PROJECT 1 : Post-Fire Performance of Concrete with Recycled Glass

Throughout the past couple of years, the University of Texas at Arlington’s (UTA) Civil Engineering Department has focused on investigating the reduction of negative effects associated with concrete creation, namely carbon dioxide emissions from chemical reactions in the concrete making process. This project involved testing concrete samples partially replaced with different amounts of fine glass and course glass aggregates, helping to diminish concrete’s carbon footprint. Because glass is a commonly recycled product, it is frequently collected in landfills and can be readily available as a potential substitute for cement in various proportions on a massive scale. Ultimately, collecting glass in this manner may not only significantly reduce landfill sizes, but also curtail cement making costs as concrete is developed in a way that is more responsible and safer for the environment.  In this research, the degree to which different proportions of glass affected the strength and durability of concrete mixes after setting and being exposed to extreme heat conditions were central to understanding key insights into recycled-glass concrete’s performance in real-world settings and on a much broader scale.

Following guidelines established by the American Society for Testing Materials (ASTM), four experiments were conducted. The first included measuring heat flow from chemical reactions of three different concrete mixes using a calorimeter. The control mix consisted of Ordinary Portland Cement while mix 2 and 3 contained 20% and 40% glass powder, respectively. Results demonstrated that over several days, no particular mix showed significantly higher heat flow. Using the same three mixes from experiment one, the second involved taking multiple length measurements of small concrete beam samples at a temperature of 80°C over the course of 16 days. Beams were placed in water initially and then sodium hydroxide to simulate accelerated concrete saturation under normal weathering conditions. For this test, where lesser percent expansion equaled greater durability, mix 1 performed more poorly than the others initially, but eventually surpassed them by a slight margin. Experiment three and four included completely different concrete mix proportions, yet the control still contained no glass and the proportion of glass gradually increased for mix 2 and 3 respectively. After curing for seven days and being heated at 538°C for 10 min, the third experiment measured compression strength of concrete cylinders as pounds of force were gradually applied until failure strain. Results suggested that mixes with higher concentrations of glass failed at lower loads. The final experiment used samples from the same concrete mixes, curing, and heating parameters of experiment three to measure tension with beams using a flexural strength testing apparatus. A load was applied to the midpoint of the beam lengthwise until bending strength failure. Similar to test three, as the proportion of glass increased, concrete strength decreased. Still, given the exponential growth of earth’s population and the resulting demand for increased infrastructure, economic and ecological factors must be considered as important components of innovation as researches seek to develop more sustainable and alternative processes for concrete production and usage.