Comparison of resistance improvement to fungal growth on green and conventional building materials by nano-metal impregnation

This study is aimed for comparing the biological resistance of green and conventional building materials (BMs) before and after nano-metal treatment, as well as exploring best nano-metals to improve fungal growth resistance of BMs. The selected BMs include wooden flooring (WF), green wooden flooring (GWF), gypsum board (GB), green gypsum board (GGB), calcium silicate board (CSB), green calcium silicate board (GCSB), mineral fiber ceiling (MFC) and green mineral fiber ceiling (GMFC). The Aspergillus brasiliensis or Penicillium funiculosum was inoculated on each sample and their growth was visually evaluated according to ASTM G21-09. The fungal growth without nano-metals on test materials did not show that green materials were more prone to fungal growth. After nano-metal treatment, the observed order of fungal growth resistance of nano-metals at their highest selected concentrations on test materials was nano-zinc = nano-copper > nano-silver for WF and GWF, nano-zinc > nano-silver = nano-copper for GB, nano-zinc > nano-silver > nano-copper for GGB, CSB and GCSB, nano-silver > nano-copper = nano-zinc for MFC, and nano-silver > nano-copper > nano-zinc for GMFC. Nano-zinc seems to be the most favorable nano-metal for wood and wood composite materials. Green materials were less resistant to fungi attack relative to their conventional counterparts treated by nano-metals, particularly GWF and WF. All test nano-metals failed to provide complete protection against fungal growth on the eight test BMs at the selected concentrations. However, the higher the nano-metal concentration was, the longer the lag period until growth began and fewer fungi grew on the materials. (C) 2015 Elsevier Ltd. All rights reserved.