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CE196H quiz 3

Terms in this set (57)

what does SCM stand for?
supplementary cementitious material
SCM's were previously known as
supplementary cementing materials, pozzolans, and mineral admixtures
How much % of concrete includes SCMs?
60%
What is the definition of an SCM?
a material that, when used with portland or blended cement, contribute to the properties of concrete through hydraulic or pozzolanic activity, or both
What is a hydraulic cement?
a hydraulic cement reacts with water and forms hydration products and is capable of doing so underwater
Why bother with SCMs?
economic benefits, environmental benefits, lower heat of hydration, and better concrete
Pozzuoli is also known as?
Pozzolana which is also known as a pozzolan
What is a pozzolana?
volcanic ash and pumice
Definition of Pozzolan
a seliceous or aluminoseliceous material that, in finely divided form and in the presence of moisture, chemically reacts with calcium hydroxide (CH) to form calcium silicate hydrate and other cementitious compounds
What is C-S-H?
primary glue that binds together aggregates and provides for strength and impermeability
What is CH?
poor binder that is prone to leaching and is easily attacked by acids, but it occupies 20-25 percent of typical cement paste
What is amorphous silica?
it is from pozzolanic material, like silica fume, fly ash, natural pozzolan
Silicon makes up what percent of the earth's crust?
28%
What are the types of SCMs?
natural pozzolans like volcanic ash, pumice, diatomaceous earth, chert, shale

processed natural like crushed brick or clay tiles, metakaolin (calcined clay)

Rice husk ash (rice-hull ash)

waste by-products like fly ash, slag cement, silica fume, these are more commonly use SCMs
Hydraulic SCMs include?
slag cement, class c fly ash, natural cement into cement rock, and hydrated lime

behaves similarly to OPC but reacts more slowly
Pozzolanic SCMs include?
clay, chert, shale, class f fly ash, silica fume, and metakaolin

material must be finely-ground (no. 325 sieve)
glassy or amorphous
combined with cement and water
Details about Fly ash? (What is it rich in, by-product of what, price and size compared to OPC, processing)
most widely used SCM in concrete
rich in silica and alumina, iron, calcium
by-product of the coal industry
cheaper than OPC and similar in size
No additional processing required
Class C fly ash characteristics (CaO level, SiO2 level, hydraulic or pozzolanic, how is it produced)
CaO is greater than 18%
SiO2 + Al2O3 + Fe2O3 > 50 %
hydraulic and pozzolanic
produced from burning PRB coal
Class F fly ash characteristics (CaO level, SiO2 level, pozzolanic or hydraulic, compared to class C)
CaO is less than or equal to 18%
SiO2 + Al2O3 + Fe2O3 >70 %
pozzolanic
more effective than class C fly ash in mitigating ASR and sulfate attack
exhibits less set retardation and lower early strengths
Fly ash particles shape
spherical, which reduce water demand compared to portland cement, which leads to increased workability (ball-bearing effect)
why are fly ash particles round?
because they are cooled very quickly
effects of fly ash on water demand (25% vs 50%)
25% fly ash gives 5.7% average water reduction
50% fly ash gives 12.7% average water reduction
effects of class c fly ash on strength compared to class f?
class c fly ash catches up to the straight cement mix in about 7 days (more hydraulic than class f)

