New Generation Geopolymer Binders Incorporating Construction Demolition Wastes

Abstract

As a result of consistently expanding urban population, continuous development and industrialization of countries' economies around the world, construction and demolition industry gained prominence, despite the fact that it is also considered to be one of the largest producers of solid wastes on a global scale. At the root of substantially increased amounts of construction and demolition waste (CDW) around the world, there, for the most part, stand the new structural applications, repair/maintenance, renovation, demolition works and infrastructural development projects. If not controlled appropriately, these wastes, most of which are going to clean landfills and which are likely to incorporate toxic substances, can endanger the health of individuals and environments surrounding them. Therefore, it is crucial to deal with CDW in proper ways for environmental, social and economic benefits. From the material greenness point of view, geopolymers have been drawing the attention of numerous researchers as promising alternatives to Ordinary Portland Cement (OPC). Geopolymer is a class of aluminosilicate-based binding materials and relies on no cement. It can be made from industrial by-products such as fly ash and slag activated by an alkaline solution. Geopolymers are appealing due to engineering performances such as higher strength and resistance to acid, corrosion, fire/temperature and frost, in addition to material greenness. The aim of this thesis is to evaluate the usability of construction demolition wastes in geopolymer production. Roof tile, red clay brick, hollow brick, concrete and glass wastes which are forming a large part of construction demolition wastes were classified, crushed and grounded right after demolition. These waste materials were used as aluminosilicate precursors individually for alkali activation without inclusion of any type of mainstream pozzolanic materials. Sodium hydroxide, sodium silicate, potassium hydroxide were used individually or combined at different ratios as alkaline activator for polymerization reactions at different molarity and concentrations. Geopolymer pastes which are based on construction demolition wastes were tested under uniaxial compressive strength loading to determine implementability of using CDW as an aluminosilicate source for geopolymers. Besides, geopolymer pastes were characterized with respect to their morphology, chemical and crystallographic structure using methods of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Thermogravimetric Analysis (TGA). Consequently, usability of the construction demolition wastes as aluminosilicate sources in the geopolymer production individually or combined at specific ratios has been proven. Results show that it is possible to obtain the desirable strength grades from geopolymer pastes by alkali activation of brick-based construction demolition waste. However, it seems necessary to place more focus on the improved usability of waste concrete and glass in the production of geopolymer pastes.