Concrete is the most widely used construction material in the world. It can be found in swathes of city pavements, bridges that span vast rivers, and the tallest skyscrapers on earth. But this sturdy substance does have a weakness: it’s prone to catastrophic cracking that costs tens of billions of dollars to repair each year. But what if we could avoid that problem, by creating concrete that heals itself?
混凝土是世界上 最廣為使用的建築材料。 用到它的地方包括城市人行道、 橫跨大河的橋樑, 以及地球上最高的摩天大樓。 但這種堅固的物質有一個弱點: 它很容易嚴重裂開, 每年要花上數百億美金在修繕上。 但如果我們能避免那個問題, 創造出會自己「痊癒」的混凝土呢? 這個點子並沒有 聽起來的那麼難以置信。
This idea isn’t as far-fetched as it may seem. It boils down to an understanding of how concrete forms, and how to exploit that process to our benefit. Concrete is a combination of coarse stone and sand particles, called aggregates, that mix with cement, a powdered blend of clay and limestone. When water gets added to this mix, the cement forms a paste and coats the aggregates, quickly hardening through a chemical reaction called hydration. Eventually, the resulting material grows strong enough to prop up buildings that climb hundreds of meters into the sky.
它可以歸結為對於混凝土 如何形成的了解, 以及如何利用那過程, 為我們帶來益處。 混凝土是粗糙石頭 和沙粒的結合,稱為聚合物, 再混入水泥,一種黏土 與石灰石的粉狀混合物, 把水加入這種混合當中, 水泥會變成糊狀, 覆蓋聚合物的表面, 透過一種叫做水合作用的 化學反應,很快硬化。 最終,產生出來的材料 會變得夠強壯, 足以支撐數百公尺高的擎天大樓。 雖然過去四千年來,
While people have been using a variety of recipes to produce cement for over 4,000 years, concrete itself has a surprisingly short lifespan. After 20 to 30 years, natural processes like concrete shrinkage, excessive freezing and thawing, and heavy loads can trigger cracking. And it’s not just big breaks that count: tiny cracks can be just as dangerous. Concrete is often used as a secondary support around steel reinforcements. In this concrete, even small cracks can channel water, oxygen, and carbon dioxide that corrode the steel and lead to disastrous collapse. On structures like bridges and highways that are constantly in use, detecting these problems before they lead to catastrophe becomes a huge and costly challenge. But not doing so would also endanger thousands of lives.
用來製造水泥的方法各式各樣, 但混凝土本身壽命卻非常短。 二十到三十年之後, 天然過程,比如混凝土收縮、 超低溫凍結和解凍, 以及很重的負重,都會引發破裂。 不只是大的裂縫才算數: 小裂隙也可能同樣危險。 混凝土通常被用來當作 鋼製增強材料周圍的第二支撐。 在這種混凝土中,即使只有小裂隙 都可能讓水、氧氣, 和二氧化碳有通路可以通過, 腐蝕鋼材,導致災難性的倒塌。 常常使用它們的建物, 如橋樑及高速公路, 在造成大災難之前 就把這些問題偵測出來 是巨大而昂貴的挑戰。 但若不這麼做, 就可能危及數千人的性命。
Fortunately, we’re already experimenting with ways this material could start fixing itself. And some of these solutions are inspired by concrete’s natural self-healing mechanism. When water enters these tiny cracks, it hydrates the concrete’s calcium oxide. The resulting calcium hydroxide reacts with carbon dioxide in the air, starting a process called autogenous healing, where microscopic calcium carbonate crystals form and gradually fill the gap. Unfortunately, these crystals can only do so much, healing cracks that are less than 0.3mm wide.
幸運的是,我們已經在實驗 讓這種材料自行修復的方法。 有些解決方案的靈感是來自 混凝土的天然自我痊癒機制。 當水進入這些微小裂隙時, 會讓混凝土的氧化鈣 發生水合作用。 產生出的氫氧化鈣 會和空氣中的二氧化碳作用, 導致自體癒合的過程, 過程中,會形成 極微小的碳酸鈣結晶, 漸漸把縫隙填起來。 不幸的是這些結晶能做的有限, 頂多填補不到小於 0.3mm 的裂縫。 材料科學家已經知道
Material scientists have figured out how to heal cracks up to twice that size by adding hidden glue into the concrete mix. If we put adhesive-filled fibers and tubes into the mixture, they’ll snap open when a crack forms, releasing their sticky contents and sealing the gap. But adhesive chemicals often behave very differently from concrete, and over time, these adhesives can lead to even worse cracks.
要如何把兩倍寬的裂縫補起來, 做法是在水泥混合當中 加入隱藏的膠。 若把充滿黏著劑的纖維物質 和管子放入混合物中, 在裂縫形成時, 它們就會突然破開, 釋放出黏著的內容物, 把裂隙封起來。 但黏著化學物的行為 和混凝土通常很不一樣, 且隨時間過去,這些黏著劑 可能會造成更糟的裂縫。 所以,也許填補 大型裂縫的最佳方式
So perhaps the best way to heal large cracks is to give concrete the tools to help itself. Scientists have discovered that some bacteria and fungi can produce minerals, including the calcium carbonate found in autogenous healing. Experimental blends of concrete include these bacterial or fungal spores alongside nutrients in their concrete mix, where they could lie dormant for hundreds of years. When cracks finally appear and water trickles into the concrete, the spores germinate, grow, and consume the nutrient soup that surrounds them, modifying their local environment to create the perfect conditions for calcium carbonate to grow. These crystals gradually fill the gaps, and after roughly three weeks, the hard-working microbes can completely repair cracks up to almost 1mm wide. When the cracks seal, the bacteria or fungi will make spores and go dormant once more— ready to start a new cycle of self-healing when cracks form again.
是提供混凝土自助的工具。 科學家已經發現有些細菌和霉菌 能夠產生出礦物質, 包括自體癒合中所發現的碳酸鈣。 混凝土的實驗性混合 就包含了這些細菌或霉菌孢子, 同時在它們的混凝土混合 當中還有營養物, 讓它們可以在那裡休眠數百年。 當裂縫終於出現, 水慢慢流入混凝土中, 孢子就會發芽、長大,並消耗 它們周圍的營養湯品, 改變它們所在處的環境, 創造出完美的條件讓碳酸鈣成長。 這些結晶會漸漸填滿裂縫, 在大約三週之後, 辛勤工作的微生物 就能完全修補好裂縫, 可修補的寬度最多能接近 1mm。 裂縫封起來之後, 細菌或霉菌就會產生孢子, 然後再次去休眠—— 準備好在裂縫再次出現時, 開始一個新的自體癒合循環。
Although this technique has been studied extensively, we still have a ways to go before incorporating it in the global production of concrete. But, these spores have huge potential to make concrete more resilient and long-lasting— which could drastically reduce the financial and environmental cost of concrete production. Eventually, these microorganisms may force us to reconsider the way we think about our cities, bringing our inanimate concrete jungles to life.
雖然這項技術已經有大量的研究, 我們還有很長的路要走, 才能將它整合到 全球混凝土的生產中。 但這些孢子有很大的潛力, 可以讓混凝土更有恢復力、更持久, 這就能大大地減少 製造混凝土的財務和環境成本。 最終,這些微生物 可能會迫使我們重新思考 我們對於城市的看法, 讓沒有生命混凝土叢林活過來。