7.4 Grout

7.4.1 Type and composition The type and composition of the grout shall be selected according to the ground conditions and specifications of the works. The national standards shall be consulted for restrictions in the use of specific types of grouts.

7.4.2 General considerations In order to achieve the performance specifications for grouting works the design shall consider:

  • the purpose of the treatment;
  • grout placement, timing and sequencing;
  • environmental conditions;
  • rheological properties of the grout and their change with time, such as the water content of the solid constituents of a grout mix;
  • setting and hardening time of the grout;
  • the compatibility of the grout with the components of the delivery system and the ground;
  • physical properties after setting;
  • the effects of syneresis on the mechanical stability of the injected ground (for silicate based grouts). The following environmental conditions shall be considered for the design:

  • the size of openings to be filled by the grout and the size of the solid (hydrated) grout constituents, particularly the sizes of the pore necks (smallest access area) rather than the porosity;
  • the permeability of the medium to be injected and the penetrability of the grout;
  • the chemistry of the groundwater, mix water, and the ground;
  • ground and grout temperature;
  • the risk and effect of grout drying out upon exposure;
  • the environmental impact during mixing, processing and the placement of the grout;
  • the pollution potential of the grout. If permeation grouting is to be undertaken, the dimensions of interconnected voids in the soil (effective porosity) or interconnected fissures in rock, should be known before designing the grout. This is particularly relevant for suspensions, where the filter criteria (relating particle size to void opening) and the stability of the mix under in situ gradients should be investigated. The cohesion of the mix should further be related to the desired reach of the treatment, and the viscosity of the grout to the permissible working pressures. The determination of the setting time depends on:

  • the volume of grout to be prepared and injected;
  • the ground permeability;
  • the interconnected porosity of the ground;
  • the rate of groundwater flow;
  • the time of injection for one pass;
  • the anticipated placement time of a prepared batch of grout.

7.4.3 Parameters and criteria The execution design shall state the range and median values of the following grout parameters for given environmental conditions:

  • density, viscosity, yield or cohesion;
  • shear and compressive strength;
  • particle size of cement or binder;
  • water retention capacity;
  • for silicate gels the relative percentage of the reagent and silicate (neutralization rate);
  • sedimentation rate. Table A.1 presents the measuring conditions for the main parameters of each class of grout. The design should further specify criteria for the selection of a specific mix if different mixes have been suggested, and the permitted maximum and minimum grout temperatures during processing and placement. In soils, a groutability ratio, such as the D10/d90 or D15/d85 criterion, can be used to assess the penetrability of particulate grouts (see glossary, annex B). In rock, the maximum particle size to fissure width is considered (a ratio of three is commonly used). Limit criteria for changing the mix design should be decided upon at the outset of the works for the case that:

  • grout takes are significantly in excess of those anticipated in the design;
  • no grout acceptance can be achieved with the design mix;
  • undesirable ground movement occurs.

7.4.4 Applicability The types of grout applicable for different types of ground are shown in Table 3.

Table 3 — Indicative grouts for different types of ground
Host medium Range Non-displacement grouting Displacement grouting
    Permeation Fissure or contact grouting Bulk filling  
Granular soil Gravel, coarse sand and sandy gravel
K > 5 × 10–3 m/s
Pure cement suspensions, Cement based suspensions      
5 × 10–5 < K < 5 × 10–3 m/s
Microfine suspensions,
    Cement based suspensions,
Medium to fine sand
5 × 10–6 < K < 1 × 10–4 m/s
Microfine suspensions,
Special chemicals
Fissured rock Faults, cracks, karst
e > 100 mm
  Cement based mortars,
Cement based suspensions (clay filler)
Cement based suspensions with short setting time,
Expansive polyurethane,
Other water reactive products
Cracks, fissures
0,1 mm < e < 100 mm
  Cement based suspensions,
Microfine suspensions
e < 0,1 mm
  Microfine suspensions
Silicate gels
Special chemicals
Cavity Large voids     Cement based mortars,
Cement based, suspensions with short setting time
Expansive polyurethane,
Other water reactive products
e = fissure width Sleeve grouts for sealing the sleeve pipe shall be designed to prevent migration along the annulus, and to facilitate fracturing between the sleeve and the ground.

EN 12715:2000 Execution of special geotechnical work – Grouting