Influence of Fly Ash on Mechanical Properties of Slag-Based Alkali-Activated Concrete with Low NaOH Concentrations

This chapter presented the effect of fly ash on the mechanical properties of Ground-Granulated Blast Furnace Slag (GGBFS) or Slag-based Alkali-Activated Concrete (SAAC) cured at room temperature with low NaOH concentrations. Using 100% GGBFS, three concrete classes were evaluated in this study: 20, 40, and 60 MPa (GGBFS). GGBFS was replaced with fly ash at 0%, 20%, 40%, 60%, 80%, and 100% in this investigation and low NaOH concentrations 1, 2, and 4 M were used. In this chapter, mechanical aspects compressive, split tensile, flexural strengths, and stress–strain relation studied. Also, from stress–strain relation, modulus of elasticity (MOE) values was determined. From the test results, the flexural strength and split tensile strength values were slightly decreased when the fly ash content was substituted from 0 to 40% and these strength values reduced greatly when more than 40% fly ash was substituted. A correlation was established between compressive strength, split tensile strength, and flexural strengths of all mixes according to the various code provisions, and the derived relations have been compared with past studies and code provisions. The developed empirical relations satisfied the most of codes and studies. Measured modulus values were drastically decreased as the fly ash increased more than 40%. Based on obtained stress–strain relationship, the maximum strain decreased as compressive strength increased. When the fly ash replacement increased from beyond 40% in 40 MPa and 60 MPa concrete grades, the (MOE) decreased by 40%–90%, while it decreased by 35%–90% in 20 MPa concrete.