Concrete Materials Flashcards
concrete is combination of
cement,
fine+coarse aggregate,
water
concrete admixtures contribute:
particular qualities
concrete strength depends on
materials/proportions
most critical factor in determining strength of concrete
water to cement ratio
Portland cement materials:
lime
+silica
+iron oxide
+alumina
Portland cement supplied in:
bulk or, 94lb bags (1cuft)
Portland Cement
Type I
general application.
“standard cement”,
“normal cement”,
Portland Cement
Type II
“modified cement”
minor sulfate resistance.
hydration heat controlled,
ex. dams/massive structures.
Portland Cement
Type III
quick set.
(+ cold-weather concreting)
“high-early-strength cement”
Portland Cement
Type IV
very slow setting.
massive structures,
to min cracking.
“low-heat”
Portland Cement
Type V
“sulfate-resisting cement”
if exposed to water or soil w/ high alkaline content
excess water not in chemical process forms
pores
typ req water
up to 25% weight of cement
extra ___% more water req’d to make a workable mix
10-15
Water type req’d for cement
potable
typ. min w/c ratio
0.35 - 0.40 by weight
4-4.5 gal per 94lb sack
laitance:
chalky surface deposit of low-strength concrete
laitance may be caused by
excess water
if addt’l conc will be poured, laitance must be:
removed in order to bond
fine aggregates pass through:
no.4 sieve
no.4 sieve has what density openings?
(4 openings per linear inch)
because cement = most $ of concrete, best mix uses
combination of aggregate sizes
that fill most volume while still delivering desired strength.
concrete mix is typ __% aggregate
70-75%
aggregate used for general concrete
sand+gravel (typ. 150 lb/ft3)
