RESIDUAL-STRESSES IN ASBESTOS-CEMENT PIPES

Longitudinal cracks were observed in asbestos-cement pipes that were in service for some time before bursting. Preliminary tests using a slitting technique showed residual stresses in the hoop directions. Absolute peak stresses are critical for determining the bursting strength of the asbestos-cement (asb/cem) pipes. The experimental techniques of photoelastic coating and the blind-hole drilling method were implemented in measuring local residual stresses and determining their principal values and directions. Relatively high residual stresses were recorded, which is an indication of the cause of the cracks. Conditions of manufacturing, storing, and environment during service are investigated. Moisture content, storing conditions, and chemical reaction of the asbestos-cement mixture seem to be the major causes of the cracks. Coating the pipes would be an effective precaution. © ASCE.