Rheological behaviour of hydraulic lime-based grouts. Shear-time and temperature dependence
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This paper deals with the coupled effect of temperature and fly ash (FA) addition on rheological behaviour of natural hydraulic lime (NHL5) based grouts, currently used in masonry consolidation. The use of a grout injection technique for masonry consolidation may lead to an increase of hydrostatic pressure and lead to structural damage. This means that the thixotropic effects become self-evident in grout design. It was shown that there is a relation between the structuration rate of each grout and the pressure that occurs inside masonry during its consolidation. According to the results, it seems also that there is a grout threshold temperature (T limit) that separates a domain where the grout build-up structure area is almost constant, from another where flocculation area starts to increase significantly. We believe that in the first region the thixotropic effects are almost isolated from the irreversible effects (due to hydration). For the NHL5 based grout T limit=20 °C and for the grout with NHL5+15 % of FA T limit=15 °C. Grouts’ characterization based on maximum resisting time, structuration rate and on the analysis of the hydraulic lime grout behaviour tested at different shear rates was performed using a shear thinning model and assuming that the structure is shear- and time-dependent.
The goal is to use this methodology during mix proportioning and design for masonry injection purpose. The tested grout compositions were optimized compositions obtained in previous research using the design of experiments method.
KeywordsHydraulic lime grout Structuration rate Temperature Fly ash Thixotropy
The authors wish to acknowledge the support of Engs. Dina Frade, Angela Nunes and Vitor Vermelhudo for the supply of natural hydraulic lime, fly ash and material characteristics’ results and Mr. Jorge Silvério who contributed to materials’ preparation.
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