Evaluating the Influence of Micro Silica Content on Concrete Mechanical Properties: (An Experimental Study)

Due to the limited area of land and the increase in the population of the land, and with the increase in demand and the need to expand construction, the role of concrete in construction projects is undeniable. The pollutant footprints caused by the cement production process include a significant part of ‎the 5-8% global CO2 emissions. Due to the use of fossil fuels in the ‎exploitation process, the transportation of limestone to cement factories, and the necessary ‎energy to convert limestone into cement, non-renewable sources are used, and a significant amount ‎of CO2 is emitted. In recent years, to reduce environmental pollution caused by ‎cement production, the need to adopt innovative methods and materials such as the use of pozzolans ‎and supplementary cementitious materials (SCMs): micro silica (MS), fly ash (FA), and silica fume ‎‎(SF) has received more attention‎. The current research examines the mechanical properties of concrete with MS contents (10%, 20%, and 30%) as a partial replacement for the weight of cement used in the mixing design. Before the ‎test date, ‎samples were prepared under standardized ‎conditions ‎‎and cured in a tank with ‎limewater ‎saturated at 23±1C°.‎ Under the standard, the average of two samples ‎calculated the unconfined compressive strength (UCS) value ‎for each ‎‎day test. ‎Mechanical properties were evaluated through unconfined UCS tests on 24 concrete 100*100*100 mm cube specimens from 4 mixing designs at 7, 14, and 28 curing days. The results indicate that the inclusion of MS enhances UCS by 14%, 24%, and 43% at the respective testing ages compared to the control specimens. The highest UCS was observed in the mix design with 30% MS replacement. Based on the findings, it can be concluded that MS addition improves the UCS of concrete specimens at all ages. Furthermore, a comparative analysis of the results reveals a direct correlation between increasing MS content and enhanced compressive strength.