A sustainable solution for the global construction industry can be partial substitution of Ordinary Portland Cement (OPC) by use of supplementary cementitious materials (SCMs) sourced from industrial end-of-life (EOL) products that contain calcareous, siliceous and aluminous materials. Candidate EOL materials include fly ash (FA), silica fume (SF), natural pozzolanic materials like sugarcane bagasse ash (SBA), palm oil fuel ash (POFA), rice husk ash (RHA), mine tailings, marble dust, construction and demolition debris (CDD). Studies have revealed these materials to be cementitious and/or pozzolanic in nature. Their use as SCMs would decrease the amount of cement used in the production of concrete, decreasing carbon emissions associated with cement production. In addition to cement substitution, EOL products as SCMs have also served as coarse and also fine aggregates in the production of eco-friendly concretes.

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More and more importance has been given lately to the use of environment-friendly materials. Natural resins of vegetal, animal or mineral origin are increasingly employed. This article studies the properties of hybrid composites, obtained by formulating the natural resin Dammar with epoxy resin. The Dammar volume proportion was of 60%, 70% and 80%, respectively. The article is divided in two parts. In the first part, the chemical composition of the natural resin Dammar is analysed. Therefore, the substance was purified by chromatography. The structure and purity of the isolated substances were investigated by 1H-NMR, 13C-NMR experiments and mass analysis. The second part concentrates on structural characterization and on some mechanical properties of the three different hybrid composites. For this purpose, the characteristic curves, modulus of elasticity, tensile strength and elongation at break were measured. Graphic abstract

In the paper, a new Euler-Bernoulli theory is presented, in which the bars eigenpulsations with rectangular section increase with the ratio between the bar width and thickness. This theory is experimentally verified for composite bars made of Dammar reinforced with cotton and flax plus one or two layers of fiber glass fabric. For the considered bars, we have experimentally determined the eigenfrequencies and the damping factor values. We have experimentally determined the Young modulus and breaking strength for the used resin and the obtained composites.

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