Reinforcement within concrete creates a composite material, with the concrete providing strength

混凝土內部的增強產生復合材料 材料，混凝土提供強度

against compressive stress while the reinforcement provides strength against tensile stress.

在加固時抵抗壓應力 提供抗拉應力的強度。

But, while steel reinforcement solves one of concrete's greatest limitations, it creates

但是，儘管鋼筋解決了一個 它最大的局限性在於

an entirely new problem: Corrosion of embedded steel rebar is the most common form of concrete

一個全新的問題：嵌入式腐蝕 鋼筋是最常見的混凝土形式

deterioration.

惡化。

So what are we doing about it?

那麼我們在做什麼呢？

Hey I'm Grady, and this is Practical Engineering.

嗨，我是Grady，這是實踐工程。

On today's episode, we're testing out some innovations in concrete reinforcement.

在今天的一集中，我們正在測試 混凝土加固方面的一些創新。

Although unprotected steel is naturally prone to corrosion, or rusting, when it gets embedded

儘管天然無保護的鋼很容易 嵌入時會腐蝕或生鏽

into concrete, certain factors usually work to protect it.

具體而言，某些因素通常會起作用 保護它。

First is the obvious protection of simply being shielded from the outside environment

首先是簡單的明顯保護 與外界環境隔離

by a relatively impermeable and durable material.

由相對不透水且耐用的材料製成。

Water and contaminants usually can't make their way through the concrete to the steel.

水和污染物通常不能 他們從混凝土到鋼材的方式。

The second form of protection is the alkaline environment.

第二種保護形式是鹼性 環境。

The high pH of normal concrete creates a thin oxide layer on the steel that provides protection

普通混凝土的高pH值產生稀薄的 提供保護的鋼上的氧化層

from corrosion.

從腐蝕。

But, in some cases, this protection isn't enough.

但是，在某些情況下，這種保護不是 足夠。

One of the main sources of corrosion to rebar is salt.

鋼筋腐蝕的主要來源之一 是鹽。

Whether through exposure to saltwater near a marine environment or application of deicing

是否通過暴露在鹽水附近 海洋環境或除冰的應用

salts to make roadways safer during the winter, these chloride ions can make their way through

鹽使冬季的道路更安全， 這些氯離子可以通過

the concrete, corroding the steel reinforcement.

混凝土，腐蝕鋼筋。

And when steel corrodes, it creates iron oxide that expands inside the concrete.

當鋼腐蝕時，會生成氧化鐵 在混凝土內部膨脹。

This expansion generates stress, sometimes called oxide jacking, and is the one of the

這種膨脹有時會產生壓力 稱為氧化頂，是其中之一

primary causes of concrete deterioration.

混凝土劣化的主要原因。

So, how do we prevent these chloride ions and other contaminants from reaching the steel

那麼，我們如何防止這些氯離子 和其他污染物進入鋼中

and causing corrosion?

並引起腐蝕？

The first line of defense is cover.

第一道防線是掩護。

Cover is the minimum distance between the outside surface of the concrete and the reinforcing

蓋之間的最小距離 混凝土外表面和鋼筋

steel.

鋼。

And, depending on exposure and application, certain codes specify different amounts of

並且，根據曝光和應用情況， 某些代碼指定了不同的數量

concrete cover, generally between 25 and 75 millimeters or 1 to 3 inches.

混凝土保護層，通常在25到75之間 毫米或1到3英寸。

Cover is one of the reasons good concrete work takes so much effort before the concrete

覆蓋物是好的混凝土的原因之一 在混凝土之前，工作需要付出巨大的努力

ever shows up on the job site.

曾經出現在工作現場。

Installing strong formwork and lots and lots of wire tying all the reinforcement together

安裝堅固的模板以及很多很多 將所有鋼筋綁在一起的過程

help to make absolutely sure that, through all the jostling and walking over and general

通過通過以下方式絕對幫助確保 所有的爭吵和步行一般

chaos that comes when it's time to actually place concrete, the rebar stays where it was

是時候開始真正的混亂了 放置混凝土，鋼筋將留在原處

designed to be embedded within the final product.

