Effect of hydration products on the mechanical behavior of reinforced concrete slabs made with ternary systems

Abstract

Durability problems occur in concretes used in underground structures due to the effect of sulphate in groundwater. However, these structures need to be manufactured quickly to avoid economic, environmental and structural adversities. In this study, by using ternary systems, both the permeability properties of the concretes were improved and high early age strength was achieved compared to conventional concretes, and it was aimed to ensure that these structures are both resistant to external influences and much faster production compared to conventional methods. Within the scope of this study, ternary mixtures were formed using Calcium Aluminate Cement, silica fume and gypsum, which can be used in such underground structures and have a higher resistance to durability problems than OPC. Reinforced concrete slabs were produced from these mixes and the structural behavior of these slabs was determined experimentally. On the other hand, the internal structures of the mixtures were determined by microstructure analysis. In the light of the data obtained, when mechanical and microstructure tests were examined together, it was found that water impermeability increased as the amount of ettringite in the ternary blends increased, particularly in the internal structure. It is also understood that the filling effect of silica fume has a positive effect on impermeability. When the ductility behavior of reinforced concrete slabs made from ternary mixtures is examined, it can be seen that the ductility in these slabs increases as the amount of ettringite increases. Also, it was determined that the water impermeability of the samples prepared with mineral additives was up to 2.75 times better than the reference sample. The compressive strengths at the end of 1 day, according to the 28-day ultimate compressive strengths of the reference, high silica fume and high gypsum samples, are 66.50 %, 41.00 % and 43.55 %, respectively. The ductility of the reference specimen on day 1 and day 28 was found to be 14.53 % and 25.94 % higher than the specimen with high silica fume content, respectively; and 50.74 % and 24.37 % higher than the specimen with high gypsum content, respectively.