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Fracture Mechanical Behavior of Aggregate-Cement Matrix Interfaces

• ID:

  966

• ESCSI:

  4378.002

• Author:

  Tschegg, E.K.; H.M. Rotter; P.E. Roelfstra; V. Bourgand; P. Jussel

• Publication Name:

  Journal of Materials in Civil Engineering

• Type of Publication:

  Paper

• Publisher:

  American Society of Civil Engineers

• Dated:

  1995

• Issue/Volume:

  November, No. 4, Vol. 7

• Other ID:

• Page(s):

  199-203

• Reference List:

  Y

• Abstract:

  This article is not about LWAC. It is of interest because of the information provided on “Contact Zone”.Cracks in concrete propagate preferentially along cement-aggregate interfaces. Therefore, these interfaces act like weak links. The fracture mechanical behavior of the interfaces can be described quantitatively by means of the specific fracture energy Gf, which is obtained from the load-displacement curve of the wedge-splitting test. The Gf values of the selected sandstone-matrix and limestone-matrix composites varied between 6 and 18 N/m, although the specific fracture energy of the matrix was about 80 N/m; this means that the resistance against crack propagation of interfaces between aggregate surfaces and matrix is only 1/6th of the cement-matrix resistance. This demonstrates the different behavior of the interfaces compared to the matrix. Testing composite specimens of different dimensions showed that there is only a small size effect in the fracture surface area range of 22.5-85 cm2 (ligament length approximately 4.8-8.4 cm). In the range of 22.5-45 cm2 (ligament length approximately 4.8 cm), an augmentation of the fracture surface area leads to an increase of the Gf value of the cement matrix. Above 45 cm2 (ligament length approximately 4.8 cm), Gf remains almost constant.