Concrete Tech.

Concrete Tech.

1. cement paste

   • non wet drying
     • slaker lime based cement wont dry
   • wet drying
     • can dry underwater e.g. portland
   • minerals(limeston) = clinker, + gypsum to make cement
   • CAN use any cement BUT
     • has implications for water needed
     • should be fit for purpose
     • wider range doesnt limit you

2. +

3. aggregate

   • relatively cheap filler
   • helps concrete resist load/weathering
   • reduces changes in concrete shape while it sets
   • use any ,but functional

4. =concrete

   • Freshs
     • should be formable(easy to mould)
     • ability to transport and placed without 'segregation' of constituents(cracking/breaking)
     • ability to compact air(within acceptable limit)
     • ability to get reuired finish
   • hardened
     • strength
     • durability
     • surface finish
     • WHAT? - when fresh concrete dries/ sets
   • not paying attention to fresh properties = honeycombing(air voids), seperation, bad finish
     • fresh properties heavily determine success of hardened

5. abrams law

   • performance of concrete inversely proportional to water/cement ration
     • balance needed

6. concrete weaknesses

   • pores/voids
     • bad packing, excess water,
     • hydration system (http://iti.northwestern.edu/cement/monograph/Monograph5_1.html)
   • interfaces
     • zone of microcracks
   • structural
     • cracks
     • incomplete compaction

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