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Some durability aspects of fiber reinforced self-compacting concrete
Self-compacting concrete can be placed and compacted under its own weight without any vibration effort, assuring complete filling of formworks even when access is hindered by close reinforcement bars. In order to achieve such a behavior, the fresh concrete must show both high fluidity and good cohesiveness at the same time. Earlier studies, without modern acrylicbased superplasticizers or the new viscosity modifying agents available, just with melamine or naphthalene based superplasticizers with a relatively high content of powdered materials showed a very high effectivity. The present work stems from that experience and aims at evaluating the durability of this material. A self-compacting concrete was designed for thin pre-cast elements, showing both high mobility through narrow sections and high segregation resistance. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel reinforcing mesh were added to the concrete mixture at a dosage of 10% by weight of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40 and the required resistance against segregation was obtained by adding a limestone powder to the mixture at a dosage of 16% by weight of cement. Compression and flexure tests were carried out up to 180 days of wet curing to assess the safety of these thin concrete elements. Moreover, some durability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out for up to 180 days of exposure in a 50% relative humidity environment, in order to evaluate the contribution of steel fibers in counteracting the high concrete strains due to a low aggregate-cement ratio. Secondly, both carbonation and chloride penetration tests were carried out to assess the vulnerability to corrosion of steel fibers. The concrete met both the self-compaction requirements, while fresh, and the compressive strength requirement of 40 MPa, when hardened. The fibers addition proved to be very effective in counteracting drying shrinkage of self-compacting concrete, which is usually a great problem for this material, rich in powders and poor in the coarse aggregate fraction. Due to the very low porosity of its cementitious matrix, this concrete was penetrated very slowly by chloride ions, after which it proved durable. As a consequence, corrosion of steel fibers does not occur, at least not within the time frame for drying shrinkage to develop.
Some durability aspects of fiber reinforced self-compacting concrete
Self-compacting concrete can be placed and compacted under its own weight without any vibration effort, assuring complete filling of formworks even when access is hindered by close reinforcement bars. In order to achieve such a behavior, the fresh concrete must show both high fluidity and good cohesiveness at the same time. Earlier studies, without modern acrylicbased superplasticizers or the new viscosity modifying agents available, just with melamine or naphthalene based superplasticizers with a relatively high content of powdered materials showed a very high effectivity. The present work stems from that experience and aims at evaluating the durability of this material. A self-compacting concrete was designed for thin pre-cast elements, showing both high mobility through narrow sections and high segregation resistance. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel reinforcing mesh were added to the concrete mixture at a dosage of 10% by weight of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40 and the required resistance against segregation was obtained by adding a limestone powder to the mixture at a dosage of 16% by weight of cement. Compression and flexure tests were carried out up to 180 days of wet curing to assess the safety of these thin concrete elements. Moreover, some durability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out for up to 180 days of exposure in a 50% relative humidity environment, in order to evaluate the contribution of steel fibers in counteracting the high concrete strains due to a low aggregate-cement ratio. Secondly, both carbonation and chloride penetration tests were carried out to assess the vulnerability to corrosion of steel fibers. The concrete met both the self-compaction requirements, while fresh, and the compressive strength requirement of 40 MPa, when hardened. The fibers addition proved to be very effective in counteracting drying shrinkage of self-compacting concrete, which is usually a great problem for this material, rich in powders and poor in the coarse aggregate fraction. Due to the very low porosity of its cementitious matrix, this concrete was penetrated very slowly by chloride ions, after which it proved durable. As a consequence, corrosion of steel fibers does not occur, at least not within the time frame for drying shrinkage to develop.
Some durability aspects of fiber reinforced self-compacting concrete
Corinaldesi, Valeria (author) / Moriconi, Giacomo (author)
2004
10 Seiten, 5 Bilder, 4 Tabellen, 10 Quellen
Conference paper
English
Some durability aspects of fiber reinforced self-compacting concrete
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