## 4 Discussion  
### Influence of Personnel, Weather, and Transport on the Observed Defects  
After their construction, a number of defects were observed on the foundations, which led to further inspections and investigations. These defects all appeared to be production related (i.e., not load-induced structural defects). Figure 14: In-situ compressive strength, \(f_{ls}\), versus (**a**) density, and (**b**) age of the concrete for test specimens taken from cores drilled on the foundations, for different depths from the top concrete surface. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Depth** & \(f_{m(n),is}\) & \(f_{is,lowest}\) & \(\sigma\) & \(f_{ck,is,1}\) (\({}^{\alpha,2}\)) & \(f_{ck,is,2}\) (\({}^{\textbf{(1)}}\)) & **Concrete Strength Class** \\
**(mm)** & **(Mpa)** & **(Mpa)** & **(Mpa)** & **(Mpa)** & **(Mpa)** & **Concrete Strength Class** \\ \hline
0–100 & 63.7 & 41.5 & 10.5 & 48.2 & 45.5 & C40/50 \\ \hline
0–100 (mod) [(3)] & 66.9 & 57.5 & 5.9 & 58.2 & 61.5 & C55/67 \\ \hline
100–200 & 60.3 & 52.0 & 8.6 & 47.6 & 56.0 & C45/55 \\ \hline
200–300 & 62.0 & 60.5 & 2.2 & 55.0 & 64.5 & C50/60 \\ \hline
0–300 (all tests) & 62.0 & 41.5 & 8.6 & 49.3 & 45.5 & C35/45 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Evaluation of the concrete strength class for the different depth ranges based on the mean and lowest in situ compressive strength (\(f_{m(n),is}\) and \(f_{is,lowest}\), respectively), and standard deviation \(\sigma\), in accordance with EN 13791 [25]. A marked difference was observed in terms of the quality between the foundations produced by the two different teams in charge of casting concrete in the project. Several differences were observed between the two teams in terms of the organisational structure, communication, experience, and mentality. Team A was led by some of the skilled workers of the team, while Team B was led by a qualified supervisor and a site manager. While both teams did not understand Swedish, communication between the general contractor and Team A was in English (which was not the native language of either party) while a translator was used to communicate with Team B. Team A had extensive experience in casting wind turbine foundations while Team B lacked previous experience. According to the general contractor's personnel, this led to Team A having high confidence in their abilities to carry out the works as they used to do while Team B was keen to learn and receive directions. For instance, several meetings were organized between Team B and the general contractor prior to the works, in which personnel from Team B described in detail how they were planning on conducting the works and received feedback. In this way, Team B benefited from the experience in previous castings held by Team A. These findings match the results observed in previous research by [PERSON] [20] that identified personnel (e.g., experience, knowledge, understanding of what is expected, and attitude) as the major factor causing variations in the quality of concrete in front of material, equipment, and workmanship in second position, and field testing in third position. Additionally, in the project studied, the attitude of the teams toward planning and learning appears to have been more important than their previous experience. It was also observed in the present study that the team that produced foundations with less defects also produced them in a shorter time. This study did not find conclusive evidence of a correlation between the weather conditions recorded (i.e., precipitations and temperatures) and the time or quality of the foundations produced under these conditions. Nevertheless, the fact that the foundations cast under precipitations have a lower defect index in average, and that the outlying foundation in Figure 12 with a remarkably low defect index was cast under heavy rain, suggest that precipitations may have led to less observable defects. Rainwater may have helped the hydration and curing processes on the top concrete surface.