beton NON SNI Ulir/Sirip 13mm

Besi Beton NON SNI Ulir/Sirip 13mm (Ukuran Sket 12.5mm)
Terdapat lagi jenis besi beton tarikan. Besi beton jenis ini biasanya tidak mempunyai panjang 12m dan tidak terdapat marking atau tanda.

Terdapat fenomena belakangan ini banyak penjual menjual kawat baja dan bukan besi beton. Besi beton dengan diameter ukuran 6-10mm yang sering kali menjadi korban. Fungsi dari kawat baja sangat berbeda dengan besi beton. Kawat baja berfungsi untuk pengikat dan besi beton berfungsi untuk penyangga. Sehingga kekuatan tarikan kawat baja jauh dibawah kekuatan besi beton. Hanya saja diameter kawat baja ini sama besar dengan besi beton ukuran tertentu. Hal ini sering kali digunakan untuk mendapatkan pasar atau pun mengeruk keuntungan maximal.
Anda dapat mempercayakan supplier besi anda kepada kami. Kami hanya menjual besi dari PT Hanil Jaya Steel - Surabaya dengan marking HIJ untuk besi beton SNI dan marking HJ untuk besi beton NON-SNI.



As he reflected on the festering wounds deepened by race and grievance that have been on painful display in America’s cities lately, President Obama on Monday found himself thinking about a young man he had just met named Malachi.

A few minutes before, in a closed-door round-table discussion at Lehman College in the Bronx, Mr. Obama had asked a group of black and Hispanic students from disadvantaged backgrounds what could be done to help them reach their goals. Several talked about counseling and guidance programs.

“Malachi, he just talked about — we should talk about love,” Mr. Obama told a crowd afterward, drifting away from his prepared remarks. “Because Malachi and I shared the fact that our dad wasn’t around and that sometimes we wondered why he wasn’t around and what had happened. But really, that’s what this comes down to is: Do we love these kids?”

Many presidents have governed during times of racial tension, but Mr. Obama is the first to see in the mirror a face that looks like those on the other side of history’s ledger. While his first term was consumed with the economy, war and health care, his second keeps coming back to the societal divide that was not bridged by his election. A president who eschewed focusing on race now seems to have found his voice again as he thinks about how to use his remaining time in office and beyond.

Continue reading the main story Video
Play Video|1:17

Obama Speaks of a ‘Sense of Unfairness’

Obama Speaks of a ‘Sense of Unfairness’

At an event announcing the creation of a nonprofit focusing on young minority men, President Obama talked about the underlying reasons for recent protests in Baltimore and other cities.

By Associated Press on Publish Date May 4, 2015. Photo by Stephen Crowley/The New York Times.

In the aftermath of racially charged unrest in places like Baltimore, Ferguson, Mo., and New York, Mr. Obama came to the Bronx on Monday for the announcement of a new nonprofit organization that is being spun off from his White House initiative called My Brother’s Keeper. Staked by more than $80 million in commitments from corporations and other donors, the new group, My Brother’s Keeper Alliance, will in effect provide the nucleus for Mr. Obama’s post-presidency, which will begin in January 2017.

“This will remain a mission for me and for Michelle not just for the rest of my presidency but for the rest of my life,” Mr. Obama said. “And the reason is simple,” he added. Referring to some of the youths he had just met, he said: “We see ourselves in these young men. I grew up without a dad. I grew up lost sometimes and adrift, not having a sense of a clear path. The only difference between me and a lot of other young men in this neighborhood and all across the country is that I grew up in an environment that was a little more forgiving.”


Organizers said the new alliance already had financial pledges from companies like American Express, Deloitte, Discovery Communications and News Corporation. The money will be used to help companies address obstacles facing young black and Hispanic men, provide grants to programs for disadvantaged youths, and help communities aid their populations.

