Combined effect of superplasticizer, silica fume and temperature in the performance of natural hydraulic lime grouts

• We studied the effect of temperature over superplasticized hydraulic lime grouts proportioned with silica fume.
• A loss of workability occurs if the grout temperature increases beyond 20 °C.
• An environmental temperature of 20 °C allowed a more complete hydration reaction.
• Grouts performance could be improved if they were properly designed and a suitable processing temperature was ensured.

Grouting is a current repair technique for consolidating and strengthening old masonry buildings. 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. Nevertheless, the grout properties are affected by a large number of parameters, including binder type and composition, mixing procedure, type and dosage of admixture, environmental conditions such as temperature that may lead to different grout injection capacities, as reported by several authors.This paper deals with the effect of environmental temperature over superplasticized 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 behaviour, injectability as well as its hydration reactions kinetics. In spite of the considerable amount of information that exists for cement based mixtures with superplasticizers, there is little information about the effects of superplasticizers when used in natural hydraulic lime mixtures proportioned with silica fume. This study aims to contribute to a better understanding of the behaviour that superplasticized 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.