Restoration and decoration


Gravitational injection

Certain existing masonry structures that cannot be removed present structural defects (dividing walls, structural elements that are costly or complex to replace). When these defects involve cracks or disintegration of roughcast mortar, gap-filling with grout can provide the appropriate binding. This technique involves injecting mixtures of binders, water and sometimes fine sand into masonry under gravitational pressure. The reinforcement of structures using this technique requires prior pointing and appropriate render. Introducing fluid materials into an already fragile assembly demands particular know-how and care. Slurries will fill the whole of the structure by hydraulic pressure: injection is generally done by pouring mortar in from a height of 50cm.

Area of use: 
Prompt natural cement based grout injections in old buildings can:

  • repair masonry structures that show structural defects which have to be maintained through the filling of gaps and cracks,
  • seal micro-piles drilled in the masonry or the surrounding ground,
  • repair water inlets and make the ground waterproof, avoiding the use of costly aquareactive resins.

Benefits of using Prompt natural cement: 
The addition of Prompt natural cement to a lime injection grout presents several advantages linked to its quick setting:

  • injection of zones on the edges of structures through rapid blockage of grout and reducing leaks outside the zone, thanks to the quick-setting of the grout – a sure saving in terms of material costs,
  • successive injections from one day to the next, or even sooner, by shortening binding times when applying, to avoid excessive hydrostatic pressure that might undermine the structure,
  • reduced leaks, grout setting more quickly,
  • possibility of working in cold weather,
  • adjustment of setting time for better control of volumes to be injected,
  • maintaining permeance of the wall, as with a hydraulic lime grout,
  • high-rise reinforcement operations.

Dosage (in volumes):

PNC NHL 3.5 Water Tempo retarding agent Strengths
3 litres 6 litres 8 litres 1 to 3 capfuls of Tempo 2 MPa at 1 year
1 bag of 25 kilos   15 à 20 litres 1 to 2 bottles 5 to 7 MPa at 3 months

The Marsh cone runoff time is 40 to 60 seconds per litre. At 20°C, setting time can be adjusted from between 5 and 30 minutes with a maximum dose of the retardant agent. In-wall setting will depend on the water absorption by the support granulates and temperature of the grout. Varying degrees of fineness of sand can be added according to the porosity to be filled. It is possible to achieve higher mechanical performances by adding water-reducing super-plastifying agents.

In case of a leak during injection, apply one volume of dry Prompt natural cement to the leak and hold in place for a few minutes. Once hydrated, it will set very quickly and block the leak. Do not inject into masonry containing traces of plaster.



Launch slideshow