Mechanical and mineralogical properties of natural hydraulic lime-metakaolin mortars in different curing conditions

Abstract

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...

New natural hydraulic lime mortars – Physical and microstructural properties in different curing conditions

“…However, mortars with MK show a general strength decrease over time for all curing conditions (except for M curing with 10% MK), suggesting instability of the hydrated compounds that are formed. This fact was discussed elsewhere based on mineralogical and chemical analysis [11] and has already been pointed out for different formulations, with air lime and MK [31] and hydraulic limes [16]. …”

“…Different curing conditions produce changes in characteristics due to the development of chemical reactions in time [16,18] and propitiate different developments in the setting and hardening reactions, which will influence the mortars strength, porosity and microstructure [11,19]. Actually, the onsite curing conditions are completely different from laboratory standardized conditions, so it is important to analyze the influence of this factor, by testing mortars with different curing conditions, either laboratorial or natural.…”

Improvements in self-consolidating cementitious composites by using micro carbonized aggregates

“…cement, sand, water and mineral or chemical additives. Various types of powders/fillers such as fly ash, silica fume, metakaolin, limestone, glass, ground granulated blast furnace slag, bentonite, rice husk ash, coconut shell ash have already been investigated by the researchers for the production of high performance cement composites [4][5][6][7][8][9][10][11][12]. The utilization of the nano/micro-sized fillers improves the mechanical performance due to the secondary hydration, heterogeneous nucleation and/or due to the filling effect of small particles C [13].…”

Investigation on masonry waste aggregate natural hydraulic lime mortars incorporating diatomite

“…The characteristics and properties NHLs present when they are used with pozzolanic materials need thorough and in-depth investigation. Grilo et al (2014) found that the strength of mortars increased when metakaolin was added to prepare NHL-based mortars, but a decrease of strength with ageing was observed with metakaolin incorporation. A high humidity condition was advantageous for hydration and pozzolanic reaction.…”