Title no. 85·M32 Effect of Temperature and Humidity on Fracture Energy of Concrete

Fracture experiments were conducted at temperatures from 20 10 200 C (68 to 392 F) to determine the dependence of che Mode I fracture energy of concrete on temperaTure as well as The specific water con-tent. The fracTure energy values were determined by testing geometri-cally similar specimens of si::es in the ratio /:2:4:8 and chen applying Bazanr's size effect law. Three-poinr bend specimens and eccenrric compression specimens are found to yield approximately the same fracture energies, regardless of temperature. To describe the temper-ature dependence of fracture energy, a recenrly derived simple for-mula based on the activation energy theory (rate process theory) is used and verified by cest results. The tempera;ure effect is deter-mined both for concrere predried in an oven and for wet (saturated) concrete. By inrerpolation, an approximate formula for the effect of moisture coment on fracture energy is also obtained. This effect is. found to be sma/l at room temperature but large at temperatures c/ose to 100 C (212 F)