What question did this study set out to answer?

The aim is to assess the utilization of coffee waste in cement and concrete, with a focus on mechanical performance and environmental impact in South Africa.

July 1, 2026Discover Civil Engineering0 citationsOpen Access

Coffee by-products in cement mortar and concrete: a comprehensive bibliometric and systematic review of its potential for the South African construction industry

ODOpeoluwa DadaUniversity of South Africa DADawit Beza AlemuUniversity of South Africa BIBolanle Deborah IkotunUniversity of South Africa

Key Points

The aim is to assess the utilization of coffee waste in cement and concrete, with a focus on mechanical performance and environmental impact in South Africa.
Systematic search of four databases yielding 1,797 records
200 reports underwent full-text assessment, culminating in the inclusion of 63 studies
Evaluation of mechanical properties, durability, and microstructural behaviour of coffee by-products
1.1% raw SCG by cement weight improves compressive strength by up to 30%
Pyrolyzed biochar reduces chloride permeability and increases matrix density
Raw SCG disrupts the Interfacial Transition Zone, increasing porosity and reducing workability

Abstract

This article systematically reviews the use of coffee waste, mainly Spent Coffee Grounds (SCG) and their derivatives, in cement and concrete, focusing on studies of mechanical performance, durability, and microstructural behaviour worldwide. A systematic search of four databases yielded 1,797 records, which, after duplicate removal and screening, left 200 reports for full-text assessment; following exclusions for lack of quantitative data, irrelevant content, or lack of South African relevance, 63 studies were finally included in the review. It synthesizes experimental, analytical, and microstructural research conducted regionally and globally to assess their applicability within the South African sustainability context. In this review, findings are categorized into four main areas: mechanical properties, durability, microstructural evolution, and environmental impact. Results show that the mechanical performance of concrete containing coffee waste depends heavily on the treatment and dosage of the waste. Optimal improvements were observed with 1.1% raw SCG by cement weight, 5% SCG ash as a cement replacement, and 15% SCG biochar as a fine-aggregate substitute, resulting in up to a 30% increase in compressive strength. However, untreated SCG reduced workability and increased shrinkage due to its high water absorption and organic content. To evaluate durability, including the Rapid Chloride Permeability Test (RCPT), water absorption, and drying shrinkage tests, it was found that raw SCG increases permeability and shrinkage. Conversely, pyrolyzed biochar significantly reduces chloride ion penetration and enhances the matrix density. Microstructural analyses reveal that raw SCG disrupts the Interfacial Transition Zone (ITZ), increasing porosity, whereas biochar promotes additional C–S–H gel formation and leads to a more refined pore structure. In the South African context, SCG biochar shows strong potential as a supplementary cementitious and insulating material, complementing fly ash and calcined clays to promote low carbon construction. Overall, the review concludes that converting SCG into biochar or ash supports sustainable waste valorization while delivering measurable improvements in mechanical performance (up to + 30%) and durability, along with a 25% reduction in chloride permeability.

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