Repair mortars. Working principles and typical properties.

Abstract

Mortars used in construction are composed by the aggregate, the binder and possibly also some additives. They also require water to form a workable paste. In building conservation, mortars are used principally as plasters or renders, bedding (masonry) mortars, pointing mortars, stone repair mortars or for laying or grouting wall or floor tiles. Soluble salt crystallization is one of the major decay mechanisms of historic constructions, and the use of appropriate plasters/renders can be one of the most effective ways to deal with it. Therefore, a special emphasis is given in this lecture to this particular use of the mortars. Overall, the lecture has the following structure: 1 Introduction 2 Binders 2.1 – Earth 2.2 – Lime: air lime; hydraulic lime 2.3 – Cement: natural cement; Portland cement 2.4 – Pozzolans: natural; artificial 3 Influence of different binders on the properties of the mortar/plaster/render 4 Plasters and renders for salt loaded walls 4.1 – Working principles 4.2 – Some influencing factors 4.2.1 - The substrate 4.2.2 - The paint layer 4.3 – How to select / prescribe?