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CONCRETE TECHNOLOGY42 CPI %u2013 Concrete Plant International %u2013 5 | 2025 www.cpi-worldwide.comare not completely filled, increasing the amount of plasticizer will not lead to further fluidization of the fresh concrete. Instead, it may result in segregation and instability due to exceeding the saturation point of the given concrete mix.In addition to a sufficient paste content, the cohesion of the paste is a crucial factor in the mix design of fresh concrete. Accordingly, when developing concrete mixes, particularly low-water concretes where consistency is primarily adjusted through the use of plasticizing admixtures, the minimum water demand of the constituent materials used becomes a key parameter. This minimum water content represents a threshold value, taking into account the specific constituent materials, that ensures both the potential for fluidization and adequate cohesion of the fresh concrete.One method for determining the minimum water demand is the approach described in Section 3. However, this requires knowledge of the aggregate properties with respect to the surface water demand Vw,s. Another method for determining the minimum water demand is the so-called \describes the consistency of a fresh concrete mix made with specific constituent materials without the use of plasticizing admixtures. Extensive practical experience with conventional concretes shows that high fluidity combined with good stability can be achieved if the fresh concrete %u2013 using the specific constituent materials and no plasticizer %u2013 reaches a slump flow of approximately 38 cm (consistency class F2). It should be noted that this value is based on practical experience and may vary depending on the approach; it can be set slightly lower or higher. Even with lower slump flows, fluidization is still possible, though the fresh concrete tends to become stickier or more viscous (higher plastic viscosity) and generally less robust. To determine \flow can be measured using the specific constituent materials while systematically varying the water content. This method directly reflects relevant influences of the mix composition and characteristics of the raw materials. Any change in the raw materials affects the zero-consistency of the resulting fresh concrete to varying degrees (see Section 3). The lower the zero-consistency, the less robust the fresh concrete becomes when adjusted to the same higher consistency through different plasticizer dosages. Consequently, higher dosages of plasticizer are needed to achieve sufficient fluidization when the fresh concrete exhibits a lower zero-consistency.Figure 4 shows the water content as a function of slump flow for various concrete mixtures with different constituent materials (cement and sand) and cement contents (340 and 360 kg/m%u00b3). As expected, slump flow increases with increasing water content across all variations. For each mixture, there is an almost linear relationship between these two parameters. Accordingly, the required water content (WNullk,38cm) to achieve a slump flow of 38 cm can be determined for a specific concrete mix using linear regression. As shown in Section 3, the required water content is particularly dependent on the fine aggregate. This is confirmed in Figures 4 and 5. Figure 5 presents the calculated WNullk,38cm values for %u201czero-consistency%u201d across all tested concrete mixtures. Changes in the type of cement lead to relatively minor differences in the required Fig. 4: Water content in fresh concrete (3-component system %u2013 without plasticizing admixtures) as a function of the resulting slump flow for various concrete mixes to determine the %u201czero-consistency%u201d (WNullk,38cm). Left: M1-x, cement content: 340 kg/m%u00b3 with varying fine aggregates; Centre: M2-x, cement content: 360 kg/m%u00b3 with varying fine aggregates; Right: M2-x, cement content: 360 kg/m%u00b3 with varying cement types.a) b) c)