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?
Beton dunyodagi eng keng tarqalgan qurilish materiali hisoblanadi. Ko'pgina shaharlarning qatnov yo'lkalari, keng daryolar uzra o'tgan ko'priklar va eng baland osmono'par binolari betondan qurilgan. Biroq bu chidamli materialda bir kamchilik bor: unga shikast yetsa, qattiq yorilib ketishi mumkin, uni ta'mirlashga har yili milliardlab dollar sarflanadi. Ammo o'z-o'zini tiklovchi betonni yaratish muammoga yechim bo'lsa-chi?
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.
G'oya g'alati tuyulishi mumkin, ammo unday emas. Avvaliga beton yaratish jarayonini o'rganish va uni o'z maqsadimizga qanday bo'ysundirishni bilish lozim. Beton shag'al va qum aralashmasidan iborat agregatlarni loy va ohaktoshning kukunli aralashmasi bo'lgan sementga qorishtirish orqali tayyorlanadi. Qorishmaga suv qo'shilgach, sement quyuqlashib, agregatlar bilan qoplanadi va gidratatsiya deb ataluvchi kimyoviy reaksiya tufayli tezda qotib qoladi. Natijada, yuzlab metr balandlikka ko'tariluvchi binolarni qurish uchun mustahkam material hosil bo'ladi.
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.
Odamlar 4000 yildan buyon sement yaratishning turli usullarini qo'llab kelishganiga qaramay, beton u qadar uzoq vaqt saqlanib turmaydi. 20-30 yil ichida sementning tirishishi, kuchli muzlash, qizish va og'ir yuklar ta'sirida yoriqlar paydo bo'ladi. Gap faqat katta yoriqlar haqida ketmayapti, arzimas darz ketishlar ham xavfli bo'lishi mumkin. Beton ko'pincha po'lat armatura atrofida yordamchi tayanch sifatida ishlatiladi. Bunday holda hatto mayda yoriqlardan ham suv, kislorod, karbonat angidrid o'tishi mumkin. Bu po'lat zanglashini keltirib chiqarib, imorat qulashiga olib keladi. Ko'prik va magistral yo'llar singari doimiy yuk ostida bo'lgan inshoot- larda bunday muammolarni falokatdan oldin aniqlash ancha qimmatga tushadi va ko'p vaqt talab etadi. Ammo qo'l qovushtirib o'tirish minglab kishilar hayotini xavf ostiga qo'yadi.
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.
Hayriyatki, biz allaqachon betonning o'zini qayta tiklashiga imkon beruvchi metodlar ustida ishlamoqdamiz. Ularning ba'zilari beton- ning o'zini o'zi tiklashining tabiiy mexanizmiga asoslangan. Kichik yoriqlar ichiga suv kirganida, u beton tarkibidagi kalsiy oksidini to'yintiradi. Havoda hosil bo'lgan kalsiy gidroksidi karbonat angidrid bilan reaksiyaga kirishadi va autogen tiklanish jarayoni boshlanadi: kalsiy karbonatining mayda kristallari hosil bo'lib, bo'shliqlarni to'ldira boshlaydi. Afsuski, bu kristallar 0,3 mm gacha hajmdagi yoriqlarnigina yopishi mumkin. Materialshunos olimlar
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.
beton aralashmasiga yashirin yelim qo'shib, yoriqlarni ikki baravar katta o'lchamda to'ldirish mumkinligini aniqladilar. Agar qorishmaga yopishqoq modda bilan to'ldirilgan tola va naychalar qo'shilsa, yoriqlar paydo bo'lganda, ular yorilib, o'zidan teshiklarni to'ldiradigan yopishqoq modda ajratib chiqaradi. Biroq, yopishqoq moddalar reaksiyasi betonnikidan farq qilib, vaqt o'tishi bilan yanada ko'proq yoriqlarga sabab bo'lishi mumkin.
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.
Ehtimol, katta yoriqlarni tuzatish- ning eng yaxshi yo'li betonga o'zini o'zi tiklashi uchun zarur vositalarni berishdir. Olimlar ba'zi bakteriya va zamburug'lar autogen tiklanish jarayonida ishtirok etuvchi kalsiy karbonat kabi minerallarni ishlab chiqarishini aniqladilar. Eksperimental beton qorishmalar shunday bakteriya yoki qo'ziqorin sporalaridan iborat bo'lib, ular ozuqa moddalari bilan o'ralgan holda yuz yillab "uyquda" yotishi mumkin. Yoriqlar paydo bo'lib, suv betonga kirganida, sporalar uyg'onib, o'sadi va atrofdagi ozuqaviy minerallarni yutib, atrof-muhitni o'zgartiradi va kalsiy karbonatning shakllanishi uchun ideal sharoit yaratadi. Bu kristallar asta-sekin bo'shliqlarni to'ldirib, taxminan uch haftada mehnatsevar mikroblar deyarli 1mm kenglikdagi yoriqlarni to'liq tuzata oladi. Yoriqlarni yamagach, bakteriya va zamburug'lar spora hosil qilib, yangi yoriqlar paydo bo'lganida o'z-o'zini tiklashning yangi siklini boshlash uchun yana uyquga ketadi.
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.
Mazkur metod har jihatdan tadqiq etilganiga qaramay, uni ommaviy beton ishlab chiqarish jarayoniga joriy qilinishiga shoshmaslik zarur. Nima bo'lganda ham bu sporalar betonni yanada ishiq va mustahkam qilish uchun katta imkoniyatlarga ega. Bu beton ishlab chiqarishning moliyaviy va ekologik xarajatlarini sezilarli darajada kamaytirish mumkin. Kun kelib bu mikroorganizmlar bizning tosh o'rmonimizga jon kiritib, shaharlar haqidagi tasavvurlarimizni o'zgartirib yuborishi mumkin.