# Testing Concrete for the Construction of Winemaking Tanks
## 1 Introduction  
The wine fermentation stage is one of the most important stages of the winemaking process, whether it is white, red or reddish (rose) winemaking. This phase can last from a few months to a few years, resulting in the wine's taste changing from wild and as stringent to soft and velvety in combination with the rich aroma that will have developed. It is usually carried out in stainless steel tanks, oak tanks or oak barrels.  
Regarding stainless steel tanks, while being highly durable, the thermal conductivity and impermeable nature of the material necessitate external cooling and micro-oxygenation systems [1]. Wine fermented in stainless steel tanks is characterized by a more stringent character than oak tanks. Regarding oak tanks and barrels, their main advantage is the fact that they allow the inflow of a small amount of oxygen (2.5 mg/L per month), which is necessary for the fermentation process [2]. They also exhibit better behaviour than stainless steel tanks in terms of their thermal conductivity [3]. At the same time, however, theyhave a limited lifespan (usually around five uses). Winemaking in oak barrels usually produces a wine with a more blunt character, while the wood itself contributes aromas to the final product, something that is usually sought in red wines. Beyond these cases, in recent years the value of winemaking in concrete tanks has begun to be recognized internationally. In recent decades, their production and use have grown rapidly in traditional wine-producing countries (France, the USA), as these tanks seem to combine the advantages of the other two options [3]. Research has been ongoing for both fermentation [4] and maturation [5] processes.  
The main advantage of concrete is its great durability over time. Also, the porosity of concrete allows for natural micro-oxygenation inside the tank [1]. At the same time, the nature of the material in combination with the thickness of the tank allows for slow (not abrupt) temperature changes inside, in relation to the environment, ensuring the maturation process [6]. These characteristics, according to the experience so far in wine production in concrete tanks, contribute to the production of wines that combine the characteristics of oak and stainless-steel tanks, i.e., full and balanced body due to the long and balanced maturation, while maintaining all the aromas of the fruit intact, as concrete does not contribute its own aromas.  
Another important advantage of concrete is the possibility of constructing tanks of particular shape that aid the winemaking process. These shapes usually refer either to amphora tanks, based on the corresponding clay containers used in antiquity, or to a more modern proposal of an oval-shaped tank, allowing the wine to be in constant motion, giving a smooth and uniform fermentation [4; 7].  
Taking into account the interests and prospects that exist internationally in this field, the present work concerns the study of concrete for the construction of oval-shaped wine-making tanks. Thus, it was chosen to design test compositions of self-compacting concrete (SCC) of strength class C 20/25, at least. The choice of SCC was made in order to achieve the correct placement of the concrete in the curved geometry of the shape [8] and to achieve the required adhesion with the concrete reinforcement [9]. The design of the test compositions and the individual materials selected for the compositions follow the requirements of the relevant regulations for the manufacture of SCC, such as the Greek National Technical Specification ELOT TC 1501-01-01-06-00 [10] and the relevant EFNARC regulation [11].