High strength artificial stoneware from marble waste via surface modification and low temperature sintering

Huge amounts of marble wastes pose serious hazards to the environment, water resource, vegetation growth as well as public health. In this work, high strength artificial stoneware was prepared from waste marble powder by the combination of surface modification and low temperature sintering. The marble powder was initially modified with silicane coupling agent, and then sintered into stoneware with the sintering binders (boehmite and silica) and filler (CaCO3). The processing parameters were investigated to clarify their effects on the bulk density and flexural strength of sintered stoneware. The elevated sintering temperatures and prolonged sintering times resulted in the thermal decomposition of calcite phase, so that the optimum sintering process was achieved at 590 °C for 90 min. Compared to silica sol, boehmite sol was more effective to increase the flexural strength. The addition of ground CaCO3 powder facilitated the densification and strengthening, while the excessive filler caused the agglomeration of filler particles and reduction of bulk density and flexural strength. The maximum flexural strength of stoneware (42.2 MPa) is high superior to that of original marble slabs. The strengthening mechanism was qualitatively discussed in terms of the densification and interface adhesion. The facile and scalable approach and high strength stoneware pave the way to the massive recycling of marble wastes in the ornamental construction tiles.