Modelling of gas permeability in selfcompacting concrete: Fid-Bau Portal

Modelling of gas permeability in selfcompacting concrete

Boel, V. / Audenaert, K. / Schutter, G. de

The past years, the applicability of self-compacting concrete (SCC) has already been proven. As this kind of concrete can be placed without any compaction some health risks as well as environmental problems can be avoided and durability problems related with badly vibrated concrete would be reduced. Two of the essential properties of SCC, a high flowability and a high segregation resistance, are obtained by a large amount of fine particles and the use of superplasticizers. Earlier research on the pore structure pointed out an important difference between SCC and traditional concrete (TC). Since the transport properties of concrete are strongly depending on its pore structure, the question rises to what extent the gas permeability of SCC gets affected by the change in mixture design. The first part of this paper reflects a more extended investigation on one SCC and one TC mixture. In the following part, the gas permeability of 16 SCC mixtures and 4 TC mixtures is being evaluated with special attention to the difference between SCC and TC, and the influence of the following parameters' type of cement, fineness of filler, type of filler, cement/powder ratio, powder content, water/cement ratio and type of aggregate. It was concluded that the gas permeability of SCC is about 5 times lower than the gas permeability of TC. The parameter with the largest impact on the gas permeability seems to be the water content and secondly, the powder content. Finally a model based on the capillary porosity is presented to predict the gas permeability of both concrete types.