Question

土木工程专业英语翻译

Curing Concrete
When a batch of concrete is first mixed, it forms aplastic mass that can be poured into prepared forms with little effort. Inabout an hour the concrete sets into a rigid mass that weighs about 150 lb percu ft. The cement paste is said to hydrate, that is, the individual particlesof cement absorb the surrounding molecules of water into their molecularstructures. As they do, the cement crystallizes into a kind of rigid gel,something like gelatine, that gradually changes with the passing of time into asolid mass of minute, interlocked crystals. The longer hydration continues, thestronger the concrete will become. It is standard engineering practice,therefore, to calculate the final design strength of concrete on the basis of a28-day curing period, although under exceptional conditions concrete has beenknown to continue increasing in strength for a quarter of a century and longer.
The time during which concrete hydrates and increasesin strength is its curing period. Concrete cannot hydrate, or cure, unlessthere is water present within the concrete. Throughout the curing period,therefore, all the exposed surfaces of the concrete must be kept moist. As longas the concrete is kept moist, curing will continue and the concrete will becomeincreasingly stronger, denser, and more impervious to water.
Once concrete is allowed to dry out completely,however, hydration stops. Usually it is the surface of concrete that isadversely affected by a too-short curing period. For example, the surface of asample of concrete that has been kept moist for 28 days will be twice as strongas a surface that has been kept moist for only 3 days.
The outside air temperature is an extremely importantfactor in proper curing. If the air temperature is too high, over 90°F, say, the water in the concrete may evaporate awaybefore hydration can be completed. An excessive internal temperature may alsointerfere with proper hydration. Concrete that has been mixed and placed duringvery hot weather is never as strong as concrete that has been placed when theair temperatures are 70°F and below,mainly because of the difficulty of keeping the concrete properly moist. Furthermore,concrete that sets too quickly during hot weather is more likely to crackafterward because it will have shrunk an excessive amount during is curing, andit will not thereafter be able to withstand the stresses imposed on it by largechanges in temperature.
Nor can concrete be placed during freezing weatherunless special precautions are taken to keep the concrete above 50°F, for at least 4 days after it has been placed. Ifthe temperature of the concrete should fall below 50°F, it will never harden properly. And if the concreteis allowed to freeze before it has set, it will be permanently damaged.

Answer 1

养护混凝土
当一批混凝土第一次被混合，它们形成流体态，可以很容易地被倒进准备好的模具里。经过大约一小时时间形成一个刚性质量体，重约150磅/立方英尺。得到的水泥砂浆是水合物，即单个粒子的水泥吸收周围的水分子进入他们的分子结构。当它们发生这样的变化时，经过数分钟，水泥结晶成一种刚性凝胶，类似于胶质，,随着时间的流逝逐渐变为固体，形成结构紧密的晶体。水化的时间越长，混凝土的强度越大。这是标准(养护)工程的通常做法，因此，在经过28天养护期的基础上计算混凝土的设计强度，尽管我们已经知道特定环境下的混凝土强度在四分之一个世纪或更长的时间内会继续增长。
混凝土形成水合物和增加强度的时期是养护期。除非混凝土含有一定的水分，否则混凝土不能形成水合物或养护,。因此，在整个养护期，混凝土所有表面的必须保持湿润。只要混凝土保持湿润,养护将继续进行，混凝土强度将不断增大，密度增大，渗水性下降。
一旦混凝土完全脱水，水合作用即停止。通常是由于养护时间不足对混凝土表面造成负面影响。例如，一块经过28天湿润养护的混凝土的强度将两倍于同样的一块只被养护3天的混凝土。
室外气温是保证合适的养护的一个非常重要的因素。如果气温太高，比如超过90°F，混凝土就会在水分完全蒸发前完成水化。过高的内部温度也会影响正常的水合作用。被混合并放置在很热的气候环境下的混凝土，其强度远不如被放置于低于70°F的气温中的那些，这主要是因为（在过高的温度条件下）很难保持混凝土的湿润。此外，那些在炎热天气里迅速成型的混凝土之后更容易产生裂缝，因为它在养护期间过度收缩，而不能承受由气温变化大而引起的拉力。
它也不能被放置在寒冷气温里，除非已经事先采用特殊措施使得混凝土温度被保持在高于50°F,且（成型后）至少被放置4天。如果混凝土养护温度低于50°F，它将永远不会达到合适的硬度。如果混凝土在养成结束前被冷冻，它将被永久破坏。

自己翻译的、