設計為嵌入最終產品中。

Neglecting these steps can cause rebar to sink to the bottom of a slab or come too close

忽略這些步驟可能導致鋼筋 下沉到板的底部或太靠近

to an outside surface before the concrete cures, eventually leading to premature corrosion

到混凝土前的外表面 治愈，最終導致過早腐蝕

of the reinforcement due to lack of cover.

由於缺乏覆蓋物而導致的加固。

But, even with adequate cover, a crack in the concrete can allow contaminants and water

但是，即使有足夠的遮蓋力， 混凝土會允許污染物和水進入

into direct contact with the reinforcement.

與鋼筋直接接觸。

And it won't surprise you to learn that cracks in concrete aren't all that rare.

學習它不會讓您感到驚訝 混凝土裂縫並不是那麼罕見。

Most concrete shrinks as it cures which can lead to cracks.

大多數混凝土在固化時會收縮， 導致裂縫。

Changes in temperature also cause expansion and contraction which can lead to cracking.

溫度變化也會引起膨脹 和收縮會導致破裂。

Concrete can also crack under normal, expected loading conditions due to the way the steel

混凝土在正常情況下也會破裂 加載條件由於鋼的方式

takes up stresses within the material.

承受材料內部的應力。

One way to solve this issue is by prestressing the rebar, a topic I discussed briefly in

解決此問題的一種方法是通過預應力 鋼筋，這是我在其中簡要討論的主題

a previous video and something I'd like to dive deeper into in the future.

以前的視頻和我想要的東西 在將來更深入地研究。

But today I want to show another option for reducing these cracks.

但是今天我想展示另一種選擇 減少這些裂縫。

Fiber reinforced concrete is pretty much exactly what you'd expect it be.

纖維增強混凝土幾乎完全是 您期望的是什麼。

It's not a new idea by any means, but our understanding and use of different kinds of

無論如何，這不是一個新主意，但我們 了解和使用不同種類的

fibers within a concrete mix continues to grow.

混凝土混合物中的纖維繼續 增長。

Adding glass, steel, or synthetic fibers to concrete can provide a lot of benefits, but

將玻璃，鋼或合成纖維添加到 混凝土可以帶來很多好處，但是

one of the most important is crack control.

最重要的之一是裂縫控制。

I constructed three nearly identical reinforced concrete beams to show how this works, and

我建造了三個幾乎完全相同的鋼筋 混凝土梁以顯示其工作原理，以及

I let them cure for about a week.

我讓他們治愈大約一個星期。

The first one only has steel rebar as reinforcement.

第一個只用鋼筋作為鋼筋。

I'm using my hydraulic press to test out the strength of each beam and see how it performs

我正在使用液壓機進行測試 每個光束的強度，並查看其性能

prior to failure.

失敗之前。

And I'm using tons as a measurement of force on these beams, just because that's what

我用噸來衡量力量 在這些光束上，僅僅是因為那是

the gauge says, but the units are completely arbitrary to the demo.

儀表說，但單位完全是 任意演示。

If you prefer SI, just pretend these are metric tonnes.

如果您喜歡SI，只需假裝這些都是公制的 噸。

As I increase the load on the beam, you see cracks starting at only around 3 tons.

當我增加樑的載荷時，您會看到 裂縫僅在3噸左右開始。

These cracks form because steel stretches a little bit as it takes up the tensile stress

這些裂紋的形成是由於鋼的拉伸 因為它吸收了拉應力

in the concrete.

在混凝土中。

The beam is holding the load just fine and isn't even close to failure, but concrete

梁將負載保持得很好，並且 甚至不是接近失敗，而是具體的

can't stretch along with the steel so it has to crack.

不能與鋼一起拉伸 必須破解。

You can imagine how these cracks could let water and air into contact with the reinforcement

您可以想像這些裂縫如何使 水和空氣與鋼筋接觸

and eventually deteriorate the concrete.

最終使混凝土變質。

Those cracks are the important part of this demo, but I went ahead and increased the load

這些裂縫是其中的重要部分 演示，但我繼續進行並增加了負載

until the beam failed because, hey, that's what hydraulic presses are good for right?

