Problem with two piece concrete window cill join

Hi

I have a leak where the two part concrete cill on one of my windows joins in the middle. There is a small gap, less than one eighth of an inch. It has been siliconed but the rule of depth not exceeding width broken so the seal has failed. Water is going through the cill into the blockwork behind render and into my conservatory.

Any advice as to how to fill the cill join gap appreciated.

Clean out the joint (hacksaw blade or similar) get some polysulphide a similar course to concrete and squeeze it into the joint, finish with a raised bead of the compound to shed water either side...pinenot

Thanks for the reply pinenot.
Not used polysulphide but is this the sort of stuff..............
http://www.ebay.co.uk/itm/geocel-20...booking_Glue_Tape_EH&var=&hash=item2308aee7dd

So 2 stage process after cleaning joint. fill to 1mm or so below cill level, let cure and then form a bead that overlaps onto the concrete cill on each side?

Thats the the stuff, gey would be a good choise.
Actually I am suggesting you do it all in one stage after rake out. By keeping the cut of the nozzle flat on the cill whilst pushing the polysulphide hard into the joint and finishing by applying a half round bead angling the nozzle down, lifting the trailing edge clear of the fill forming a bead as you go. Finish all this at the bottom of the front edge, the polysulphide will form a soft but touchable skin...pinenot