Ashkan Saradar

Ultra-high-performance concrete (UHPC) is recognized as one of the most advanced concrete materials used in the construction and execution of concrete structures and precast components in civil engineering. These types of concrete, characterized by very high compressive strength and exceptional durability properties, are primarily utilized to fabricate precast parts in bridges and buildings. One of the main challenges associated with these concretes is the high consumption of cement, which this research addresses. In this study, nine mix designs were defined, incorporating 0%, 5%, and 10% calcium carbonate (CaCO3) as a partial substitute for cement, alongside 15%, 20%, and 25% silica fume also as a replacement for cement, to investigate the effects of these two additives on the properties of UHPC. Compression and electrical resistance tests were conducted at ages 7, 28, and 90 days, revealing the optimal percentages of 20% silica fume and 5% CaCO3. Additionally, tests for final water absorption and accelerated chloride ion penetration demonstrated a reduction in the permeability of these concretes with an increase in the silica fume content by up to 25%.

The increasing global emphasis on sustainable construction practices has spurred significant international research into developing durable and eco-friendly concrete materials. This study investigates the potential of metakaolin and glass powder as supplementary aluminosilicate materials in slag- based geopolymer mortars, aiming to enhance their mechanical properties and durability. To further improve the performance, polypropylene fibers were incorporated at various dosages. Therefore, 13 mixtures of geopolymer mortar based on blast furnace slag have been developed. The control mix does not contain fibers or slag replacement materials, whereas in the other formulations, glass powder and metakaolin have been employed as substitutes for slag at weight percentages (relative to the weight of slag) of 5% and 10%, separately and in combination. Additionally, the fiber-containing samples are divided into two groups based on the volume percentage of polypropylene fibers, comprising 0.2% and 0.4%. The results of the investigation show that the use of glass powder, particularly at a replacement percentage of 10%, leads to an improvement in the 28-day compressive strength. Furthermore, the mixes containing glass powder demonstrated higher flexural strength compared to those containing metakaolin, irrespective of the volume percentage of fibers. The best performance in the rapid chloride permeability test is associated with the mix containing a combination of glass powder and metakaolin at a replacement percentage of 10%. Satisfactory results have been obtained when using fibers at volume percentages of 0.2% and 0.4%. Additionally, this study utilized a fuzzy inference system to predict compressive strength. The results indicate that, by considering uncertainties, the compressive strength of the mortar can be predicted with an error of less than 1% without the need for complex mathematical calculations.