直到光束失效，因為，那是 哪些液壓機最適合？

For these next two beams, I included fibers in the concrete mix: one beam has steel fibers

對於接下來的兩束，我加入了纖維 在混凝土混合物中：一根梁含有鋼纖維

and the other has glass fibers.

另一種是玻璃纖維。

The steel rebar and fibers team up to resist tensile stresses in the beams.

鋼筋和纖維共同抵抗 梁中的拉應力。

The rebar provides large scale reinforcement to resist tension across the entire structural

鋼筋可進行大規模加固 抵抗整個結構的張力

member, and the fibers provide small scale reinforcement to resist localize tension that

成員，並且纖維提供小規模 增強抵抗局部張力的能力

causes cracking.

導致破裂。

When I load these beams to 3 tons, you can't see a single crack.

當我將這些梁加載到3噸時， 看到一個裂縫。

In fact, for both of these beams, I didn't see any cracks form until almost double that.

實際上，對於這兩個光束，我都沒有 看到任何裂縫，直到幾乎翻倍。

and even then the cracks were much smaller.

即使這樣，裂縫也很小。

Both beams failed at about the same load as first, one, which I expected.

兩個梁在大約相同的載荷下失效 首先，這是我所期望的。

Like I said, the fibers don't really add much overall strength to the beam, but you

就像我說的，纖維並沒有真正添加 光束的整體強度很高，但是您

can easily see they could go a long way in preventing corrosion of steel rebar.

可以很容易地看到他們可以走很長一段路 防止鋼筋腐蝕。

You may be wondering why are we even using steel for reinforcement at all?

您可能想知道我們為什麼還要使用 完全可以加固的鋼？

Steel is relatively inexpensive, well-tested, and strong, but there are lots of other materials

鋼材相對便宜，經過了嚴格的測試， 堅固，但還有許多其他材料

that with excellent mechanical properties that don't face this issue of corrosion.

具有優異的機械性能 不會遇到腐蝕問題。

For very corrosive environments, we sometimes use epoxy-coated rebar or even stainless steel,

對於腐蝕性很強的環境，有時 使用環氧塗層的鋼筋甚至不銹鋼，

but there are some emerging alternatives like Fiber Reinforced Polymers or FRP bars.

但是有一些新興的替代方案，例如 纖維增強聚合物或FRP筋。

This is reinforcement made of basalt, remelted volcanic rock forced through tiny nozzles

這是玄武岩製成的加固物，經過重熔 穿過微小噴嘴的火山岩

to create fibers that are extremely strong.

產生非常堅固的纖維

Options like this often cost cost more than steel rebar, in some cases a lot more.

這樣的選擇通常花費比 鋼筋，有時甚至更多。

But, the major impediment to the use of these newer, more innovative types of reinforcement

但是，使用這些工具的主要障礙 更新，更創新的加固類型

isn't just the cost.

不只是成本。

It's easy to see that those additional costs may be offset by the increased lifespan of

顯而易見，這些額外費用 可能會因使用壽命的延長而被抵消

the concrete.

具體。

Another inhibition comes simply from the lack of widespread use.

另一個阻礙來自缺乏 廣泛使用。

Innovation happens slowly in civil engineering because the consequences of failure are so

創新在土木工程中進展緩慢 因為失敗的後果是如此

high.

高。

Gaining confidence in a design has as much to do with engineering theory as it does to

對設計充滿信心 與工程理論一樣

simply seeing how well similar designs have performed in the past.

只是看到相似的設計有多好 在過去表演。

But many engineering disasters have come not at the expense of bad design, but actually

但是許多工程災難並沒有到來 以不佳的設計為代價，但實際上

bad maintenance, so long-term durability can be just as important to public safety as other

維護不好，因此長期耐用 對公共安全同樣重要

design criteria.

設計標準。

We'll certainly be seeing more innovative ways to reinforce concrete in the future,

我們肯定會看到更多創新 將來加固混凝土的方法，

including the options I mentioned in this video.

包括我在此提到的選項 視頻。

Thank you for watching, and let me know what you think!

感謝您的收看，讓我知道 您認為！