Performance improvement of hydraulic lime based grouts for masonry consolidation: An experimental study

Grouting is currently a repair technique for consolidating and strengthening old masonry structures. Grouts can be seen as mixtures of binder with water, admixtures and/or additives, which should present low viscosity and high penetrability. The grout specification involves the knowledge of the flow capacity within the masonry inner core and physic-chemical compatibility with the original materials present in the historic structures. Nevertheless, the grout properties are affected by a large number of parameters, including binder type and composition, mixing procedure, admixture type and dosage, environmental conditions, like temperature that may lead to different grout injection capacities, as reported by other studies. This paper deals with the effect of environmental temperature over superplasticised hydraulic lime-based grouts with partial replacement of lime by silica fume. Grout performance was analysed in fresh and hardened state by testing its rheological and mechanical behaviour, as well as its hydration reactions kinetics. In spite of the considerable amount of information that exists for cement based mixtures with superplasticisers, there is little information about the effects of superplasticisers when used in natural hydraulic lime mixtures proportioned with silica fume. This study aims to contribute to better understand the behaviour that superplasticised hydraulic lime grouts present under different temperatures. The results showed that hydraulic lime grouts performance could be improved, regarding rheological parameters and strength capacity if they are properly design and a suitable processing temperature were ensured.