class F usually takes 28 to 56 days to reach the strength of the straight cement mix, more pozzolanic than class c fly ash
What is slag cement previously known as?
ground granulated blast furnace slag (GGBFS)
Slag must be quenched with?
water or else slag won't be reactive
slag cement characteristics of air-cooled vs quenched
air-cooled has a crystal structure
quenched has a glassy structure
Slag cement includes what chemicals?
CaO (32-45), SiO2 (32-42), Al2O3 (7-16), Fe2O3 (0.1-1.5), MgO (5-15), and MnO (0.2-1)
slag cement characteristics? (Price compared to OPC, hydration products compared to OPC, when it's combined with OPC, higher temperature and high fineness give what reaction, U.S. replacement %)
as expensive as OPC
similar hydration products to OPC (no CH) but reaction is slow
when combined with OPC, alkalies and lime act as activators and allow slag to react faster
higher temperature, higher reaction
higher fineness, higher reaction
U.S. has up to 50% replacement
Europe has 80% replacement and requires additional activator like NaOH
slag cement particle shape?
angular- shaped, most particles smaller than 45 micrometers (same size as cement)
why use slag cement? (Environment, heat of hydration)
environmental benefit
mass concrete- lower heat of hydration at high replacement levels
long-term strength and durability
marine concrete (dense concrete with low permeability)
Silica fume is known as
microsilica, which is residue from producing silicon metals and ferrosilicon alloys
Silica fume products
as-produced silica fume, which creates densified silica fume (most common) and silica fume slurry
Silica fume characteristics (ASTM, SiO2 level, particle description)
ASTM C 1240
typically 90-99% SiO2
gas rapidly cooled into solid creates amorphous spherical particles
silica fume particle sizes? (Size compared to OPC, description, how many fume particles for everyone one OPC particle)
0.1 micrometer, 100x smaller than PC
fine glassy spherical particles
for concrete mix with 8% silica fume, there are about 275,000 silica fume particles for every one OPC particle
increased particle packing means higher strength and durability
silica fume challenges (price, where is it produced, side effects of health and production)
600-700$ per ton
mainly produced by nordic countries
can cause lung cancer
requires a superplasticizer
requires (high-shear mixer)
requires special care after casting to prevent plastic shrinkage cracking
silica fume applications
marine concrete
high-rise buildings
parking structures
shotcrete
bridge decks
ultra high performance concrete
calcined clay characteristics
most common natural pozzolan
calcined kaolin or metakaolin is the most common
metakaolin characteristics (calcined at what temp, size of particles, size compared to PC and silica fume, weight, dosage)
calcined at 650 to 800 C
ground to 1-2 micrometers, about 1/10th the size of PC and 10 times the size of silica fume
high whiteness
300-500 per ton
10 - 15 % dosage
What is ITZ?
interfacial transition zone, weakest part of concrete
what is the wall effect?
higher packing density in middle (away from wall), lower packing density at wall
Wall effect in concrete?
higher packing density away from aggregate, lower packing density at aggregate
SCMs lead to what in the ITZ?
reduced porosity, reduced permeability, increased compressive, tensile and bond strength
Higher SCM% gives you faster or slower rate of carbonation?
faster
faster carbonation gives you higher or lower corrosion probability?
higher
Which of the following will lower water demand?
A) class f, class c, silica fume
B) class f, metakaolin
C) class f, class c, slag cement
D) calcined shale, calcined clay
C
Which of the following will increase water demand?
A) class f, class c, silica fume
B) silica fume, metakaolin
C) class f, class c, slag cement
D) calcined shale, calcined clay
B
Which of the following has no impact on water demand?
A) calcine shale, calcined clay
B) silica fume, metakaolin
C) class f, class c, slag cement
D) calcined shale, calcined clay, metakaolin
A
which of the following will increase workability?
A) class f, class c, slag cement, silica fume, metakaolin
B) class f, class c, slag cement, silica fume, calcined shale
C) class f, class c, slag cement, calcined shale, calcined clay
D) metakaolin, class c, slag cement, silica fume, calcined shale
C
which of the following will decrease workability?
A) slag cement, silica fume
B) silica fume, metakaolin
C) slag cement, class c fly ash
D) silica fume, class f fly ash
B
which of the following increases setting time?
A) class f, slag cement
B) class c, slag cement
C) metakaolin, calcined clay
D) metakaolin, silica fume
A
which of the following may increase or decrease setting time?
A) metakaolin
B) calcined clay
C) class c
D) class f
C
which of the following has no impact on setting time?
A) silica fume, calcined shale, calcined clay, metakaolin
B) silica fume, calcined shale, metakaolin, class c
C) silica fume, calcined shale, calcined clay, class f
D) silica fume, calcined shale, calcined clay, slag cement
A
which of the following will decrease heat of hydration?
A) class f, slag cement, metakaolin, calcined clay
B) class f, slag cement, silica fume , calcined clay
C) class f, slag cement, calcined shale, metakaolin
D) class f, slag cement, calcined shale, calcined clay
D
which of the following may increase or decrease heat of hydration?
A) class c
B) class f
C) calcined shale
D) calcined clay
A
which of the following has no impact on heat of hydration?
A) silica fume, calcined clay
B) silica fume, metakaolin
C) silica fume, class c
D) silica fume, class f
B
which of the following increases long term strength gain?
A) class f, slag cement, silica, calcined clay, calcined shale, metakaolin
B) class f, class c, slag cement, calcined clay, calcined shale, metakaolin
C) class f, class c, slag cement, silica, calcined clay, calcined shale, metakaolin
D) class c, slag cement, silica, calcined clay, calcined shale, metakaolin
C
which of the following decreases permeability and absorption?
A) class f, class c, slag cement, silica, calcined clay, calcined shale, metakaolin
B) class f, slag cement, silica, calcined clay, calcined shale, metakaolin
C) class f, class c, slag cement, calcined clay, calcined shale, metakaolin
D) class c, slag cement, silica, calcined clay, calcined shale, metakaolin
A
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