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18 Cards in this Set
- Front
- Back
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Disadvantages of Conventional Concrete |
low young modulus low compressive, tensile and flexural strength high porosity fractures easily |
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Hardened Cement Paste |
multiphase composite material consists of a plastic network of hydrated cement particles, unhydrated cement, pores, and water |
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Pores in HCP |
Interlayer pores Capillary pores Air pores |
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Fundamental concept of improved concrete |
enhanced micro structure |
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Role of superplasticizers |
reduction in water demand without ruining workabiliby better packing in the matrix deflocculation of cement particles |
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Main exothermic reaction |
cement and water makes CSH (calcium silicate hydrate) which provides the strength |
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Types of admixtures |
plasticizers set-controllers air-entrainers |
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What makes good concrete? |
workability and cohesiveness in fresh state strength and durability in hardened state |
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Factors influencing concrete strength |
water:cement ratio aggregates temperature humidity age cement type |
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Advances in concrete technology |
new admixtures supplementary cementitious materials (fly ash, ggbfs, silica fume) |
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Supplementary cementitious materials Fly ash and GGBFS use |
can replace over 40-80% of concrete w/out strength reduction sustainable durable (less porous) increased workability void reduction |
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Supplementary cementitious materials Silica fume use |
used as a filler improves packing of particles increases strength and durability |
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Geopolymer "cementless" concrete |
uses alkaline solutions instead of water to insure activation of a reaction for bonding |
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Self-compaction concretes |
high fluidity (super plasticisers) silica fume of 5-15% increased workability must maintain cohesiveness less coarse aggregates more uniform nicer surface |
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Nano tech concrete |
more water is needed because of the small particle size (increase absorption) |
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Characteristic strength |
value that below it is unlikely that more than 5% of results will fall |
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Concrete Mix Design Steps |
1: select slump 2: max aggregate size 3: water, air 4: water:cement ratio 5: cement content 6: coarse aggregates 7: fine aggregates 8: water corrections (step 3 + absorption - moisture) |
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Future developments for concrete |
mix optimization waste material utilization composite applications increased durability retrofitting nanomaterial developement |
