APPARENT STRENGTH RETROGRESSION OF SILICA-FUME CONCRETE

In recent years, use of silica-fume concrete has become more prevalent . Recently, a few researchers expressed concerns about the long-term s trength retrogression they found when studying the compressive and fle xural strengths of air-cured silica-fume concrete, while other researc hers did not find any strength retrogression in apparently similar exp erimental conditions. These contradictory results are not supported by the few field results obtained on cores where compressive strength st ability, at least, has always been observed. The objective of this pap er is to develop fundamental information on the long-term behavior of some silica-fume concretes after a long dry air curing. Scope of the w ork includes a review of available literature on long-term compressive strength of concrete specimens submitted to air curing. This literatu re review is followed by the presentation of the drying behavior of tw o silica-fume concretes and one that does not contain silica fume. Exp erimental results show that these three concretes dry in different way s. After a certain period of time, one can exhibit a strong moisture g radient, while others do not. An explanation of the apparent strength loss of the silica-fume concrete is proposed. If this explanation is a ccepted, it is shown that the apparent strength loss can never be more than two times the tensile strength of concrete. This theoretical max imum strength retrogression agrees well with the published data.