Microstructural and Strength Characteristics of High-Strength Mortar Using Nontraditional Supplementary Cementitious Materials

Abstract

This paper presents the investigation of the strength characteristics and microstructural analysis of cement composite mortar developed using nontraditional cement replacement materials. Three types of materials, namely palm oil fuel ash (POFA), treated palm oil fuel ash (TPOFA), and bottom ash (BA) were used as partial cement replacement materials at replacement levels of 0%, 10%, 20%, and 30% by weight. The water to binder ratio (w/b) of 0.32 was used for all mortars. The chemical composition and morphology of binder materials were examined by X-ray florescence (XRF) and scanning electron microscope (SEM) techniques. The fresh and hardened properties of mortar were determined in accordance with ASTM standards and the microstructure of mortar was investigated using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The results showed pozzolanic activity through formation of C-S-H and CH as confirmed by XRD, TGA, and FTIR. Partial replacement of cement with 10%, 20%, and 30% of TPOFA produced higher compressive strengths of 101.4, 88.4, and 83.6 MPa, respectively, which is slightly closer to 110.0 MPa obtained for control specimen at 90 days. Moreover, higher strength activity index for TPOFA and BA specimens showed better pozzolanic activity as compared to POFA-based mortar. Overall, the use of 10% of POFA, TPOFA, and BA is recommended as a cement replacement in the development of high-strength mortar of strength range of 60 to 100 MPa.