چكيده به لاتين
In this thesis, the durability indices of self-consolidating concrete containing tuff and silica fume and their relationship with packing density have been investigated. Governments spend a lot of money every year on building concrete structures. However, the CO2 production caused by this leads to an increase in greenhouse gases and their irreparable consequences. On the other hand, the abundant presence of natural minerals like green tuff in Iran, along with silica fume, can replace a portion of the cement used in the concreting process, resulting in reduced costs and CO2 gas production. Taking into account the density of accumulation as a criterion to show how solid particles are placed in the mixture, we investigated the optimal combination of coarse and fine aggregates and their effect on the thickness of the concrete layer and durability indicators. During this research, we made 7 concrete samples, each containing 15 specimens, and measured mechanical indicators such as compressive strength and durability indicators such as water absorption, ultrasonic wave speed, electrical resistance, and accelerated migration of chloride ions at the ages of 7, 28, and 90 days. The results of this research showed that in samples without supplementary cementitious material and with a maximum aggregate size of 19 mm, packing density increased from 0.7975 to 0.8168 as n increased from 0.2 to 0.3, respectively. However, as n increased to 0.35, the packing density decreased. Additionally, replacing tuff and silica fume slightly increased the packing density compared to the reference concrete. Increasing the distribution modulus from n=0.2 to n=0.3 resulted in an 11.58% increase in compressive strength, a 35% decrease in water absorption, a 31% increase in electrical resistance, and a 49% decrease in chloride ion diffusion in concrete. Concrete containing tuff performed poorly compared to the reference concrete at early ages. At the age of 90 days, compared to the reference concrete, compressive strength increased by 11%, water absorption decreased by 27%, electrical resistance increased by 127%, and chloride ion diffusion decreased by 54%. The replacement of silica fume in concrete also increased the electrical resistance and chloride ion diffusion resistance by 175% and 86%, respectively, by improving the quality of the concrete.
