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

翻译人员: Wanna Shi 校对人员: Liu Qi

Concrete is the most widely used

混凝土是世界上 使用最广泛的建筑材料。

construction material in the world.

It can be found in swathes of city pavements,

常见于一条条城市道路，

bridges that span vast rivers,

跨江大桥，

and the tallest skyscrapers on earth.

和高耸入云的摩天大楼。

But this sturdy substance

但是这种坚固的物质有一个弱点：

does have a weakness:

it’s prone to catastrophic cracking

容易出现毁灭性的裂缝，

that costs tens of billions of dollars

每年要花费数百亿美元 来修补这些裂缝。

to repair each year.

But what if we could avoid that problem,

如果我们能发明自我修复的混凝土 来避免这个问题呢？

by creating concrete that heals itself?

This idea isn’t as far-fetched

这个想法并不像 看上去那么遥不可及。

as it may seem.

It boils down to an understanding

简单来说是要明白

of how concrete forms,

混凝土是怎么形成的，

and how to exploit that process

并且要知道怎样才能 利用这一过程。

to our benefit.

Concrete is a combination of coarse stone

混凝土是一种混合物，

由粗石料和沙砾，称为集料，

and sand particles, called aggregates,

that mix with cement, a powdered blend

与水泥混合，

水泥是黏土和石灰岩 构成的粉状混合物。

of clay and limestone.

When water gets added to this mix,

在混合物中加入水后，

the cement forms a paste and

水泥变成糊状物，

coats the aggregates, quickly hardening

包裹住集料，

通过化学反应迅速硬化，

through a chemical reaction

called hydration.

这一过程即水合反应。

Eventually, the resulting material

最终形成的材料

grows strong enough to prop up buildings

十分强固，

足以用来建设百米高楼，高耸入云。

that climb hundreds of meters

into the sky.

While people have been using

虽然人们尝试了各种方法生产水泥，

a variety of recipes to produce cement

for over 4,000 years,

已经有 4000 多年的历史了，

concrete itself

但混凝土本身的寿命 却出人意料地短暂。

has a surprisingly short lifespan.

After 20 to 30 years,

混凝土浇筑二三十年后，

natural processes like concrete shrinkage,

自然过程，例如混凝土收缩、

excessive freezing and thawing,

过度融冻，

and heavy loads can trigger cracking.

及负荷过重都会引发裂缝。

And it’s not just big breaks that count:

危险的不仅仅是大裂缝，

tiny cracks can be just as dangerous.

小裂缝也同样危险。

Concrete is often used

混凝土一般用作 钢结构周围的二级支撑。

as a secondary support

around steel reinforcements.

In this concrete, even small cracks

混凝土中的小裂缝

can channel water, oxygen,

会成为水、氧气和二氧化碳的通道，

and carbon dioxide that corrode the steel

而这些物质会腐蚀钢结构，

and lead to disastrous collapse.

导致灾难性坍塌。

On structures like bridges and highways

针对桥梁、道路

that are constantly in use,

这类频繁使用的结构物，

detecting these problems

在灾难形成前，

before they lead to catastrophe

进行问题排查，

becomes a huge and costly challenge.

是一项巨大而昂贵的挑战。

But not doing so

但不这么做的话，

would also endanger thousands of lives.

又会危及数千条生命。

Fortunately, we’re already experimenting

幸运的是，我们正在试验各种方法，

with ways this material

could start fixing itself.

让混凝土进行自我修复。

And some of these solutions

其中一些方法，

are inspired by concrete’s

灵感来自于混凝土天然的 自我修复机制。

natural self-healing mechanism.

When water enters these tiny cracks,

水进入小裂缝之后，

it hydrates the concrete’s calcium oxide.

会与混凝土的氧化钙发生水合作用，

The resulting calcium hydroxide

产生的氢氧化钙

reacts with carbon dioxide in the air,

与空气中的二氧化碳反应，

starting a process called

于是，混凝土开始了自我修复，

autogenous healing, where

microscopic calcium carbonate crystals

也就是微小的额碳酸钙晶体形成，

form and gradually fill the gap.

逐渐填补裂缝的过程。

Unfortunately, these crystals

不幸的是，

can only do so much, healing cracks

碳酸钙晶体“能力有限”，

只能填补宽度小于 0.3 mm的裂缝。

that are less than 0.3mm wide.

Material scientists have figured out how

材料科学家已经找到了

to heal cracks up to twice that size by

让修复宽度翻一倍的方法，

adding hidden glue into the concrete mix.

即在混凝土混合物中加入胶粘剂。

If we put adhesive-filled fibers

如果我们将纤维胶液管，

and tubes into the mixture,

加入到混凝土混合物中，

they’ll snap open when a crack forms,

那么在出现裂缝时，

纤维胶液管就会破裂，

releasing their sticky contents

释放出胶粘剂修复裂缝。

and sealing the gap.

But adhesive chemicals often behave

但是胶粘剂化学物质的运动

very differently from concrete,

与混凝土截然不同，

and over time, these adhesives

所以时间一长，

can lead to even worse cracks.

胶粘剂反而会造成更大的裂缝。

So perhaps the best way to heal

或许大裂缝最好的修复方式是

large cracks is to give concrete

给混凝土提供自我愈合的工具。

the tools to help itself.

Scientists have discovered that

科学家已经发现

some bacteria and fungi

一些细菌和真菌 能够生成矿物质，

can produce minerals,

including the calcium carbonate

还有可以自我愈合的碳酸钙。

found in autogenous healing.

Experimental blends of concrete

混凝土试配中，

include these bacterial or fungal spores

在混凝土混合物中 加入细菌和真菌孢子

alongside nutrients in their concrete mix,

以及养分，

where they could lie dormant

这些孢子可以在此休眠， 时间长达数百年。

for hundreds of years.

When cracks finally appear

最终当裂缝出现， 水渗入混凝土裂缝时，

and water trickles into the concrete,

the spores germinate, grow, and consume

孢子就会开始发芽生长，

the nutrient soup that surrounds them,

消耗周围养分，

modifying their local environment

改变周围环境，

to create the perfect conditions

为碳酸钙的形成

for calcium carbonate to grow.

创造完美条件。

These crystals gradually fill the gaps,

碳酸钙晶体会慢慢填补裂缝，

and after roughly three weeks,

大约三周后，

the hard-working microbes

这些勤勤恳恳的微生物

can completely repair cracks

就能完全修复

up to almost 1mm wide.

宽达 1mm 的裂缝。

When the cracks seal,

当裂缝修复后，

the bacteria or fungi will make spores

这些细菌和真菌会 重新回到孢子状态，

and go dormant once more—

重新进入休眠状态。

ready to start a new cycle of self-healing

等待裂缝再次出现时，

when cracks form again.

开始新一轮的自我修复。

Although this technique

虽然这项技术已经被广泛研究，

has been studied extensively,

we still have a ways to go

但是将这种办法用于全球混凝土生产，

before incorporating it

in the global production of concrete.

还有很长的路要走。

But, these spores have huge potential

不过这些孢子拥有巨大的潜力，

to make concrete

能使混凝土更加持久耐用——

more resilient and long-lasting—

which could drastically reduce

这能大大降低混凝土生产的 资金和环境成本。

the financial and environmental cost

of concrete production.

Eventually, these microorganisms

最后，或许这些微生物

may force us to reconsider

会促使我们重新审视 我们看待城市的方式，

the way we think about our cities,

bringing our inanimate concrete jungles

让毫无生气的混凝土丛林 焕发勃勃生机。

to life.