appliccrtion/ and onologie/
edited by: RON DELORENZO Middle Oewgia College Cochran. Georgia 31014
Growing Concrete Ronald DeLorenzo
HIRE R S H THAT CAN BE EASILY SHAPED INTO ANY FORM
Middle Oeorgia College Cochran. GA 31014
Scientists have worked out a way to "grow"concrete. Various structures, such as buildings, dams, jetties, reefs, pipes, and industrial huildine comoonents. can he "erown" under water hy making rath,'&n out of metal meshshaped in the form of the desired structure. Electrol\~sismaker minerals i n theseawater adhere to the mesh and ihe resulting structure, which has the color and texture of concrete. hut which is a t least 30% stronger, grows a t a rate of 1 in. in thickness per every six weeks. I t has been estimated that many prefahricated industrial building components could be produced and delivered much less expensively by "growing" them under water than by casting them in concrete on site. During electrolysis, hydrogen ions are reduced a t the cathode mesh. and the hvdroeen eas which forms can he trapped, liquefied, and o r &ked ashore as a useful bv-~roductto fuel Dower stations. Hvdroxide ion is also orod;cid. Along with hydrogen . . ions, other vositive metal ions (cations), s k h as magnesium and calci&, are attracted to the cathode. Magnesium and calcium do not plate out a t the cathode because they are more active than hydrogen. As the concentration of magnesium and calcium ions increase in the area of the cathode, however, the K,,'s of magnesium hydroxide (2 X lo-") and calcium carhonate (5 X 10-9) are exceeded and these salts precipitate (see figure). The "concrete" produced is primarily magnesium hydroxide but includes considerable calcium carhonate and smaller quantities of other material. ~
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DEPOSITS OF MGNESIUN AND u L c l u n SALTS BEGIN TO ADHERE TO THE HESH
SOLID WALL (OR OTHER SHAPE) F o u m THAT LOOKS LIKE AND FEELS LIKE CONCRETE
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Example Problem Assume that seawater in the immediate vicinity of a cathode has an approximate pH of 11. What magnesium ion concentration must be present for precipitation of Mg(OHJ2?
Famstion 01 "concrete" by electrolysis
Reference Next. 5 6 6 3 IAoril 1980).
Why Oatmeal Sticks to Your Ribs
Solution pH = 11
Ronald DeLorenzo Middle 080(qa College Cochran. GA 31014
[H+]E 10-11 [OH-] = lo-'
In cold weather it is common for people who eat oatmeal for breakfast to say that the oatmeal sticks to their ribs (rives them a sense of being full longer than would cold cereal).
= [Mg2+][0H-]2 2 x 10-'I = [ M ~ Z 110-92 +J
ms feahre pesems a rnllecna, d wp~icafiarrand analog&
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r e a h have landto be uoeful when pesanling s ~ m 0IUwdinicult e ccmwa hequenlly ewcwtwed in chemish. The blendingof chemisby wlm current applicationsand analogies placer bob chemistry and st+ dent Into a familiar selling, stimulates student interest, and praduces an educated (versus trained) student. Contributions that will produce a greater appreciation and knowledge of pglilical. religious, economic. histwical. and scientific aspects of life are encouraged.
If you have a bowl of cold cereal with a glass of milk, your body must raise the temperature of the cold cereal and the approximately 400 g of cold milk to hody temperature. This is accomplished by the expenditure of as much as 15,000 calories.' Example Problem How many calories must your hody burn to warm 400 g of milk from O°C to 3I0C (normal hody temperature)? Assume, for simplicity, that milk has the same specific heat as water. Volume 58 Number 10 October 1981
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