DEVELOPMENT REPORT - Long-Life Concrete Bridges
DEVELOPMENT REPORT - Long-Life Concrete Bridges
By Jill Moss 1
Broadcast: Monday, June 07, 2004
This is Robert Cohen with the VOA Special English Development Report.
Each year, road accidents kill a million people and injure millions more. The economic costs are greatest for developing countries. Earlier this year, the United Nations called for a campaign to improve road safety.
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One way to avoid accidents is better driving. Another is better roads and bridges. Engineers in the United States have designed ten new concrete mixtures that they think could make bridges last longer.
Professor Paul Tikalsky leads the experiments by a team at Pennsylvania State University. He says bridges made of concrete now last about twenty-five to thirty-five years. But he says the new mixtures might extend 3 that to seventy-five or even one-hundred years.
Concrete is made of stone, sand, water and cement 4. The materials in the cement hold the concrete together. Ancient Romans built with concrete. Yet strengthened concrete bridges did not appear until the late eighteen-hundreds. People keep looking for new ways to improve concrete. Professor Tikalsky says it is one of the most complex of all chemical systems.
The new mixtures designed by his team contain industrial waste products. He says these make the concrete better able to resist damage from water and salt over time. One of the products is fly ash. This is released 5 into the air as pollution when coal is burned.
Professor Tikalsky says particles 6 of fly ash are almost exactly the same size and chemical structure as Portland cement. This is the most costly 7 material in concrete. So using fly ash to replace some of it would save money.
Over the next two years, engineers will study ten bridges in Pennsylvania. These were built from the different cement mixtures designed by Professor Tikalsky's team. He says longer-lasting bridges could save the state more than thirty-five-million dollars a year. And he says the materials would be environmentally friendly.
The federal 8 government is paying for part of the research. Engineers anywhere can use the technology. Professor Tikalsky says some of the ideas have already been put to use in China, the Philippines and other countries.
You can find more about this research on the Pennsylvania State University Web site. The address is www.psu.edu. Again, the site is www.psu.edu.
This VOA Special English Development Report was written by Jill Moss. This is Robert Cohen.
- Moss grows on a rock.苔藓生在石头上。
- He was found asleep on a pillow of leaves and moss.有人看见他枕着树叶和苔藓睡着了。
- The book gave a graphic description of the war.这本书生动地描述了战争的情况。
- Distinguish important text items in lists with graphic icons.用图标来区分重要的文本项。
- Can you extend your visit for a few days more?你能把你的访问再延长几天吗？
- The examinations extend over two weeks.考试持续两个星期。
- We need 100 tons of cement at most for this project.这项工程满打满算有一百吨水泥就足够了。
- Let's cement the parts together.咱们来把这些部件粘接在一起吧。
- He was released on bail pending committal proceedings. 他交保获释正在候审。
- With hindsight it is easy to say they should not have released him. 事后才说他们本不应该释放他，这倒容易。
- These small particles agglomerate together to form larger clusters. 这些颗粒聚结形成较大的团。
- The nucleus of an atom consists of neutrons, protons and other particles. 原子核由中子、质子和其他粒子构成。
- It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
- This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。