This work describes in detail the experimental investigation of the physico-mechanical properties of nonstructural hemp concrete (usually used as insulating wall material) when the Air-lime based Tradial PF70 binder is partially replaced using Metakaolin. The objective is to reduce the amount of free Ca2+ ions in the binder as these are responsible for the degradation of vegetables particles and can therefore induce a loss of mechanical perfor-mances. In order to assess the effectiveness of pozzolanic reaction, amounts of 0%, 10%, and 20% vol. of Air-lime binder were replaced by the Metakaolin material, while testing the mechanical properties of concrete specimens containing 200% and 300% of hemp particles. Through SEM and EDX analysis, a tight relationship has been found to exist between the Metakaolin content and physical-mechanical properties of specimen. The pozzolanic reaction consumes calcium hydroxide from binder to produce Hydrated Calcium Silicates (C-S-H) and in turn, this leads to a decrease in the pH-value of the pore solution which is the main factor responsible for hemp particle degradation.