Evaluation of the residual prestress force in aged railway concrete sleepers considered for reuse
type: CreativeWork
description: The increasing demand for railway transport in South Africa has led to the expansion and upgrade of the existing track infrastructure in recent years. Given the high costs associated with new development or refurbishment of existing infrastructure, asset owners and managers are faced with the challenge of optimising expenditures while extending the service life of their infrastructure. One of the essential structural components of a conventional railway track is the prestressed concrete sleeper. In South Africa, these sleepers are designed to last for 40 years, and their replacement plan is aligned with their design life. Given the desire to extend the useful life of sleepers, aged concrete sleepers are often removed from primary running lines for second-hand use in branch, sidings and yard lines. However, the current quality assurance system for reusing sleepers relies mainly on visual condition assessments, which only consider the external surface of the concrete, neglecting the internal condition of the reinforcing and prestress steel and, critically, the remaining prestress force, which is crucial for the flexural strength. To address this gap, a study was conducted to determine the prestressing force of concrete sleepers post-design life using the dynamic relaxation method. The study involved sampling 21 P2 concrete sleepers, comprising eighteen old sleepers (manufactured in 1977) and three new sleepers (manufactured in 2006). Six of the 21 sleepers were used to determine compressive and tensile strength values of concrete and steel wires, respectively, while the remaining 15 sleepers were subjected to dynamic relaxation testing. Visual condition assessment revealed several types of concrete damage caused by operation and maintenance activities, with notable bending cracks propagating from the sleeper base around the rail seat region. Additionally, concrete surface abrasion was identified on the base, sleeper sides, and on the rail seat area. The two steel comp…
abstract: The increasing demand for railway transport in South Africa has led to the expansion and upgrade of the existing track infrastructure in recent years. Given the high costs associated with new development or refurbishment of existing infrastructure, asset owners and managers are faced with the challenge of optimising expenditures while extending the service life of their infrastructure. One of the essential structural components of a conventional railway track is the prestressed concrete sleeper. In South Africa, these sleepers are designed to last for 40 years, and their replacement plan is aligned with their design life. Given the desire to extend the useful life of sleepers, aged concrete sleepers are often removed from primary running lines for second-hand use in branch, sidings and yard lines. However, the current quality assurance system for reusing sleepers relies mainly on visual condition assessments, which only consider the external surface of the concrete, neglecting the internal condition of the reinforcing and prestress steel and, critically, the remaining prestress force, which is crucial for the flexural strength. To address this gap, a study was conducted to determine the prestressing force of concrete sleepers post-design life using the dynamic relaxation method. The study involved sampling 21 P2 concrete sleepers, comprising eighteen old sleepers (manufactured in 1977) and three new sleepers (manufactured in 2006). Six of the 21 sleepers were used to determine compressive and tensile strength values of concrete and steel wires, respectively, while the remaining 15 sleepers were subjected to dynamic relaxation testing. Visual condition assessment revealed several types of concrete damage caused by operation and maintenance activities, with notable bending cracks propagating from the sleeper base around the rail seat region. Additionally, concrete surface abrasion was identified on the base, sleeper sides, and on the rail seat area. The two steel comp…
author: Seketema, Nonofo Olefile
language: en
keywords: Aged railway, concrete sleepers
date published: 2025
date modified: 2026-07-22T22:22:58Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Civil Engineering

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/42664