Investigation of the Influence of Pine Cone and Pine Resin Addition on the Properties of Plaster Composites

The physical characteristics of gypsum plaster composites made from agricultural wastes of pine cones (PCs) and pine resin (PR), as sustainable substitutes for traditional natural fillers, are examined in this work. Particle sizes of 3–5 mm, 0–3 mm, and powder were used to classify the PCs after grinding. First, gypsum plaster was replaced with PC particles at 20%, 40%, 60%, and 80% by weight for each group to produce resin-free specimens. To create artificial porosity and improve the matrix’s binding strength, 1% PR by total weight was then added to duplicate mixes, yielding 24 different sample combinations. In resin-free samples, the addition of 3–5 mm, 0–3 mm, and powder PC (in ratios ranging from 20% to 80%) reduced the thermal conductivities by 35.16%, 33.84%, and 34.97%, respectively, and the compressive strength values by 82.00%, 77.18%, and 77.50%. Further decreases in thermal conductivity (29.36%, 32.05%, and 33.66%) and compressive strength (76.89%, 75.64%, and 75.48%) were observed in PR-modified samples. The results show that adding PCs and PR to gypsum plaster considerably improves the plaster’s thermal insulation while marginally reducing its compressive strength loss.