## 2 Materials and Methods
### Testing Methods  
After mixing, the following properties of the fresh concrete were evaluated: density (EN 12350-6), temperature and air content (EN 12350-7) [38; 39]. For the NC1 and NC2 mixes, the consistency was evaluated using a slump test (EN 12350-2) [40]. For the SCC mixtures, the workability was evaluated by testing the flowability with the slump flow test (EN 12350-8), the viscosity with the V-funnel test (EN 12350-9), the passing ability with the L-box test (EN 12350-10) and the resistance to segregation with the sieving test (EN 12350-11) [41; 42; 43; 44]. Figure 3 shows the L-box test and the measurement of the flowability of SCC.  
Concrete cylinders with a diameter of 150 mm and a length of 300 mm were used to determine the compressive strength of the concrete, the static Young's modulus in compression and to measure shrinkage and creep strain. For each test, one specimen was taken from the first batch and two specimens from the second batch of concrete. The compressive strength was tested at a concrete age of 2 and 28 days in accordance with standard EN 12390-3 [45]. The Young's modulus was determined at the age of 28 days as the secant modulus after three loading-unloading pre-cycles in accordance with EN 12390-13 [46]. The compressive strength at the specimen age of 2 days was determined with the aim of assessing the development of the early compressive strength and to obtain the characteristic value of the strength required for the compressive loading of the specimens during the creep deformation test.  
Drying shrinkage length change was determined in accordance with ISO 1920-8 [47]. After demoulding, measuring pins were glued to opposite sides of each cylinder at a distance of 200 mm and the initial value was recorded. The change in length was measured with a length comparator and the displacement was measured with a digital indicator. Parallel to the samples for shrinkage measurement, pins were also attached to the samples for creep test. The samples were loaded at an age of 2 days to a value of 30% of the achieved compressive strength. The load after 2 days was chosen to simulate the process of introducing the prestressing force into prefabricated, prestressed structural elements. The creep test was carried out in accordance with the ISO 1920-9 standard [48]. The load frame for the creep test consisted of a spring system to maintain the load and a permanently installed load cell to read and adjust the load force. Figure 4 shows some details of the measurement procedures. During the creep and shrinkage measurements, the ambient temperature was kept at 20 \(\pm\) 2 \({}^{\circ}\)C and the relative humidity at 60 \(\pm\) 5%.  
Figure 3: Testing of fresh SCC properties: (**a**) passing ability using L-box test; (**b**) slump flow test.  
The measurement of shrinkage and creep was carried out up to a concrete age of 180 days. An exception is the SCC50 mixture, for which the measurements were carried out up to a concrete age of 90 days. Previous investigations of the deformation properties of SCC with recycled aggregate have shown that the shrinkage and creep deformations become stable after 180 days and approach the asymptotic final value [35].  
The creep coefficient of concrete under compressive load is calculated as follows:  
\[\Phi(t,t_{0})=\frac{\varepsilon_{p}(t,t_{0})}{\varepsilon_{el}(t_{0})} \tag{1}\]  
\[\varepsilon_{p}(t,t_{0})=\varepsilon_{tot}(t,t_{0})-\varepsilon_{el}(t_{0})- \varepsilon_{s}(t)+\varepsilon_{s}(t_{0}) \tag{2}\]  
where \(\Phi(t,t_{0})\), \(\varepsilon_{p}(t,t_{0})\) and \(\varepsilon_{tot}(t,t_{0})\) are the creep coefficient, the creep strain and the total strain of the specimens under load, respectively, at concrete age \(t\), which were subjected to a constant load at age \(t_{0}\). \(E_{el}(t_{0})\) is the elastic strain at loading, while \(\varepsilon_{s}(t)\) and \(\varepsilon_{s}(t_{0})\) are the shrinkage strains at age \(t\) and \(t_{0}\) respectively.