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Ancient builders across the world created structures that are still standing today, thousands of years later.
世界各地的古代建造者所建造的建筑物在几千年后的今天仍然屹立不倒。
Roman engineers built thick concrete sea barriers, for example.
例如，罗马工程师建造了厚厚的混凝土海堤。
Mayan builders created sculptures to their gods, and Chinese builders raised walls against invaders.
玛雅工匠建造神像雕塑，中国工匠筑起城墙抵御入侵者。
But there are many recent structures that are already starting to fail.
但最近的许多建筑物已经开始倒塌。
The concrete that makes up much of our modern world lasts around 50 to 100 years.
用来筑造我们现代世界大部分建筑物的混凝土可以持续大约50到100年。
A growing number of scientists have been studying materials from long-ago.
越来越多的科学家开始研究很久以前的材料。
They are breaking apart pieces of buildings and reading historical texts hoping to learn how they have stood for thousands of years.
他们正在拆解建筑物碎片，阅读历史文献，希望了解它们屹立数千年不倒的原因。
The research has turned up a surprising list of materials that were mixed into old buildings.
这项研究发现了一系列被混合进古建筑物、令人惊讶的材料。
They include tree bark, volcanic ash, rice, beer and even urine.
其中包括树皮、火山灰、大米、啤酒，甚至尿液。
These unexpected materials could have the ability to get stronger over time and "heal" cracks when they form.
这些意想不到的材料可能会随着时间的推移变得更强，并在裂缝形成时“弥合”它们。
Figuring out how to copy these features could have real impacts today.
如今弄清楚如何复制这些特征可能会产生真正的影响。
While our modern concrete has the strength to hold up very tall buildings and heavy infrastructure, it cannot compete with the endurance of these ancient materials.
虽然我们的现代混凝土具有支撑非常高的建筑和重型基础设施的强度，但它无法与这些古老材料的耐久性竞争。
With the rising threats of climate change, there is a growing call to make construction more sustainable.
随着气候变化的威胁日益加剧，越来越多的人呼吁提高建筑物的可持续性。
A recent UN report estimates that the built environment is responsible for more than a third of carbon dioxide emissions worldwide.
联合国最近的一份报告估计，建筑环境排放的二氧化碳占全球二氧化碳排放量的三分之一以上。
Cement production alone makes up more than 7 percent of those emissions.
仅生产水泥就占这些排放量的7%以上。
Many researchers have turned to the Romans.
许多研究人员把重点转向了罗马人。
Starting around 200 BCE, the Roman Empire was building concrete structures that have stood the test of time.
从公元前200年左右开始，罗马帝国开始建造混凝土建筑，而这些建筑经受住了时间的考验。
That includes the Pantheon to the aqueducts that still carry water today.
其中包括万神庙和至今仍在输送水的渡槽。
Even in places where seawater has been hitting structures for ages, you will find concrete "basically the way it was when it was poured 2,000 years ago," said John Oleson.
约翰·奥利森表示，即使是在海水长期冲刷建筑物的地方，你也会发现混凝土“基本上还是2000年前浇注时的样子”。
He is an archaeologist at the University of Victoria in Canada.
他是加拿大维多利亚大学的考古学家。
Most modern concrete starts with Portland cement, a powder made by heating limestone and clay to super-high temperatures and grinding them up.
大多数现代混凝土都是从波特兰水泥开始的，这是一种将石灰石和粘土加热到超高温之后研磨而成的粉末。
That cement is mixed with water to create a paste.
这种水泥与水混合成糊状。
Then, materials like rock and gravel are added.
然后，加入岩石和砾石等材料。
Records from ancient builders show the Roman process was similar.
古代建筑者的记录显示，罗马人的建造过程与此类似。
The ancient builders mixed materials like burnt limestone and volcanic sand with water and gravel, creating chemical reactions to tie everything together.
古代建筑者将烧焦的石灰岩和火山砂等材料与水和砾石混合，产生化学反应，从而将所有物质粘合在一起。
Now, scientists think they have found an important reason why some Roman concrete has held up structures for thousands of years.
如今，科学家认为，他们已经找到了一些罗马混凝土能够支撑建筑物数千年的重要原因。
The ancient material has an unusual power to repair itself.
这种古老的材料具有一种不同寻常的自我修复能力。
Exactly how is not yet clear, but scientists are starting to find reasons why.
具体原因尚不清楚，但科学家正开始寻找原因。
Admir Masic is a civil and environmental engineer at the Massachusetts Institute of Technology.
阿德米尔·马西奇是麻省理工学院的土木和环境工程师。
In a study, he said this power comes from chunks of limestone throughout the Roman material that is not mixed in evenly.
在一项研究中，他说，这种力量来自罗马材料中没有被均匀混合的石灰石块。
Researchers used to think these chunks were a sign that the Romans were not mixing up their materials well enough.
研究人员过去认为，这些石灰石块表明了罗马人没有充分混合材料。
Instead, the scientists found that the chunks could fuel the material's "self-healing" abilities.
相反，科学家发现，这些石灰石块可以增强材料的“自我修复”能力。
When cracks form, water enters the concrete, Masic explained.
马西奇解释说，当裂缝形成时，水就会进入混凝土。
That water activates the leftover lime, creating new chemical reactions that can fill in the damaged sections.
水激活了剩余的石灰，产生了新的化学反应，从而可以填充受损的部分。
Today's builders cannot just copy the ancient processes.
如今的建筑者不能简单地照搬古代工艺。
Even though Roman concrete lasted a long time, it could not hold up heavy buildings.
即使罗马混凝土经久耐用，但它也无法支撑起沉重的建筑物。
"You couldn't build a modern skyscraper with Roman concrete," Oleson said. "It would collapse when you got to the third story."
奥利森说：“你不可能用罗马混凝土建造一座现代化的摩天大楼，当你建到第三层时，它就会倒塌。”
Instead, researchers are trying to take some of the ancient materials and add them into modern mixes.
相反，研究人员试图将一些古代材料加入到现代混合物中。
Masic is part of a company that is trying to build new projects using "self-healing" concrete.
马西奇所在的公司正试图使用“自我修复”混凝土建造新项目。
People do not need to make things last quite as long as the Romans did to have an impact, Masic said.
马西奇说，人们不需要像罗马人那样建造持续时间很长的建筑物以产生影响。
If we add 50 or 100 years to concrete's lifespan, he said, "we will require less demolition, less maintenance and less material in the long run."
他说，如果我们把混凝土的寿命延长50年或100年，“从长远来看，我们需要拆除和维护得就更少、需要的材料也会更少。”
I'm Dan Novak.
丹·诺瓦克为您播报。
译文为可可英语翻译，未经授权请勿转载！
