Coating Delamination by Radial Tension in Prestressed Concrete Pipe. II: Analysis

Abstract

Part II of a two‐part paper studying the delamination by radial tension of mortar coating of prestressed concrete cylinder pipe. Part II contains the results of the analysis of mortar coating behavior using a finite‐element model. The results provide an understanding of the stress states in the mortar coating and the mechanics of coating delamination when the coating is subjected to shrinkage, an applied radial tension, a wire radial expansion resulting from the Poisson effect of a stress reduction in the prestressing wire, or a combination of these effects. The results of the analysis support the experimental observations that shrinkage and wire spacing in the range of two wire diameters or more have small effects on the radial tensile strength of the mortar coating, but wire spacing of less than twice the wire diameter increases the radial tensile stress in mortar between the wires and the propensity of the pipe's coating to delaminate. The results of analytical and experimental studies also indicate that in early‐age pipe, coating delamination is governed by the failure criterion of maximum tensile stress or by linear elastic fracture mechanics, with no significant softening of mortar between the wires. As mortar matures, radial tensile strength, of the coating increases, and coating delamination becomes governed more by the average tensile strength of mortar between the wires.