Synthesis and characterization of one-part geopolymer from fly ash and water treatment sludge

• Main Author: Ho, Vuong T.
• Format: text
• Language: English
• Published: Animo Repository 2017
• Subjects: Water treatment plant residuals; Fly ash; Binders (Materials)
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/5785
• Institution: De La Salle University

Development of geopolymer from wastes or by-products introduces a sustainable approach to replace ordinary Portland cement (OPC) - based concrete with an eco-material of lower green-house gases emissions. However, safety concerns related to the conventional two-part geopolymer has limited large-scale applications of the product. With the aim of developing a one-part geopolymer from coal fly ash and water treatment sludge, this study has focused on finding the optimal formulation for the binder. In particular, alkaline dosage and mixing proportion of each precursor were examined. Raw aluminosilicate sources were activated by two alkali activators including sodium hydroxide and sodium aluminate. Effects of each components as well as interactions between them were accessed by step wise regression analysis. Chemical bonding, microstructural and mineralogical characteristics of raw materials were determined by X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR) analyses. Also, the transformation of raw materials to geopolymer was indicated by FTIR, SEM and XRD analyses. It was found that high alkali content decreased the compressive strength of binder. Meanwhile, the incorporation of sludge in this system helps reduce the unit weight of samples. Multiple response analysis that maximized compressive strength and minimized unit weight resulted in the optimal combination of 18.86% sludge, 76.14% fly ash and 5% NaOH. Acid resistance test has proved that the new binder had great durability against sulphuric acid attack. After 28 days immersion in 5% H2SO4 solution, compressive strength of the binders was significantly increased. It was demonstrated that strong acid immersion did not create any noticeable effect on the weight and strength of one-part geopolymer system developed from coal fly ash and water treatment sludge.