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Fosroc Conbextra HS Grout 20kg

Code: 40-FC502000-20KG
U.O.M. - Each
Conbextra HS is a shrinkage compensated ultra high-strength cementitious precision grout, supplied as a ready to use dry powder. The addition of a controlled amount of clean water produces a free-flowing precision grout for gap thicknesses 10 mm up to 125 mm. Conbextra HS is a blend of Portland cements, graded fillers and chemical additives which impart controlled expansion in both the plastic and hardened states. The filler grading minimises segregation and bleeding over a wide range of application consistencies.


High flow, high ultimate strength, dual shrinkage compensated, precision cementitious grout. It is suitable for gaps from 10mm to 125mm, where high flow and high ultimate strength is required. Its low water requirement ensures high early strength and long term durability. Conbextra HS is a blend of Portland cements, graded fillers and chemical additives which impart controlled expansion in both the plastic and hardened states.


  • Non-metallic dual expansion system compensates for shrinkage in both the plastic and hardened states
  • Excellent initial flow and flow retention suitable for large and small grout pours
  • Rapid strength gain facilitates efficient installation and operation of plant
  • High ultimate strength and low permeability ensure durability of the hardened grout
  • Hydrogen-free gaseous expansion
  • Chloride free
  • Suitable for pumping or pouring over a large range of application consistencies and temperatures
  • Ideal for:

  • Grouting baseplates and soleplates of large machines subject to moderate dynamic loads
  • Crane rail soleplates
  • Precast wall panels, beams, columns and structural building members

    Surface Preparation:

    The substrate surface must be free from oil, grease or any loosely adherent material. Bolt holes or fixing pockets must be blown clean of any dirt or debris. Several hours prior to grouting, the area of cleaned foundation should be flooded with fresh water. Immediately before grouting takes place, any free water should be removed. Particular care should be taken to blow out all bolt holes and pockets. It is essential that the base plate / grout interface is clean and free from oil, grease, scale, paint or coating of any kind. Air pressure relief holes should be provided to allow venting of any isolated high spots.

    Formwork should be constructed to be leakproof as Conbextra HS is a free flowing grout. This can be achieved by using foam rubber strip or silicone beneath the constructed formwork and between joints.

    The unrestrained surface area of the grout must be kept to a minimum. Generally the gap width between the perimeter formwork and the plate edge should not exceed 150mm on the pouring side and 50mm on the opposite side. There should be no gap at the flank sides.


    A forced-action mixer is essential. Larger quantities will require a high shear vane mixer. Do not use a colloidal impeller mixer. It is essential that machine mixing capacity and labour availability is adequate to enable grouting operation to be carried out continuously. This may require the use of a holding tank with provision for gentle agitation to maintain fluidity. The selected water content should be accurately measured into the mixer. Slowly add the total contents of the Conbextra HS bag, mix continuously for 5 minutes, ensuring a smooth, even consistency is obtained.


    Place the grout within 15 minutes of mixing to gain the full benefit of the expansion process. Conbextra HS can be placed in thicknesses up to 125mm in a single pour. Any bolt pockets must be grouted prior to grouting between the substrate and the base plate. Continuous grout flow is essential. Filling/bulking out of the grout should not exceed a ratio of 2:1 (Grout: Aggregate).

    For larger pours the grout may be hand placed or pumped into a removable hopper (trough). Sufficient grout must be available prior to starting and the time taken to pour a batch must be regulated to the time taken to prepare the next one. Continual grout pour must be ensured. The mixed grout should be poured only from one side of the void to eliminate the entrapment of air or surplus pre-soaking water. The grout head must be maintained at all times so that a continuous grout front is achieved.

    Where large volumes have to be placed Conbextra HS may be pumped. A heavy duty diaphragm pump is recommended for this purpose. Screw feed and piston pumps may also be suitable.

    On completion of the grouting operation, exposed areas should be thoroughly cured. This should be done by the use of Concure curing membrane, continuous application of water and/or wet hessian.

    Clean Up:

    Remove from tools and equipment with clean water immediately after use. Cured material can be removed mechanically.


    Shelf life of 24 months if kept in a dry store in sealed bags.


    A 20 kg bag yields 9.8 litres of flowable grout, or 10.1 litres of high flow grout.

    Additional Information

    CODE 40-FC502000-20KG
    10/4 - 4/10 Delivery Yes
    U.O.M Each
    Brand Fosroc
    Range / Model Conbextra
    Size 20 kg
    Appearance / Composition Powder
    Application Thickness (mm) 10 mm to 125 mm
    Cure Time Initial - 2.5 hours, Final - 5 hours
    Compressive Strength at 7 days (MPa) 80 (flowable), 70 (fluid) at 23 degrees Celsius
    Compressive Strength at 28 days (MPa) 100 (flowable), 85 (fluid) at 23 degrees Celsius
    Yield 9.8L (flowable), 10.1L (high flow)
    Approvals & Certifications AS1478.2-2005 Appendix E test for early volume change
    AS1478.2.2005 (table for workability
    Fire rating Class A1 Non-combustible
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