What if cracks in concrete could fix themselves? - Congrui Jin

譯者: Lilian Chiu 審譯者: Helen Chang

Concrete is the most widely used

混凝土是世界上 最廣為使用的建築材料。

construction material in the world.

It can be found in swathes of city pavements,

用到它的地方包括城市人行道、

bridges that span vast rivers,

橫跨大河的橋樑，

and the tallest skyscrapers on earth.

以及地球上最高的摩天大樓。

But this sturdy substance

但這種堅固的物質有一個弱點：

does have a weakness:

it’s prone to catastrophic cracking

它很容易嚴重裂開，

that costs tens of billions of dollars

每年要花上數百億美金在修繕上。

to repair each year.

But what if we could avoid that problem,

但如果我們能避免那個問題，

by creating concrete that heals itself?

創造出會自己「痊癒」的混凝土呢？

This idea isn’t as far-fetched

這個點子並沒有 聽起來的那麼難以置信。

as it may seem.

It boils down to an understanding

它可以歸結為對於混凝土 如何形成的了解，

of how concrete forms,

and how to exploit that process

以及如何利用那過程， 為我們帶來益處。

to our benefit.

Concrete is a combination of coarse stone

混凝土是粗糙石頭

and sand particles, called aggregates,

和沙粒的結合，稱為聚合物，

that mix with cement, a powdered blend

再混入水泥，一種黏土 與石灰石的粉狀混合物，

of clay and limestone.

When water gets added to this mix,

把水加入這種混合當中，

the cement forms a paste and

水泥會變成糊狀， 覆蓋聚合物的表面，

coats the aggregates, quickly hardening

透過一種叫做水合作用的 化學反應，很快硬化。

through a chemical reaction

called hydration.

Eventually, the resulting material

最終，產生出來的材料 會變得夠強壯，

grows strong enough to prop up buildings

足以支撐數百公尺高的擎天大樓。

that climb hundreds of meters

into the sky.

While people have been using

雖然過去四千年來，

a variety of recipes to produce cement

用來製造水泥的方法各式各樣，

for over 4,000 years,

concrete itself

但混凝土本身壽命卻非常短。

has a surprisingly short lifespan.

After 20 to 30 years,

二十到三十年之後，

natural processes like concrete shrinkage,

天然過程，比如混凝土收縮、

excessive freezing and thawing,

超低溫凍結和解凍，

and heavy loads can trigger cracking.

以及很重的負重，都會引發破裂。

And it’s not just big breaks that count:

不只是大的裂縫才算數：

tiny cracks can be just as dangerous.

小裂隙也可能同樣危險。

Concrete is often used

混凝土通常被用來當作

as a secondary support

鋼製增強材料周圍的第二支撐。

around steel reinforcements.

In this concrete, even small cracks

在這種混凝土中，即使只有小裂隙

can channel water, oxygen,

都可能讓水、氧氣，

and carbon dioxide that corrode the steel

和二氧化碳有通路可以通過，

腐蝕鋼材，導致災難性的倒塌。

and lead to disastrous collapse.

On structures like bridges and highways

常常使用它們的建物， 如橋樑及高速公路，

that are constantly in use,

detecting these problems

在造成大災難之前 就把這些問題偵測出來

before they lead to catastrophe

becomes a huge and costly challenge.

是巨大而昂貴的挑戰。

But not doing so

但若不這麼做，

would also endanger thousands of lives.

就可能危及數千人的性命。

Fortunately, we’re already experimenting

幸運的是，我們已經在實驗

with ways this material

讓這種材料自行修復的方法。

could start fixing itself.

And some of these solutions

有些解決方案的靈感是來自

are inspired by concrete’s

natural self-healing mechanism.

混凝土的天然自我痊癒機制。

When water enters these tiny cracks,

當水進入這些微小裂隙時，

it hydrates the concrete’s calcium oxide.

