In the last decades, several alternative materials have been developed to mitigate the impact of waste management, especially in the construction industry. In this framework, geopolymers have gained popularity as substitutes for ordinary Portland cement due to both mechanical and manufacturing characteristics (e.g., low energy consumption and high compressive strength) [1]. To improve both the tensile and the environmental behaviour geopolymers have been proposed as packaged matrices by adding natural fibres. The presence of natural fibres as well as the improvement in the mechanical behaviour due to the fibres make geopolymers very interesting also in restoration and/or up-dating interventions. The presence of natural fibres makes the geopolymers a composite material which must be suitably characterized from a mechanical point of view [2]. As it is well known, the first step in composite characterization is the complete mechanical characterization of the matrix and fibres. The paper aims to analyse the matrix mechanical behaviour and in detail the role of pores by analysing the relative density influences on the mechanical characteristic of the material starting with the pores analysis obtained from a computer tomography related to the relative density, and to the mechanical behaviour in terms of the compressive stress-strain curve. The results show that the pores play a fundamental role which must be taken into consideration. Future developments are represented by the suitable modelling of the pore presence in FEM analysis and the correlation with other mechanical behaviour such as tensile and flexural ones. Finally, the role of the fibres will be also investigated once the matrix has been fully characterized. REFERENCES [1] M. Alhawat, A. Ashour, G. Yildirim, A. Aldemir, M. Sahmaran, Properties of geopolymers sourced from construction and demolition waste: A review, J. Build. Eng. 2022, 50 104104. doi: 10.1016/j.jobe.2022.104104 [2] A. Karimah, M.R. Ridho, S.S. Munawar, D.S. Adi, Ismadi, R. Damayanti, B. Subiyanto, W. Fatriasari, A. Fudholi, A review on natural fibers for development of eco-friendly bio-composite: characteristics and utilizations, J. Mater. Res. Technol. 2021, 13, 2442–2458. doi: 10.1016/j.jmrt.2021.06.014.