Recycled glass could become a staple ingredient in building, paving the way for greener construction materials and more sustainable development.
In a study, published in Discover Civil Engineering, scientists tested the potential for using recycled glass, in powdered form, as a stabilising agent in compressed earth blocks.
Building blocks made of soil mixed with water, and compressed at high pressure (compressed earth blocks), are usually stabilised with cement. Scientists – including a team from the University of Portsmouth – appear to have found that a reliable level of stabilisation can be achieved with a mix that includes recycled glass together with lime and a significantly reduced amount of cement.
Testing was undertaken on compressed earth blocks prepared with recycled waste glass particles (RWGP) in the mix at ratios of zero to 25 per cent. Apart from determining the mechanical properties, the blocks were examined for microstructural characteristics using an electron microscope for 28 days.
Co-author, Dr Muhammad Ali, Associate Professor in Materials and Environmental Innovation at the University of Portsmouth’s School of Civil Engineering and Surveying, said: “There is an increased demand for the use of recycled industrial waste as sustainable building and construction materials so we wanted to assess the properties of compressed earth blocks using recycled glass particles.
“At each percentage level we tested for water absorption, how resistant to breaking the blocks were when compressed, and to determine the maximum stress the block could withstand while being stretched or pulled, before breaking or becoming deformed.
“After testing blocks with varying mixes using lime and recycled waste glass, we found that a composition of 10 per cent lime and 10 per cent recycled glass particles produced the strongest blocks with no cracking under intense pressure.”
The highest compressive strength of 5.77 MPa (megapascal – a unit of pressure) was achieved at 10 per cent recycled waste glass particles (RWGP) and 10 per cent lime compressed earth blocks (CEB), while the unstabilised specimens achieved 3.03 MPa at 28 days of curing, representing about 90 per cent improvement. The highest tensile strength of 0.52 MPa was achieved at 10 per cent RWGP and lime CEBs, while the unstabilised specimens achieved 0.40 MPa at 28 days of curing, which represents a 30 per cent improvement.
The microstructural analysis showed no visible cracks in the 10 per cent RWGP and lime mixes, while the 25 per cent showed micro-cracks in the earth blocks. Future studies could assess the thermal and durability properties of these greener construction materials.
Scientists from four universities took part in this study. Alongside the University of Portsmouth in England, colleagues involved in the collaboration came from the Akenten Appiah-Menka University in Ghana, London South Bank University in England and the Federal University of Technology in Nigeria together with colleagues from the CSIR-Forestry Research Institute of Ghana.
