Foam glass derived from ferrochrome slag and waste container glass: Synthesis and extensive characterizations

Abstract Lately, energy-saving attempts in the construction and building materials industry have become more popular due to the diminishing natural resources. With this motivation, we investigated the first foam glass consisting of ferrochrome slag (FS) and waste soda-lime glass (SLG) for potential use as a heat insulation material. For this, FS and SLG waste materials were valorized as main constituents, whereas a mixture of water glass (WG) & glycerol (G) and a sufficient amount of water (W) was used as a foaming agent and a moisturizer in the batch mixture, respectively. The studied series was prepared with the composition of 20FS-70SLG-xG-(8-x)WG-2W where x: 2, 4, and 6 wt%. After that, three different process temperatures (800, 825, and 850 °C), two distinct heating rates (5 and 10 °C/min), and two discrete dwell times (15 and 30 min) paved the way for the synthesis of 36 different foam glass samples. Eventually, the fabricated 36 different samples were subjected to physical, thermal, mechanical, and microstructural evaluations. According to the findings, one can say that samples synthesized with a lower G-to-WG ratio, higher process temperature, lower heating rate, and higher dwell time have the best features. From the physical property determinations, we found out that bulk density (ρbulk) varied between 233 and 903 kg m−3 while the estimated porosity (P) ranged from 59.4 to 89.5%. Further, thermal conductivity (k) measurements demonstrated that the fabricated foam glass series provides lower values, namely from 0.038 to 0.130 W m−1 K−1. Besides, compressive strength (CS) values were found to be changing from 0.127 to 2.225 MPa. Microstructural evaluations via scanning electron microscopy (SEM) revealed the pore formations and the relevant alterations as a result of the different parameters. All in all, the authors concluded that a heat insulation material composed of nearly fully waste substances can effectively be produced.