CIVE 202 Study Guide - Final Guide: Ground Granulated Blast-Furnace Slag, Gypsum, Fly Ash

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25 Aug 2016
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CIVE 202 Review
Concrete
Additional water added to concrete during mixing is detrimental, but applying water
during curing is beneficial. Explain the difference between the effects of water
addition at these two times and describe what specific point in the microstructure
development of the hydration cement paste separates them.
Adding additional water during mixing will push cement grains fallen apart, so that they may
not be able to interlock and form the cement matrix
Additional water may also create excess voids
Adding water during the set is beneficial, once the cement grains have interconnected, no
amount of water will displace them and we want to completely hydrate them. Now we want
to add as much water as possible to hydrate the interconnected cement grains.
The specific point is when mix starts interlocking.
At what point is gypsum added during cement production? What would happen to
concrete made with cement that contained an insufficient amount of gypsum? Why?
Gypsum (CaSO4 •2H2O) is added during grinding during cement production.
Gypsum is added to react with the aluminum phases and prevent a fast set of the cement in
concrete. If the amount of gypsum is insufficient, the concrete would set very rapidly.
What effects do air entraining admixtures have on hardened concrete? Why? 8
Air entraines create very small air filled void spaces,
Results in stable bubbles that persist through hydration
this helps hardened concrete last longer and be more durable, but lowers strength.
During freeze/thaw water will have pores to expand into -- Freeze-Thaw durability
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