Properties of lime–metakolin mortars for the restoration of historic masonries

Mortars were prepared by mixing metakaolin/hydrated lime (with a ratio of ≤ 1 by mass) with sand and were evaluated in order to be used as restoration mortars on historic masonries. During 12-months curing time the chemical reactions were evaluated by thermal analysis (DTA/TG), the microstructural properties by mercury intrusion porosimetry (MIP) and the mechanical characteristics (flexural and compressive strength, static modulus of elasticity) by conventional mechanical tests. As the metakaolin/lime ratio increased, the content of total bound water, the static modulus of elasticity, the compressive and flexural strength increased while the pore size distribution shifted to smaller values. All mixes presented sufficient mechanical and microstructural properties comparable to traditional structural materials.

Research highlights
► The mechanical strength increased with the mixing ratio of metakaolin/lime (with a ratio of ≤ 1 by mass).
► The pore size distribution shifted to narrower pores with increasing the mixing ratio of metakaolin/lime.
► All mixtures revealed mechanical and microstructural properties comparable to traditional structural materials.