A comparison of effectiveness of three waterborne preservatives against decay fungi in underground mines- An appraisal
To understand the effectiveness of waterborne preservatives and to explore the behaviour of roof supporting poles after pressure treatment, an experiment was conducted and thorough investigation was carried out during the last decade in the underground mines. Prior to commencement of the experiment, a survey was conducted at different depths in underground mines and collected decayed wood samples and got them identified.
The waterborne preservatives used in underground mines were CCA, CCB and ACC. Two species of timbers namely Casuarina equisetifolia and Eucalyptus hybrid were treated by pressure process. Absorption of preservatives were calculated and penetrations were carried out on selected poles. Retention of salts were estimated. Preservative treated poles along with controls were installed at different depths consisted of varied environmental conditions of relative humidity, temperature and water seepage in underground mines. Absorption on the condition of test poles and effectiveness of preservatives were carried out after every six months for over 8 years. Observation revealed that untreated controls were destroyed by decay fungi within 3 to 5 years, whereas treated poles remained serviceable even after 8 years of exposure and estimated to last for over 12 years. Environmental factors like warm and humid air coupled with water seepage contributed for rapid decay of timbers in mines. The overall observation on the efficacy of preservatives indicated that in spite of a close competition among preservatives for superiority, CCA and CCB were found effective against decay fungi as compared to ACC.
Keywords: Casuarina equisetifolia, Eucalyptus hybrid, waterborne preservatives, decay fungi, warm and humid air, underground mines, penetration and absorption