Page 37 - Demo

CONCRETE TECHNOLOGYwww.cpi-worldwide.com CPI %u2013 Concrete Plant International %u2013 5 | 2025The aim of this paper is to demonstrate the influence of different granulometric properties of fine aggregates on the workability and water demand of fresh concrete, based on systematic investigations. The effects of various fine natural aggregates on the consistency of fresh concrete are examined and evaluated. In addition to common physical properties, the water required to wet the surface of the aggregates is also determined experimentally. Building on these experimental investigations, a concept is presented for estimating the minimum water content necessary to fluidize fresh concrete using plasticizing admixtures, taking into account the granular constituent materials used. This forms the basis for fundamental principles in the design of concrete with the lowest possible water content. 2 Constituent materials 2.1%u0009 Fine and coarse aggregatesFine natural aggregates (0/2 mm) from four different extraction sites in Germany (S1 = Weser River, S2 = Rhine River, S3 = Elbe River, S4 = Main River) were characterized with respect to their physical properties. Coarse aggregates (2/8 mm and 8/16 mm) were obtained and characterized from only one extraction site (Weser River). The following methods were applied for characterization:%u2022 Grain size distribution according to DIN EN 933-1 [8]%u2022 Density according to DIN EN 1097-6 [9]%u2022 Determination of particle shape parameters using the Litesizer DIA 500 (by the company Anton Paar)%u2022 Determination of the water demand (Vw,s) for surface wetting based on [10, 11]. The dry aggregate (magg.,dry) was placed into a container and completely flooded with water. Next, the water was fully removed using a water jet pump, so that only the water adhesively bound to the surface remained. The mass of the moist aggregate (magg.,wet) was then determined, and the water demand (Vw,s) for surface wetting was calculated as follows:Vw,s = (magg.,wet %u2013 magg.,dry)/Vaggregate %u00b7 100 = mw,s/Vaggregate %u00b7 100Figure 1 (a) shows the grain size distributions of the different fine aggregates used. Table 1 presents additional physical properties of the fine aggregates. The different fine aggregates exhibited significant differences in grain size distribution, which is particularly evident when considering the content of powder particles (d %u2264 0.125 mm) and fine sand particles (d %u2264 0.25 mm). As expected, it was also observed that the water demand for surface wetting increases with increasing powder content or fineness (see Table 1). The finer the aggregate, the larger the specific surface area and consequently the greater the required water demand for surface wetting. Furthermore, Figure 1 (b) illustrates the particle shape parameters %u2013 form index and sphericity %u2013 of the different fine aggregates, which also have a significant influence on the water demand of the aggregate [12, 13].YOUR WET CAST EXPERTSAUTOMACAD.COM 1 450.632.6323STREAMLINEDFLEXIBLE & VERSATILEBOOST YOUR PRODUCTIONWITH ADAPTIVE AUTOMATION