Masonry units bound with waste vegetable oil – Chemical analysis and evaluation of engineering properties

• Provides further confirmation of the positive use of recycled binders in construction materials.
• Improves the understanding of the mechanism of the vegetable oil based binder.
• Generates further clarification of the chemical changes that occur during the curing process.
• Examines the significance of the chemical changes on some of the physical properties.
• Apparently the stiffness of the oil is not down to cross-linking and increased molecular weight.

Masonry units with attractive environmental credentials can be produced from waste aggregate materials and vegetable oils. Heat curing at low temperatures induces chemical changes in the binder which stiffen the block and afford them a compressive strength which can be compared to existing blocks and bricks. This method allows use of 100% waste materials, which far exceeds the level of replacement possible in traditional concrete and clay matrices. To better understand the chemistry of the vegetable oil binder at different stages of the curing process a range of experiments have been performed including infrared spectroscopy, liquid chromatography and mass spectrometry. Results show production of chain-shortened and oxygenated derivatives and the nature of reactions based on curing time and physical environment of the binder. Compressive strength and mass loss are dependent on curing time and the altered molecular architecture of the oil, but other physical properties are independent of the chemistry and reliant on physical concerns such as aggregate selection.