Prediction model for optimized compositions of Formulated Limes (EN 459) for restoration and reconstruction mortars

Abstract eng:
The use of lime for the construction of buildings and monuments has a long tradition. Therefore, limebased materials are also predominantly used and often even required in the field of reconstruction and restoration. The demands on mortars and thus the binders vary due to purpose, exposition and affected/surrounding materials. While chemical admixtures or modern cement mortars are often unwanted and not compatible for restoration work, mortars made of Formulated Limes (FL) offer an alternative with a wide spectrum of possible properties. The latest version of EN 459 added the Formulated Limes as a new group of limes with hydraulic properties. A wide range of possible amounts and combinations enables an enormous spectrum of mortar mixes with different properties. The EN 459 considers only few of these for the classification of the FL. The classification is based on the content of available lime and the values of compressive strengths after 28 days. By these demands nine different FL classes can be defined. The possible mixing proportions are not considered. In order to predict the material properties for all possible mixtures of FL, a model was developed providing a general database. This allows quantifying the interactions of various components in different amounts as well as their influence on the properties of fresh and hardened lime based mortars.By means of statistical experiments selected possible mixtures were chosen to prepare mortar samples for analysing bending tensile- and compressive strength as well as density, pore size distribution and modulus of elasticity. Furthermore, the durability of differently composed mortar samples was studied by testing capillary water transport, efflorescence, and sulphate- as well as freeze thaw resistance. Accompanied by a computer programme this model reveals information about the mortar properties by the input of kind and amount of raw materials.

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