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The decomposition of organic waste going to landfills produces methane gas, which is 21 times worse than CO 2 in its global warming potential. Spent coffee grounds (SCG) are one type of organic waste that makes up a significant proportion of the organic waste going to landfills. Therefore, it becomes imperative to look for a recycling solution to transform this waste into a valuable resource. The concrete industry has the potential to contribute significantly to increasing the recycling rate of this waste material. However, due to its high organic content, it is unsuitable to be used directly in structural concrete. Therefore, this experimental project looks at pyrolysing this waste at different temperatures (350 and 500 °C) to identify its suitability in improving the physicochemical and mechanical properties of concrete. The raw and pyrolysed forms of SCG were used as a replacement of fine aggregates (FA; sand) at 5, 10, 15 and 20% volume replacement levels. X-ray fluorescence (XRF), Carbon, Hydrogen, Nitrogen, and Sulfur (CHNS) analysis, laser diffraction particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and compressive strength tests were undertaken to investigate the properties of the raw material and their performance in the blended concrete composites. The results show that the leaching of organic compounds from the SCG hinders the hydration reaction of cement particles, thereby significantly hampering the compressive strength of SCG-blended concrete. However, pyrolysing the SCG at 350 °C led to a significant improvement in its material properties, which resulted in a 29.3% enhancement in the compressive strength of the composite concrete blended with coffee biochar. [Display omitted] • Spent coffee grounds (SCG) leach organic compounds that hinder the hydration reaction and compressive strength of concrete. • SCG pyrolysed at 350 and 500 °C show strong bond formation with the cement matrix. • 15 vol% replacement of sand with pyrolysed SCG at 350 °C provides ∼30% improvement in concrete strength. • 100% of 75,000 tonnes of waste SCG produced in Australia can be utilised in structural concrete. [ABSTRACT FROM AUTHOR]

With the ongoing global pandemic due to Coronavirus (COVID-19), the use of personal protective equipment (PPE), specifically single-use surgical masks, have been on a sharp incline. Currently, many countries are experiencing second and third waves of COVID-19 and as such have resorted to making face masks a mandatory requirement. The repercussions of this have resulted in millions of single-use face masks being discharged into the environment, washing up on beaches, floating beneath oceans and ending up in vulnerable places. The global pandemic has not only affected the economy and health of the world's population but now is seriously threatening the natural environment. The main plastic in single-use face masks is polypropylene which in landfill can take more than 25 years to break down. This paper explores an innovative way to use pandemic waste in concrete construction with the main focus on single-use face masks. Single-use masks have been cut-up by first removing the ear loops and inner nose wire to size and spread throughout five different mix designs to explore the possible benefits and uses within concrete. The masks were introduced by volume at 0% (control), 0.10%, 0.15%, 0.20% and 0.25% with testing focusing on compressive strength, indirect tensile strength, modulus of elasticity and ultrasonic pulse velocity to test the overall quality of the concrete. The introduction of the single-use face masks led to an increase in the strength properties of the concrete samples, as well as an increase in the overall quality of the concrete. However, beyond 0.20%, the trend of increasing strength began to decrease. • An innovative method is proposed to alleviate the waste generation issue associated with COVID-19. • The disposed surgical masks can be used to improve the strength of concrete. • The inclusion of 0.20% by volume of shredded surgical masks to concrete provided the highest strength properties. [ABSTRACT FROM AUTHOR]