The effect of microsilica percentage on the tensile properties of high-strength concretes with silica aggregates

Ali Khanalizadeh¹ Fazel Bahnia² Seyyed Mohammad Reza Hassani³ Mohammad Mahdi Soleimani⁴

1) Master of Civil Engineering, Surveying, Qom Municipality Employee
2) Bachelor of Civil Engineering, Qom Municipality
3) PhD in Civil Engineering, Instructor, National Skill University, Qom Branch -
4) Bachelor s degree student in Civil Engineering, National Skill University, Qom Branch

IOI Code : AAGF-AAEHAF
Publication : 9th International Conference on Applied Researches in Science & Engineering (carseconf.com/9th)
Abstract :
    In this study, the effect of different percentages of microsilica as a pozzolanic material replacing part of cement on the mechanical properties of high-strength concrete containing silica aggregates was investigated. The main objective was to evaluate the changes in tensile and compressive strength as well as workability and density of concrete due to the gradual increase of microsilica up to 40% by weight. For this purpose, 41 mix designs with different percentages of microsilica from 0 to 40% were prepared and tests including compressive strength (at 28 days), indirect tensile strength, slump test and determination of concrete density were conducted. The results showed that by increasing the percentage of microsilica up to about 15%, the compressive and tensile strength of concrete increased significantly. The maximum compressive strength of 68 MPa was achieved at about 20% microsilica and the maximum tensile strength was also achieved at about 15%. However, percentages higher than 20% caused a relative decrease in the strengths and workability of concrete. This performance loss can be attributed to the excessive addition of fines, the reduction of the effective water-cementitious materials ratio, and the reduction of the fluidity of the mixture. Overall, the findings indicate that the use of microsilica in the range of 10 to 15% can effectively improve the mechanical properties and durability of high-strength concretes. This result is important for the design of reinforced concrete structures with high mechanical requirements, especially in areas prone to tensile stresses.

Keywords : microsilica high strength concrete tensile strength compressive strength silica aggregate concrete performance