Dave's ESL Cafe's Student Discussion Forums

[christina_nguyen]

"There are many reasons for studying the rate of a reaction. To begin with, there is intrinsic curiosity abou thwy reactions have such vastly different rates. Some processes, such as the initial steps in vision and photosynthesis and nuclear chain reactions, take place on a time scale as short as 10 to the -12 second to 10 to the -16 second. Others, like the CURING OF CEMENT and the conversion of graphite to diamond, take years or millions of years to complete."


what does CURING OF CEMENT mean??

thanks for answering my question.

[asterix]

According to the Portland Association, whose members ought to know:--

After concrete is placed, a satisfactory moisture content and temperature (between 50�F and 75�F) must be maintained, a process called curing. Adequate curing is vital to quality concrete.

Curing has a strong influence on the properties of hardened concrete such as durability, strength, watertightness, abrasion resistance, volume stability, and resistance to freezing and thawing and deicer salts. Exposed slab surfaces are especially sensitive to curing. Surface strength development can be reduced significantly when curing is defective.

Curing the concrete aids the chemical reaction called hydration. Most freshly mixed concrete contains considerably more water than is required for complete hydration of the cement; however, any appreciable loss of water by evaporation or otherwise will delay or prevent hydration. If temperatures are favorable, hydration is relatively rapid the first few days after concrete is placed; retaining water during this period is important. Good curing means evaporation should be prevented or reduced.