Used Coffee Grounds Enhance the Strength of Concrete by 30%
Scientists have discovered that by substituting a portion of sand with discarded coffee grounds – a substantial organic waste generated in significant quantities, typically destined for landfills – concrete can be fortified by 30%. This technique not only reinforces the concrete but also lessens the demand for natural resources such as sand, aligning with a more environmentally sustainable circular economy approach to construction.
60 Million Tons of Used Coffee Grounds Annually
Globally, it is approximated that a staggering 60 million tons (or 54 million tonnes) of used coffee grounds (SCG) are generated each year, rendering it the most plentiful waste product originating from coffee preparation. Conventionally, the majority of these coffee grounds find their way into landfills.
Presently, a team of researchers hailing from RMIT University has identified a novel and practical application for this specific type of waste. They have devised a pioneering method of integrating it into concrete. According to Rajeev Roychand, the study’s primary investigator, the motivation behind their research was to discover an inventive means of utilizing the substantial quantities of coffee waste in construction endeavors, as opposed to simply discarding it in landfills. Their aim was to offer coffee a second opportunity to be useful.
Unlocking the Potential of Spent Coffee Grounds (SCG) in Civil and Construction Applications
Due to their fine particle size, spent coffee grounds (SCG) have been suggested as a valuable component for civil and construction applications. To investigate this potential, the researchers embarked on a series of experiments. Initially, they gathered SCG from various cafés in Melbourne, Australia, and subjected them to a drying process to eliminate moisture.
Subsequently, the dried organic material underwent heating at two different temperatures: either 350 °C (662 °F) or 500 °C (932 °F), using a low-energy, oxygen-free procedure known as pyrolysis, resulting in the creation of biochar.
To assess the impact of SCG on the mechanical and microstructural properties of concrete, the researchers employed twelve distinct mix designs. These designs involved untreated SCG, SCG heated to 350 degrees, and SCG heated to 500 degrees. These SCG variants were integrated into ordinary Portland cement at volumes of 0%, 5%, 10%, 15%, and 20%, serving as a replacement for the fine aggregate, with natural sand used as the original fine aggregate material.
The Concrete Experimentation Process
The process involved pouring fresh concrete into molds, vibrating it to eliminate air voids, and subsequently curing it at room temperature for 24 hours. Afterward, the concrete samples were demolded and further cured in a water tank before undergoing testing for compressive strength. Additionally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the concrete’s microstructure. Compressive strength, in this context, refers to the maximum compressive stress that a solid material can withstand before breaking.
Among the various concrete mixtures they assessed, the research revealed that substituting 15% of sand with SCG that had undergone pyrolysis at 350 °C (662 °F) resulted in a significant enhancement in material properties, leading to a substantial 29.3% increase in compressive strength.
Although this research is still in its initial phases, the outcomes appear promising and have the potential for widespread use in construction worldwide due to the abundance of coffee.
Concrete Industry’s Role in Organic Waste Reduction
Shannon Kilmartin-Lynch, one of the co-lead authors, emphasized, “The concrete industry has the potential to play a significant role in reducing the disposal of organic waste like used coffee. While our research is in its early stages, these exciting findings present an innovative approach to greatly reduce the volume of organic waste sent to landfills.”
In addition to reducing landfill usage, this concrete production method addresses another environmental concern: the depletion of finite natural resources. Each year, we extract approximately 40 to 50 billion tons of sand and gravel for construction purposes.
Preserving Natural Resources with a Circular Economy Approach
Jie Li, co-corresponding author of the study, pointed out, “The continued extraction of natural sand from riverbeds and banks to meet the rapidly growing demands of the construction industry has a significant environmental impact. Adopting a circular economy approach would not only divert organic waste from landfills but also help preserve our natural resources, such as sand.”
The researchers have plans to conduct extensive mechanical and durability assessments on the coffee biochar pyrolyzed at 350 degrees for potential applications in the construction sector. They also intend to explore the impact of using different pyrolysis temperatures on the material’s performance.
Read the original article on: New Atlas
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