How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

罗马混凝土为何能历经千年不朽？一座 1900 年前的厕所提供了线索

The Canopus, a pool at Hadrian’s Villa in Tivoli, Italy. Ancient Roman infrastructure has stood the test of time. Today, you can walk through Italy and see concrete buildings, roads and aqueducts that have survived for about two millennia. Modern concrete, on the other hand, usually crumbles within roughly 100 years. 位于意大利蒂沃利的哈德良别墅中的卡诺普斯水池。古罗马的基础设施经受住了时间的考验。今天，走在意大利的土地上，你依然可以看到那些历经约两千年风雨的混凝土建筑、道路和渡槽。相比之下，现代混凝土通常在 100 年内就会崩解。

Scientists have long tried to uncover the secrets of Roman concrete’s durability. For years, they assumed that its longevity was thanks to one key chemical process: the pozzolanic reaction, which occurs when volcanic ash reacts with the chemical lime and water. While that still holds, there seems to be more to the story. It turns out that another chemical reaction, known as carbonation, might also contribute to Roman concrete’s longevity. The findings, published in the journal Science Advances on July 8, could help researchers develop more sustainable and resilient concrete materials. 科学家们长期以来一直试图揭开罗马混凝土耐用性的秘密。多年来，他们认为其长寿归功于一个关键的化学过程：火山灰反应，即火山灰与熟石灰和水发生反应。虽然这一理论依然成立，但事实似乎远不止于此。研究发现，另一种被称为“碳化”的化学反应也可能对罗马混凝土的持久性做出了贡献。这项于 7 月 8 日发表在《科学进展》杂志上的研究成果，可能有助于研究人员开发出更具可持续性和韧性的混凝土材料。

For the new work, researchers traveled to the 1,900-year-old Hadrian’s Villa, a UNESCO World Heritage site that sits about 17 miles east of Rome. The sprawling estate is an architectural marvel, but one of its scientific gems are the communal toilets. They offer an unprecedented opportunity to study Roman concrete in its original state, unaltered by modern hands. “Nobody restores a latrine,” says Paulo J. M. Monteiro, a study co-author and civil engineer at the University of California, Berkeley, to Scientific American. “So, the material sat undisturbed for 19 centuries, quietly running an experiment no one alive could start.” 为了这项新研究，研究人员前往拥有 1900 年历史的哈德良别墅，这是一处位于罗马以东约 17 英里处的联合国教科文组织世界遗产。这座庞大的庄园是建筑史上的奇迹，但其科学瑰宝之一却是公共厕所。它们提供了一个前所未有的机会，让人们能够研究处于原始状态、未受现代人工干预的罗马混凝土。“没有人会去修复厕所，”加州大学伯克利分校的土木工程师、该研究的合著者保罗·J. M. 蒙泰罗（Paulo J. M. Monteiro）对《科学美国人》表示，“因此，这些材料在 19 个世纪里一直未受干扰，静静地进行着一场无人能及的实验。”

Need to know: Who was Hadrian? Hadrian was the emperor of Rome from 117 to 138 C.E. He’s well known for having a wall, called Hadrian’s Wall, built in northern England to protect the Roman province of Britannia from neighbors in what’s now Scotland. 知识点：哈德良是谁？ 哈德良是公元 117 年至 138 年间的罗马皇帝。他最出名的事迹是在英格兰北部修建了“哈德良长城”，以保护罗马的不列颠行省免受现今苏格兰地区邻近部落的侵扰。

Monteiro and his colleagues took a concrete sample from underneath a toilet seat. Back in the lab, they examined it under a high-powered microscope, scanned it with X-rays and analyzed its chemical composition. As expected, the specimen contained evidence that volcanic ash, lime and water had been combined to form the material. However, a closer look at the concrete’s pores and fractures revealed that calcite, a mineral with calcium, carbon and oxygen, was the primary binding agent. 蒙泰罗和他的同事从一个马桶座圈下方取样了混凝土样本。回到实验室后，他们用高倍显微镜观察、X 射线扫描并分析了其化学成分。正如预期的那样，样本中含有火山灰、石灰和水混合形成该材料的证据。然而，对混凝土孔隙和裂缝的进一步观察显示，方解石（一种含有钙、碳和氧的矿物）才是主要的粘合剂。

When atmospheric carbon dioxide reacts with the calcium compounds in the concrete, it forms the hard mineral calcite, which contains a lot of the compound calcium carbonate. The mineral fills small cracks and pores in the concrete, allowing ancient structures to strengthen and heal over time. “While the pozzolanic reaction is of fundamental importance, our findings suggest that carbonation over a long period of time also enhances the durability of concrete and can help it seal cracks as it ages,” Monteiro says in a statement. 当大气中的二氧化碳与混凝土中的钙化合物发生反应时，会形成坚硬的方解石矿物，其中含有大量的碳酸钙。这种矿物会填充混凝土中的微小裂缝和孔隙，使古老的建筑结构随着时间的推移而不断加固和自我修复。“虽然火山灰反应至关重要，但我们的研究结果表明，长期的碳化作用也增强了混凝土的耐久性，并能帮助它在老化过程中封闭裂缝，”蒙泰罗在声明中说道。

The work builds on a study published in 2023 that suggested that Roman concrete could repair cracks on its own because it was created with chemical reactions involving quicklime, a form of limestone, which left behind calcium-rich deposits in the material. The deposits could react with water, such as rain, and recrystallize to fill in any gaps. With the new study, carbonates have entered the limelight. The research “strengthens the idea that carbonates are more dynamic in these systems and play a fundamental role, not a marginal one,” says Admir Masic, a materials scientist at MIT who co-authored the 2023 study but was not involved in the new work, to Scientific American. 这项工作建立在 2023 年发表的一项研究基础上，该研究指出罗马混凝土能够自行修复裂缝，因为它在制造过程中涉及生石灰（一种石灰石）的化学反应，在材料中留下了富含钙的沉积物。这些沉积物可以与雨水等水分发生反应并重结晶，从而填补缝隙。随着这项新研究的发布，碳酸盐成为了焦点。麻省理工学院的材料科学家阿德米尔·马西奇（Admir Masic）对《科学美国人》表示，这项研究“强化了这样一种观点，即碳酸盐在这些系统中更具动态性，并发挥着基础性而非边缘性的作用”。马西奇是 2023 年那项研究的合著者，但未参与此次新研究。

Monteiro and his colleagues hope that by understanding how Roman concrete worked, modern-day experts can build concrete that has less of an environmental impact. Concrete is one of the world’s most consumed materials, but its production emits an enormous amount of heat-trapping carbon dioxide—about 8 percent of emissions worldwide. According to the United Nations, roughly half of the buildings that will exist by 2050 have not yet been built, which is why it’s important to develop construction materials that have a reduced carbon footprint. 蒙泰罗和他的同事希望，通过了解罗马混凝土的原理，现代专家能够制造出对环境影响更小的混凝土。混凝土是世界上消耗量最大的材料之一，但其生产过程会排放大量的温室气体二氧化碳，约占全球排放量的 8%。据联合国统计，到 2050 年将存在的建筑中，约有一半尚未建造，这就是开发低碳足迹建筑材料至关重要的原因。

“This study shows how exploring ancient engineering techniques can lead to important revelations,” Monteiro says in the statement. “We hope that by unlocking Roman secrets for enhancing concrete durability, we can someday attain sustainable modern infrastructure development.” “这项研究表明，探索古代工程技术可以带来重要的启示，”蒙泰罗在声明中说，“我们希望通过破解罗马人增强混凝土耐久性的秘密，有朝一日能够实现可持续的现代基础设施建设。”