Performance evaluation of date-pit-reinforced unsaturated-polyester–dune-sand mortars

Polymer mortars are increasingly used in modern construction for rapid and effective repairs, outperforming traditional Portland cement mortars. Concurrently, the availability of natural aggregates, which constitute a significant proportion of mortar and concrete mixes, is becoming increasingly limited. This scarcity of natural aggregates strains finite resources and presents challenges for the construction industry. Simultaneously, the date palm industry generates substantial waste in the form of discarded date pits (DP), creating economic and environmental challenges. This study examined the feasibility of using industrial DP waste as a partial aggregate replacement in unsaturated polyester resin (UPR)–dune sand (DS) polymer mortars. The mortar formulations contained 3, 5, 7, and 10 wt% of DS with DP in a 60/40 DS/UPR mix. The physical, thermal, mechanical, and durability properties were comprehensively evaluated. To validate the findings, a range of analytical techniques was employed, including thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The incorporation of DP moderately improved the compressive, tensile, and flexural strengths, with optimal values of 82.4, 18.5, and 7.5 MPa, respectively, achieved at 5 wt% DP loading (5DP–UPRM). Furthermore, DP incorporation decreased the thermal conductivity, ranging from 0.479 to 0.595 W/m·K, thereby enhancing the insulation capability. The DP-containing mortars also exhibited reduced densities of 1645–1800 kg/m³. These findings support the use of DP as an alternative aggregate in polymer mortars, thereby highlighting its potential value in construction applications.