Comparative Evaluation of Effect of Fly Ash and Microsilica on the Development of Compressive Strength and Electrical Resistance of Concretes Exposed to Sulfate-Rich Waters

Document Type : Original Article


1 Ph.D. Student, Department of Civil Engineering, Islamic Azad University Tabriz Branch, Iran

2 Department of Civil Engineering - Technical and Engineering Faculty - Islamic Azad University Tabriz Branch - Tabriz - Iran

3 Department of Civil Engineering - Technical and Engineering Faculty - Islamic Azad University - Tabriz Branch - Tabriz - Iran



Reinforced concrete is one of the most widely used building materials in the construction industry. The sulfate attack on concrete structures is one of the factors effectively causing the reduced durability of concrete and structural damage. In the design and construction of concrete structures, service life, sustainable development, and environmental issues are important indicators considered by researchers in optimizing materials to achieve sustainable concrete with high strength by substituting various types of pozzolans for cement. The present study aims to compare the effects of fly ash and micro-silica on the development of the compressive strength, and electrical resistance of concretes exposed to sulfate-rich waters. The plans of this study include two types of conventional concretes and concretes containing pozzolanic material. Concrete mixing plans in sulfate medium were divided into 11 groups. The first group, with no additive material as a substitution for cement, included one plan (control plan), and the other 10 groups included 8 plans with the substitution of different percentages of micro-silica and fly ash powders for cement in concrete. Accordingly, 81 plans, each with 4 samples (7, 14, 28, and 42-day ages), were constructed to test compressive strength (N=324 plans). The results indicate that in the sulfate medium, with an optimal mixing design, the concrete containing standard sand reinforced with fly ash and microsilica pozzolans had higher strength compared to the concrete with no pozzolan, Moreover, the maximum (a 6% reduction in strength) and minimum (a 28% reduction in strength) durability was obtained for Samples # 5 and 6 of Group 2 and Samples #30 and 31, respectively. Also, with the substitution of 15% microsilica, a 1.58-fold increase in the electrical resistance was observed in the 90 day-old concrete sample compared to the 28 day-old sample


Main Subjects

  • Receive Date: 30 December 2021
  • Revise Date: 19 February 2022
  • Accept Date: 05 April 2022
  • First Publish Date: 05 April 2022