Browsing by Author "Elias, Aklilu"
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Item Early age thermal cracking tendency assessment on mass concrete (Controlling temperature by pre cooling method)(Addis Ababa University, 2019-04) Elias, Aklilu; Esayas, Gebreyouhannes (PhD)Thermal dilation and autogenous shrinkage are produced by the continued hydration of cement, this volume changes are partly or wholly restrained, and therefore they induce stress. This is issue for massive concrete especially at early age when concrete is immature. This thesis presents assessment on the tendency of cylindrical axisymmetric strictures and massive wall at early age with multiple thickness and placement temperatures. This master thesis focuses on assessment of cracking tendency of massive concrete structures which are subjected to realistic field temperature boundary conditions at early age. The assessment is based on the analysis results of analytical models. This work also shows the efficiency of precooling method in controlling of temperature differential and cracking tendency structures by comparing with reference placement temperature (placement temperature without introducing pre cooling). At early age, the core of thin sections of mass concrete structures have high tendency of cracking. The reason is that the high temperature drops of the core during cooling phase. Cracking tendency at cores of thin sections is high at high placement temperature. This susceptibility of cracking of thin section structures are controlled by precooling method. Similarly surface of mass concrete structures are susceptible for cracking at early age in moderately hot weather. The tendency of surface cracks can be significantly minimized by reducing the placement temperature but for thick sections precooling method should combined with other temperature differential controlling methods (e.g. surface insulation) to minimize surface early age cracking tendency.