| Abstract [eng] |
Concrete is one of the most widely used building materials in the world due to its excellent load-bearing properties. However, cement, which is one of the main components of concrete, reacts with water to generate a huge amount of heat inside the structure during hydration. This rise in temperature is becoming a huge problem for massive concrete structures such as hydroelectric power stations, dams, foundations, wall structures because natural cooling is no longer enough to cool the foundation. As the temperature rises, stresses develop in the concrete, which can lead to thermal cracking of the structure, which would significantly affect the strength of the load-bearing properties. Nowadays, in practice, there are many ways to control this radiant heat. There are two groups of solutions - mineral, replacing part of the cement with impurities and thus reducing its amount, and technological, externally controlling the heat released, preventing it from rising to a dangerous level. Limestone, fly ash, slag can be used as a substitute, and it is also effective to increase the size of the aggregates or cool them before use. The most effective technological solution would be to cool the structure along its entire volume by placing pipes that flow with water at a much lower temperature during hydration or using ice, also reducing the amount of water used in the mixture. In the final master's thesis, the following methods of temperature reduction are compared by performing numerical simulations with the help of the temperature calculation program HACON 3. After obtaining the theoretical results, they are compared with the experimental ones received during monitoring of the bridge foundation and observing real temperature release and development at site. The results show that the most effective solution for cooling of the foundation is technological method - the use of cooling pipes. Data obtained during simulation was proportional to the practical results obtained during monitoring of the bridge. Some small discrepancies were found - in practice it was found that temperature rose to 63,3 ° C during hydration, which is slightly more than theoretical results, where the maximum temperature was registered as 51,5 ° C. It would be possible to continue the study by finding ways to achieve the closest possible cooling result (to the one using pipes) by using different concrete admixtures or mixing them together. |
