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经济学人科技 || 治愈“混凝土癌症”

Civil engineering

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Summer(琚儿),女,QE在职,梦想能仗翻译/音乐 /健康走天涯

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Curing concrete cancer
治愈混凝土癌症

英文部分选自经济学人191102science and technology版块

Civil engineering

土木工程


Curing concrete cancer

治愈混凝土癌症


Two Australian bridges try to stand the test of time

两座澳大利亚桥梁试图抵御时间侵蚀


Modern civilisation is built on concrete and steel. Put the two together, though, and you can generate a problem. Reinforcing concrete with steel rods called rebars is the basis of modern construction. But because water gets in through tiny cracks, the rebars rust. This causes them to expand, widening the cracks and weakening the concrete. Hence such structures require constant attention and often have design lives of only 60-100 years. That is pitiful compared with, say, the concrete dome of the Pantheon in Rome—which was completed in 125ad and still stands.

 

现代文明建立在水泥和钢铁之上。但把这两者放在一起,就会出现一个问题。在混凝土中加入钢条让水泥更坚硬(也就是我们说的钢筋混凝土)构成了现代建筑的根基。但由于水可以从混凝土的微小裂缝中渗入,钢筋会被腐蚀生锈。这会导致钢筋膨胀,进而撑大裂缝,削弱混凝土的坚固性。因此,钢筋混凝土结构需要经常性维护,通常的设计年限也只有60-100年。而混凝土材质的罗马万神殿穹顶建于公元125年,二者相较,不免有些相形见绌。

 

Various ways of delaying or preventing concrete cancer, as this corrosion is known colloquially, have been tried. These include recipes for concrete that is less permeable to water, and rebars made from rust-resistant materials such as stainless-steel or composites. Such approaches work, but they can be expensive.

 

这种腐蚀现象被称作混凝土癌症为了延缓或者防止这一现象的发生,人们尝试了很多不同的方法。包括使用水更难渗漏的混凝土配方,用合金或者不锈钢等防锈材料制作钢筋。这些方法颇有成效,但是都价格高昂。

 

This may be about to change. Next year, if all goes well, a pair of footbridges intended to be cancer-proof will open in Geelong, a town 75km south-west of Melbourne, Australia. These bridges, which will act as prototypes for more than 150 others planned for the expanding city, will be constructed using a novel approach that combines glass-fibre and carbon-fibre rebars. They will, though, cost about the same as equivalent conventional bridges.

 

这一现状可能将发生改观。如果一切顺利,一对具有抵抗“混凝土癌症设计的人行桥明年将在吉朗市(澳大利亚离墨尔本75公里的一个小城)对大众开放。这对桥使用了玻璃纤维和碳纤维棒相结合的新型建筑方法,并将作为城市扩张的范本推广到150项规划的建筑当中。将来,这些桥的建造成本将和传统桥梁持平。

 

The new design is the brainchild of a joint team of researchers from Deakin, a local university, and Austeng, the firm contracted to build the bridges. This team began with commercially available rebars made from carbon-fibre composite. Although these are as strong as steel ones, they are expensive. They are, therefore, most often used in specialist structures such as buildings to house mri hospital scanners, where electromagnetic interference from metal can cause problems.

 

这一新设计是当地的迪肯大学和人行桥承建方Austeng集团共同努力的结果。他们首先使用了市面上能买得到的商用碳纤维棒化合物。虽然它们的强度和钢筋相当,但是却非常昂贵。这些碳纤维棒通常主要用于例如建造医院中放置MRI扫描仪的建筑,因为如果使用钢铁会对MRI产生电磁干扰,造成麻烦。

 

To get around this the team have worked out how to minimise cost by using carbon-fibre rebars only where strictly necessary. In other places they use glass fibre, which is cheaper. The result is a frame that acts as a skeleton for precast concrete sections which can then be assembled into a bridge.

