To determine the impact of formwork on thermal cracking, it’s essential to comprehend its effect on concrete temperature. While timber formwork provides better insulation, leading to a higher overall temperature rise and peak hydration temperature, it also reduces the temperature gradient across the concrete element. In contrast, steel formwork allows for faster heat dissipation, resulting in a lower overall temperature but a steeper temperature gradient.
Therefore, the choice between steel and timber formwork for thermal crack control depends on the specific constraints and dimensions of the concrete section. In thick sections where internal restraint is the primary cause of cracking, timber formwork is preferable due to its ability to minimize temperature differentials within the concrete. Conversely, in situations where external restraint is the main concern, steel formwork is advantageous as it promotes faster cooling and reduces the overall temperature rise.
In summary, the selection of formwork material for thermal crack control is a nuanced decision. It necessitates a comprehensive assessment of the concrete section’s characteristics and the dominant restraint mechanisms. By understanding these factors and their interplay, engineers can make informed choices that effectively mitigate thermal cracking risks.