Creep is a key factor in the early and long-term cracking of cement-based structures and is typically characterised using static creep tests, a well-established experimental method. However, when testing cement paste—the main contributor to viscoelastic behaviour in cement-based materials—several challenges arise due to the absence of standardised testing protocols, with practical solutions rarely addressed in depth in the literature. This work addresses some challenges of conducting static creep tests on cement paste, focusing on practical solutions based on the author’s experience. The testing rig was an adapted oedometer frame, originally designed for soil testing, combined with a radially distributed array of Linear Variable Differential Transformers (LVDTs) mounted on the specimen with bolt-fixed rings to measure delayed displacements. Precautions for assembling this test setup were identified and commented on. Hollow, thin cylindrical specimens were developed to ensure adequate stress levels during testing. Specific challenges of moulding these samples and potentialities that arise from such specimen geometry are discussed. A custom system was also designed to monitor the load application, eliminating the need for load cells while allowing the determination of the instant of full load application. Additionally, a custom Python-based post-processing library was implemented to automate the analysis of experimental data. Exemplary results of creep tests illustrate the performance of the test setup and the typical dispersion of results.

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Experimental Challenges in Static Creep Testing of Cement Pastes

  • Renan Rocha Ribeiro,
  • José Granja,
  • Rodrigo Lameiras,
  • Miguel Azenha

摘要

Creep is a key factor in the early and long-term cracking of cement-based structures and is typically characterised using static creep tests, a well-established experimental method. However, when testing cement paste—the main contributor to viscoelastic behaviour in cement-based materials—several challenges arise due to the absence of standardised testing protocols, with practical solutions rarely addressed in depth in the literature. This work addresses some challenges of conducting static creep tests on cement paste, focusing on practical solutions based on the author’s experience. The testing rig was an adapted oedometer frame, originally designed for soil testing, combined with a radially distributed array of Linear Variable Differential Transformers (LVDTs) mounted on the specimen with bolt-fixed rings to measure delayed displacements. Precautions for assembling this test setup were identified and commented on. Hollow, thin cylindrical specimens were developed to ensure adequate stress levels during testing. Specific challenges of moulding these samples and potentialities that arise from such specimen geometry are discussed. A custom system was also designed to monitor the load application, eliminating the need for load cells while allowing the determination of the instant of full load application. Additionally, a custom Python-based post-processing library was implemented to automate the analysis of experimental data. Exemplary results of creep tests illustrate the performance of the test setup and the typical dispersion of results.