 

为了能成功达到目的,该团队已经想出了如何最小化成本的方法,只在必须使用的建筑部位使用碳纤维螺纹钢筋,剩下的部位使用便宜的玻璃纤维,这样就使得集成于桥梁中预先浇铸的钢筋混凝土具有了骨架。


According to Mahbube Subhani, one of the researchers at Deakin, a three-metre-long version of such a section has just been tested and has passed local building codes. The group is now pressing ahead with the first of the ten-metre sections needed to construct the bridges themselves.

 

迪肯大学的一位研究员Mahbube Subhani表明,长达3米的产品已经实测过了,并且已经达到了当地的建筑规范准则。该团队正在推进制造第一个长达10米的产品,并将其用于制造自己的桥梁中。

 

The new castings are, as was hoped, both stronger and lighter than steel-reinforced concrete. Tests showed that the prototype’s load-carrying capacity was 20% better, even though its cross-section was 15% smaller. Production costs are “a little bit higher”, Dr Subhani admits. But in the long run, he says, the bridges will work out cheaper because they should last for at least 100 years without any maintenance being required.

 

不出所料,新的产品比于钢筋混凝土质量更好、重量更轻。实测结果显示,尽管产品横截面积比小了15%,但是负载能力提升了20%Dr Subhani研究员承认这样的产品生产成本相对较高,但是从长远的角度来看,产品实际的使用成本相对较低,因为即使不用任何保养,它们的寿命亦可达100年之久。

 

They will also be more environmentally friendly, for the concrete surrounding the skeleton is unconventional, too. Normal concrete is bound with Portland cement, which is made by roasting a mixture that includes limestone (calcium carbonate). This process drives off carbon dioxide, a greenhouse gas, and cement-making is a big source of such emissions.

 

同时它们对环境更加友好,因为环绕在骨架周围的混凝土有别于传统材料。传统的混凝土与波特兰水泥(盐酸特质)结合在一起,而波特兰水泥主要石灰石(碳酸钙特质)的混合物。混合的过程会释放二氧化碳(温室气体),同时生产水泥也是温室气体主要来源之一。

 

Geelong’s bridges, by contrast, will be made with geopolymer concrete. This uses cement made from a different mixture of ingredients, including furnace fly-ash, which do not release carbon dioxide when being processed.

 

相比之下,位于吉朗的桥梁将采用地聚合物混凝土。这种混凝土混合方法中使用的是由包括炉灰在内的不同成分混合而成的水泥,在其加工过程中不会释放二氧化碳。 


Further down the line Deakin’s researchers are looking into making rebars out of basalt, an abundant volcanic rock, by melting it and extruding it into fibres. That could provide a cheaper and greener alternative to carbon fibres, which are usually made from oil-based polymers. Some commercial basalt-fibre composites are already available, but the team think they can improve the performance of such fibres further, by adding other materials.

 

不仅如此,迪肯的研究人员正在研究如何通过将玄武岩(一种储量丰富的火山岩)熔化并挤压成纤维的方法,从玄武岩中提取钢筋这可能为碳纤维(一种通常是由石油聚合物制成的聚合物)提供一种更便宜、更环保的替代品。虽然已经有了一些商业化的玄武岩纤维复合材料,但是研究小组认为他们可以通过添加其他材料来进一步提高这种纤维的性能。

 

Coincidentally, one of the ingredients of the Pantheon’s concrete dome is pumice, another volcanic rock. Whether basalt-fibre concrete will similarly stand the test of time only future architects will know.

 

无巧不成书,罗马万神殿的混凝土圆顶的成分之一就是浮石(另一种火山岩)。那么,究竟玄武岩纤维混凝土能否同样地经受住时间的考验呢,看来只有未来的建筑师才会知道了。


翻译组:

Cindy,女,未来外贸工,TE粉

Frank,男,小硕,经济学人的死侍

Alex,男,工科研究生,文学与科学爱好者,经济学人忠实读者

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Lee ,爱骑行的妇女之友,Timberland粉

Rachel:学理工科,爱跳芭蕾,热爱文艺的非典型翻译

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