Re-using glass in concrete

As the use of glass products grows, so does the need for recycling. Glass is a unique inert substance that can be repeatedly recycled without altering its chemical properties. But recycling costs, impurities and mixed colours means that you can't recycle all the used glass into new glass products. How else then to provide an environmentally-friendly solution and avoid landfill?

Researchers from the University of Sulaimani in Kurdistan are addressing the problem and investigating using powdered waste glass to replace cement in concrete.

Glass in itself has little cementitious value, but in powdered form and in the presence of water, react chemically with lime to form cement-like compounds.

Several attributes of glass used in this way affect the mechanical properties of the concrete, including chemical composition and particle size.

In a paper published in the European Journal of Environmental and Civil Engineering, researchers Brwa Omer and Jalal Saeed studied the impact of glass particle size and proportion. They made 14 mixtures of various particle sizes, percentages and water-to-binder ratios and used these to make concrete cylinders.

After 28 days they made strain measurements of each of the cylinders using two electrical resistance strain gauges. (Twenty-eight days is an industry standard age for measuring strength of concrete.) They placed strain gauges half way up the concrete cylinders and connected these to a Microlink 851 data acquisition system to measure stress and corresponding strain values over steadily increasing loads. Windmill software showed the results graphically.

Testing stress and strain in concrete made with glass

The experimental results were used to predict the modulus of elasticity of GP-modified concrete based on certain concrete properties.

Further Reading

Microlink 851 - Data Acquisition over Internet and Ethernet
Windmill Software
Brwa Omer and Jalal Saeed (2021) Effect of water to binder ratio and particle size distribution of waste glass powder on the compressive-strength and modulus of elasticity of normal-strength concrete, European Journal of Environmental and Civil Engineering, DOI: 10.1080/19648189.2021.1893227