Free Water in Concrete Pores: an Attempt of Physical Explanation of Concrete Dynamic Behavior

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Title: Free Water in Concrete Pores: an Attempt of Physical Explanation of Concrete Dynamic Behavior

Author(s): Francois Toutlemond and Pierre Rossi

Publication: Special Publication

Volume: 175

Issue:

Appears on pages(s): 261-280

Keywords: compressive strength; concretes; dynamic loads; tests; water-cement ratio

Date: 12/1/1998

Abstract:
A large experimental program has been carried out in order to better under-stand basic physical mechanisms explaining rate effects on concrete strength. Direct tensile tests and compressive tests were performed on different con cretes. Slab tests using a shock tube were also carried out using the same materials. It has been demonstrated that for intermediate strain rates (about 1O-5 to 1 s ) the strength enhancement can be explained by the presence of free water in the nanopores of concrete. A mathematical expression is pro-posed which accounts for the role of significant parameters. The slab tests confirm the physical analysis developed at the material level. Some specific phenomena (possible occurrence of either shear failure or bending failure, relative smaller strength enhancement than in direct tension) confirm the ne-cessity of models based more on the physical properties of the material for structural analysis in dynamics.