concrete 4

Question 1

what are the 2 types of deformation in concrete?

Answer 1

initial deformation and long term deformation

Question 2

draw the graph for the initial deformation?

Answer 2

see notes

Question 3

what are the 2 types of plastic shrinkage in concrete?

Answer 3

thermal shrinkage and drying shrinkage

Question 4

what is the cause of long term deformation?

Answer 4

loss of stiffness

Question 5

what is another meaning of stiffness?

Answer 5

modulus of elasticity

Question 6

draw the graph for the long term deformation?

Answer 6

see notes

Question 7

what are the equations given by the eurocode 2 for finding the modulus of elasticity

Answer 7

see notes

Question 8

how does creep affect the stiffness?

Answer 8

it causes the stiffness to decrease; concrete loaded for 28 days loses 2/3 of stiffness

Question 9

why does concrete need to be durable?

Answer 9

it is expensive to repair and maintain

Question 10

what are the 2 types of durability?

Answer 10

visual deterioration (colour change, visual cracks and moulds) and internal deterioration (chemical. physical and steel rusting)

Question 11

what does the durability rate depend on?

Answer 11

air, water, chemicals, porosity and permeability

Question 12

what is porosity?

Answer 12

how much water can get in

Question 13

what is permeability?

Answer 13

how much water passes through it

Question 14

what is freeze thaw?

Answer 14

when the water within he concrete freezes due to cold weather which causes cracks within the concrete

Question 15

what can reduce porosity?

Answer 15

admixtures and compaction

Question 16

describe 3 chemical internal deterioration?

Answer 16

sulphate attack, seawater attack and acid attack (carbonation) see notes

Question 17

list ways to reduce sulphate attacks and acid attacks

Answer 17

sulphate attacks: additives (PFA, GGBS)

acid attacks: thick concrete, covering steel with zinc, using stainless steel