With energy costs spiralling worldwide, there is an increasing demand for construction materials that can balance thermal comfort with lower energy consumption in buildings. Newcastle University researchers have developed a new cement mortar mix made from recycled plastic and silica aerogel, which not only improves thermal insulation but also mitigates the rising problem of plastic waste.

The cement mortar blend uses silica aerogel and recycled PET plastic instead of sand, with test results showing improved thermal insulation and lower weight. Known for their high insulation properties, aerogels are increasingly used for thermal insulation, particularly within the building and aerospace sectors.

According to the researchers, this new building material could reduce heating and cooling bills, and offers a more environment-friendly option, thereby, improving sustainable construction practices.

Published in the journal Construction and Building Materials, the study revealed that the new mortar mix reduced heat loss by up to 55% compared to conventional mortar, while maintaining the required strength for masonry construction.

It also meets international standards (BS-EN 413-1:2011, ASTM C270-10, AS 1012/AS 3700), presenting an eco-friendly alternative for energy-efficient and sustainable construction.

Professor Lidija Šiller, Professor of Nanoscale Science at Newcastle University’s School of Engineering and one of the lead authors, says, “This study demonstrates that our formulation of recycled PET plastic waste can be used to produce cement-based mortars, and it is an effective way to reduce their impact on the environment.’’

The researchers tested seven different formulations alongside traditional mortar with the most effective of the new mortar mixes proving to be 7% untreated silica aerogels replacing natural sand combined with 3% recycled PET plastic, which came from shredded plastic bottles.

The new formulation helped reduce the thermal conductivity of mortar by up to 55%, compared to standard mortar samples.

Study lead author Kaniaw Marof, PhD researcher at the School of Engineering, says, “Improvement of the thermal performance of masonry buildings by reducing the energy required for heating and cooling in buildings to meet the users' comfort is one of the main topics considered in the modern construction sector. In our work, the modification of the surface of silica aerogel particles was a crucial step towards successfully implementing silica aerogel particles within the cement binder and PET plastic.”

The next step is to test the new mortar in a large-scale, real-world setting, for which the researchers are looking to collaborate with a construction company. “This will allow us to provide the direct evidence of potential energy savings and assess the economics for masonry buildings applications,” Professor Šiller says.

Reference: Kaniaw Marof and Lidija Šiller, “Enhancing thermal insulation in cement mortar with silica aerogel and recycled PET plastic’’, Construction and Building Materials, 467 (2025) 140320 https//doi.org/10.1016/j.conbuildmat.2025.140320

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