metakaolin; SCM; SCC; mortar spread; flow time; viscosity

What is it about?

Self-compacting concrete (SCC) production is a complex operation that requires finding a good combination and suitable dosages for its constituents. Several formulation methods have been developed to meet the workability requirements of SCC. Mortar spread is used to estimate SCC’s rheological properties, but the use of supplementary cementitious materials, such as metakaolin, could affect the accuracy of the estimation. In this paper, the relationships between the fresh properties of local-metakaolin (MK)-based SCC and the spreading of its mortar portion were investigated. The results showed the existence of good correlations between the spreading of mortar portion of SCC and its fresh state properties. The partial substitution of cement with MK did not affect these correlations. The mortar flow should be chosen according to the required rheological properties of the SCC. This can be achieved by using an appropriate viscosity-enhancing agent (VEA).

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Why is it important?

The content of MK as cement substitution does not change the relationship between the SCM and its related SCC properties such as slump flow spread, V-funnel time, L-box filling rate, J-ring height difference and segregation resistance. The choice of spreading value of the SCM can be used to obtain the SCC fresh properties with a Dmax equal to 20 mm. These include a spread value of the SCC between 600 mm and 750 mm, a flow time (Tv) of 10 s, a filing rate value between 0.80 and 0.85, and a Pj value less than 10 mm. The use of VEA for an SCC with a higher spread (Class SF) and low viscosity (Class VS1) is needed to have a good resistance to segregation.

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