BE-13 Renovation: Lining with Cured-In-Place Pipes - F...

3-Point Flexural Test

3-Point Flexural Test

The 3-point flexural test (EN ISO 178 and EN ISO 11296-4) is used to determine the short-term flexural modulus and the flexural stress at first break.

In addition, the static load-bearing design thickness and the total thickness of the CIPP liner are determined, for which specifications from the static calculation and from the construction contract are available.

Target specifications for the mechanical characteristic values “flexural modulus” and the “flexural stress“ can be found in the general building authority approvals for the respective lining tube (in short: DIBt approval).

The size of the flexural modulus is influenced by many factors, including:

  • Temperature
  • Humidity
  • Speed of testing
  • Curing degree
  • Geometry
  • Fibre connection
  • Fibre alignment
  • Filler content
  • Cross-linking density
  • Proportion of residual monomer
  • Proportion of additives (oils)
 

Table: 

3-point flexural test specifications according to [ENISO 11296-4:2018]
Characteristic Requirementa Test parameters
Parameter Value
Short-term flexural modulus, E0
Declared value in MPa
Number of test samples
Speed of testing
5

10 mm/min
Flexural stress at first break, σfb
Declared value in MPa
Flexural strain at first break, εfb
Declared value but not less than 0,75 %
a Declared values refer to the mean value of each characteristic as determined from the results of tests on a set of the specifies number of test pieces.

 

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