會讓混凝土的氧化鈣 發生水合作用。

The resulting calcium hydroxide

產生出的氫氧化鈣

reacts with carbon dioxide in the air,

會和空氣中的二氧化碳作用，

starting a process called

導致自體癒合的過程，

autogenous healing, where

microscopic calcium carbonate crystals

過程中，會形成 極微小的碳酸鈣結晶，

form and gradually fill the gap.

漸漸把縫隙填起來。

Unfortunately, these crystals

不幸的是這些結晶能做的有限，

can only do so much, healing cracks

that are less than 0.3mm wide.

頂多填補不到小於 0.3mm 的裂縫。

Material scientists have figured out how

材料科學家已經知道

to heal cracks up to twice that size by

要如何把兩倍寬的裂縫補起來，

adding hidden glue into the concrete mix.

做法是在水泥混合當中 加入隱藏的膠。

If we put adhesive-filled fibers

若把充滿黏著劑的纖維物質 和管子放入混合物中，

and tubes into the mixture,

they’ll snap open when a crack forms,

在裂縫形成時， 它們就會突然破開，

releasing their sticky contents

釋放出黏著的內容物， 把裂隙封起來。

and sealing the gap.

But adhesive chemicals often behave

但黏著化學物的行為 和混凝土通常很不一樣，

very differently from concrete,

and over time, these adhesives

且隨時間過去，這些黏著劑 可能會造成更糟的裂縫。

can lead to even worse cracks.

So perhaps the best way to heal

所以，也許填補 大型裂縫的最佳方式

large cracks is to give concrete

是提供混凝土自助的工具。

the tools to help itself.

Scientists have discovered that

科學家已經發現有些細菌和霉菌

some bacteria and fungi

can produce minerals,

能夠產生出礦物質，

including the calcium carbonate

包括自體癒合中所發現的碳酸鈣。

found in autogenous healing.

Experimental blends of concrete

混凝土的實驗性混合

include these bacterial or fungal spores

就包含了這些細菌或霉菌孢子，

alongside nutrients in their concrete mix,

同時在它們的混凝土混合 當中還有營養物，

where they could lie dormant

讓它們可以在那裡休眠數百年。

for hundreds of years.

When cracks finally appear

當裂縫終於出現， 水慢慢流入混凝土中，

and water trickles into the concrete,

the spores germinate, grow, and consume

孢子就會發芽、長大，並消耗

the nutrient soup that surrounds them,

它們周圍的營養湯品，

modifying their local environment

改變它們所在處的環境，

to create the perfect conditions

創造出完美的條件讓碳酸鈣成長。

for calcium carbonate to grow.

These crystals gradually fill the gaps,

這些結晶會漸漸填滿裂縫，

and after roughly three weeks,

在大約三週之後，

the hard-working microbes

辛勤工作的微生物 就能完全修補好裂縫，

can completely repair cracks

up to almost 1mm wide.

可修補的寬度最多能接近 1mm。

When the cracks seal,

裂縫封起來之後，

the bacteria or fungi will make spores

細菌或霉菌就會產生孢子，

and go dormant once more—

然後再次去休眠——

ready to start a new cycle of self-healing

準備好在裂縫再次出現時，

when cracks form again.

開始一個新的自體癒合循環。

Although this technique

雖然這項技術已經有大量的研究，

has been studied extensively,

we still have a ways to go

我們還有很長的路要走，

before incorporating it

in the global production of concrete.

才能將它整合到 全球混凝土的生產中。

But, these spores have huge potential

但這些孢子有很大的潛力，

to make concrete

可以讓混凝土更有恢復力、更持久，

more resilient and long-lasting—

which could drastically reduce

這就能大大地減少

the financial and environmental cost

製造混凝土的財務和環境成本。

of concrete production.

Eventually, these microorganisms

最終，這些微生物

may force us to reconsider

可能會迫使我們重新思考 我們對於城市的看法，

the way we think about our cities,

bringing our inanimate concrete jungles

讓沒有生命混凝土叢林活過來。

to life.