Joe Echevarria, a former chief executive of Deloitte, the accounting and consulting firm, will lead the alliance, and among those on its leadership team or advisory group are executives at PepsiCo, News Corporation, Sprint, BET and Prudential Group Insurance; former Secretary of State Colin L. Powell; Senator Cory Booker, Democrat of New Jersey; former Attorney General Eric H. Holder Jr.; the music star John Legend; the retired athletes Alonzo Mourning, Jerome Bettis and Shaquille O’Neal; and the mayors of Indianapolis, Sacramento and Philadelphia.

The alliance, while nominally independent of the White House, may face some of the same questions confronting former Secretary of State Hillary Rodham Clinton as she begins another presidential campaign. Some of those donating to the alliance may have interests in government action, and skeptics may wonder whether they are trying to curry favor with the president by contributing.

“The Obama administration will have no role in deciding how donations are screened and what criteria they’ll set at the alliance for donor policies, because it’s an entirely separate entity,” Josh Earnest, the White House press secretary, told reporters on Air Force One en route to New York. But he added, “I’m confident that the members of the board are well aware of the president’s commitment to transparency.”

The alliance was in the works before the disturbances last week after the death of Freddie Gray, the black man who suffered fatal injuries while in police custody in Baltimore, but it reflected the evolution of Mr. Obama’s presidency. For him, in a way, it is coming back to issues that animated him as a young community organizer and politician. It was his own struggle with race and identity, captured in his youthful memoir, “Dreams From My Father,” that stood him apart from other presidential aspirants.

But that was a side of him that he kept largely to himself through the first years of his presidency while he focused on other priorities like turning the economy around, expanding government-subsidized health care and avoiding electoral land mines en route to re-election.

After securing a second term, Mr. Obama appeared more emboldened. Just a month after his 2013 inauguration, he talked passionately about opportunity and race with a group of teenage boys in Chicago, a moment aides point to as perhaps the first time he had spoken about these issues in such a personal, powerful way as president. A few months later, he publicly lamented the death of Trayvon Martin, a black Florida teenager, saying that “could have been me 35 years ago.”

President Obama on Monday with Darinel Montero, a student at Bronx International High School who introduced him before remarks at Lehman College in the Bronx. Credit Stephen Crowley/The New York Times

That case, along with public ruptures of anger over police shootings in Ferguson and elsewhere, have pushed the issue of race and law enforcement onto the public agenda. Aides said they imagined that with his presidency in its final stages, Mr. Obama might be thinking more about what comes next and causes he can advance as a private citizen.

That is not to say that his public discussion of these issues has been universally welcomed. Some conservatives said he had made matters worse by seeming in their view to blame police officers in some of the disputed cases.

“President Obama, when he was elected, could have been a unifying leader,” Senator Ted Cruz of Texas, a Republican candidate for president, said at a forum last week. “He has made decisions that I think have inflamed racial tensions.”

On the other side of the ideological spectrum, some liberal African-American activists have complained that Mr. Obama has not done enough to help downtrodden communities. While he is speaking out more, these critics argue, he has hardly used the power of the presidency to make the sort of radical change they say is necessary.

The line Mr. Obama has tried to straddle has been a serrated one. He condemns police brutality as he defends most officers as honorable. He condemns “criminals and thugs” who looted in Baltimore while expressing empathy with those trapped in a cycle of poverty and hopelessness.

In the Bronx on Monday, Mr. Obama bemoaned the death of Brian Moore, a plainclothes New York police officer who had died earlier in the day after being shot in the head Saturday on a Queens street. Most police officers are “good and honest and fair and care deeply about their communities,” even as they put their lives on the line, Mr. Obama said.

“Which is why in addressing the issues in Baltimore or Ferguson or New York, the point I made was that if we’re just looking at policing, we’re looking at it too narrowly,” he added. “If we ask the police to simply contain and control problems that we ourselves have been unwilling to invest and solve, that’s not fair to the communities, it’s not fair to the police.”

Moreover, if society writes off some people, he said, “that’s not the kind of country I want to live in; that’s not what America is about.”

His message to young men like Malachi Hernandez, who attends Boston Latin Academy in Massachusetts, is not to give up.

“I want you to know you matter,” he said. “You matter to us.”

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