Abstract
The injection of grouts is a consolidation technique suitable for overcoming the structural deterioration of old stone masonry walls. Grouting operations involve introducing a suspension (grout) into a masonry core with the aim of improving the load capacity of the wall, as well as reducing its brittle mechanisms. The yield stress of injection grouts will affect the injection pressure and their flow inside the masonry. However, the determination of some rheological properties such as yield stress in hydraulic grout is challenging, due to the combined effects of hydration reactions and interactions between the particles present in the suspension. In this study, the determination of the yield stress of natural hydraulic lime-based grouts with polypropylene fibers was carried out. The changes in yield stress with time, fibers content and hydration were evaluated by two measurement methods using a rotational rheometer. Additionally, the static and dynamic yield stress as well as the critical shear–strain rate were determined, which provided useful information on the grout design in order to achieve successful grouting operations.
Highlights
Ordinary or historical buildings in most european cities until the mid-20th century were built with stone masonry walls
It should be highlighted that the shear–strain rate range tested corresponded to the typical shear rate range during the grout injection process in order to reveal representative rheological parameters
−1 to s would lead to a static yield stress, while shear–strain rates higher than s would provide to 1 s would lеad to a static yiеld strеss, whilе shear–strain ratеs highеr than 3 s would providе aa dynamic dynamic yield yiеldstress
Summary
Ordinary or historical buildings in most european cities until the mid-20th century were built with stone masonry walls. Several studies show that yield stress exists and, when the suspension is thixotropic, the yield stress strongly depends on a build-up and break-down of the material [7,8,9]. Besides the improvement of mechanical properties that PP fibers can provide, the rheological properties, especially the yield stress, of grouts containing PP fibers should be examined for an accurate injection. Within this scope, this work aimed to determine both the static and dynamic yield stress of NHL grouts, including the contribution of thixotropy, time period and PP fibers content, by means of two measurement methods using a rotational rheometer. Several correlations between yield stress, time and critical shear–strain rate (marking the transition from dynamic to static yield stress) were developed
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