concrete 4 Flashcards
what are the 2 types of deformation in concrete?
initial deformation and long term deformation
draw the graph for the initial deformation?
see notes
what are the 2 types of plastic shrinkage in concrete?
thermal shrinkage and drying shrinkage
what is the cause of long term deformation?
loss of stiffness
what is another meaning of stiffness?
modulus of elasticity
draw the graph for the long term deformation?
see notes
what are the equations given by the eurocode 2 for finding the modulus of elasticity
see notes
how does creep affect the stiffness?
it causes the stiffness to decrease; concrete loaded for 28 days loses 2/3 of stiffness
why does concrete need to be durable?
it is expensive to repair and maintain
what are the 2 types of durability?
visual deterioration (colour change, visual cracks and moulds) and internal deterioration (chemical. physical and steel rusting)
what does the durability rate depend on?
air, water, chemicals, porosity and permeability
what is porosity?
how much water can get in
what is permeability?
how much water passes through it
what is freeze thaw?
when the water within he concrete freezes due to cold weather which causes cracks within the concrete
what can reduce porosity?
admixtures and compaction
describe 3 chemical internal deterioration?
sulphate attack, seawater attack and acid attack (carbonation) see notes
list ways to reduce sulphate attacks and acid attacks
sulphate attacks: additives (PFA, GGBS)
acid attacks: thick concrete, covering steel with zinc, using stainless steel
