A systematic review of sustainable geopolymer concrete incorporating coconut fiber and marble powder with emphasis on mechanical performance, durability and optimal replacement levels

This systematic review investigates the use of coconut fiber and marble powder as alternative aggregates in geopolymer concretes, focusing on their mechanical performance and durability. Conducted systematically between July and November 2025, this study analyzed 75 records identified across Scopus, Web of Science, SciELO, and Google Scholar, covering publications from 2010 to 2025. Following a rigorous selection process that excluded non-experimental patents and secondary reviews, 55 primary publications (articles, dissertations, and theses) were critically evaluated. Although replacement levels of up to 40% have been reported in the literature, the most consistent evidence supports replacement rates between 15 and 20% for marble powder and up to 8% for coconut fiber. Higher substitution levels may produce satisfactory results under specific experimental conditions, particularly when coupled with alkaline activation (NaOH/Na₂SiO₃); however, these outcomes are not consistently reported across studies. Therefore, caution is recommended when extrapolating higher values. It is concluded that incorporating these industrial and agricultural residues represents a viable and sustainable alternative for the construction industry, provided that their utilization is supported by careful technical optimization.