# Testing Concrete for the Construction of Winemaking Tanks
## 2 Materials and Methods
### Composition of Concrete Specimens  
All the above-mentioned parameters regarding the geometry of the tanks in combination with the existence of the required reinforcement impose the use of aggregates with a maximum grain size of 16 mm. After carrying out test granulometric compositions and preparing test compositions of SCC, the final composition of the aggregates was decided, the granulometric curve of which is given in Figure 1. To improve the workability of the concrete, quartz sand of gradation 0-0.3 mm was added as filler. Quartz sand, in comparison to other aggregate fillers (e.g., limestone), exhibits reduced water absorption, which is necessary for the SCC mixture so that the amount of free water in the mixture would not be affected by fine aggregates. As for the chemical admixtures, a third-generation superplasticizer was used, based on polycarboxylate polymer technology, as well as a viscosity modifier, based on a modified starch complex. The concrete mix design was carried out through successive optimization of each of the parameters that were necessary for the desired final mix. These parameters are summarized in the following points:  
* Total amount of binder;
* Water/Binder ratio;
* Cement replacement percentage and fineness of pozzolan;  
Figure 1: The granulometric curve of the aggregate mix, consisting of 50% \(w/w\) 0–4 mm fine aggregate, 30% \(w/w\) 4–8 mm coarse aggregate and 20% \(w/w\) 8–16 mm coarse aggregate. * Amount of filler (kg/m\({}^{3}\)) in the mixture;
* Amount of superplasticizer (% \(w/w\) of fines) in the mixture;
* Amount of viscosity modifier (% \(w/w\) of fines) in the mixture. The main criterion for the study of the compositions is the properties of the fresh concrete, which were measured after each composition in order to decide the next steps. Two of these tests are standardized, while all of them are described by the corresponding National Technical Specification [10] and EFNARC [11]. Slump-flow test: The slump-flow test is used to assess the free horizontal flow of fresh concrete without obstruction and is based on the corresponding concrete slump test (EN 12350-2 [16]). Along with the diameter of mixture spreading on a flat surface (recommended values \(\geq\) 650 \(\pm\) 50 mm) the time required for the diameter of the concrete circle to reach 500 mm (T500) is also measured. Comparatively short times indicate high flowability. L-box test: The test is used to assess the flowability of the SCC, as well as the degree to which the SCC dogs the reinforcement. The test is also described in the EN 12350-10 [17] regulation. The device is essentially an L-shaped duct of rectangular cross-section, where the vertical section is separated from the horizontal section by a removable door in front of which vertical reinforcement bars are placed. The vertical box is filled with SCC and then the door is lifted, allowing the mixture to flow into the horizontal section. When the flow is complete, the ratio H2/H1 of the surface level of the mixture in the horizontal and vertical sections is calculated. The closer this ratio is to the value 1 (ideal water flow condition), the better the flowability of the concrete. Segregation resistance test: The test is used to assess the resistance to segregation (stability) of the SCC, by pouring a quantity of the mixture (10 L) through a sieve with a 5 mm opening. The result is expressed as a percentage of the mass passing to the initial mass of the material placed on the sieve. For values above 15% and especially above 30% there is a significant possibility of segregation of the SCC. A decisive factor for the development of the test compositions is also the mechanical behaviour of concrete. For this reason, 15 cm cube specimens were produced, following the requirements of EN 12390-3 [18], for the determination of compressive strength. Table 2 summarizes the preliminary compositions carried out, with all of the aforementioned parameters that were investigated, showing how the optimization of the mixture evolved.