Discarded cathode ray tube glass as an alternative for aggregate in a metakaolin-based geopolymer

Cathode Ray Tube (CRT) glass belongs to the group of wastes which are hard to be recycled due to their toxic metals content. Geopolymers are relatively new environmentally friendly materials which allow for the use of different types of wastes within their matrix. The following paper combines both issues and presents a new geopolymer mixture containing discarded CRT glass as a replacement for an aggregate. The main goal of the paper is to describe the basic mechanical behavior of the new type of metakaolin-based geopolymer and to discuss different factors influencing it. After the preliminary research, the mixture containing 50% of CRT glass was chosen for further tests. However, according to results, CRT glass content has no evident influence on flexural or compressive strength. Summarizing the second part of the research, it was decided that the following parameters are optimal from the mechanical, economic and environmental points of view: metakaolin to CRT glass ratio 1:1 (by mass), CRT glass of size up to 4 mm, curing at the room temperature, sodium hydroxide concentration 10 mol/L. According to the authors, the presented geopolymer is a promising building material. Further tests shall be done to describe new material more precisely.