Biomimic conservation of weathered calcareous stones by apatite

Conservation of the weathered historic calcareous stones by apatite was studied. By mimicking the growth of bone, calcium and phosphorus were introduced into the weathered stone and then mineralized at room temperature. The conservation efficiency was investigated by SEM, EDX, XRD, "Scotch Tape Test" (STT), compressive strength test, capillary water uptake test, water vapor permeability test and weather resistance test. The results of SEM, EDX and XRD showed that the produced bone-like hydroxyapatite could bind the introduced calcium carbonate and the weathered stone blocks together. The test results also indicated that this conservation method could improve the surface strength, compressive strength and weather resistance of the treated samples significantly. Besides, due to the porous nature of the bone-like apatite, the water vapor permeability of the treated stone was not affected and its "breathe function" was retained. Therefore, the proposed method will be a good candidate for the in situ conservation of historic calcareous stones.