Nano-lime as a binder for injection grouts and repair mortars

Abstract eng:
Lime water, esters of silicic acid and plastics are common materials used for the conservation of historic mortars. Injection grouts containing cement or hydraulic lime are also employed. In recent years, the usage of hydrated lime has increased; however, the mechanical properties of the repaired material are often unsatisfactory. In many cases, due to the large particle sizes of the lime used, only loose connections with the sub-surface are obtained. The availability of materials containing lime [Ca(OH)2] nano-particles offers the possibility of creating injection grouts and repair mortars with extremely small particle sizes. All systems suggested in this paper are characterised by solids with particle sizes smaller than 6µm. They can be used to consolidate mortars and to fill voids. An important feature is that the injection grouts are able to migrate into the space between loose particles and to stabilise these areas. The materials developed are aqueous with a high stability. The solids formed by their use are characterised by having a high porosity and demonstrate good capillarity. They are hydrophilic. Typical properties of solids formed from an injection grout are: 36% porosity, 4.3 N/mm² compressive strength after 30 days, 1.1 N/mm² flexural strength, 23 wt.% water uptake and 0.4% shrinkage. This paper summarises the design and development of injection grouts and repair mortars and presents results from initial applications. The concept developed allows the adjustment of the properties of the injection grouts and repair mortars to the properties of the mortars that have to be consolidated.

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