科学美国人60秒 新的混凝土配方可以减少道路裂缝（在线收听）

There's a stretch of highway in Pennsylvania, along U.S. 422. "And like every probably 20 feet you see a big pothole or cracking at the joint. Like everywhere. It was so bad." Yaghoob Farnam is a construction materials engineer at Drexel University in Philly. And this road is pretty much his worst nightmare. "Yeah and just imagine I was driving like 60 miles per hour, I could see, I could feel it, I was driving, I was so mad, like, 'what is going on with this?'"

宾夕法尼亚州有一段美国422号高速公路的延伸路段。“几乎每隔20英尺，你就会在接合处看到一个大凹坑或者裂化。它们好像无处不在。而这真是糟透了。”雅各布·法南姆是费城德雷塞尔大学的一名建筑材料工程师。这条路对他来说简直是最可怕的噩梦。“想象一下，我以时速60英里的速度在这条路上行驶，我能看到、感觉到这些凹坑，而我正在开车，而且感到非常生气，恨不得冲它吼‘这条路到底是怎么回事?’”

The culprit, he says, may be calcium chloride road salt, used to de-ice highways in the winter. Because calcium chloride reacts with a compound in concrete called calcium hydroxide to form something called calcium oxychloride. "It's a huge molecule that causes a lot of pressure inside concrete. And starts degradation of concrete."

法南姆说，罪魁祸首可能是用以冬季公路除冰的氯化钙路盐。由于氯化钙会与复合混凝土中一种叫做氢氧化钙的物质发生反应，从而形成一种叫做氯氧化钙的物质。“这是一种会给混凝土造成很大压力的巨大分子，并且会使混凝土开始降解。”

The solution? Novel blends of concrete that use cheap leftover materials from the coal and steel industries: fly ash, silica fume and slag. In his latest work, Farnam and his team created plugs of these experimental concretes, and submerged them in salty solutions—along with plugs of conventional concrete. Then they eavesdropped on any cracking with high-sensitivity acoustic sensors. And they tracked heat flow through the material, to monitor chemical reactions.

解决方案？——使用来自煤炭和钢铁工业中廉价的剩余材料——粉煤灰、硅粉和矿渣的新型混凝土混合物。在其最新研究中，法南姆和他的团队发明了这些实验混凝土堵头，并将其与传统混凝土堵头一起浸入含盐的溶液中。然后，他们通过高灵敏度的声传感器对裂化声进行窃听，并通过这些材料进行热流量跟踪，以监测化学反应。

The results: concrete slugs made with ingredients like fly ash and slag held up remarkably well after more than a month. Whereas normal concrete was cracked to pieces in just a week. Their recipes are in the journal Cement and Concrete Composites.

结果显示:用粉煤灰和矿渣等原料制成的混凝土块，一个多月后质地仍保持得很好，而普通混凝土仅在一周内就裂成了碎片。他们的制作配方发表在《水泥和混凝土复合材料》杂志上。

Farnam says some states have actually started using this sort of concrete—because it's already known to make the material more durable against other factors, like corrosion of internal steel reinforcement. As for those cracks on U.S. 422, and elsewhere? Farnam has another project in the works—to apply a bacterial slurry, which forms limestone when it interacts with salt, plugging up the gaps. But he says that work is still a ways…down the road.

法南姆表示，其实一些州已经开始使用这种混凝土了，因为相对其他因素——例如钢筋内部腐蚀，它能使材料更耐用的特性已被人们熟知。至于美国422号公路和其他公路上的裂痕？法南姆正在进行另一个项目——即填涂能与盐相互作用形成石灰石的细菌泥浆，从而封堵开裂处。不过他表示，该项目仍然……还在进行中。