Term
| Supplementary Cementing Materials (SCMs) contributes to properties of hardened concrete through: |
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Definition
-Hydraulic Activity
-Pozzolanic Activity
-Both |
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Term
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Definition
Siliceous or alumino-siliceous, finely divided, reacts with hydation products
ei. Silica Fume, Fly Ash |
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Term
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Definition
Natural Material
May be calcined (rice husks) or not (volcanic Ash) |
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Term
(cement) C3S,C2S,C3A,C4AF + Water --> hydration products (CSH, CH) + Heat
What are CSH and CH? |
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Definition
CSH - calcium silicate hydrat, is the binder or glue
CH - calcium hydroxide, no contribution to strength |
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Term
| What will adding silica fume do? |
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Definition
| increase the reaction with S(silicate) with CH to make CSH. |
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Term
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Definition
1) Enhancement of mechanical properties and durability
2) refinement of porosity
3) densification of aggregate-cement paste interface |
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Term
| 1) Enhancement of mechanical properties and durability or Pozzolanic reaction |
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Definition
| increase the reaction with S(silicate) with CH to make CSH. |
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Term
| 2) Refinement of Porosity or physical filler effect |
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Definition
| small particles get in between cement grains to reduce size of voids and permeability (note that # of voids may increase) |
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Term
| 3) Densification of Aggregate cement paste transition zone |
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Definition
| Transition zone between cement paste and aggregate is the weakest and most permeable location. Fine pozzolans play role in transition zone through physical and chemical effects |
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Term
| 5 characteristics of silica fume |
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Definition
smoke-by-product
High silica content
particle size less than 1 micron
Highly reactive pozzolan
surface area 13,000 to 30,000 m^2/kg |
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Term
| Pozzolanic activity measurement |
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Definition
Strength activity index = (A/B) *100
A= compressive strength of blended cement cubes
B= compressive strength of pure cement cubes |
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Term
| silica fume effects on voids and permeability |
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Definition
voids increase, void size decrease, permeability decrease
Also Cohesive and less prone to segregation |
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Term
| Silica fume effects on chloride diffusion |
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Definition
| reduces chloride diffusion and corrosion, increases durability |
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Term
| In order to get increase in durability of adding silica fume you must... |
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Definition
| prevent drying shrinkage cracks to achieve gains in durability of silica fume concrete |
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Term
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Definition
-by product of coal burning
-made of spherical particles
-less effective filler than silica fume |
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Term
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Definition
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Term
| Class F Fly ash (four characteristics) |
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Definition
Low calcium oxide
Calcination of bituminous coal
pozzolanic properties
increases sulfate ressistance |
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Term
| Class C fly ash (four characteristics) |
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Definition
High calcium oxide
calcination of subbituminous coal of lignite
pozzolanic + cementous properties
does not effect sulfate ressistance |
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Term
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Definition
| higher pozzolanic activity |
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Term
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Definition
moderate or severely extended depending on properties of fly ash, temp and mixture properties
Finer fly ash - shorter setting time
Higher Cao content - Shorter setting time |
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Term
| Fly ash on workability and strength |
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Definition
Workability - increases
Strength gain - slower in early phases but final strength is usually higher |
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Term
| Fly ash required to prevent expansion damage due to ..... may be greater than amount necessary for ... |
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Definition
Alkali-aggregate reaction
strength and workability |
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Term
| How does heat of hydration cause cracks? |
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Definition
| On massive concrete elements heat gradient between middle of element and outside can cause cracks |
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Term
| How does fly ash prevent heat of hydration? |
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Definition
| Fly ash reduces core temperature, reduces heat differential |
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Term
| 5 characteristics of Granulated Blast Furnace Slag (GBFS) |
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Definition
Smoother particles
density is lower than concrete, replacement by weight leads to higher paste volume and better workability
at low temperature setting time is increase (slower hydration)
used in low heat of hydration cements |
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Term
| GBFS strength developments |
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Definition
| starts slow but is faster and better at later stages |
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Term
| 3 characteristics of GBFS in Cement |
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Definition
improves fire resistance
lower permeability
expansion due to alkali aggregate reaction lowered as slag increases |
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Term
| 2 types of natural pozzolans |
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Definition
1)Raw volcanic ash
2) calcined (rice husk) |
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