A Systematic Review of the Durability of Natural Fiber-Reinforced Cement Composites Under Accelerated Aging

Plant fiber-reinforced fiber–cement composites are promising sustainable products, but their durability under alkaline and moisture-variable conditions remains a key limitation. This systematic review critically examines accelerated aging methodologies applied to plant fiber-reinforced fiber–cement/mortar composites. It links protocol severity to degradation mechanisms and performance evolution. Following PRISMA guidelines, 518 records were retrieved from SciFinder, Scopus and Web of Science. After screening, 41 experimental studies (2013–2023) were included. Wetting–drying (W/D) cycles dominate the evidence base (36 studies), whereas freeze–thaw (F/T) protocols are scarce (five studies) and other methods (immersion, induced reactions, biological agents) appear only once each, representing clear research gaps. Methodological appraisal showed that 87.5% of the aging studies adequately described the exposure protocol, whereas only 32.5% used multiple aging checkpoints and 26.8% included complementary microstructural or chemical validation. Mechanistically, durability losses are mainly governed by coupled matrix transport/alkalinity effects and fiber–matrix interface degradation, while matrix densification may mask deterioration if flexural strength is used alone. Quantitatively, severe W/D protocols at 70 °C produced post-cracking strength losses of up to 87–90% and toughness losses of 95–99% within 10–30 cycles, whereas under moderate or EN-type protocols MOR could remain stable or increase despite reductions of approximately 50–90% in toughness-related metrics. Matrix composition modification (SCMs/low-alkalinity binders) is identified as the predominant and most transferable durability strategy compared with fiber treatments or hybrid reinforcements. Based on evidence consistency, a reference W/D protocol is proposed (200 cycles; wetting at ~20–25 °C; drying at 60 °C; balanced phase durations with intermediate checkpoints), together with recommended durability tests prioritizing post-cracking metrics and multi-scale validation.