Adaptation of the standard EN 196-1 for mortar with accelerator

In certain applications, accelerators are added to favour a rapid evolution of mechanical properties in mortar and concrete. In order to assure adequate performance, it is necessary to test the compatibility between the accelerator and other components of the mixture. The EN 934-5 establishes that such evaluation of accelerators should be performed according with the procedure established in the EN 196-1. However, this standard does not take into account the inclusion of the accelerators or the particularities of the mortar produced with these admixtures. The objective of this paper is to adapt the EN 196-1 in order to characterize the strength of mortars with accelerator. First, an experimental parametric study to evaluate the influence of the production procedure on the results was conducted. Based on the results obtained, a modified production process was proposed. Then, a wide experimental program including a total of 40 mixes of mortars with different formulations and contents of accelerators was performed. Based on a statistical analysis, a new admissible variation used to calculate the compressive strength was proposed

Alternative quality control of steel fibre reinforced sprayed concrete (SFRSC)

Steel fibre reinforced sprayed concrete (SFRSC) is used in applications with high structural capacity requirements. The quality control of SFRSC typically includes the assessment of toughness-related properties and measurement of the fibre content. The toughness may be measured with the beam test to EN 14488-3:2006, whereas the fibre content is generally measured by manual methods, such as collecting and weighing the fibres. Both procedures are time-consuming, difficult to perform and challenging to conduct with specimens extracted from the in-situ structure. These difficulties can therefore limit the frequency of characterization and hence potentially compromise the reliability of the information obtained, thus hindering the capacity of engineers to either detect potential problems or to optimize the material. The objective of this work therefore is to explore a simpler SFRSC quality control system that includes the inductive method for the assessment of fibre content and the Barcelona test for the assessment of toughness. Dry-mix SFRSC with five fibre contents were sprayed and tested with beam, Barcelona and inductive tests. Results confirm the greater sensitivity of the Barcelona test and the advantages of combining it with the inductive method for an enhanced quality control. Furthermore, equations are proposed to predict the beam test results using the Barcelona test results. These equations provide a good fit (R2 = 0.97) regardless of the fibre content in the mix, thus confirming the robustness of the approach both for the classification and for the quality control of SFRSC.</p