What is it about?

A simple analysis procedure is presented to quantify the tensile creep properties of shotcrete using results obtained from standard ring tests and mechanical property tests. Both free and restrained shrinkage tests were performed to derive the total tensile strain behavior (i.e., creep effect) of wet-mix and dry-mix shotcretes.

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Why is it important?

It showed that adding silica fume, fly ash, polymer, shrinkage-reducing admixture (SRA), and crack-reducing admixture (CRA) reduces the total tensile strain properties of shotcrete. However, the decrease observed when using SRA and CRA does not increase the risk of early-age cracking because shrinkage is also reduced


To reduce the potential for shrinkage cracking of shotcrete, it may be necessary to rethink the use of silica fume and fly ash in dry-mix shotcrete. Keeping in mind that these mineral additives are used principally to reduce material rebound rate, it is recommended to use SRA or CRA to minimize their impact on the shrinkage cracking sensitivity of dry-mix shotcrete. A similar recommendation could be made when shotcrete is modified with a polymer. Overall, the approach presented in this paper provides an improvement to the use and interpretation of ring test results, which is much awaited in the repair industry, to assist both the development of crack-free repair materials and the issuance of improved materials performance specifications. Further work is needed to demonstrate its applicability to a wider range of shotcretes and its usefulness in applications such as concrete repair.

Dr. Bruce Menu
Universite Laval

Read the Original

This page is a summary of: Evaluation of Early-Age Volume Changes of Shotcrete Using Ring Specimens, Journal of Materials in Civil Engineering, November 2023, American Society of Civil Engineers (ASCE),
DOI: 10.1061/jmcee7.mteng-16125.
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