Fracture properties and process zone length of high strength concrete using size effect method

Abstract EN

This paper gives a report on a fracture mechanics study of high strength concrete with compressive strength up to 80 MPa.

6 mixes were selected, designed to achieve a slump above 100 mm and strength up to 80 MPa..

The investigation used three levels of silica fume (0, 10%, 20% by weight of cement) and two coarse aggregate proportions of total aggregate (0.48, 0.65 by volume) In each case, compressive strength, splitting tensile strength, flexural strength fracture energy Gf and fracture process zone cf were determined.

A test method for determining fracture energy Gf and process zone length cf, defined by the size effect law and its generalized theory, has been proposed.

It allows the use of specimens of the different size and shape but with same notch lengths.

This paper proposes test and data analysis procedures.

The results obtained by the Size effect law (SEL) apparently follow the trend of fracture energy increasing as the compressive strength of the concrete increases.

On the other hand, process zone length cf decrease considerably with increase in strength.

The Bazant’s size effect law gives a very good account of the size dependency of flexural strength for both normal and high strength concrete.

As observed in the size effect curve, the fracture behavior of the HSC seems to be more brittle than that of the normal strength concrete.

Linear elastic fracture mechanics (LEFM) may be applicable to HSC in the normal size range than nonlinear fracture mechanics.