Stone used in the construction of the 8th-11th century Maya structures at Xunantunich in Belize is a low strength, porous limestone that is nearly pure calcium carbonate. Degradation of archaeologically excavated stone structures in the humid, tropical environment of Belize is caused mainly by wind and water erosion and wide cyclic variations of humidity and temperature. However, damage to the limestone is accelerated to varying extents by the chemical and mechanical effects of lichens, mosses, algae, fungi, and bacteria that are endemic to the region. To evaluate the effectiveness of possible stabilization treatments, tests were conducted in which stone-penetrating consolidant solutions were applied to limestone samples, which were then exposed to both sunny and shaded environments over a period of about four years. The results of these treatments were evaluated by particle and water erosion resistance measurements on the aged samples. The effectiveness of several biocides in controlling the establishment and growth of microflora on the exposed samples and on in situ, ancient stone walls was also studied. Some tests were conducted to determine if the organic polymer consolidants would support, or even accelerate, the growth of microflora on the stone and how the concurrent use of biocides would affect the results. Several consolidant solutions were found that could penetrate and stabilize the usually moist limestone and, in combination with biocides, would minimize the growth of the local microflora.

Key words: biocides, biodegradation, consolidants, limestone, Maya pyramid conservation