Formulating Stone Wastes and Unsaturated Polyester Resin for Building Material Using an Extreme Vertices Mixture Design

The incorporation of waste stone into polymer resins to create artificial stone has received a lot of attention because it can replace a limited amount of natural stone and at the same time recycle unused waste stone. In this study, the development of artificial stone aims to replace padas stone from Bali, Indonesia, to achieve a similar colour and satisfactory flexural strength using three different types of stone waste (tabas, red brick, and pumice). The results show that the lower colour difference (∆E) to padas stone resulted by a formula with high content of red brick, in which the optimum formula was predicted at 42.64% unsaturated polyester resin, 3.48% dyes, 0% tabas, 26.56% red brick, and 27.32% pumice resulted in ∆E =̃ 16.0. The flexural strength values for all formulas (12–26 MPa) have exceeded the control value (0.7 MPa). The morphological analysis of the optimized sample showed good compatibility between resin and stone waste, as noted by small pores that result in higher mechanical properties (19.732±1.398 N/mm2 in flexural strength, 20.283±2.393 N/mm2 in compressive strength and 258.50±8.18 N/mm2 in hardness) than the control sample. The water absorption test results also show that the artificial stone is more resistant to a humid environment.