Reduction of the thermal gradient in concrete mixture in dry and hot climates using Phase Change Materials.

摘要

Dynamic development of construction industry and related with it implementation of more and more modern design, forces the use of more advanced concreting technology. Tight, short construction deadlines force the contractors often to conduct works, regardless of weather conditions. The development of materials technology, implementation of new products, measurement techniques and methods of registration "data" information makes regardless of still useful, traditional tools for rising concrete structure, there must be sought and developed new methods for reduction of adverse events inside the concrete elements, but also allowing faster construction rising. Ageing of concrete is a result of cement hydration, which is an exothermic process. Approximately a full hydration of 1 kg of standard Portland cement causes emission of approximately 400 kJ of heat. The ambient temperature and emition of hydration heat of fresh concrete mix and encountered difficulties in transmitting heat to the outside of the element initiates the formation of thermal gradient in the concrete structure. As time goes by, as a result of hydration process progress, the hardening concrete acquires mechanical characteristics (it increases its strength). If the resulting stress, caused by the temperature gradient, exceed at any given time the strength of the forming "concrete structure", it is followed by its destruction, and result in emerging fractures and cracks in the constructed element [1]. From the above it can be concluded that the proper thermal care becomes one of the primary factors determining a solid monolithic concrete structure, hence the idea of application of PCM (Phase Change Materials) for the care of the inner concrete mix when ageing in hot and dry climates.