6 Materials and products

6.1 General

6.1.1 All material and products for incorporation into the micropiles shall comply with the specification for the works.

6.1.2 The sources of supply materials shall be documented and shall not be changed without prior notification.

6.2 Reinforcement and load bearing elements

6.2.1 Steel for reinforcement cage elements Steel bars for the reinforcement of concrete micropiles shall comply with EN 10080. When selecting the type and grade of steel, attention shall be given to the assembly of reinforcement cages and the weldability requirements.

6.2.2 Steel for load bearing elements Steel bearing elements shall comply:

  • with EN 10080 or prEN 10138–4 when bars are used;
  • with EN 10210 or EN 10219 or EN ISO 11960 when hollow sections (e.g. tubes) are used;
  • with EN 10025 , when hot rolled products (e.g. H–sections) are used. When selecting the type and grade of steel, attention shall be given to weldability requirements when relevant. Connecting elements shall not compromise the required capacity of the bearing element. Re–used and second choice steel elements shall as a minimum comply with the requirements concerning geometrical and material properties specified in the design and shall be free from damage, deleterious matter and corrosion that would affect strength and durability.

6.2.3 Other materials for reinforcement and load bearing elements Cast iron for bearing elements and castings shall comply with the project specifications and with the specifications of the manufacturer. Other materials may only be used if their suitability has been proven and they are approved by the Client's Technical Representative.

6.3 Materials for grout, mortar and concrete

6.3.1 Cement Cement for micropiles shall be in accordance with EN 197–1. When selecting the type of cement, account shall be taken of the aggressiveness of the environment. The exposure class shall be defined in accordance with EN 206–1. High sulphate content cements shall not be used in contact with prestressing steel according to prEN 10138–4.

6.3.2 Aggregates Aggregates shall comply with EN 206–1. Rounded aggregates should be preferred when placing mortar or concrete by tremie or by pumping.

6.3.3 Water Mixing water should comply with EN 206–1.

NOTE Potable water is acceptable for the preparation of grout, mortar or concrete. Mixing water obtained from natural sources on site should be tested, particularly for chlorides, sulphates and organic matter, and approved by the Client's Technical Representative. Acceptance criteria and water testing methods as required by subclause shall comply with EN 1008.

6.3.4 Additions and admixtures Additions and admixtures shall comply:

  • a) with EN 206–1 and EN 934–2;
  • b) with the approval documents and the manufacturer's instructions.

6.4 Cement grout

6.4.1 Grout composition and the grouting or filling technique and procedure shall be planned and carried out in a manner appropriate to the application and the ground conditions.

6.4.2 Sand and fillers can be used in cement grouts as bulking agent or as a means of varying the consistency of the grout, its resistance to wash out or segregate.

NOTE Cement grouts to which filler or sand (maximum grain size 2 mm) is added to a quantity by weight of less than 1,0 times the cement quantity are still considered as a cement grout. For more quantity of filler or sand, the mix shall be considered as a mortar.

6.4.3 Water/cement ratio should be appropriate to actual ground conditions and unless otherwise specified, not more than 0,55.

6.4.4 Unless otherwise specified the minimum unconfined compressive strength shall be at least 25 MPa at 28 days (or at the date of the first loading of the micropile if it is carried out before this delay) with cylindrical test samples having height–diameter ratio equal to 2.

6.4.5 Laboratory and field tests should be undertaken to verify mixture, mixture efficiency, setting time and performance. These tests should be undertaken in accordance with EN 445 where applicable.

6.4.6 The allowable bleed after 2 h should be less than 3 %.

6.4.7 For cement–grout used to encase a reinforcement within an encapsulation, the mix should be designed to minimize bleeding and shrinkage according to EN 447.

6.4.8 Quality control The quality of the grout shall be controlled during the works. On site, the grouts should be subjected to the following routine tests:

  • density at the mixer and, if applicable, at the inlet and at the outlet of the borehole;
  • viscosity (Marsh value), where applicable;
  • bleed. Unless otherwise specified, for each site and for each period of maximum 7 working days, at least 2 sets of 3 samples (cylinders or cubes) shall be taken and tested for compressive strength. When mixing automatically, the batching process shall be checked periodically and when not mixing automatically, the batching process shall be recorded.

6.5 Mortar and Concrete

6.5.1 Mortar and concrete in situ The mix composition shall be designed in accordance with EN 206–1, unless otherwise specified. Mortar and concrete for micropiles shall:

  • a) have a high resistance against segregation;
  • b) be of high plasticity and good cohesiveness;
  • c) have good flow properties;
  • d) have the ability to self – compact;
  • e) be sufficiently workable for the duration of the placement procedure, including the removal of any temporary casing;
  • f) have a minimum unconfined compressive strength of 25 MPa at 28 days (or at the date of the first loading of the micropile if it is carried out before this delay, determined on cylindrical test samples having a height–diameter ratio equal to 2. Unless otherwise specified for placement in submerged conditions the cement content shall be at least 375 kg/m3, with water cement ratio < 0,6. For mortar, the size of the aggregates shall not exceed the following grain size distribution:

  • d85 ≤ = 4 mm;
  • d100 ≤ = 8 mm. For concrete, the maximum grain size of the aggregates shall not exceed 16 mm, 1/4 of the clear distance of the longitudinal bars and 1/6 of the internal diameter of the used tremie pipe or pumping pipe, whichever is the lowest value.

6.5.2 Other concrete For driven prefabricated concrete elements the materials and fabrication, including joints, shall comply with EN 12794. Concrete which is subsequently cast inside a micropile casing is covered by 6.5.1.

6.6 Spacers, centralizers and other components

6.6.1 Spacers or centralizers may be used to provide the grout or concrete cover specified in subclause 7.6.

6.6.2 Spacers and centralizers shall be designed and manufactured using durable materials which will not lead:

  • to corrosion of the reinforcement or bearing element;
  • to spalling of the grout, mortar or concrete cover.

6.6.3 Materials for spacers, centralizers and other components shall be compatible with the materials of the micropile and shall not compromise the corrosion protection.

6.7 Coatings and corrosion protection compounds

6.7.1 Coatings and compounds for corrosion protection shall comply with the design specifications. The continuity of the protection, close to the connection elements shall comply with the specifications and the design.

6.7.2 Protection compounds used with high strength steel and prestressing steel as defined in 7.7.2. shall be in accordance with 6.10 of EN 1537:1999.

6.7.3 Coatings used to reduce the shaft friction shall comply with the specification and the design.

EN 14199:2005 Execution of special geotechnical works — Micropiles