Study of self consolidating concretes stability during their placement

Because of their great fluidity, Self Consolidating Concretes (SCCs) can be poured into large-sized formworks or through a thick iron framework without using vibration. However, a wrong proportion of concrete or an unsuited method of filling can generate a heterogeneous distribution of its various constituents. Numerous devices have been developed to locate the heterogeneities. Some of them allow on-site measurement, while others require sampling. A technique of gamma-ray attenuation was adapted to measure local changes in concrete density. SCC with different castings process in formworks of 15 m long and 5 m high and others with 10 m high and 5 m long were investigated. Test results show a variation of aggregates concentration in the concrete wall according to the flowing distance or to the pouring height. The paste thickness at the wall could be appreciated with this technique.

► Gamma absorptiometry is an effective non-destructive method to follow the fresh concrete flowing.
► The casting process by pumping presents a better homogeneity of the concrete inside the formwork.
► The quality of the coating can be evaluated for different casting processes with gamma-ray attenuation measurement.
► Mechanism taking place in the injection zone responsible of some heterogeneities can be observed.
► The maximum distance of SCC flowing across frameworks or along a surface from large-sized walls can be evaluated.