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Grilo, J.; Faria, P.; Veiga, R.; Santos Silva, A.; Silva, V.; Velosa, A. New natural hydraulic lime mortars Physical and microstructural properties in different curing conditions. Construction and Building Materials, v. 54, p. 378-384, 2014. March 2014 1 Keywords (max. 10 words)EN 459-1:2010; natural hydraulic lime; mortar; curing condition; metakaolin; laboratory characterization Grilo, J.; Faria, P.; Veiga, R.; Santos Silva, A.; Silva, V.; Velosa, A. New natural hydraulic lime mortars Physical and microstructural properties in different curing conditions.

This work evaluates the influence of the binder:aggregate ratio in respect to mineralogical and mechanical properties of air lime-metakaolin mortars.Mineralogical analysis showed that binder:aggregate ratios modifies the extent of carbonation and pozzolanic reactions with curing. The pozzolanic reaction occurs mostly at lower curing times (28 days), while, at higher curing ages, carbonation reaction is mostly dominant. The exceptions are mortars with 1:1 (air:lime) volumetric ratio with 30% and 50% MK in which the pozzolanic reaction is still dominant.For conservation purposes, the mechanical tests demonstrated that 1:2 and 1:3 mortar volumetric ratios were considered adequate proportions since 1:1 was considered a "strong" ratio, as it can induce tensions and mortar shrinkage that can damage historic masonries. Keywords

Grilo, J.; Santos Silva, A.; Faria, P.; Gameiro, A.; Veiga, R.; Velosa, A. Mechanical and mineralogical properties of natural hydraulic lime-metakaolin mortars in different curing conditions. Construction and Building Materials, v. 51, p. 287-294, 2014. January 2014 1 Tests were conducted at different curing ages, using compressive and flexural strength tests and thermogravimetric and X-ray diffraction techniques.NHL mortars cured at high humidity levels in natural and artificial environments present interesting results and some could be used in old masonries repair.The incorporation of MK improves the NHL mortars strength, being this increase mostly associated to the pozzolanic reaction. KeywordsHydraulic mortars; NHL3.5; metakaolin; curing conditions; characterization; XRD; TG-DTA;Grilo, J.; Santos Silva, A.; Faria, P.; Gameiro, A.; Veiga, R.; Velosa, A. Mechanical and mineralogical properties of natural hydraulic lime-metakaolin mortars in different curing conditions. Construction and Building Materials, v. 51, p. 287-294, 2014. January 2014 2 IntroductionEarly civilizations, namely the Greeks and Romans, produced limes to employ in mortars for construction. The durability of these mortars is recognized worldwide, even in buildings exposed to water and is mainly attributed to the use of natural earth- The use of hydraulic lime, that also goes back to antiquity with the use of limes with various levels of hydraulicity, has been revived in the past few years, especially when the conservation of historical buildings is pursued. In particular, the natural Grilo, J.; Santos Silva, A.; Faria, P.; Gameiro, A.; Veiga, R.; Velosa, A. Mechanical and mineralogical properties of natural hydraulic lime-metakaolin mortars in different curing conditions. Construction and Building Materials, v. 51, p. 287-294, 2014. January 2014 3 hydraulic limes seem to have the possibility to be an adequate choice due to their improved compatibility with old masonry, by having low shrinkage, resistance to salt and frost damage, in comparison with PC or other hydraulic lime mortars, as well as higher deformability and water vapour permeability [5,9,12].NHL are obtained by calcining mixtures of clayish or siliceous limestones at temperatures below the clinkering point, before being reduced to a powder by adding controlled amounts of water. A fundamental characteristic of these lime mortars is the fact that they have two hardening phases: a hydraulic phase, based on its hydration, resulting in the formation of calcium and calcium-aluminum silicate hydrates, and another developed during the CO 2 contact, and designated as carbonation [11,13,14]. Pozzolans are composed by siliceous and silico-aluminous substances, which when hydrated do not harden with water; however, when they are powdered and in presence of calcium hydroxide they react to form new compounds, such as silicates and calcium aluminate hydrates, with hydraulic properties [1,17,18].Besides the influence of the addition of pozzolanic materials the mortars' curing conditions...

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Mortars constituted of lime mixtures with pozzolanic additions have been extensively used in the past for the construction of historic and traditional buildings. This paper presents the results of blended pastes of lime and metakaolin (MK), namely compounds formed and their stability over time. This research is part of an extensive study aiming at the formulation of lime based mortars for restoration purposes. It has been shown for several years that MK has been applied in inorganic binders due to its capacity to react vigorously with calcium hydroxide (CH). In the presence of water originating a series of major hydrated phases, namely tetra calcium aluminate hydrate (C4AH13), calcium silicates hydrates (CSH) and calcium aluminium silicate hydrates (stratlingite-C2ASH8). Several blended pastes of lime and MK, with different substitution rates of lime by MK (wt%) were prepared and cured at a temperature of 20 •C and relative humidity RH > 95%. The phase composition of the formed hydrated phases was determined by X-ray diffraction (XRD) and simultaneous thermal analysis (TG-DTA). The obtained results showed that lime/MK pastes compositions displayed different reaction kinetics during curing time, being the pozzolanic products content directly proportional to the substitution rate of lime by MK. Also, a relationship between the increase stratlingite content and the MK substitution rate of lime by MK was found.

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