concrete time depandant behavoiur

Question 1

What influences the time dependent behaviour of concrete ?

Answer 1

• Age / Maturity
• Environmental influences and storing conditions (temperature, humidity, loading time)
• Type of loading (cyclic, constant)

Question 2

Deformation behaviour of Concrete

Answer 2

The deformation of concrete are divided in stress independent and stress dependent. The two are further divided in time independent, instantaneous and cyclic

Question 3

What is the Rheological and the Burgers model of concrete?

Answer 3

• Rheological model of concrete is a combination of three elements:
  
  • spring
  • dashpot
  • St. Venant element (in case of cracking)
• Burgers model used to describe the behavior of concrete: Concrete shows visco-elastic behavior

Question 4

Shrinkage (contracción) & Creep

Answer 4

• Creep and shrinkage are time-dependant deformations.
• The factors influencing the time dependent deformations are age/maturity, environmental influences and storing conditions (humidity, temperature, loading time) and type of loading (cyclic, constant).
• Creep and shrinkage, along with cracking provide the biggest concerns in design.

Question 5

On what depends the amount of shrinkage and what is the autogeneous shrinkage?

Answer 5

• The amount of shrinkage depends on:
  
  • Time, humidity, type of concrete (high or normal strength), temperature of the environment
• Autogenous shrinkage:
  
  • Sum of chemical shrinkage due to hydration, and internal drying
  • Drying of the specimen results in selfstresses which could cause cracking

Question 6

Define Creep and relaxation. Use diagrams

Answer 6

• The creep factor depends on age, humidity and strength of concrete.
• If deformations are present, the stress will decrease due to relaxation.