Lime grout injection is used for repair and conservation of masonry structures, often in a heritage context, where the use of historic material is preferable or obligatory. A frequent application is to link delaminated masonry.
Hydraulic lime grout is injected using a diaphram pump at low pressure to avoid movement to the masonry or backfill. As the material has a low viscosity it can be injected through a 10mm probe, the minimal drill holes helping to retain the visual appearance of the structure.
Low pressure injection assists absorption, as the injected material can easily replace water or air in the structure. The grout replaces missing mortar, penetrates cracks, and fills any voids.
The low-pressure approach also allows work from underneath the soffit, with the structure remaining in full use – offering a low impact alternative to conventional methods of repair, and in most cases making traffic management unnecessary.
The lime grout’s inherent fluidity enables penetration into the masonry, and backfill where applicable.
With heritage approval the lime grout can have added non-cementitious blenders to increase the strength and fluidity. This can be useful for heritage road bridges as it retains the natural benefits of lime, including longevity, repelling water, flexibility and self-healing, while increasing the structures strength: a high strength blend can reach up to 16 N/mm of compressive strength. In comparison, pure lime grout matching existing lime putty mortar reaches a strength of 1 N/mm2. Another blender could achieve a grout equivalent of NHL 5, with 5 N/mm2 of compressive strength.
No cements are included in any of the lime grout material formulation. Lime grout injection has been used successfully on hertiage projects like churches and cemetary walls, as well as historic road bridges.
- Ideal for heritage structures
- Will link delaminated masonry Fills any large voids
- Reinforces backfill to thicken arch barrel
- Use of low pressure allows saturation of a structure
- Retains appearance of existing structure, can be injected through 10mm probes
- All quantities can be measured and recorded
- Work can be carried out from below or above
- Can be used to increase strength of the structure
- Can be used in conjunction with a acrylic waterproof system – see Masonry Waterproofing. This is also Heritage approved if it is injected into the backfill.
Application Conditions & Limitations
- Any structure that has flowing water will require some injection of waterproofing grout before the lime grout is applied. The waterproofing grout must only be applied in carefully selected locations and in controlled amounts, so as not to use up spaces that will need to be injected with the strengthening material. On a typical masonry structure, localised injection of the waterproofing grout into the backfill would give temporary relief from the flowing water to enable the lime injection to be effective. Acrylic waterproofing grout has received Heritage approval in a number of structures into the backfill.
- If substantial masonry repairs are required, these should be carried out before grouting works commence to allow the new brickwork sections to be fully bonded with the existing structure.
- Where there is a lot of missing pointing, this should be replaced as the grout is generally fine enough to run out through the missing pointing areas and will result in product loss.
- Bugle Bridge, Monmouthshire County Council
- Pont Gilbert, Monmouthshire County Council
- Ruins Bridge, Surrey County Council
- Mill Lane Bridge, Surrey County Council
- Milner Hall, Winchester, The Parish of Hampshire Downs
- Langley Park Hotel, HS-DEV