9 step of Grouting process for post tensioned concrete girder and segments.

IMAGE CREDIT : MIDAS

After stressing all the cables, grouting should be taken up at the earliest. Strands are cut to a minimum length, keeping about one inch from the bearing plate. The grout cap is to be fitted before the grouting operation.

9 Steps of the grouting process for post-tensioned concrete girder and segments.

STEP-1 Remove loose material/dirt etc. from the cable duct by passing water through the threaded grout hole of the tube unit. A ball valve and a threaded pipe are fitted to this grout hole of the tube unit.

STEP-2 After flushing the duct with water, it must be ensured that clean water comes out from the other end. Compressed air may also be used to remove Traces of water from the duct.

STEP-3 Ball valves should be fixed at the inlet location and are connected to the grouting Pump with a high-pressure hosepipe.

STEP-4 Dual piston electrically operated grouting pump, developing a pressure of Minimum 10 kg/cm2 and a delivery of 20 litres per minute will be used.

STEP-5 Grout should be made in a drum of 250 ltrs capacity and a grout agitated by grout agitator to make a colloidal mix. First, water should be added to the drum.  Cement bags are to be emptied into the drum. This mix should be agitated by keeping the electrical agitator on the top of the drum.

An non shrink additive, generally FOSROC Conbex - 100 or equivalent, is used in a proportion of 0.5% by weight of cement.  

The water-cement ratio of the mix is between 0.4 and 0.45. The temperature of the grout should be controlled in case of a hot atmosphere by using ice water.  The agitated grout should be passed to the small drum by sieving to remove lumps or minor unwanted particles.

STEP-6 The properties of grout, such as compression strength is to be checked on a 100mm cube. The minimum strength on days is to be 17 Mpa.

STEP-7 The grout shall be made just before the grouting operation and shall be kept agitated until it is pumped. Grout once made shall be consumed within 30-45 minutes.

STEP-8 Grouting shall be carried out in one continuous operation. The grout should be pumped from one end of the girder. The grout should be allowed to pass through the other end with the same consistency before closing the grout hole opening. The bolt fitted to the grout cap should be loosened or refitted on the other end to ensure air is expelled.

STEP-9 After a consistent grout starts coming out of the outlet, it shall be closed and the pressure maintained at 5 Kg/cm2 for at least 30 seconds.  Once the grouting operation is complete, the inlet ball valve should be closed. The grout in the pump line should be bypassed to remove the pressure at the pump end. Shift the pump for the next grouting operation.

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