Air drying characteristics of garjan Dipterocarpus spp. railway sleepers were investigated employing 1 x 5, 2 x 5, 1 x 7 and 2×7 piling methods. Although there was no significant difference among the drying periods in different methods, the 2×7 method appeared to be the most efficient one. This method exhibited a relatively shorter drying time irrespective of higher density and higher initial moisture content of sleepers as compared to those in other methods. The faster drying in the 2×7 method was attributed to better air circulation. Sleepers stacked in the month of April, dried down to 28% mosisture content in about eight months on
the average. It is recommended that garjan sleepers be air dried following the 2×7 method during the active drying season beginning November, instead of April, as was done in the present study, with a view to achieving further reduction in total drying time.
The moisture distribution inside the sleepers was highly variable ; the moisture gradient was steeper with increasing depth of the zone, but the steepness of the gradient decreased with increasing drying time.