Fosroc Conbextra GP

Fosroc Conbextra GP is used for free flow, non-shrink, cementitious grouting of gap thicknesses 10 to 75 mm. London Underground approved.

Best Uses

Fosroc Conbextra GP is supplied as a ready to use dry powder. The addition of a controlled amount of clean water produces a free-flowing grout for gap thicknesses up to 75mm. The low water requirement ensures high early strength and long-term durability. Conbextra GP is a blend of Portland cements, graded fillers and chemical additives. The filler grading produces a highly flowable grout which will not segregate or bleed.

Recommended applications of Fosroc Conbextra GP include:

• Stanchion baseplates
• Joints between pre-cast concrete panels
• Grouting applications where pouring access is restricted
• Anchoring of reinforcing steel bars
• Installation of tie bars
• Trowelling consistency can be used for bedding and in lieu of dry packs

Fosroc Conbextra GP benefits from being non-shrink, high strength and chloride free. Can be used at flowable or trowellable consistency. Conbextra GP complies with LU Standard 1-085 Fire Safety Performance of Materials.

Application

Preparation Foundation Surface
The substrate surface must be free from oil, grease or any loosely adherent material. If the concrete surface is defective or has laitance, it must be cut back / scabbled to a sound base. Boltholes or fixing pockets must be blown clean of any dirt or debris.

Pre-soaking
For a minimum of 2 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 boltholes and pockets. In certain situations, such as likelihood of damage to surrounding areas, water flooding / prolonged soaking of the concrete substrate may not be possible. In such cases, immediately prior to the grout application, the cleaned concrete should be water wetted, for example by spraying, until the surface becomes saturated / no longer shows signs of rapid drying; particular care to be taken on hot days and or in direct sunlight. Before grouting takes place, any free water should be removed, taking care to blow out all boltholes and pockets.

Base plate
It is essential that this is clean and free from oil, grease or scale. Air pressure relief holes should be provided to allow venting of any isolated high spots.

Levelling shims
If these are to be removed after the grout has hardened, they should be treated with a thin layer of grease.

Formwork
The formwork should be constructed to be leakproof, as Conbextra GP is a free-flowing grout. This can be achieved by using foam rubber strip or Fosroc Nitoseal MS60* beneath the constructed formwork and between joints. In some cases it is practical to use a sacrificial semi-dry sand and cement formwork. The formwork should include outlets for the pre-soaking water. 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 150 mm on the pouring side and 50 mm on the opposite side. There should be no gap at the flank sides.

Mixing
Water addition: Flowable: 4.0 - 4.5 litres per 25Kg bag / Trowellable: 3.0 - 3.6 litres per 25Kg bag
For mixing quantities up to 50 kg a high power, 280 to 640 rpm, 110 volt drill, fitted with a Fosroc Conbextra Mixing Paddle (MR3) is suitable.

Follow guidance on Product Data Sheet for full preparation and installation instructions.